Photo, pH and redox multi-responsive nanogels for drug delivery and fluorescence cell imaging

Here a novel photo, pH, and redox triple-responsive nanogel of poly(acrylic acid-co-spiropyran methacrylate) crosslinked by disulfide-containing N, N-bis(acryloyl) cystamine was prepared. Upon UV light irradiation or at low pH, the hydrophobic spiropyran (SP) isomerized to the hydrophilic merocyanine (MC) and the nanogels swelled-up. Upon the addition of reductant agents, the nanogels were disrupted due to the oxidative scission of the disulfide crosslinkers. The anticancer drug doxorubicin (Dox) could be loaded into the nanogels based on electrostatic interactions with the acrylic acids on the NGs, which would be released upon the stimulation of light, pH and DTT. The in vitro cytotoxicity study indicates that the nanogels loaded with anticancer drugs could kill the cancer cells effectively and the effect would be enhanced when irradiated by UV light. Interestingly, the isomerized MC in nanogels could emit intensive green light even endocytosed into the nucleus of the cancer cells, which afforded great potential in fluorescence cell imaging.