Acid degradable ZnO quantum dots as a platform for targeted delivery of an anticancer drug

Efficacious chemotherapy mainly hinges on the tumor-specific delivery of anticancer drugs. Herein we report a successful fabrication of highly photoluminescent and water dispersible ZnO quantum dots via a new ligand exchange free strategy. In addition to bioimaging, ZnO QDs have also been evaluated as a platform for targeted and pH responsive intracellular delivery of an anticancer drug. The cancer targeting feature is endowed by conjugating folic acid on to the surface of ZnO-NH2 QDs via an amidation reaction. Doxorubicin (DOX) is then successfully loaded onto the folic acid functionalized ZnO QDs by capitalizing on its marked tendency towards the formation of metal complexes. Drug loaded ZnO-FA QDs remain stable at physiological pH but readily disintegrate in the mildly acidic intracellular environment of cancer cells as validated by a drug release profile, confocal microscopy and a cell-cytotoxicity assay. Compared to the conventional drug nanovector, ZnO-FA QDs themselves manifest a significant therapeutic activity after reaching their targeted site, therefore, combined DOX and ZnO QDs can be more efficacious than either alone. Hence, this approach provides a valuable ZnO QDs-based nanovector that can simultaneously realize targeting, diagnosis, and therapy of cancer cells.