Synthesis and pH-Responsive “Schizophrenic” Aggregation of a Linear-Dendron-Like Polyampholyte Based on Oppositely Charged Polypeptides

Abstract

A novel linear-dendron-like polyampholyte, poly(L-lysine)-b-D2-poly(L-glutamic acid) [PLL-b-D2-(PLGA)4], where D2 is the second generation of poly(amido amine), was prepared by hydrolyzing poly(ε-benzyloxycarbonyl-L-lysine)-b-D2-poly(γ-benzyl-L-glutamate) copolymer which was synthesized via a combination of ring-opening polymerization and click chemistry. The pH-responsive self-assembly behaviors of PLL-b-D2-(PLGA)4 were investigated in detail. It is found that PLL-b-D2-(PLGA)4 can self-assemble into PLGA-core aggregates at acidic pH and PLL-core aggregates at alkaline pH, which was accompanied with the coil-to-helix conformational transition of PLGA and PLL segments, respectively. The self-assembled aggregates with various morphologies, such as large compound micelles, worm-like micelles, large compound vesicles, simple vesicles, and rigid tubular structures have been obtained in "schizophrenic" aggregation process with simply increasing the solution pH. The hierarchical assembled fractal structures of PLL-b-D2-(PLGA)4 were observed during the solvent evaporation at high pH value.