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Sterically stabilized polyionic complex nanogels of chitosan lysate and PEG-b-polyglutamic acid copolymer for delivery of irinotecan active metabolite (SN-38).

BACKGROUND
Polyionic Complex (PIC) nanogels are promising delivery systems with numerous attractions such as simple, fast, and organic solvent-free particle formation and mild drug loading conditions. Among polyelectrolytes, poly (L-amino acid) copolymers such as poly (ethylene glycol)-block-poly (L-glutamic acid) copolymers (PEG-b-PGlu) are interesting biocompatible and biodegradable candidates bearing carboxylic acid functional groups.


OBJECTIVES
Aiming to solubilize and to preserve short-acting irinotecan active metabolite (SN38), sterically stabilized PIC nanogels were prepared through electrostatic charge neutralization between PEG-b-PGlu and chitosan lysate, a polycationic natural polymer obtained through digestion of chitosan by hydrogen peroxide oxidation and is soluble in a wide range of pH.


METHODS
Synthesis of PEG-b-PGlu was accomplished by N-carboxyanhydride polymerization of γ -benzyl L-glutamic acid, which is initiated by methoxy PEG-NH2 and successive debenzylation reaction.


RESULT
The resulting block copolymer was characterized by FTIR, 1H-NMR, and Size Exclusion Chromatography (SEC). Self-assembling properties of the PIC nanogels were investigated by pyrene assay, Dynamic Light Scattering (DLS), and Transmission Electron Microscopy (TEM), indicating formation of homogeneous spherical particles with a mean size of 28 nm at the PEG-b-PGlu concentrations/LMWC weight ratio of 5:1. Upon direct loading of SN38, the drug solubility enhanced more than 4×103 folds with a mean loading efficiency of 89% and the drug loading of 30%. PIC nanogels exhibited zeta potential of +1 mV, acceptable biocompatibility, and superior cytotoxicity in murine colorectal carcinoma (CT26 cell line) compared to free drug.


CONCLUSION
In addition, the PIC nanogels provided SN38 protection against hydrolytic degradation in physiologic condition. Conclusively, the well-tuned PIC nanogels are suggested as a potential biocompatible nanocarrier for SN38 delivery.