Nanocomposites of Spiropyran-Functionalized Polymers and Upconversion Nanoparticles for Controlled Release Stimulated by Near-Infrared Light and pH

Here a near-infrared light and pH responsive nanocomposite comprising spiropyran-functionalized amphiphilic polymers and upconversion nanoparticles (UCNPs) is reported, which is prepared through the self assembly of the amphiphilic polymers and the encapsulation of the UCNPs in the core of the self-assemblies. Upon near-infrared light irradiation, the upconversion fluorescence can induce the hydrophobic spiropyran to be isomerized to the hydrophilic merocyanine and disrupt the spherical morphology of the nanocomposites. Meanwhile, at low pH, the hydrophobic spiropyran can be also protonated to become hydrophilic merocyanine, and the self-assemblies are swollen. Model molecules, hydrophobic Coumarin 102, are demonstrated to be released from the nanocomposites triggered by the near-infrared light and acidic pH. In addition, the cytotoxicity of the nanocomposites loaded with anticancer drugs Doxorubicin on cancer cells indicates that the loaded drugs can be released and kill the cells effectively and the efficiency can be enhanced significantly upon near-infrared light irradiation.