Poly(vinylcaprolactam)-Based Biodegradable Multiresponsive Microgels for Drug Delivery

Poly(vinylcaprolactam) (PVCL)-based biodegradable microgels were prepared for the biomedical application as drug delivery system via precipitation polymerization, where N,N-bis(acryloyl) cystamine (BAC) served as cross-linker, methacrylic acid (MAA) and polyethylene glycol (PEG) methyl ether methacrylate acted as comonomers. The microgels with excellent stability had distinct temperature sensitivity as largely observed in the case of PVCL-based particles and their volume phase transition temperature (VPTT) shifted to higher temperature with increasing MAA content and ambient pH. In the presence of reducing agent glutathione (GSH) or dithiothreitol (DTT), the microgels could be degraded into individual linear polymer chains by the cleavage of the disulfide linkages coming from the cross-linker BAC. The microgels could effectively encapsulate Doxorubicin (DOX) inside and presented stimuli-triggered drug release in acidic or reducing environment. The results of the cytotoxicity assays further demonstrated that the blank microgels were nontoxic to normal cells while DOX-loaded microgels presented efficient antitumor activity to HeLa cells.