Temperature/pH dual responsive microgels of crosslinked poly(N-vinylcaprolactam-co-undecenoic acid) as biocompatible materials for controlled release of doxorubicin

Undecenoic acid functionalized thermo/pH responsive microgels, poly(N-vinylcaprolactam-co-undecenoic acid) [pol-( VCL-co-UA)], were synthesized by precipitation emulsion copolymerization. The microgels exhibit reversible thermo/pH responsive phase transition behavior, which can be tuned by varying the monomer feed ratio. The lower critical solution temperatures (LCSTs) of the materials are close to body temperature. As a result, when temperatures rise above ca. 37°C, a rapid thermal gelation process occurs, accompanied by a phase transition, resulting in expulsion of encapsulated compound. In vitro experiment evaluated its applicability as a drug carrier for controlled release of an anticancer agent (doxorubicin) and showed that the drug encapsulation efficiency (EE), releasing rate, and kinetics are dependent on the temperature and pH value as expected. Minimal cytotoxicity of the microgels was observed by a cytotoxicity assay using 3T3 fibroblast cells. Our finding suggests that the poly(VCL-co-UA) based microgels may be considered a promising candidate for temperature or pH-controlled delivery of anticancer drugs.