pH-Triggered Charge-Reversal Polyurethane Micelles for Controlled Release of Doxorubicin.

A series of pH-triggered charge-reversal polyurethane copolymers (PS-PUs) containing methoxyl-poly(ethylene glycol) (mPEG), carboxylic acid groups, and piperazine groups is presented in this work. The obtained PS-PUs copolymers can form into stable micelles at pH 7.4, which response to a narrow pH change (5.5-7.5) and show a tunable pH-triggered charge-reversal property. Doxorubicin (DOX) is encapsulated into the PS-PU micelles as a model drug. The drug release of DOX-loaded PS-PU micelles shows an obviously stepped-up with reducing the pH. Meanwhile, it is found that the charge-reversal property can improve the cellular uptake behavior and intracellular drug release in both HeLa cells and MCF-7 cells. Additionally, the time-dependent cytotoxicity of the DOX-loaded PS-PU micelles is confirmed by MTT assay. Attributed to the tunable charge-reversal property through changing the molar ratio of piperazine/carboxyl, the PS-PU micelles will be a potential candidate as an intelligent drug delivery system in future studies.