Synthesis and characterization of amphiphilic PLA-(PαN3CL-g-PBA) copolymers by ring-opening polymerization and click reaction

The present study prepared novel amphiphilic block-graft PDLLA-b-(P alpha N3CL-g-PBA) and PLLA-b-(P alpha N3CL-g-PBA) functional polyesters, containing a hydrophilic poly(alpha-azido-epsilon-caprolactone-graft-alkyne) (P alpha N3CL-g-alkyne) segment and a hydrophobic poly(DL-lactide) (PDLLA) or poly(L-lactide) (PLLA) segment, using ring-opening polymerization of alpha-chloro-epsilon-caprolactone (alpha ClCL) with a hydroxyl-terminated macroinitiator of PDLLA or PLLA, substituting pendent chloride with sodium azide. The copolymers were subsequently used for grafting of 2-propynyl-terminal benzoate moieties by way of Cu(I)-catalyzed Huisgen's 1,3-dipolar cycloaddition, thus producing a "click" reaction. Differential scanning calorimetry (DSC) and H-1 NMR, FT-IR, and GPC examined the characteristics of the copolymers. The critical micelle concentration (CMC) ranged from 2.7 mg L-1 to 24.6 mg L-1 at 25 degrees C and the average micelle size ranged from 106 nm to 297 nm. The length of the hydrophilic segment and the configuration of the lactide both influenced micelle stability. The micelle of PLLA-b-(P alpha N3CL-g-PBA) provided high drug entrapment efficiency and loading content. The results from in vitro cell viability assays indicated that PLA-b-(P alpha N3CL-g-PBA) shows low cytotoxicity. Crown Copyright (C) 2012 Published by Elsevier Ltd. All rights reserved.