PH and thermo dual-responsive starch-g-P(DEAEMA-co-PEGMA): Synthesis via SET-LRP, self-assembly and drug release behaviors

Abstract

A novel pH and thermo dual-responsive graft copolymer, starch-graft-poly(N,N-diethyl aminoethyl methacrylate-co-poly(ethylene glycol) methyl ether methacrylate) [starch-g-P(DEAEMA-co-PEGMA)], was successfully synthesized through single-electron transfer living radical polymerization (SET-LRP). The structure and molecular weight of the grafted chains were confirmed by 1H NMR. These graft copolymers can self-assemble into micelles with starch backbone and PDEAEMA as the core and PPEGMA as the corona in water at pH 7.4. The critical micelle concentration (CMC) of the graft copolymers varied between 0.0313 and 0.1364 mg/mL, decreasing with an increase in the molecular weight of the grafted chains and the ratio of PDEAEMA and PPEGMA segments. The pH and thermo dual-responsive behaviors of starch-g-P(DEAEMA-co-PEGMA) micelles were investigated by DLS and TEM. As the pH decreasd from 8.0 to 5.5, the micelle sizes continued to increase due to the protonation of the PDEAEMA segments, and as the pH decreased to below 5.5, the micelles began to disassemble, which was verified by TEM observations. Upon heating, the size of the micelles decreased because of the shrinkage of the PDEAEMA segments. The pH and thermo dual-responsive behaviors of the starch-g-P(DEAEMA-co-PEGMA) micelles are reversible. Doxorubicin (DOX), a hydrophobic drug, was encapsulated in the micelles, and in vitro release from the drug-loaded micelles displayed good pH-responsive behavior.