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Three-dimensional hydrogel supports for mesenchymal and neural stem cells (NSCs) are promising materials for tissue engineering applications such as spinal cord repair. This study involves the preparation and characterization of superporous scaffolds based on a copolymer of 2-hydroxyethyl and 2-aminoethyl methacrylate (HEMA and AEMA) crosslinked with ethylene dimethacrylate. Ammonium oxalate is chosen as a suitable porogen because it consists of needle-like crystals, allowing their parallel arrangement in the polymerization mold. The amino group of AEMA is used to immobilize RGDS and SIKVAVS peptide sequences with an N-γ-maleimidobutyryloxy succinimide ester linker. The amount of the peptide on the scaffold is determined using 125I radiolabeled SIKVAVS. Both RGDS- and SIKVAVS-modified poly(2-hydroxyethyl methacrylate) scaffolds serve as supports for culturing human mesenchymal stem cells (MSCs) and human fetal NSCs. The RGDS sequence is found to be better for MSC and NSC proliferation and growth than SIKVAVS.
Superporous RGDS-poly(2-hydroxyethyl methacrylate) scaffold supports mesenchymal and neural stem cell attachment, proliferation, and growth. This makes the scaffold attractive for accommodation of cells in tissue engineering applications such as spinal cord repair.
The development of delivery systems efficiently uptaken by cells is of due importance since sites of drug action are generally localized in subcellular compartments. Herein, naked and core–shell polymeric nanoparticles (NPs) have been produced from poly(lactic-co-glycolic acid)—PLGA, poly(ethylene oxide)-b-poly(ε-caprolactone)—PEO-b-PCL, and poly(ethylene oxide)-b-poly(lactic acid)—PEO-b-PLA. The nanostructures are characterized and the cellular uptake behavior is evaluated. The data evidence that cellular uptake is enhanced as the length of the hydrophilic PEO-stabilizing shell reduces and that high negative surface charge restricts cellular uptake. Furthermore, NPs of higher degree of hydrophobicity (PEO-b-PCL) are more efficiently internalized as compared to PEO-b-PLA NPs. Accordingly, taking into account our recent published results and the findings of the current investigation, there should be a compromise regarding protein fouling and cellular uptake as resistance to nonspecific protein adsorption and enhanced cellular uptake are respectively directly and inversely related to the length of the PEO-stabilizing shell.
The cellular uptake behavior of a library of polymeric nanoparticles is evaluated. The experimental results evidence that cell internalization is inversely related to the length of the hydrophilic corona. Additionally, higher degree of core hydrophobicity and high negative surface charge respectively enhances and restricts cellular uptake.
Electrically conductive biomaterials that can efficiently deliver electrical signals to cells or improve electrical communication among cells have received considerable attention for potential tissue engineering applications. Conductive hydrogels are desirable particularly for neural applications, as they can provide electrical signals and soft microenvironments that can mimic native nerve tissues. In this study, conductive and soft polypyrrole/alginate (PPy/Alg) hydrogels are developed by chemically polymerizing PPy within ionically cross-linked alginate hydrogel networks. The synthesized hydrogels exhibit a Young's modulus of 20–200 kPa. Electrical conductance of the PPy/Alg hydrogels could be enhanced by more than one order of magnitude compared to that of pristine alginate hydrogels. In vitro studies with human bone marrow-derived mesenchymal stem cells (hMSCs) reveal that cell adhesion and growth are promoted on the PPy/Alg hydrogels. Additionally, the PPy/Alg hydrogels support and greatly enhance the expression of neural differentiation markers (i.e., Tuj1 and MAP2) of hMSCs compared to tissue culture plate controls. Subcutaneous implantation of the hydrogels for eight weeks induces mild inflammatory reactions. These soft and conductive hydrogels will serve as a useful platform to study the effects of electrical and mechanical signals on stem cells and/or neural cells and to develop multifunctional neural tissue engineering scaffolds.
Conductive and soft polypyrrole/alginate hydrogels are synthesized by chemically polymerizing polypyrrole within alginate hydrogel networks for human mesenchymal stem culture. The conductive hydrogels can display more than ten times high electrical conductivities and softness (<200 kPa Young's modulus). These conductive hydrogels promoted human mesenchymal stem cell adhesion and growth, and also greatly up-regulated neural differentiation markers.
A bioactive scaffold with desired microstructure is of great importance to induce infiltration of somatic and stem cells, and thereby to achieve the in situ inductive tissue regeneration. In this study, a scaffold with oriented pores in the radial direction is prepared by using methacrylated hyaluronic acid (HA-MA) via controlled directional cooling of a HA-MA solution, and followed with photo-crosslinking to stabilize the structure. Poly(lactide-co-glycolide) (PLGA) is further infiltrated to enhance the mechanical strength, resulting in a compressive modulus of 120 kPa. In vitro culture of bone marrow stem cells (BMSCs) reveals spontaneous cell aggregation inside this type of scaffold with a spherical morphology. In vivo transplantation of the cell-free scaffold in rabbit knees for 12 w regenerates simultaneously both cartilage and subchondral bone with a Wakitani score of 2.8. Moreover, the expression of inflammatory factor interleukin-1β (IL-1β) is down regulated, although tumor necrosis factor-α (TNF-α) is remarkably up regulated. With the anti-inflammatory, bioactive properties and good restoration of full thickness cartilage defect in vivo, the oriented macroporous HA-MA/PLGA hybrid scaffold has a great potential for the practical application in the in situ cartilage regeneration.
Methacrylated hyaluronic acid/PLGA scaffolds with radially oriented pores are fabricated, which are able to realize in situ inductive regeneration of cartilage in a full thickness articular cartilage defect model in rabbit without employment of any extraneous cells or chondrogenetic growth factors.
Hyaluronic acid nanogel (HyA-AT) is a redox sensitive crosslinkable nanogel, obtained through the conjugation of a thiolated hydrophobic molecule to the hyaluronic acid chain. Engineered nanogel was studied for its biocompatibility, including immunocompatibility and hemocompatability. The nanogel did not compromise the metabolic activity or cellular membrane integrity of 3T3, microvascular endothelial cells, and RAW 264.7 cell lines, as determined by the 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazolium bromide and lactate dehydrogenase release assays. Also, we didn't observe any apoptotic effect on these cell lines through the Annexin V-FITC test. Furthermore, the nanogel cell internalization was analyzed using murine bone marrow derived macrophages, and the in vivo and ex vivo biodistribution of the Cy5.5 labeled nanogel was monitored using a non-invasive near-infrared fluorescence imaging system. The HyA-AT nanogel exhibits fairly a long half-live in the blood stream, thus showing potential for drug delivery applications.
Crosslinkable Hyaluronic acid nanogels immunocompatibility and hemocompatability and general biocompatibility is assessed in this work. Cytotoxicity on three different cell lines is confirmed through various approaches. Further, BMDM nanogels uptake suggests low recognition by immune system and in vivo results confirms its long circulation time.
The recurrence of acute gout attacks remains an unsolved problem in clinical therapy. In order to tackle this problem, poly(ε-caprolactone) (PCL)/gelatin composite fibrous devices loaded with luteolin are presented via electrospinning for the therapy of gout and its recurrence. The luteolin-loaded fibrous device has the capability of inhibiting metabolic activities and reducing inflammation-associated cytokine productions (TNF-a, IL-1β, IL-6) that are secreted by lipopolysaccharide stimulated RAW 264.7 macrophages. The device can also suppress the reaction activities of xanthine oxidase for 7 d in vitro. In vivo, acute gout model is established by injecting monosodium urate (MSU) crystals into New Zealand rabbits' knees, then the luteolin-loaded PCL/gelatin (5:5) nanofiber device is implanted near the gout sites. The results show that the device can alleviate the acute gouty arthritis. In the mean time, the luteolin-loaded PCL fiber device with a longer drug release profile is implanted in a recurrent gout model, which is constructed by injecting MSU crystals into rabbits' knees three times. The results on day 21 reveal that this device has the potential to overcome the recurrence of gout. Therefore, the drug-loaded polymer fiber device can be an inspiration for potential gout therapy to overcome recurrent attacks.
A biodegradable polymer composite fiber device loading with luteolin is successfully developed via an electrospinning technology. The loaded drug can be controlled release from this device by simply adjusting the blend ratio of polymers, enabling it to potentially treat gout attacks.
Cell-laden micrometer-sized hydrogels (microgels) hold great promise for improving high throughput ex-vivo drug screening and engineering biomimetic tissues. Microfluidics is a powerful tool to produce microgels. However, only a limited amount of biomaterials have been reported to be compatible with on-chip microgel formation. Moreover, these biomaterials are often associated with mechanical instability, cytotoxicity, and cellular senescence. To resolve this challenge, dextran-tyramine has been explored as a novel biomaterial for on-chip microgel formation. In particular, dextran-tyramine is compared with two commonly used biomaterials, namely, polyethylene-glycol diacrylate (PEGDA) and alginate, which crosslink through enzymatic reaction, UV polymerization, and ionic interaction, respectively. Human mesenchymal stem cells (hMSCs) encapsulated in dextran-tyramine microgels demonstrate significantly higher (95%) survival as compared to alginate (81%) and PEGDA (69%). Long-term cell cultures demonstrate that hMSCs in PEGDA microgels become senescent after 7 d. Alginate microgels dissolve within 7 d due to Ca2+ loss. In contrast, dextran-tyramine based microgels remain stable, sustain hMSCs metabolic activity, and permit for single-cell level analysis for at least 28 d of culture. In conclusion, enzymatically crosslinking dextran-tyramine conjugates represent a novel biomaterial class for the on-chip production of cell-laden microgels, which possesses unique advantages as compared to the commonly used UV and ionic crosslinking biomaterials.
Cell encapsulating microgels are a promising tool for drug screening and tissue engineering approaches. However, only a limited amount of biomaterials have been reported to be compatible with on-chip microgel formation. Here, on-chip fabrication of dextran-tyramine microgels has been explored and reported that these microgels possess significant advantages over commonly used biomaterials, including improved cell survival, metabolic activity, and microgel stability.
The development of effective nonviral vectors for gene therapy is still a challenge in research, due to the high toxicity of many existing polycationic nanocarriers. In this paper, the development of two pH-cleavable polyglycerol-amine-based nanocarriers is described. The benzacetal bond represents the pH-sensitive cleavage site between dendritic polyglycerol (dPG) and glycerol-based 1,2-diamines that can complex genetic material. Due to the acid lability of the acetal moiety, the cleavable dPG-amines are less toxic in vitro. Cell-mediated degradation results in non-toxic dPG with low amine functionalization and low molecular weight cleavage products (cp). The genetic material is released because of the loss of multivalent amine groups. Interestingly, the release kinetics at the endosomal pH could be controlled by simple chemical modification of the acetals. In vitro experiments demonstrate the ability of the cleavable dPG-amine to transfect HeLa cells with GFP-DNA, which resulted in cell-compatible cleavage products.
This paper describes the development of two pH-cleavable polyglycerol-amine-based nanocarriers. The benzacetal bond represents the pH-sensitive cleavage site between dendritic polyglycerol (dPG) and glycerol-based 1,2-diamines that can complex genetic material. In vitro experiments demonstrate the ability of the cleavable dPG-amine to transfect HeLa cells with GFP-DNA, which resulted in cell-compatible cleavage products.
Polymeric micelles (PM) have been extensively used for tumor-targeted delivery of hydrophobic anti-cancer drugs. The lipophilic core of PM is naturally suitable for loading hydrophobic drugs and the hydrophilic shell endows them with colloidal stability and stealth properties. Decades of research on PM have resulted in tremendous numbers of PM-forming amphiphilic polymers, and approximately a dozen micellar nanomedicines have entered the clinic. The first generation of PM can be considered solubilizers of hydrophobic drugs, with short circulation times resulting from poor micelle stability and unstable drug entrapment. To more optimally exploit the potential of PM for targeted drug delivery, several physical (e.g., π–π stacking, stereocomplexation, hydrogen bonding, host–guest complexation, and coordination interaction) and chemical (e.g., free radical polymerization, click chemistry, disulfide and hydrazone bonding) strategies have been developed to improve micelle stability and drug retention. In this review, the most promising physico-chemical approaches to enhance micelle stability and drug retention are described, and how these strategies have resulted in systems with promising therapeutic efficacy in animal models, paving the way for clinical translation, is summarized.
In this review, the most promising physico-chemical approaches to enhance polymeric micelle stability and drug retention are described, and how these strategies contribute to polymeric micelles with promising therapeutic efficacy in animal models, paving the way for clinical translation, is summarized.
Poly(2-hydroxypropylene imine)s containing segments of cystamine (PHPI-CA) are synthesized by polycondensation of 1,3-dibromo-2-propanol with a mixture of 1,3-diamino-2-propanol and cystamine. High molecular weight fractions of these polymers are collected by ultrafiltration and characterized by chemical analysis, 1H and 13C-NMR spectroscopy, size-exclusion chromatography with triple detection, and potentiometric titration, and are tested for DNA delivery in vitro. It is shown that PHPI-CA are highly branched polymers containing disulfide linkages. Transfection efficiency of PHPI-CA for DNA gives similar results to that of PHPI with GFP+ cell percent reaching 80–90%. Cytotoxicity levels for PHPI-CA are lower than that of PHPI. Novel polymers containing different amounts of disulfide linkages are able to disintegrate and release DNA following the treatment with reducing agent 1,4-dithiothreitol. Downstream application of PHPI-CA transfected cells for RNA purification shows that RNA yield is not affected even after the double transfection suggesting that these polymers could be great candidates for in vitro and in vivo transfection.
Novel polymers containing different amounts of disulfide linkages. Polymers are able to break down and release DNA following the treatment with reducing agent 1,4-dithiothreitol. Downstream application of poly(2-hydroxypropylene imines) containing segments of cystamine transfected cells for RNA purification shows that RNA yield is not affected even after the double transfection suggesting that these polymers could be great candidates for in vitro and in vivo transfection.
This study aims to develop an effective method to control motile microorganisms and enable their manipulation as functional 'live micro/nano robots'. A novel strategy based on Fe3O4 nanoparticle-doped alginate hydrogel is developed to fashion an artificial extracellular matrix (ECM) for microbial cells (e.g., Saccharomyces cerevisiae and Flavobacterium heparinum). During this strategy, a single layer of alginate hydrogel is coated around the microbial cells doped with Fe3O4 nanoparticles to form the alg-mag-cells. Transmission electron microscopy shows that Fe3O4 nanoparticles are uniformly distributed in the hydrogel shell. Together with maintaining the cell activity and metabolism, the hydrogel coated microbial cells demonstrate high magnetic responsiveness in an external magnetic field and are able to form micro-scaled patterns using the magnetic template designed in this study. This strategy provides a building block to fabricate advanced biological models, medical therapeutic products, and non-medical biological systems using different microorganisms.
The creation of artificial extracellular matrix (ECM) for microbial cells using alginate hydrogels can maintain the cell activity and metabolic level. After Fe3O4 nanoparticles are doped into the matrix, the treated cells display high magnetic responsiveness in an external magnetic field and thus are expected to work as nano/micro robots. This can be easily done by manipulating the 'robots' to form micro-scaled patterns on a magnetic template with a specific design.
Chitosan-based molecular imprinted polymer (CS-MIP) nanogel is prepared in the presence of morphine template, fully characterized and used as a new vehicle to extend duration of morphine analgesic effect in Naval Medical Research Institute mice. The CS-MIP nanogel with ≈25 nm size range exhibits 98% loading efficiency, and in vitro release studies show an initial burst followed by an extended slow release of morphine. In order to study the feasibility of CS-MIP nanogel as morphine carrier, 20 mice are divided into two groups randomly and received subcutaneous injection of morphine-loaded CS-MIP and morphine (10 mg kg−1) dissolved in physiologic saline. Those received injection of morphine-loaded CS-MIP show slower and long lasting release of morphine with 193 min effective time of 50% (ET50) analgesia compared to 120 min ET50 in mice received morphine dissolved in physiologic saline. These results suggest that CS-MIP nanogel can be a possible strategy as morphine carrier for controlled release and extension of its analgesic efficacy.
Chitosan-based molecular imprinted polymer (CS-MIP) nanogel is prepared in the presence of morphine template. This new drug vehicle is to extend duration of morphine analgesic effect in mice. The results suggest that CS-MIP nanogel can be a possible strategy as morphine carrier for controlled release and extension of its analgesic efficacy.
With the aim to develop biomaterials for temporary medical devices, a series of novel reducible and/or degradable elastomers has been prepared from PLA-b-PEG-b-PLA copolymers photo-crosslinked with diallyl sulfide or pentaerythritol tetrakis(3-mercaptopropionate). Thermal and mechanical properties, including elastic limit and Young modulus, are assessed. Degradation is then evaluated under standard hydrolytic conditions. Reducibility of a selected elastomer is then illustrated using 2-mercaptoethanol or glutathione as reducing agents. The redox-sensitivity of the selected elastomer and the possibility to modulate the degradability are shown. Considering drug-eluting elastomeric devices applications, anti-inflammatory drug ibuprofen loading is illustrated with the two simplest elastomer formulations. A rapid or slow linear release is observed as a function of the low or high molecular weight of the triblock pre-polymers. Finally, the cytocompatibility of the degradable elastomers is assessed with regard to their potential to favor or inhibit L929 murine fibroblasts proliferation as a function of the hydrophilicity/hydrophobicity of the triblock copolymers.
Degradable elastomers for soft tissue-related medical devices are proposed. These poly(lactic acid)–poly(ethylene glycol)-based biomaterials have mechanical properties suitable for soft tissue applications, and feature a bimodal redox/hydrolytic degradation. Besides, they offer drug loading and drug release ability, as well as a tunable cell compatibility that makes them anti- or proproliferative biomaterials.
A hydrophobic/amino functionalized derivative of hyaluronic acid (HA-EDA-C18) has been processed by salt leaching technique as porous scaffold without need of chemical crosslinking. Aim of this work is to demonstrate the improved versatility of HA-EDA-C18 in terms of processing and biological functionalization. In particular, the chemical procedure to tether thiol bearing RGD peptide has been described. Moreover, the possibility to load and to control the release of slightly water soluble effectors has been demonstrated by using dexamethasone. First, the swelling and degradation profiles of the scaffolds have been investigated, then the evaluation of metabolic activity of bovine chondrocytes, the histological analysis, and microscope observations has been performed to evaluate cellular adhesion and proliferation as well as the production of collagen type II.
Hyaluronic acid derivative physically assembled into porous scaffold, versatile for bio effectors loading and tethering. Physicochemical properties of derivative allow production of scaffolds without chemical crosslinking. Hydrophobic coils allow loading of dexamethasone and its sustained release. Chemical versatility of this hyaluronic acid derivative is exploited for arginylglycylaspartic acid (RGD) tethering. Improvement of chondrocyte adhesion and maintenance of phenotype is obtained.
Using a well-defined poly(2,2-bis(hydroxymethyl)propanoic acid) dendrimer scaffold, a series of G1 to G3 dendrons is functionalized at the periphery with alkynes to enable "Click" functionalization via the copper-catalyzed alkyne–azide cycloaddition (CuAAC). The resulting dendrons are further functionalized at the core with a dipicolylamine (DPA) moiety to enable radiolabeling with 99mTc for molecular imaging applications. Efficient CuAAC coupling is achieved using an azide-functionalized triethylene glycol monomethyl ether (TEG-N3). Removal of copper from the DPA ligand is successfully performed on G1 and G2 dendrimers prior to radiolabeling with 99mTc. Radiolabeling of the G3 dendrimer is accomplished via transmetallation of the [CuDPA]2+ ligand with 99mTc, further demonstrating the feasibility of the synthetic strategies in the preparation of dendritic imaging agents. Subsequent attachment of an acyloxymethyl ketone (AOMK) derivative for targeting of cathepsin B is also explored. Despite demonstrating the ability to ligate multiple AOMK ligands, the AOMK–dendrimer conjugates are not able to bind to cathepsin B, which may be attributed to steric hindrance at the dendrimer periphery.
Dendritic scaffolds that can be site-specifically radiolabeled with 99mTc at their core, and efficiently decorated with multiple targeting ligands at their periphery are reported. These structures are functionalized with acyloxymethyl ketones as targeting ligands for cathepsin B.
Complementary nucleobase-functionalized polymeric micelles, a combination of adenine-thymine (A-U) base pairs and a blend of hydrophilic–hydrophobic polymer pairs, can be used to construct 3D supramolecular polymer networks; these micelles exhibit excellent self-assembly ability in aqueous solution, rapid pH-responsiveness, high drug loading capacity, and triggerable drug release. In this study, a multi-uracil functionalized poly(ε-caprolactone) (U-PCL) and adenine end-capped difunctional oligomeric poly(ethylene glycol) (BA-PEG) are successfully developed and show high affinity and specific recognition in solution owing to dynamically reversible A-U-induced formation of physical cross-links. The U-PCL/BA-PEG blend system produces supramolecular micelles that can be readily adjusted to provide the desired critical micellization concentration, particle size, and stability. Importantly, in vitro release studies show that doxorubicin (DOX)-loaded micelles exhibit excellent DOX-encapsulated stability under physiological conditions. When the pH value of the solution is reduced from 7.4 to 5.0, DOX-loaded micelles can be rapidly triggered to release encapsulated DOX, suggesting these polymeric micelles represent promising candidate pH-responsive nanocarriers for controlled-release drug delivery and pharmaceutical applications.
A new series of supramolecular polymer micelles containing complementary nucleobase molecular recognition exhibits excellent drug-loading and pH-triggered drug-release ability in aqueous solution due to the presence of physical cross-links.
The properties as biointerfaces of electroactive conducting polymer–peptide biocomposites formed by poly(3,4-ethylenedioxythiophene) (PEDOT) and CREKA or CR(NMe)EKA peptide sequences (where Glu has been replaced by N-methyl-Glu in the latter) have been compared. CREKA is a linear pentapeptide that recognizes clotted plasma proteins and selectively homes to tumors, while CR(NMe)EKA is an engineer to improve such properties by altering peptide–fibrin interactions. Differences between PEDOT-CREKA and PEDOT-CR(NMe)EKA reflect dissemblance in the organization of the peptides into the polymeric matrix. Both peptides affect fibrinogen thrombin-catalyzed polymerization causing the immediate formation of fibrin, whereas in the absence of thrombin this phenomenon is only observed for CR(NMe)EKA. Consistently, the fibrin-adsorption capacity is higher for PEDOT-CR(NMe)EKA than for PEDOT-CREKA, even though in both cases adsorbed fibrin exhibits round-like morphologies rather than the characteristic fibrous structure. PEDOT-peptide films coated with fibrin are selective in terms of cell adhesion, promoting the attachment of metastatic cells with respect to normal cells.
The properties as biointerfaces of biocomposites formed by the conjugation of poly(3,4-ethylenedioxythiophene) and CREKA or CR(NMe)EKA peptides (where Glu has been replaced by N-methyl-Glu in the latter) have been compared. Analyses have been focused on the influence of such peptides in the formation of specific interactions with fibrin and the selective attachment of metastatic cells with respect to normal cells.
Triolimus is a multi-drug loaded polymeric micelle containing paclitaxel (PTX), 17-allylamino-17-demethoxygeldanamycin (17-AAG), and rapamycin (RAP). This study examines the radiosensitizing effect of Triolimus in vitro and in vivo. Radiosensitizing effects of Triolimus on A549 cells are dose dependent and at 2 × 10−9m, Triolimus shows significant radiosensitization even at low radiation doses (2 Gy). By sensitivity enhancement ratio, PTX alone, dual drug combinations, and Triolimus treatment at 2 × 10−9m have radiosensitizing effects with potency as follows: PTX alone (PTX) > PTX and RAP (P/R) > Triolimus (TRIO) > PTX and 17-AAG (P/17) >17-AAG and RAP (17/R). In vivo, fractionated radiation of 15 Gy preceded by infusion of PTX alone, dual drug combinations, or an intermediate dose of Triolimus (Int. TRIO: PTX/17-AAG/RAP at 15/15/7.5 mg kg−1) strongly inhibits A549 tumor growth. Notably, pretreatment with high dose of Triolimus (High TRIO: PTX/17-AAG/RAP at 60/60/30 mg kg−1) before the fractionated radiation leads to tumor control for up to 24 weeks. An enhanced radiosensitizing effect is observed without an increase in acute toxicity compared to PTX alone or radiation alone. These results suggest that further investigations of Triolimus in combination with radiation therapy are merited.
Triolimus, a multi-drug loaded PEG-b-PLA polymeric micelle containing paclitaxel, 17-allylamino-17-demethoxygeldanamycin and rapamycin shows significant radiosensitization toward cancer cells. Pretreatment of Triolimus before fractionated radiation leads to tumor control. Triolimus in combination with radiation therapy is merited.
Microbial colonization of indwelling devices remains a major concern in modern healthcare. Developing approaches to prevent biomaterial-associated infections (BAI) is, therefore, in great demand. This study aimed to immobilize two antimicrobial peptides (polymyxins B and E) onto polydimethylsiloxane (PDMS) using two polydopamine (pDA)-based approaches: the conventional two-step method involving the deposition of a pDA layer to which biomolecules are immobilized, and a one-step method where peptides are dissolved together with dopamine before its polymerization. Surface characterization confirms the immobilization of polymyxins onto PDMS at a non-toxic concentration. Immobilization of polymyxins using a one-step pDA-based approach is able to prevent Pseudomonas aeruginosa adhesion and kill a significant fraction of the adherent ones. Living cells adhered to these modified surfaces exhibit the same susceptibility pattern as cells adhered to unmodified surfaces, highlighting no resistance development. Results suggest that polymyxins immobilization holds a great potential as an additional antimicrobial functionality in the design of biomaterials.
Immobilization of polymyxins onto polydimethylsiloxane, using dopamine-based coating strategies, renders the surfaces with antimicrobial properties, without causing any harm to mammalian cells. Furthermore, cells adhered to these surfaces exhibit the same susceptibility pattern as cells adhered to unmodified surfaces, which suggests no resistance development. Polymyxins immobilization holds, therefore, a great potential as an additional antimicrobial functionality in the design of biomaterials.
In this study, double-emulsion capsules (DECs) capable of concealing drug-incorporated targeted-supermolecules are developed to achieve "on-demand" supermolecule release and enhanced sequential targeting for magneto-chemotherapy. These water-in-oil-in-water DECs less than 200 nm in diameter are synthesized using a single component of PVA (polyvinyl alcohol) polymer and the magnetic nanoparticles, which are capable of encapsulating large quantities of targeted supermolecules composed of palitaxel-incorporated beta-cyclodextrin decorated by hyaluronic acid (HA, a CD44-targeting ligand) in the watery core. The release profiles (slow, sustained and burst release) of the targeted supermolecules can be directly controlled by regulating the high-frequency magnetic field (HFMF) and polymer conformation without sacrificing the targeting ability. Through an intravenous injection, the positive targeting of the supermolecules exhibited a 20-fold increase in tumor accumulation via the passive targeting and delivery of DECs followed by positive targeting of the supermolecules. Moreover, this dual-targeting drug-incorporated supermolecular delivery vehicle at the tumor site combined with magneto-thermal therapy suppressed the cancer growth more efficiently than treatment with either drug or supermolecule alone.
The double emulsion capsules can improve the accumulation of drug-incorporated targeted-supermolecules at targeted tumor site through an external magnetic field (high-frequency magnetic field) stimulus. Targeted thermal chemotherapy of supermolecules involves an internalization of large amounts of drugs to cancer cell, which is actuated by cancer-cell binding proteins on supermolecules, all contributing to cell kill.
RNA interference (RNAi) as a mechanism of gene regulation provides exciting opportunities for medical applications. Synthetic small interfering RNA (siRNA) triggers the knockdown of complementary mRNA sequences in a catalytic fashion and has to be delivered into the cytosol of the targeted cells. The design of adequate carrier systems to overcome multiple extracellular and intracellular roadblocks within the delivery process has utmost importance. Cationic polymers form polyplexes through electrostatic interaction with negatively charged nucleic acids and present a promising class of carriers. Issues of polycations regarding toxicity, heterogeneity, and polydispersity can be overcome by solid-phase-assisted synthesis of sequence-defined cationic oligomers. These medium-sized highly versatile nucleic acid carriers display low cytotoxicity and can be modified and tailored in multiple ways to meet specific requirements of nucleic acid binding, polyplex size, shielding, targeting, and intracellular release of the cargo. In this way, sequence-defined cationic oligomers can mimic the dynamic and bioresponsive behavior of viruses.
Polyplexes form through electrostatic interaction of negatively charged siRNA and multifunctional sequence-defined oligocations. Shielded and targeted polyplexes are taken up via receptor-mediated endocytosis. An increased density of positive charges upon endosomal acidification leads to an influx of chloride and water, resulting in osmotic pressurizing. Lytic domains further promote pH-triggered vesicle burst and thus the release of siRNA into the cytosol.
There is a need for new and smart formulations that will help overcome the limitations of organic dyes used in photodynamic (PDT) and photothermal (PTT) therapy and significantly accelerate their clinical translation. Therefore the aim of this work was to create a responsive nanogel scaffold as a smart vehicle for dye administration. We developed a methodology that enables the conjugation of organic dyes to thermoresponsive nanogels and yields biocompatible, nanometer-sized products with low polydispersity. The potential of the dye-nanogel conjugate as a photothermal and photodynamic agent has been demonstrated by an in vitro evaluation with a model human carcinoma cell line. Additionally, confocal cell images showed their cellular uptake profile and their potential for bioimaging and intracellular drug delivery. These conjugates are a promising scaffold as a theranostic agents and will enable further applications in combination with controlled drug release.
Cyanin dye conjugated nanogels are designed and evaluated in vitro as a polyvalent platform for photothermal and photodynamic therapy. Along with their biocompatible profile, their near infrared light-to-heat transducing property, and their imaging ability, they offer possibilities for their further use as a theranostic agent in vivo.
Targeting nanoparticles for drug delivery has great potential for improving efficacy and reducing side effects from systemic toxicity. New developments in the assembly of materials afford the opportunity to expose cryptic targeting domains in tissue-specific microenvironments in which certain proteases are expressed. Here, recombinant proteins are designed to combine the responsiveness to environmental proteases with specific targeting. Materials made recombinantly allow complete control over amino acid sequence, in which each molecule is identically functionalized. Previously, oleosin, a naturally occurring plant protein that acts as a surfactant, has been engineered to self-assemble into spherical micelles—a useful structure for drug delivery. To make oleosins that are locally activated to bind receptors, oleosin is genetically modified to incorporate the integrin-binding motif RGDS just behind a domain cleavable by thrombin. The resulting modified oleosin self-assembles into spherical micelles in aqueous environments, with the RGDS motif protected by the thrombin-cleavable domain. Upon the addition of thrombin, the RGDS is exposed and the binding of the spherical micelles to breast cancer cells is increased fourfold.
A naturally occurring protein surfactant is genetically modified to incorporate bioactive motifs that enables controlled breast cancer cell line targeting. The recombinant protein surfactant self-assembles into nanoscale micelles in aqueous environments, exposing the bioactive motif RGDS only upon reaction with thrombin protease. The recombinant protein is a flexible model that can be precisely engineered, and offers a promising approach for cell targeting and potential drug release.
Electrospun poly-l-lactic acid (PLLA) nanofiber mats carrying surface amine groups, previously introduced by nitrogen atmospheric pressure nonequilibrium plasma, are embedded into aqueous solutions of oligomeric acrylamide-end capped AGMA1, a biocompatible polyamidoamine with arg-gly-asp (RGD)-reminiscent repeating units. The resultant mixture is finally cured giving PLLA-AGMA1 hydrogel composites that absorb large amounts of water and, in the swollen state, are translucent, soft, and pliable, yet as strong as the parent PLLA mat. They do not split apart from each other when swollen in water and remain highly flexible and resistant, since the hydrogel portion is covalently grafted onto the PLLA nanofibers via the addition reaction of the surface amine groups to a part of the terminal acrylic double bonds of AGMA1 oligomers. Preliminary tested as scaffolds, the composites prove capable of maintaining short-term undifferentiated cultures of human pluripotent stem cells in feeder-free conditions.
New bioactive composites based on poly-l-lactic acid (PLLA) mats carrying surface amine groups, introduced by nitrogen plasma treatment, and AGMA1, a biocompatible polyamidoamine with RGD-mimic repeating units, are obtained. These composites absorb large amounts of water becoming translucent, soft, pliable, yet mechanically strong materials. Preliminary experiments show that the PLLA-AGMA1 composites successfully support short-term undifferentiated human pluripotent stem cell cultures.
New poly(L-lysine)-b-poly(ethylene glycol) copolypeptides have been prepared, where the side-chain amine groups of lysine residues are modified to contain ortho-amine substituted phenylboronic acid, i.e., Wulff-type phenylboronic acid (WBA), groups to improve their pH responsive, carbohydrate binding properties. These block copolymers form nanoscale complexes with glycosylated proteins that are stable at physiological pH, yet dissociate and release the glycoproteins under acidic conditions, similar to those found in endosomal and lysosomal compartments within cells. These results suggest that WBA modified polypeptide copolymers are promising for further development as degradable carriers for intracellular protein delivery.
Wulff-type phenylboronic acid functionalized polypeptide block copolymers form nanoscale complexes with glycosylated proteins that are stable at physiological pH, yet dissociate and release the glycoproteins at acidic conditions, such as found in endosomal and lysosomal compartments within cells. These new functional polypeptide copolymers are promising for further development as carriers for intracellular protein delivery.
Photo-crosslinking and self-healing have received considerable attention for the design of intelligent materials. A novel photostimulated, self-healing, and cytocompatible hydrogel system is reported. A coumarin methacrylate crosslinker is synthesized to modify the polyacrylamide-based hydrogels. With the [2+2] cyclo-addition of coumarin moieties, the hydrogels exhibit excellent self-healing capacity when they are exposed to light with wavelengths at 280 and 365 nm, respectively. To enhance cell compatibility, a poly (amidoamine) crosslinker is also synthesized. Variations in light exposure times and irradiation wavelengths are found to alter the self-healing property of the hydrogels. The hydrogels are shown to induce a regular cellular pattern. The hydrogels are used to regulate bone marrow stromal cells differentiation. The relative mRNA expressions are recorded to monitor the osteogenic differentiation of the cells.
Novel photostimulated self-healing and biocompatible polyacrylamide hydrogels are reported. A coumarin crosslinker endows superb self-healing capacity upon exposure to 280 and 365 nm light. A polyamidoamine crosslinker enhances cell compatibility. The hydrogels induce a regular cellular pattern and regulate osteogenic differentiation of bone marrow stromal cell.
Due to the adsorption of biomolecules, the control of the biodistribution of nanoparticles is still one of the major challenges of nanomedicine. Poly(2-ethyl-2-oxazoline) (PEtOx) for surface modification of nanoparticles is applied and both protein adsorption and cellular uptake of PEtOxylated nanoparticles versus nanoparticles coated with poly(ethylene glycol) (PEG) and non-coated positively and negatively charged nanoparticles are compared. Therefore, fluorescent poly(organosiloxane) nanoparticles of 15 nm radius are synthesized, which are used as a scaffold for surface modification in a grafting onto approach. With multi-angle dynamic light scattering, asymmetrical flow field-flow fractionation, gel electrophoresis, and liquid chromatography-mass spectrometry, it is demonstrated that protein adsorption on PEtOxylated nanoparticles is extremely low, similar as on PEGylated nanoparticles. Moreover, quantitative microscopy reveals that PEtOxylation significantly reduces the non-specific cellular uptake, particularly by macrophage-like cells. Collectively, studies demonstrate that PEtOx is a very effective alternative to PEG for stealth modification of the surface of nanoparticles.
While biomedical applications of nanoparticles are steadily increasing, undesirable adsorption of biomolecules in biological fluids represents one major challenge. Here, biocompatible poly(2-ethyl-2-oxazoline) (PEtOx) for the stealth modification of nanoparticles is probed. Comparing protein adsorption and cellular uptake of PEtOxylated nanoparticles to other modifications, it is demonstrated that PEtOx is at least as effective as the gold standard poly(ethylene glycol).
The harmful Esca disease in vine plants caused by wood-inhabiting fungi including Phaeomoniella chlamydospora (Pch) is spreading all across the world. This disease leads to poor vine crops and a slow decline or to a sudden dieback of the vine plants. The pruning wounds of vine plants are the main entry point for Pch. While model experiments with aerosol particles recommend electrospun nonwovens as a suitable barrier to block Pch, tests with living spores show clearly that only electrospun fibrous nonwovens do not prevent Pch invasion. However it is found, that with antifungal additives electrospun nonwovens could be applied successfully for blocking of Pch to infect the substrate. Thereby, a highly useful concept for the protection of vine plants against Esca disease is provided which could also serve as a concept for related plant diseases.
Electrospun nonwovens with antifungal additives for active blocking of spores to prevent Esca infections of vine plants are presented. The disease leads to poor vine crops or to a sudden dieback of the vine plants. The combination of antifungal properties and breathable electrospun nonwovens could be a suitable way to inhibit the spreading of the disease.
Using suitable polymers as a carrier for growing and delivering retinal progenitor cells (RPCs) is a promising therapeutic strategy in retinal cell-replacement therapy. Herein recently developed polymer, poly(sebacoyl diglyceride) (PSeD), is selected and its nonhydroxylized counterpart poly(1,3-propylene sebacate) (PPS) is designed to evaluate their potentials for RPC growth and future RPC application. The structures and mechanical properties of the polymers are characterized. The cytocompatibility and effects of these polymers on RPC proliferation, differentiation, and migration are systematically investigated in vitro. Our data show that PPS and PSeD display excellent cytocompatibility with low expression of inflammation and apoptosis factors, which benefit RPC growth. In proliferation assays reveal that RPCs expands well on the polymers, but PPS performs the best for RPC expansion, indicating that PPS can remarkably promote RPC proliferation. In differentiation conditions, RPCs grown on PSeD are more likely to differentiate toward retinal neurons, including photoreceptors, the most interesting type of cells for retinal cell-replacement therapy. Additionally, our results demonstrate that RPCs grown on PSeD display an outstanding ability to migrate. In conclusion, PPS can markedly promote RPC proliferation, whereas PSeD can enhance RPC differentiation toward retinal neurons, suggesting that PSeD and PPS have potential applications in future retinal cell-replacement therapies.
This study investigates the effects of poly(sebacoyl diglyceride) (PSeD) and its counterpart poly(1,3-propylene sebacate) (PPS) on retinal progenitor cell (RPC) proliferation, differentiation, and migration. Our results show that PPS significantly enhances RPC proliferation, whereas PSeD largely promotes RPCs' differentiation toward retinal neurons with superior migration capacity, indicating that PPS and PSeD may have potential applications in future retinal cell-replacement therapies.
Mimicking the complex intricacies of the extra cellular matrix including 3D configurations and aligned fibrous structures were traditionally perused for producing cartilage tissue from stem cells. This study shows that human adipose derived mesenchymal stem cells (hADMSCs) establishes significant chondrogenic differentiation and may generate quality cartilage when cultured on 2D and randomly oriented fibrinogen/poly-lactic acid nanofibers compared to 3D sandwich-like environments. The adhering cells show well-developed focal adhesion complexes and actin cytoskeleton arrangements confirming the proper cellular interaction with either random or aligned nanofibers. However, quantitative reverse transcription-polymerase chain reaction analysis for Collagen 2 and Collagen 10 genes expression confirms favorable chondrogenic response of hADMSCs on random nanofibers and shows substantially higher efficacy of their differentiation in 2D configuration versus 3D constructs. These findings introduce a new direction for cartilage tissue engineering through providing a simple platform for the routine generation of transplantable stem cells derived articular cartilage replacement that might improve joint function.
The illustration of the preparation steps for the 2D and 3D constructs, including: (1) production of samples via deposition of random or aligned electrospun nanofibers on gel slices, (2) seeding of ADSCs and their propagation up to confluency, (3) assembly of the constructs, either in 2D (single slides) or 3D (sandwich-like) configuration, and (4) cultivation of living construct in chondrogenic differentiation medium.
Electrospun fibers of hydrophilic polymers meet challenges in a rapid degradation of fiber matrices and discharge of antibiotics to comply with requirements of infection control as a dermal regeneration template. In the current study, a pH conversion process is initially developed to ensure fluent electrospinning, an efficient in situ cross-linking of electrospun gelatin fibers with oxidized alginate and simultaneous loading of gentamicin sulfate (GS) and hydrophobic ciprofloxacin into fibers. The dual drug-loaded fibers indicate a complete release of GS during 6 d and a sustained release of ciprofloxacin for over three weeks, and the antibiotics release indicates significant growth inhibitions on Pseudomonas aeruginosa and Staphylococcus epidermidis. The wound healing efficacy is evaluated on a deep burn model infected with 108 CFU of P. aeruginosa. Compared with fibers with loaded individual drugs, the concomitant release of GS and ciprofloxacin significantly reduces the bacteria numbers in wound and livers, at around 2.30 × 105 and 1.25 × 103 CFU after 3 d, respectively. The wound re-epithelization, blood vessel formation, collagen deposition, and tissue remodeling process are accelerated with a complete healing observed after 21 d. This study provides a feasible strategy to design cross-linked hydrophilic fibers with an extended drug release for biomedical applications.
A pH conversion process has been initially developed to prepare electrospun gelatin fibers cross-linked in situ with oxidized alginate and simultaneously load gentamicin sulfate and hydrophobic ciprofloxacin into fibers. The rapid release of gentamicin and extended release of ciprofloxacin from fibers accelerate the wound healing process through controlling the bacteria infection in the deep burn wounds.
Polyelectrolyte block copolymer micelles assembled thin film is switched in response to local photocatalytic reactions on titanium dioxide, resulting in a layer of variable height, stiffness in response to visible light irradiation. Preosteoblasts migrate toward stiffer side of the substrates.
Photocatalytic reactions on titanium dioxide in response to visible light irradiation are used to regulate polyelectrolyte block copolymer micelles assembled thin film. Irradiation results in change of film height, stiffness. Film can be switched in response to local irradiation. Preosteoblasts migrate toward stiffer side of the substrates.
There is a growing interest in modern healthcare to develop systems able to fight antibiotic resistant bacteria. Antimicrobial cationic biodegradable polymers able to mimic antimicrobial peptides have shown to be effective against both Gram-positive and Gram-negative bacteria. In these systems, the hydrophilic–hydrophobic ratio and the cationic charge density play a pivotal role in defining the killing efficiency. Nevertheless, many of these antimicrobial polymers show relatively low selectivity as defined by the relative toxicity to mammalian cells or hemolysis relative to pathogens. In this study, a series of polycarbonates containing pendant quaternary ammoniums are used to understand the role of different counter-anions including chloride, citrate, malonate, benzoate, acetate, lactate and trifluoroacetate, and the antibiotic penicillin on antimicrobial efficacy and selectivity. Interestingly, it is found that in spite of the strong antimicrobial activity of trifluoroacetate and benzoate anions, they prove to be much less hemolytic than chloride anion. It is believed that the proper selection of the anion could enhance the potential of antimicrobial polymers to fight against clinically relevant pathogenic infections, while concurrently mitigating harmful side effects.
A series of polycarbonates containing pendant quaternary ammoniums are used to understand the role of different counter-anions on antimicrobial efficacy and selectivity. Interestingly, it is found that in spite of the strong antimicrobial activity of trifluoroacetate and benzoate anions, they prove to be much less hemolytic than chloride anion.
Although biodegradable amphiphilic block copolymer micelles have been widely applied in the clinical applications as drug delivery nanocarriers, low-efficiency cellular internalization frequently reduces therapeutic efficacy of the loaded drugs. Here, photothermal effect-promoted cellular internalization of finely tuned thermo-responsive amphiphilic biodegradable block copolymer nanocarriers via noninvasive stimuli of near-infrared (NIR) light irradiation is demonstrated. Amphiphilic block copolymers, poly(ε-caprolactone)-block-poly(N-isopropylacrylamide-co-N,N-dimethylacrylamide) (PCL-b-P(NIPAM-co-DMA)), are prepared with finely tuned compositions of P(NIPAM-co-DMA) for desirable lower critical solution temperature of the block copolymer micelles in aqueous solution. The block copolymers are then used to co-encapsulate doxorubicin and indocyanine green, which show high encapsulation efficiency and significant photothermal effect upon exposure to NIR light irradiation. The photothermal effect-induced collapse and hydrophilic-to-hydrophobic transition of P(NIPAM-co-DMA) shells significantly enhance the interactions between drug-loaded micelles and cell membranes, which dramatically promote the cellular internalization of the micelles and therapeutic efficacy of loaded anticancer drugs.
Amphiphilic block copolymer micelles with finely tuned thermo-responsive coronas are constructed for high-efficiency co-delivery of doxorubicin and indocyanine green, which show photothermal effect-triggered efficient cellular uptake upon near-infrared light exposure. The design represents a facile strategy to achieve efficient cellular internalization of stealthy drug delivery systems in a spatiotemporally controlled manner.
The condensation of nucleic acids into compact nanoparticles with cationic carriers is a powerful tool for translocating exogenous nucleic acids into cells. To date, most efforts have been focused on the development of novel gene carriers for safe and efficient gene delivery. However, small interfering RNA (siRNA) is generally not strongly associated with cationic carriers due to its stiff structure and low spatial charge density. To overcome this limitation, this work introduces a well-defined dimeric conjugate of small internally segment interfering RNA (sisiRNA) linked via a disulfide bond for enhanced cellular uptake and gene silencing. Dimeric sisiRNA is synthesized through oxidizing two monomeric sisiRNA molecules, each of which consists of a sense strand carrying a nick and an antisense strand modified with a thiol group at the 3′-end. The nick in the sense strand enables the dimeric sisiRNA to be more effectively condensed into nanosized complexes due to the increased structural flexibility, which results in a higher gene silencing efficiency compared with the dimeric siRNA containing the intact sense strands. The results indicate that the discontinuity of the sense strands is a simple method of adding more flexibility to various siRNA-based nanostructures for enhanced gene silencing.
A single-stranded nick in an siRNA duplex provides enhanced structural flexibility in engineered siRNA nanostructures. Dimeric nicked siRNA conjugates can strongly interact with conventional cationic carriers to generate compact nanoparticles capable of facilitating cellular uptake due to their high charge density and structural flexibility. The resultant complexes exhibit efficient polymeric condensations and gene silencing efficiencies compared with nonnicked siRNA conjugates.
A timesaving and convenient method for bacterial detection based on one-step, one-tube deoxyribonucleic acid (DNA) hybridization on hydrogel array while target gene amplification is described. The hydrogel array is generated by a fast one-pot synthesis, where N,N′-dimethylacrylamide/polyethyleneglycol(PEG1900)-bisacrylamide mixture polymerizes via radical photoinitiation by visible light within 20 min concomitant with in situ capture probe immobilization. These DNA-functionalized hydrogel droplets arrayed on a planar glass surface are placed in the polymerase chain reaction (PCR) mixture during the thermal amplification cycles. The bacterial cells can be implemented in a direct PCR reaction, omitting the need for prior template DNA extraction. The resulting fluorescence signal is immediately detectable after the end of the PCR (1 h) following one short washing step by microscopy. Therefore a valid signal can be reached within 1.5 h including 10 min for pipetting and placement of the tubes and chips. The performance of this novel hydrogel DNA array was successfully proven with varying cell numbers down to a limit of 101 Escherichia coli cells.
This work presents a timesaving combined 3D in gel polymerase chain reaction (PCR)/hybridization protocol for bacteria detection concomitant with an easy hydrogel chip fabrication. The isolated bacterial cells and the hydrogel chip are added directly in the PCR tube containing the required PCR components. During the ongoing specific PCR, deoxyribonucleic acid amplicons binds to gel immobilized capture probes and the fluorescence signal is generated already during the amplification process.
Cells interact mechanically with their environment, exerting mechanical forces that probe the extracellular matrix (ECM). The mechanical properties of the ECM determine cell behavior and control cell differentiation both in 2D and 3D environments. Gelatin (Gel) is a soft hydrogel into which cells can be embedded. This study shows significant 3D Gel shrinking due to the high traction cellular forces exerted by the cells on the matrix, which prevents cell differentiation. To modulate this process, Gel with hyaluronic acid (HA) has been combined in an injectable crosslinked hydrogel with controlled Gel–HA ratio. HA increases matrix stiffness. The addition of small amounts of HA leads to a significant reduction in hydrogel shrinking after cell encapsulation (C2C12 myoblasts). We show that hydrogel stiffness counterbalanced traction forces of cells and this was decisive in promoting cell differentiation and myotube formation of C2C12 encapsulated in the hybrid hydrogels.
Injectable gelatin hyaluronic acid (HA) mixtures are synthesized to modulate matrix stiffness. The addition of small amounts of HA to gelatin significantly reduces hydrogel shrinking after cell encapsulation. Hydrogel stiffness counterbalances traction forces of cells, promoting cell differentiation.
Given alginate's contribution to Pseudomonas aeruginosa virulence, it has long been considered a promising target for interventional therapies, which have been performed by using the enzyme alginate lyase. In this work, instead of treating pre-established mucoid biofilms, alginate lyase is immobilized onto a surface as a preventive measure against P. aeruginosa adhesion. A polydopamine dip-coating strategy is employed for functionalization of polycarbonate surfaces. Enzyme immobilization is confirmed by surface characterization. Surfaces functionalized with alginate lyase exhibit anti-adhesive properties, inhibiting the attachment of the mucoid strain. Moreover, surfaces modified with this enzyme also inhibit the adhesion of the tested non-mucoid strain. Unexpectedly, treatment with heat-inactivated enzyme also inhibits the attachment of mucoid and non-mucoid P. aeruginosa strains. These findings suggest that the antibacterial performance of alginate lyase functional coatings is catalysis-independent, highlighting the importance of further studies to better understand its mechanism of action against P. aeruginosa strains.
Immobilization of alginate lyase onto polycarbonate surfaces, using a dopamine-based coating strategy, renders the surfaces with the ability to prevent Pseudomonas aeruginosa adhesion, regardless of its mucoid or non-mucoid phenotype. This ability is not compromised by enzyme's heat denaturation, suggesting a catalysis-independent performance. Further studies to more comprehensively understand its mechanism of anti-adhesive action should, therefore, be performed.
Fluorescence resonance energy transfer (FRET) is applied to investigate the enzyme-responsive payload release from a macromolecular therapeutic. The donor Cy5 is attached to the N-(2-hydroxypropyl)methacrylamide (HPMA) copolymer backbone and the acceptor Cy7 is bound to the termini of enzyme-sensitive peptide side chains. Upon exposure to an enzyme, the bond between the peptide and Cy7 is cleaved, thereby leading to the loss of FRET signal. This enzyme response is visualized at the cell, tissue and whole-body levels. The in vitro results demonstrate that high expression of cathepsin B in tumor cells induces effective release of the drug model from conjugates resulting in a high concentration of payload inside tumor cells. The in vivo and ex vivo images show that the conjugate releases drug model faster in the ovarian tumor than in the normal tissues. The information will enhance the understanding of enzyme-responsive polymer carriers and help to shape their design.
Cy5/Cy7-paired fluorescence resonance energy transfer (FRET) is applied to investigate the enzyme-responsive payload release in a N-(2-hydroxypropyl)methacrylamide copolymer-based drug delivery system. Upon exposure to lysosomal enzymes, the model drug Cy7 is cleaved, resulting in the loss of FRET signal. The enzyme response is visualized at the cell, tissue, and whole-body levels, indicating an effective release of payload in tumor cells.
Traditionally, conductive materials for electrodes are based on high modulus metals or alloys. Development of bioelectrodes that mimic the mechanical properties of the soft, low modulus tissues in which they are implanted is a rapidly expanding field of research. Many polymers exist that more closely match tissue mechanics than metals; however, the majority do not conduct charge. Integrating conductive properties via incorporation of metals and other conductors into nonconductive polymers is a successful approach to producing polymers that can be used in electrical interfacing devices. When combining conductive materials with nonconductive polymer matrices, there is often a tradeoff between the electrical and mechanical properties. This review analyzes the advantages and disadvantages of approaches involving coating or layer formation, composite formation via dispersion of conductive inclusions through polymer matrices, and in situ growth of a conductive network within polymers.
There is a need for soft, biocompatible materials to support regeneration, stimulation, and recording of excitable tissue activity. This review analyzes the key approaches used to fabricate soft, conductive polymers including: coating a bulk polymer with a conductive component, dispersion of conductive inclusions through a polymer, and in situ growth of a conductive network within a polymer matrix.
The use of light-sensitive polymers for the release of therapeutics is an important approach allowing the timing and amount of the release to be controlled precisely. The use of light has been pioneered to control insulin release from a dermal photoactivated depot, or PAD. One of the main impediments to the use of light-sensitive polymers in this context is the density of the materials: The large majority of the material is the carrier polymer, with the minority being the therapeutic. In this work, the feasibility of using insulin itself as a monomer in the polymerization process is demonstrated. Insulin modified with either one or two light cleavable azide groups is polymerized with a tridentate alkyne-bridging monomer using a click reaction. The resulting material called a "macropolymer" is ≈85% insulin, is insoluble in aqueous solvent, and releases native, soluble insulin upon irradiation.
To make highly efficient light-activated depots of insulin, insulin itself has been used as a monomer during click-driven polymerizations. The resultant materials have the key desired properties including high insulin density, insolubility prior to irradiation and release of native insulin in response to light.
The preparation of novel macromolecular prodrugs via the conjugation of two platinum(IV) complexes to suitably functionalized poly(organo)phosphazenes is presented. The inorganic/organic polymers provide carriers with controlled dimensions due to the use of living cationic polymerization and allow the preparation of conjugates with excellent aqueous solubility but long-term hydrolytic degradability. The macromolecular Pt(IV) prodrugs are designed to undergo intracellular reduction and simultaneous release from the macromolecular carrier to present the active Pt(II) drug derivatives. In vitro investigations show a significantly enhanced intracellular uptake of Pt for the macromolecular prodrugs when compared to small molecule Pt complexes, which is also reflected in an increase in cytotoxicity. Interestingly, drug-resistant sublines also show a significantly smaller resistance against the conjugates compared to clinically established platinum drugs, indicating that an alternative uptake route of the Pt(IV) conjugates might also be able to overcome acquired resistance against Pt(II) drugs. In vivo studies of a selected conjugate show improved tumor shrinkage compared to the respective Pt(IV) complex.
Two monofunctionalized platinum(IV) complexes are conjugated to degradable poly(organo)phosphazenes to give soluble macromolecular prodrugs designed to undergo rapid, triggered intracellular release from the carrier and simultaneous reduction to the active, cytotoxic platinum(II) species. The preparation of the conjugates, as well as their in vitro and in vivo behavior, is reported.
There is an actual need of advanced materials for the emerging field of bioelectronics. One commonly used material is the conducting polymer poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) due to its general use in organic electronics. However, depending on the application in bioelectronics, PEDOT:PSS is not fully biocompatible due to the high acidity of the residual sulfonate protons of PSS. In this paper, the synthesis and biocompatibility properties of new poly(3,4-ethylenedioxythiophene):GlycosAminoGlycan (PEDOT:GAG) aqueous dispersions and its resulting films are shown. Thus, negatively charged GAGs as an alternative to PSS are presented. Three different commercially available GAGs, hyaluronic acid, heparin, and chondroitin sulfate are used. Indeed, PEDOT:GAGs dispersions are prepared through an oxidative chemical polymerization in water. Biocompatibility assays of the PEDOT:GAGs coatings are performed using SH-SY5Y and CCF-STTG1 cell lines and with ATP and Ca2+. Results show full biocompatibility and a pronounced anti-inflammatory effect. This last characteristic becomes crucial if implanted in the body. These materials can be used for in vivo applications, as transistor or electrode for electrical recording and for all the possible situations when there is contact between electronic circuits and living tissues.
Poly(3,4-ethylenedioxythiophene):GlycosAminoGlycan (PEDOT:GAG) dispersion are easily synthesized in water via oxidative chemical polymerization. The conductive materials are bio-tested using SH-SY5Y and CCF-STTG1 cell lines and with ATP, Ca2+, and H2O2. PEDOT/GAGs results more biotolerated than the commercial PEDOT/poly(styrene sulfonate) dispersion and have a pronounced anti-inflammatory effect. These materials can be used in all the possible situations when there is contact in between electronic circuits and living tissues.
Poly(2-alkenyl-2-oxazoline)s are promising functional polymers for a variety of biomedical applications, such as drug delivery systems, peptide conjugates, or gene delivery. In this study, poly(2-isopropenyl-2-oxazoline) (PIPOx) is prepared through free-radical polymerization initiated with azobisisobutyronitrile. Reactive 2-oxazoline units in the side chain support an addition reaction with different compounds containing a carboxylic group, which facilitates the preparation of polymers labeled with two different fluorescent dyes. The cytotoxicities of 2-oxazoline monomers, PIPOx, and fluorescently labeled PIPOx are evaluated in vitro using an 3-(4,5-Dimethyldiazol-2-yl)-2,5-diphenyl tetrazolium bromide assay and ex vivo using a cell proliferation assay with adenosine triphosphate bioluminescence. The cell uptake of labeled PIPOx is used to determine the colocalization of PIPOx with cell organelles that are part of the endocytic pathway. For the first time, it is shown that poly(2-isopropenyl-2-oxazoline) is a biocompatible material and is suitable for biomedical applications; further, its immunomodulative properties are evaluated.
Poly(2-isopropenyl-2-oxazoline) is a promising functional polymer for a variety of biomedical applications. Addition reactions with different compounds containing a carboxylic group enable the functionalization of the polymer with fluorescent dyes or biomolecules. In vitro cytotoxicity, an ex vivo cell proliferation assay, and a colocalization study are used to demonstrate that poly(2-isopropenyl-2-oxazoline) is a biocompatible material suitable for biomedical applications.
This study reports a series of novel amino acid based dual-responsive hydrogels. Prepared by a facile one-pot 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC) coupling reaction, the solid content, structure, and mechanical behavior of hydrogels could be easily adjusted by changing the concentrations of the polymers and the crosslinkers. With pH-responsive anionic pseudo-peptides as backbones and disulfide-containing l-cystine dimethyl ester as crosslinkers, these hydrogels are able to collapse and form relatively compact structure at an acidic pH, while swelled and partly dissociated at a neutral pH. Further addition of dithiothreitol (DTT) facilitated complete degradation of hydrogels. The high loading efficiency, rapid but complete triggered-release, and good biocompatibility make these hydrogels promising candidates for oral delivery.
Hydrogels with dual responsiveness are prepared by 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC) coupling of pH-responsive anionic pseudo-peptides as backbones and disulfide-containing l-cystine dimethyl ester as crosslinkers. These hydrogels show high loading efficiency, rapid but complete triggered-release and good biocompatibility, thus having potential applications for oral delivery.
New biomaterials with the properties of both bone and cartilage extracellular matrices (ECM) should be designed and used with co-culture systems to address clinically applicable osteochondral constructs. Herein, a co-culture model is described based on a trilayered silk fibroin-peptide amphiphile (PA) scaffold cultured with human articular chondrocytes (hACs) and human bone marrow mesenchymal stem cells (hBMSCs) in an osteochondral cocktail medium for the cartilage and bone sides, respectively. The presence of hACs in the co-cultures significantly increases the osteogenic differentiation potential of hBMSCs based on ALP activity, RT-PCR for osteogenic markers, calcium analyses, and histological stainings, whereas hACs produces a significant amount of glycosaminoglycans (GAGs) for the cartilage region, even in the absence of growth factor TGF-β family in the co-culture medium. This trilayered scaffold with trophic effects offers a promising strategy for the study of osteochondral defects.
New biomaterials with the properties of both bone and cartilage extracellular matrices (ECM) should be designed and used with co-culture systems to address clinically applicable osteochondral constructs. Herein, a co-culture model based on a trilayered silk fibroin and peptide amphiphile (PA) scaffolds to achieve cartilage and bone tissues in a single system is developed.
Injectable and biodegradable supramolecular hydrogel mPECT NP/α-CDgel composed of high-concentration nanoparticle dispersion (≤20% W/V) and α-cyclodextrins (α-CD) are prepared by a two-level physical cross-linking using amphiphilic block polymer methoxy poly(ethylene glycol)-b-poly(ε-caprolactone-co-1,4,8-trioxa[4.6]spiro-9-undecanone) (mPECT) and α-CD. The gelation behavior depends on the concentration of nanoparticles and α-CD. The viscoelasticity and shear thinning of mPECT NP/α-CDgel are confirmed. In vitro hydrogel erosion is demonstrated to be mainly a concentration-dependent dissociation process with general release of discrete mPECT nanoparticles about 50 nm that can be easily taken up by cells. The in vitro release behavior can be modulated by changing the concentration of nanoparticles or α-CD. In vitro and in vivo cytotoxicity study demonstrates its biocompatibility and biosafety. Gel formation after subcutaneous injection is also confirmed and mPECT NP/α-CDgel shows about 2 weeks retention time. This work validates the potential application for this supramolecular hydrogel in local and sustained delivery of nanoparticles.
Supramolecular hydrogel mPECT NP/α-CDgel composed of polymer nanoparticles dispersion with high solid content (≤20% W/V) and α-CD are constructed. mPECT NP/α-CDgel can general release discrete nanoparticles of ≈50 nm lasting for more than 3 weeks in situ. The present hydrogel system can anchor a large amount of nanoparticles in situ, providing sustained and targeted nanoparticles delivery.
A series of novel pH-sensitive gene delivery vectors (POEI 1, 2, and 3) are synthesized through Michael addition from low molecular weight PEI (LMW PEI) via acid-labile ortho ester linkage with terminal acrylates (OEAc) by various feed molar ratios. The obtained POEI 1 and POEI 2 can efficiently condense plasmid DNA into nanoparticles with size range of 200–300 nm and zeta-potentials of about +15 mV while protecting DNA from enzymatic digestion compared with POEI 3. Significantly, ortho ester groups of POEI main-chains can make an instantaneous degradation-response to acidic endosomal pH (≈5.0), resulting in accelerated disruption of polyplexes and intracellular DNA release. MTT assay reveals that all POEIs exhibit much lower cytotoxicity in different cells than branched PEI (25 KDa). As expected, POEI 1 and POEI 2 perform improved gene transfection in vitro, suggesting that such polycations might be promising gene vectors based on overcoming toxicity-efficiency contradiction.
Polycationic vectors (POEIs) have been synthesized via Michael addition from LMW PEI and acid-labile ortho ester linkage with terminal acrylates (OEAc). The formed POEIs/pDNA complexes can make a quick degradation-response to mildly acidic pHs, consequently facilitating endosomal escape and potentiating improved gene transfection in vitro, while maintaining low cytotoxicity.
In this study, human dental pulp stem cells (hDPSCs) are examined as a cellular source for bone tissue engineering using an in vivo-forming hydrogel. The hDPSCs are easily harvested in large quantities from extracted teeth. The stemness of harvested hDPSCs indicates their relative tolerance to ex vivo manipulation in culture. The in vitro osteogenic differentiation of hDPSCs is characterized using Alizarin Red S (ARS), von Kossa (VK), and alkaline phosphatase (ALP) staining. The solution of hDPSCs and a methoxy polyethylene glycol-polycaprolactone block copolymer (PC) is easily prepared by simple mixing at room temperature and in no more than 10 s it forms in vivo hydrogels after subcutaneous injection into rats. In vivo osteogenic differentiation of hDPSCs in the in vivo-forming hydrogel is confirmed by micro-computed tomography (CT), histological staining, and gene expression. Micro-CT analysis shows evidence of significant tissue-engineered bone formation in hDPSCs-loaded hydrogel in the presence of osteogenic factors. Differentiated osteoblasts in in vivo-forming hydrogel are identified by ARS and VK staining and are found to exhibit characteristic expression of genes like osteonectin, osteopontin, and osteocalcin. In conclusion, hDPSCs embedded in an in vivo-forming hydrogel may provide benefits as a noninvasive formulation for bone tissue engineering applications.
Human dental pulp stem cells for bone tissue engineering using in vivo-forming hydrogel: Human dental pulp stem cells (hDPSCs) are easily harvested from extracted teeth and can successfully differentiate into osteogenic cells in in vivo-forming hydrogel. This study demonstrates that hDPSCs can be acted as an excellent cell source in bone tissue engineering using in vivo-forming hydrogel.
Molecularly Imprinted Polymers (MIPs) are highly advantageous in the field of analytical chemistry. However, interference from secondary molecules can also impede capture of a target by a MIP receptor. This greatly complicates the design process and often requires extensive laboratory screening which is time consuming, costly, and creates substantial waste products. Herein, is presented a new technique for screening of "virtually imprinted receptors" for rebinding of the molecular template as well as secondary structures, correlating the virtual predictions with experimentally acquired data in three case studies. This novel technique is particularly applicable to the evaluation and prediction of MIP receptor specificity and efficiency in complex aqueous systems.
A novel method for "virtual molecular imprinting" and evaluation of the resulting receptor for docking specificity and affinity: the greater degree of ab initio insight that this technique provides to the scientist regarding receptor affinity and design can greatly reduce the workload and waste production, thus creating a more efficient and greener laboratory.
Hyaluronic acid (HA) provides many advantages to regenerative implants through its bioactive properties, but it also has many limitations as a biomaterial if it is not chemically modified. In order to overcome some of these limitations, HA has been combined with poly(ethyl acrylate) in the form of interpenetrating polymeric networks (IPNs), in which the HA network is crosslinked with divinyl sulfone. Scaffolds of this IPN have been produced through a template-leaching methodology, and their properties have been compared with those of single-network scaffolds made of either PEA or crosslinked HA. A fibroblast cell line has been used to assess the in vitro performance of the scaffolds, revealing good cell response and a differentiated behavior on the IPN surface when compared to the individual polymers. Altogether, the results confirm that this type of material offers an interesting microenvironment for cells, which can be further improved toward its potential use in medical implants.
Interpenetrating networks of hyaluronic acid (HA) and poly(ethyl acrylate) (PEA) are prepared in the shape of porous scaffolds through a template-leaching technique; combining properties of these two materials. Both physicochemical and biological responses of these interpenetrating polymeric network scaffolds are studied, including their cytotoxicity and their effects in cell proliferation and attachment; comparing them to those of HA and PEA porous single-network scaffolds.
The aim of this study is to design a polymeric nanogel system with tailorable degradation behavior. To this end, hydroxyethyl methacrylate-oligoglycolates-derivatized poly(hydroxypropyl methacrylamide) (pHPMAm-Gly-HEMA) and hydroxyethyl methacrylamide-oligoglycolates-derivatized poly(hydroxyethyl methacrylamide) (pHEMAm-Gly-HEMAm) are synthesized and characterized. pHEMAm-Gly-HEMAm shows faster hydrolysis rates of both carbonate and glycolate esters than the same ester groups of pHPMAm-Gly-HEMA. pHEMAm-Gly-HEMAm nanogels have tailorable degradation kinetics from 24 h to more than 4 d by varying their crosslink densities. It is shown that the release of a loaded macromolecular model drug is controlled by degradation of nanogels. The nanogels show similar cytocompatibility as PLGA nanoparticles and are therefore considered to be attractive systems for drug delivery.
Two polymers (pHPMAm-Gly-HEMAm and pHEMAm-Gly-HEMAm) with different degrees of substitution (DS) are synthesized, and used for preparation of nanogels. In vitro degradation studies under physiological conditions demonstrate that pHEMAm-Gly-HEMAm nanogels degrade faster than pHPMAm-Gly-HEMA nanogels. The release of a loaded macromolecular model drug is controlled by degradation of nanogels.
Front Cover: Unique telechelic-type polypeptides were synthesized by the facile and environmentally benign enzymatic polymerization using a telechelic initiator. The telechelic polyalanine was found to assemble into long nanofibers by the antiparallel β-sheet structure whereas the conventional linear polyalanine showed a granule-like morphology. Further details can be found in the article by Kousuke Tsuchiya, Keiji Numata on page 1001.
Back Cover: Micelles prepared by self-assembly of an amphiphilic furoxan-bearing block copolymer release nitric oxide in response to cysteine and potentiate the anti-proliferative effect of ibuprofen in human colon cancer cells. Further details can be found in the article by U. Hasegawa, T. J. Wang, J. Y. Chen, H. Uyama, and A. J. van der Vlies on page 1009.
Biosensing is an important and rapidly developing field, with numerous potential applications in health care, food processing, and environmental control. Polymer–graphene nanocomposites aim to leverage the unique, attractive properties of graphene by combining them with those of a polymer matrix. Molecular imprinted polymers, in particular, offer the promise of artificial biorecognition elements. A variety of polymers, including intrinsically conducting polymers (polyaniline, polypyrrole), bio-based polymers (chitosan, polycatechols), and polycationic polymers (poly(diallyldimethylammonium chloride), polyethyleneimine), have been utilized as matrices for graphene-based nanofillers, yielding sensitive biosensors for various biomolecules, such as proteins, nucleic acids, and small molecules.
Biosensors can take advantage of and translate the potential of the information provided by the "-omics" into the clinic. Recent developments in polymer science, nanotechnology, and carbon-nanomaterials—graphene in particular—offer a great deal of promise in achieving the goal of an ideal biosensor: sensitive and specific, fast, affordable, and simple.
Cardiovascular disease is a leading cause of death worldwide. Since adult cardiac cells are limited in their proliferation, cardiac tissue with dead or damaged cardiac cells downstream of the occluded vessel does not regenerate after myocardial infarction. The cardiac tissue is then replaced with nonfunctional fibrotic scar tissue rather than new cardiac cells, which leaves the heart weak. The limited proliferation ability of host cardiac cells has motivated investigators to research the potential cardiac regenerative ability of stem cells. Considerable progress has been made in this endeavor. However, the optimum type of stem cells along with the most suitable matrix-material and cellular microenvironmental cues are yet to be identified or agreed upon. This review presents an overview of various types of biofunctional materials and biomaterial matrices, which in combination with stem cells, have shown promises for cardiac tissue replacement and reinforcement. Engineered biomaterials also have applications in cardiac tissue engineering, in which tissue constructs are developed in vitro by combining stem cells and biomaterial scaffolds for drug screening or eventual implantation. This review highlights the benefits of using biomaterials in conjunction with stem cells to repair damaged myocardium and give a brief description of the properties of these biomaterials that make them such valuable tools to the field.
Biofunctional materials offer a potential approach to manipulate stem cell behavior in vitro and in vivo. A variety of bioactive materials can be synthesized in combination with stem cells to engineer the new generation of biomedical therapeutics to repair and regenerate damaged tissues, in particular cardiac tissues. This article explores the emerging techniques with biofunctional materials to enhance stem cell function in heart and for cardiac tissue engineering.
Pinosylvin is a natural stilbenoid known to exhibit antibacterial bioactivity against foodborne bacteria. In this work, pinosylvin is chemically incorporated into a poly(anhydride-ester) (PAE) backbone via melt-condensation polymerization, and characterized with respect to its physicochemical and thermal properties. In vitro release studies demonstrate that pinosylvin-based PAEs hydrolytically degrade over 40 d to release pinosylvin. Pseudo-first order kinetic experiments on model compounds, butyric anhydride and 3-butylstilbene ester, indicate that the anhydride linkages hydrolyze first, followed by the ester bonds to ultimately release pinosylvin. An antibacterial assay shows that the released pinosylvin exhibit bioactivity, while in vitro cytocompatibility studies demonstrate that the polymer is noncytotoxic toward fibroblasts. These preliminary findings suggest that the pinosylvin-based PAEs can serve as food preservatives in food packaging materials by safely providing antibacterial bioactivity over extended time periods.
Pinosylvin, analog of resveratrol, possesses antibacterial bioactivities against common foodborne bacteria. To prolong pinosylvin's valuable antibacterial effects and further its usage as a natural food preservative, the natural stilbenoid is chemically incorporated into a poly(anhydride-ester) backbone. Physicochemical and thermal testing reveal successful synthesis while in vitro hydrolytic degradation of the polymer confirms sustained bioactive release of pinosylvin over 40 d.
Phospholipid-detergent conjugates are proposed as fusogenic carriers for gene delivery. Eleven compounds are prepared and their properties are investigated. The ability of the conjugates to promote fusion with a negatively charged model membrane is determined. Their DNA delivery efficiency and cytotoxicity are assessed in vitro. Lipoplexes are administered in the mouse lung, and transgene expression Indeterminate inflammatory activity are measured. The results show that conjugation of 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) with C12E4 produces a carrier that can efficiently deliver DNA to cells, with negligible associated toxicity. Fusogenicity of the conjugates shows good correlation with in vitro transfection efficiency and crucially depends on the length of the polyether moiety of the detergent. Finally, DOPC-C12E4 reveals highly potent for in vivo DNA delivery and favorably compares to GL67A, the current golden standard for gene delivery to the airway, opening the way for further promising developments.
Cationic lipids are widely used synthetic carriers for in vitro gene delivery. Cationic phospholipid-detergent conjugates are designed so they display intrinsic fusogenic properties, thus enhancing cellular uptake of the corresponding DNA lipoplexes. 1,2-Dioleoyl-sn-glycero-3-phosphocholine-C12E4 conjugate 10 is a highly efficient transfection vector for both in vitro gene delivery and in vivo gene delivery. Administration of lipoplexes in mouse airway results in high transgene expression while inflammatory response that characterizes lipid-mediated gene transfer is not observed.
A visible light and pH responsive anticancer drug delivery system based on polymer-coated mesoporous silica nanoparticles (MSNs) has been developed. Perylene-functionalized poly(dimethylaminoethyl methacrylates) sensitive to visible light and pH are electrostatically attached on the surface of MSNs to seal the nanopores. Stimulation of visible light and acid can unseal the nanopores to induce controlled drug release from the MSNs. More interestingly, the release can be enhanced under the combined stimulation of the dual-stimuli. The synergistic effect of visible light and acid stimulation on the efficient release of anticancer drugs from the nanohybrids endows the system with great potential for cancer therapy.
Visible light and pH responsive nanocarriers based on polymer-coated mesoporous silica nanohybrids have been developed by electrostatic self-assembly. Visible light and acid stimulation can induce the nanopores unsealed. The synergistic effect of the stimuli on the efficient release of anticancer drugs from the nanohybrids endows the system with great potential for cancer therapy.
A collagen sheet with highly aligned collagen fibers is fabricated by continuous cyclic stretch. The rearrangement of the collagen fibers depends on the different process parameters of the cyclic stretch, including magnitude, frequency, and period of stretch. The collagen fibers are aligned perpendicularly to the direction of the stretch. Corneal stromal cells and smooth muscle cells cultivated on the highly aligned collagen sheet show alignment along the collagen fibers without the stretch during culture. Thus, the sheet can be a suitable scaffold for use in regenerative medicine.
A collagen sheet with highly aligned collagen fibers is fabricated by continuous cyclic stretch. The collagen fibers are aligned perpendicularly to the direction of the stretch. Corneal stromal cells and smooth muscle cells on the collagen sheet show alignment along the fibers without the stretch during culture. Thus, the sheet can be a suitable scaffold for use in regenerative medicine.
In order to construct unique polypeptide architectures, a novel telechelic-type initiator with two leucine ethyl ester units is designed for chemoenzymatic polymerization. Glycine or alanine ethyl ester is chemoenzymatically polymerized using papain in the presence of the initiator, and the propagation occurs at each leucine ethyl ester unit to produce the telechelic polypeptide. The formation of the telechelic polypeptides is confirmed by 1H NMR and MALDI-TOF mass spectroscopies. It is revealed by AFM observation that long nanofibrils are formed from the telechelic polyalanine, whereas a conventional linear polyalanine with a similar degree of polymerization shows granule-like structures. The telechelic polyglycine and polyalanine show the crystalline structures of Polyglycine II and antiparallel β-sheet, respectively. It is demonstrated that this method to synthesize telechelic-type polypeptides potentially opens up a pathway to construct novel hierarchical structures by self-assembly.
Telechelic type polypeptides are prepared by chemoenzymatic polymerization of glycine or alanine using papain in the presence of a telechelic initiator. The telechelic polyglycine and polyalanine show crystalline structures based on Polyglycine II and antiparallel β-sheet, respectively. Long nanofibrils are formed by the telechelic polyalanine, which differs from the morphology prepared from a conventional linear polyalanine.
Furoxans, or 1,2,5-oxadiazole-N-oxides, are a class of nitric oxide (NO)-donating compounds that release NO in response to thiol-containing molecules. In this study, polymeric micelles bearing furoxan moieties are prepared from an amphiphilic block copolymer consisting of a hydrophobic furoxan-bearing block and a hydrophilic poly(N-acryloylmorpholine) block. The block copolymer is prepared using a combination of the reversible addition–fragmentation chain transfer polymerization and the copper-catalyzed Huisgen cycloaddition techniques. The block copolymers form spherical micelles with a diameter of 50 nm by self-assembly in water. The micelles release NO in response to cysteine and show improved stability against hydrolytic decomposition. Furthermore, the micelles show a synergistic anti-proliferative effect with ibuprofen in human colon cancer cells.
Nitric oxide (NO)-releasing polymeric micelles bearing furoxan moieties are prepared from an amphiphilic block copolymer consisting of a hydrophobic furoxan-bearing block and a hydrophilic poly(N-acryloylmorpholine) block. The micelles release NO in the presence of cysteine and potentiate the anti-proliferative effect of ibuprofen, a nonsteroidal anti-inflammatory drug, in human colon cancer cells.
Poly (ethylene glycol) (PEG) based hydrogels have been widely used in many biomedical applications such as regenerative medicine due to their good biocompatibility and negligible immunogenicity. However, bioactivation of PEG hydrogels, such as conjugation of bioactive biomolecules, is usually necessary for cell-related applications. Such biofunctionalization of PEG hydrogels generally involves complicated and time-consuming bioconjugation procedures. Herein, we describe the facile preparation of bioactive nanocomposite PEG hydrogel crosslinked by the novel multifunctional nanocrosslinkers, namely polydopamine-coated layered double hydroxides (PD-LDHs). The catechol-rich PD-LDH nanosheets not only act as effective nanocrosslinkers reinforcing the mechanical strength of the hydrogel, but also afford the hydrogels with robust bioactivity and bioadhesion via the cortical-mediated couplings. The obtained nanocomposite PEG hydrogels with the multifunctional PD-LDH crosslinking domains show tunable mechanical properties, self-healing ability, and bioadhesion to biological tissues. Furthermore, these hydrogels also promote the sequestration of proteins and support the osteogenic differentiation of human mesenchymal stem cells without any further bio-functionalization. Such facile preparation of bioactive and bioadhesive PEG hydrogels have rarely been achieved and may open up a new avenue for the design of nanocomposite PEG hydrogels for biomedical applications.
A bioactive nanocomposite poly (ethylene glycol) (PEG) hydrogel crosslinked polydopamine-coated layered double hydroxide (PD-LDH) nanosheet. The catechol-rich PD-LDH nanosheets not only act as effective nanocrosslinkers reinforcing the hydrogel, but also afford robust bioactivity and bioadhesion via the cortical-mediated couplings. Furthermore, these hydrogels also promote the sequestration of proteins and support the osteogenic differentiation of human mesenchymal stem cells without any further biofunctionalization.
Recently, the application of nanostructured materials in the field of tissue engineering has garnered attention to mediate treatment and regeneration of bone defects. In this study, poly(l-lactic acid) (PLLA)/gelatin (PG) fibrous scaffolds are fabricated and β-cyclodextrin (βCD) grafted nano-hydroxyapatite (HAp) is coated onto the fibrous scaffold surface via an interaction between βCD and adamantane. Simvastatin (SIM), which is known to promote osteoblast viability and differentiation, is loaded into the remaining βCD. The specimen morphologies are characterized by scanning electron microscopy. The release profile of SIM from the drug loaded scaffold is also evaluated. In vitro proliferation and osteogenic differentiation of human adipose derived stem cells on SIM/HAp coated PG composite scaffolds is characterized by alkaline phosphatase (ALP) activity, mineralization (Alizarin Red S staining), and real time Polymerase chain reaction (PCR). The scaffolds are then implanted into rabbit calvarial defects and analyzed by microcomputed tomography for bone formation after four and eight weeks. These results demonstrate that SIM loaded PLLA/gelatin/HAp-(βCD) scaffolds promote significantly higher ALP activity, mineralization, osteogenic gene expression, and bone regeneration than control scaffolds. This suggests the potential application of this material toward bone tissue engineering.
β-Cyclodextrin grafted hydroxyapatite nanoparticles are coated onto the surface of PLLA/gelatin fibrous scaffolds by an inclusion complex system. To provide a favorable microenvironment for bone tissue regeneration, simvastatin, an osteoinductive drug, is loaded into β-cyclodextrin within the hydroxyapatite nanoparticle.
To simultaneously control inflammation and facilitate dentin regeneration, a copolymeric micelle-in-microsphere platform is developed in this study, aiming to simultaneously release a hydrophobic drug to suppress inflammation and a hydrophilic biomolecule to enhance odontogenic differentiation of dental pulp stem cells in a distinctly controlled fashion. A series of chitosan-graft-poly(lactic acid) copolymers is synthesized with varying lactic acid and chitosan weight ratios, self-assembled into nanoscale micelle-like core–shell structures in an aqueous system, and subsequently crosslinked into microspheres through electrostatic interaction with sodium tripolyphosphate. A hydrophobic biomolecule either coumarin-6 or fluocinolone acetonide (FA) is encapsulated into the hydrophobic cores of the micelles, while a hydrophilic biomolecule either bovine serum albumin or bone morphogenetic protein 2 (BMP-2) is entrapped in the hydrophilic shells and the interspaces among the micelles. Both hydrophobic and hydrophilic biomolecules are delivered with distinct and tunable release patterns. Delivery of FA and BMP-2 simultaneously suppresses inflammation and enhances odontogenesis, resulting in significantly enhanced mineralized tissue regeneration. This result also demonstrates the potential for this novel delivery system to deliver multiple therapeutics and to achieve synergistic effects.
Micelles in microspheres are assembled from chitosan-graft-poly(lactic acid) (CS-g-PLA) copolymers. Hydrophobic biomolecules (green dots) are bound to hydrophobic cores of CS-g-PLA micelle-like nanospheres and hydrophilic biomolecules (red dots) are bound to hydrophilic shells and interspaces of CS-g-PLA nanospheres.
Healing of tendon ruptures represents a major challenge in musculoskeletal injuries and combinations of biomaterials with biological factors are suggested as viable option for improved healing. The standard approach of repair by conventional suture leads to incomplete healing or rerupture. Here, a new elastic type of DegraPol® (DP), a polyester urethane, is explored as a delivery device for platelet-derived growth factor—BB (PDGF-BB) to promote tendon healing. Using emulsion electrospinning as an easy method for incorporation of biomolecules within polymers, DegraPol® supports loading and release of PDGF-BB. Morphological, mechanical and delivery device properties of the bioactive DP scaffolds, as well as differences arising due to different electrospinning parameters are studied. Emulsion electrospun DP scaffolds result in thinner fibers than pure DP scaffolds and experience decreased strain at break [%], but high enough for successful surgeon handling. PDGF-BB is released in a sustained manner from emulsion electrospun DP, but not completely, with still large amount of it being inside the polymeric fibers after 30 d. In vitro studies show that the bioactive scaffolds promote tenocyte proliferation in serum free and serum+ conditions, demonstrating the potential of this surgeon-friendly bioactive delivery device to be used for tendon repair.
A new emulsion electrospun double-layered tube based on an elastic and biodegradable block copolymer (DegraPol®), delivering proteins in a sustained manner has been developed. Aimed to be used for tendon rupture repair application, it allows sustained delivery of bioactive PDGF-BB, thus promoting tenocyte proliferation in vitro.
An increased structural variety expands the number of putative applications for cyanophycin (multi-l-arginyl-poly-[l-aspartic acid], CGP). Therefore, structural modifications of CGP are of major interest; these are commonly obtained by modification and optimization of the bacterial producing strain or by chemical modification. In this study, an enzymatic modification of arginine side chains from lysine-rich CGP is demonstrated using the peptidyl arginine deiminase from Oryctolagus cuniculus, purified from Escherichia coli after heterologous expression. About 10% of the arginine side chains are converted to citrulline which corresponds to 4% of the polymer's total side chains. An inhibition of the reaction in the presence of small amounts of l-citrulline is observed, thereby explaining the low conversion rate. CGP dipeptides can be modified with about 7.5 mol% of the Asp-Arg dipeptides being converted to Asp-Cit. These results show that the enzymatic modification of CGP is feasible, opening up a whole new area of possible CGP modifications for further research.
The purified type II peptidyl arginine deiminase of Oryctolagus cuniculus is used for the first enzymatic modification of arginine residues of the biopolymer cyanophycin and its dipeptides. About 4 mol% of the polymer side chains and 7.5 mol% of the dipeptides can be converted to citrulline. An inhibitory effect for free citrulline can be identified.
Development of bioadhesive formulations for tissue fixation remains a challenge. The major drawbacks of available bioadhesives are low adhesion strength, toxic byproducts, and complexity of application onto affected tissues. In order to address these problems, this study has developed a hydrogel bioadhesive system based on poly amido amine (PAMAM) dendrimer, grafted (conjugated) with UV-sensitive, 4-[3-(trifluoromethyl)-3H-diazirin-3-yl] benzyl bromide (PAMAM-g-diazirine). This particular diazirine molecule can be grafted to the surface amine groups of PAMAM in a one-pot synthesis. Diazirine functionalities are carbene precursors that form covalent crosslinks with hydrated tissues after low-power UV activation without necessity of free-radical initiators. The rheological properties and adhesion strength to ex vivo tissues are highly controllable depending on diazirine grafting, hydrogel concentration, and UV dose intensity fitting variety types of tissues. Covalent bonds at the tissue/bioadhesive interface provide robust adhesive and mechanical strength in a highly hydrated environment. The free flowing hydrogel conversion to elastic adhesive after UV activation allows intimate contact with the ex vivo swine tissue surfaces with low in vitro cytotoxicity observed, making it a promising bioadhesive formulation toward clinical applications.
This paper describes a bioadhesive system aimed at reconnection of soft tissues. The bioadhesive is based on poly amido amine dendrimer, grafted with UV-sensitive, diazirine,-4-[3-(trifluoromethyl)-3H-diazirin-3-yl] benzyl bromide. The dendrimer formulation adheres to hydrated tissues upon low power UV activation. The adhesion strength and mechanical modulus are dependent on grafting concentration and the energy of UV light.
Chondrocyte-seeded, photo-cross-linked hydrogels prepared from solutions containing 50% mass fractions of methacrylated glycol chitosan or methacrylated hyaluronic acid (MHA) with methacrylated chondroitin sulfate (MCS) are cultured in vitro under static conditions over 35 d to assess their suitability for load-bearing soft tissue repair. The photo-cross-linked hydrogels have initial equilibrium moduli between 100 and 300 kPa, but only the MHAMCS hydrogels retain an approximately constant modulus (264 ± 5 kPa) throughout the culture period. Visually, the seeded chondrocytes in the MHAMCS hydrogels are well distributed with an apparent constant viability in culture. Multicellular aggregates are surrounded by cartilaginous matrix, which contain aggrecan and collagen II. Thus, co-cross-linked MCS and MHA hydrogels may be suited for use in an articular cartilage or nucleus pulposus repair applications.
Photo-cross-linked hydrogels formed from solution blends of methacrylated glycol chitosan, methacrylated hyaluronic acid (MHA), and methacrylated chondroitin sulfate (MCS) are assessed for their ability to support chondrocyte viability and extracellular matrix (ECM) accumulation in static culture. MHAMCS hydrogels possess equilibrium moduli appropriate for load-bearing soft tissue regeneration while also providing the best environment for chondrocyte ECM production.