PEG-l-PAF and PEG-d-PAF: Comparative Study on Thermogellation and Biodegradation

Citations Over TimeTop 19% of 2012 papers

Abstract

l-Polypeptides and d-polypeptides can be prepared from natural l-amino acids and non-natural d-amino acids, respectively. In this study, poly(ethylene glycol)–poly(l-alanine-co-l-phenyl alanine) (PEG-l-PAF) and poly(ethylene glycol)–poly(d-alanine-co-d-phenyl alanine) (PEG-d-PAF) with similar molecular weight and composition, but different stereochemistry were investigated, focusing on thermogelling behavior and biodegradation. The sol-to-gel transition temperature of both PEG-l-PAF and PEG-d-PAF aqueous solutions decreased from 26 to 7 °C as the concentration increased from 4.0 wt % to 9.0 wt %. Dynamic light scattering, transmission electron microscopy, circular dichroism spectra, and 13C NMR spectra suggested that the sol-to-gel transition involved changes in molecular assemblies resulting from dehydration of PEG for both PEG-l-PAF and PEG-d-PAF. In particular, the significant differences between PEG-l-PAF and PEG-d-PAF were observed for histocompatibility as well as in vitro/in vivo degradation. Only PEG-l-PAF was significantly degraded by cathepsin B and elastase, as well as under in vivo conditions. The histocompatibility assayed by the H&E staining method showed that formation of the collagen capsule around the PEG-d-PAF gel was thicker than the PEG-l-PAF gel, indicating that acute inflammation was milder with PEG-l-PAF gel than with PEG-d-PAF gel. Current study emphasizes the significance of stereochemistry in biomaterial development.

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