Positively charged nanomicelles in water of amphiphilic copolymer chitosan-g-polylactide as drug carrier of photoporphyrin IX for photodynamic therapy

摘要

Preparation of amphiphilic graft copolymers of chitosan-g-methacrylate-terminated poly(lactic acid) (CS-g-MPLA(n)) with various chain length of lactic acid monomers in the copolymers (n = 20, 40, and 70) has been successfully carried out by "grafting on" free radical polymerization. Beside to offer a tunable and easy preparation of chitosan (CS)-based amphiphilic copolymers, the specific purpose is to study the effects of poly(lactic acid) chain length on the micelle properties of the copolymers in water. First, oligomer CS was synthesized by partial oxidation. Second, the methacrylate-terminated poly(lactic acid) with different chain length were synthesized by ring opening polymerization of lactide monomer using 2-hydroxyethyl methacrylate and Sn(Oct)(2) as initiator and catalyst, respectively. Finally, the grafting process was carried out by free radical copolymerization using cerium(IV) sulfate as initiator at 70 degrees C for 24 h. The CS-g-MPLA(n) amphiphilic copolymers were characterized by Fourier transform infrared and proton nuclear magnetic resonance. The hydrophobic drug nanomicelles in water with a narrow-size distribution, positively charged and high stability have been confirmed. The micelle size is significantly bigger on longer chain of poly(lactic acid); however, the stability, loading capacity, and encapsulation efficiency are independent on the chain length. The high-loading capacity and encapsulation efficiency for hydrophobic drug protoporphyrin IX as the model are ensuring the hydrophobic drugs efficacy in photodynamic therapy applications.