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The Effects of Thin Patterned Poly(caprolactone) Films on Cell Behavior

Increasing amounts of emphasis is being placed on keeping the older generation in proper health as the average human lifespan increases. But as the average human ages, problems within the body such as organ failure inevitably arise. This then leads to a demand for donor organs as a means for replacement. However, the demand for donor tissue far surpasses the availability of donor tissue. As a result, many patients unfortunately die while still waiting for tissue [1]. Tissue engineering, a new and emerging field in the advancement of science and medicine, combines living cells with natural or artificial polymers in order to create viable bioartifical organs or tissues in attempt to ease the demand for donor organs. Tissue engineering is one of a few techniques used in attempt to regenerate as well as repair damaged tissue [1-2]. Although artificial tissues are all ready being constructed and used in the medical setting [3], still in the process of research is a better understanding of the cellular composition of different organs. While some scientists are seeking for the best selection of cells--most particularly human cells--for the creation of bioartificial tissues, others scientists are searching for ways to induce and control growth of blood vessels within these engineered organs that will effectively provide nutrient, exchange gases, regulate temperature, and remove waste for the survival of larger engineered organs. However, most important of all, scientists are seeking for the best artificial or and biocompatible material to utilize in the creation of scaffolds to serve as the basis for tissue engineering [1, 4, 5]. Designing the scaffolds for tissue engineering is extremely important. Scaffolds serve as an extracellular matrix for cell adhesion. Prior to its natural degradation, the scaffolds are to serve as a foundation for cell seeding, migration, and differentiation [6]. In addition, the scaffold material should be able to withhold appropriate amounts of mechanical stress during engineering, it should be porous and permeable to allow cell migration and passage of nutrients, and it should exhibit proper chemistry and surface structure to allow for cell adhesion and proliferation [3]. Numerous research projects are being conducted on the biocompatibility of different materials with cells as well as different patterning of materials to form scaffolds. Different types of materials include poly(DL-lactide-co-glycolide) (PLGA), collagen, poly(ε-caprolactone) (PCL), poly(lactic acid) (PLA), calcium phosphate ceramic (CaP), and bioactive glass foams [6-8]. Different materials have different mechanical properties and different degradation rates. Hence, different materials would be appropriate for different tissue engineering. Furthermore, different approaches for creation of scaffolds include solid freeform fabrication, electrospinning, as well as microembossing [8-10]. Although electrospinning and solid freeform fabrication has their advantages [8-9], microembossing of materials allows for more efficient production as well as uniform two dimensional layers of scaffold while providing control of porosity within the scaffolds. In addition, scaffold layers created from microembossing can be stacked to form three dimensional scaffolds which can better mimic tissues and organs [10]. The aim of my research is to contribute to the study of biomaterials as well as the best patterning of materials for the creation of scaffolds for tissue engineering. I will be using microembossing, because of its advantages, to create different layers of scaffolds with different patterning of materials. To start, I will be using already manufactured and patterned silicon chips provided by Dr. Jian Tan for the molding of two dimensional scaffolds. The silicon chips take on patterns of pillars and channels of various widths apart. These silicon chips will be used to create an inverse mold on Silicone Elastomer. Because poly(caprolactone) (PCL) is a stable material with a slow degradation rate [10], PCL will be used primarily throughout this experiment. PCL will be used to fill the inverse mold of the silicone elastomer, to take on the pattern of the silicon chip, with the use of microembossing. These scaffold will then be tested for cell interaction [11]. Different cell properties, i.e. cell viability, proliferation, morphology, as a result of interacting with the scaffold layers will be assessed to see which pattern of scaffolds provides the best environment for cells. Human Saos-2 cells will be cultured onto the scaffold and examined. Because Saos-2 cells behave like osteoblasts, cell differentiation into bone-like cells will be tested. Marker proteins will be analyzed to evaluate cell differentiation. Morphology will be assessed by comparing cells grown on the two dimensional scaffold to cells grown on tissue culture flasks under fluorescent microscope. The degree of adhesion will be measured by counting the number of cells that adhered to the scaffolds after four hours of cell plating. Proliferation will be measured by calculating the number of population doublings after three days of cell culture [12]. Results for one type of patterning will be compared to results of other types of patterning as well as with the control. Ultimately, the patterning which provides the most favorable environment for cell culture should be found. If time permits, different materials will be used to create the two dimensional scaffolds and two dimensional scaffolds can be stacked to create three dimensional scaffolds. These can then be used to examine cell interaction as well.