Synthesis, characterization, and degradation of a novel L-tyrosine-derived polycarbonate for potential biomaterial applications

摘要

A novel class of pseudo-poly(amino acid)s was synthesized with a cyclic dipeptide as new diphenole. Nonpeptide bonds alternating with a peptide bond structure were introduced into the backbone of the pseudopoly(amino acid)s. The cyclic dipeptide in this study was obtained from natural L-tyrosine. L-tyrosine is a major nutrient amino acid with a phenolic hydroxyl group, so a polycarbonate derived from the cyclic dipeptide should possess more optimum mechanical properties, bioactivity, and biocompatibility. The hydrolytic specimen of the resulting polycarbonate was prepared by a modified solvent evaporation process. Under strongly alkaline conditions, degradation testing was performed. The tyrosine-derived polycarbonate possessed a low glass-transition temperature value and a high thermal decomposition temperature value, which formed a broad mean thermal processing range. The most important results of our study were the effects of the polycarbonate degradation on the local pH values, which were smaller than those of other biodegradable polymers [e.g., poly(lactic acid), poly(glycolic acid), and poly(lactic glycolic acid)]. The synthesized polymer and cyclic dipeptide were characterized with Fourier transform infrared, C-13-NMR, and H-1-NMR spectroscopy to determine their chemical structures; by differential scanning calorimetry and thermoogravimetric analysis to determine the thermal properties of the polymer; by gel permeation chromatography to determine the polymer's molecular weight; and by X-ray diffraction to determine the polymer's morphology. (C) 2008 Wiley Periodicals, Inc.