Multifunctional Up-Converting Nanocomposites with Smart Polymer Brushes Gated Mesopores for Cell Imaging and Thermo/pH Dual-Responsive Drug Controlled Release

Multifunctional nanocarriers based on the up-conversion luminescent nanoparticles of NaYF 4 :Yb 3+ /Er 3+ core (UCNPs) and thermo/pH-coupling sensitive polymer poly[( N -isopropylacrylamide)- co -(methacrylic acid)] (P(NIPAm- co -MAA)) gated mesoporous silica shell are reported for cancer theranostics, including fluorescence imaging, and for controlled drug release for therapy. The as-synthesized hybrid nanospheres UCNPs@mSiO 2 -P(NIPAm- co -MAA) show bright green up-conversion fluorescence under 980 nm laser excitation and the thermo/pH-sensitive polymer is active as a “valve” to moderate the diffusion of the embedded drugs in-and-out of the pore channels of the silica container. The anticancer drug doxorubicin hydrochloride (DOX) can be absorbed into UCNPs@mSiO 2 -P(NIPAm- co -MAA) nanospheres and the composite drug delivery system (DDS) shows a low level of leakage at low temperature/high pH values but significantly enhanced release at higher temperature/lower pH values, exhibiting an apparent thermo/pH controlled “on-off” drug release pattern. The as-prepared UCNPs@mSiO 2 -P(NIPAm- co -MAA) hybrid nanospheres can be used as bioimaging agents and biomonitors to track the extent of drug release. The reported multifunctional nanocarriers represent a novel and versatile class of platform for simultaneous imaging and stimuli-responsive controlled drug delivery.