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Enhancing the Biocompatibility and Biodegradability of Linear Poly(ethylene imine) through Controlled Oxidation

Englert, Christoph, Hartlieb, Matthias, Bellstedt, Peter, Kempe, Kristian, Yang, Chuan, Chu, Swee Kwang, Ke, Xiyu, Garcı́a, Jeannette M., Ono, Robert J., Fevre, Mareva, Wojtecki, Rudy J., Schubert, Ulrich S., Yang, Yi Yan, Hedrick, James L.
Macromolecules 2015 v.48 no.20 pp. 7420-7427
biocompatibility, biodegradability, chemical structure, coagulation, composite polymers, cytotoxicity, ethylene, gel chromatography, human cell lines, hydrogen peroxide, imines, infrared spectroscopy, methanol, nuclear magnetic resonance spectroscopy, oxidation, proteinases, temperature, water solubility
(Bio)degradable poly(ethylene imine-co-glycine)s (P(EI-co-Gly)) were synthesized through efficient and controlled oxidation of linear poly(ethylene imine) (LPEI) using hydrogen peroxide in a methanol/water mixture. Temperature, peroxide concentration, and reaction time were varied to adjust the degree of oxidation (DO). At low temperatures, the oxidation process was found to be well-controlled with almost 85% of ethylene imine units converted to the corresponding amide. Importantly, oxidation of more than 10% of the LPEI rendered the polymers water-soluble. The oxidation reaction and molecular structure of P(EI-co-Gly)s were studied in detail by various nuclear magnetic resonance (NMR) methods, infrared (IR) spectroscopy, and size exclusion chromatography (SEC). The introduction of backbone amide groups to the P(EI-co-Gly)s facilitated its (bio)degradation under acidic conditions or by proteases. Moreover, the P(EI-co-Gly)s exhibited negligible cytotoxicity, particularly relative to LPEI. The interaction of the copolymers with serum-containing medium was investigated showing no indication of coagulation. Preliminary studies indicate that P(EI-co-Gly) is a promising biodegradable polymer with negligible toxicity in human cell lines.