Biodegradable Controlled Drug Delivery Platform Based on Carboxylated Mesoporous Silica Nanoparticles––Zinc Oxide Quantum Dots

A biodegradable delivery platform is constructed for controlled drug delivery. Carboxylated biodegradable mesoporous silica nanoparticles (COOH–BMSNs) are synthesized to load the chemotherapy drug methotrexate (MTX), and the mesopores of BMSN are blocked by ZnO quantum dots (QDs) through an amidation reaction to encapsulate the loaded MTX. The ZnO QDs are decomposed under mildly acidic conditions which is characteristic of a tumor microenvironment, resulting in the release of MTX; additionally, glutathione (GSH) can reduce the disulfide bonds (−S–S−) in a BMSN into sulfhydryl (−SH), causing the decomposition of the BMSN and the release of MTX. Therefore, the responsiveness of pH and GSH to MTX delivery can be achieved with ZnO–BMSN–MTX. Notably, in vitro cytotoxicity testing reveals that the drug-free carrier (ZnO–BMSN) exhibits good biocompatibility, whereas the controlled delivery platform (ZnO–BMSN–MTX) exhibits significant cytotoxicity against SMMC-7721 tumor cells benefiting from the synergistic effect of MTX and Zn2+.