Methotrexate-conjugated AgInS₂/ZnS quantum dots for optical imaging and drug delivery

The ability to conjugate drugs with quantum dots (QDs) offers excellent prospects in pharmacotherapy for the improvement of diagnosis and treatment of human diseases. Here, we report a facile strategy to prepare dual-functional nanomaterials consisting of QDs and an anticancer drug. Hydrophilic AgInS ₂/ZnS QDs were obtained through an ultrasonication process by introducing the amphiphilic polymer, poly(maleic anhydride-alt-1-octadecene) (PMAO). Subsequently, the anticancer drug methotrexate (MTX) was covalently coupled to the surface of the AgInS₂/ZnS QDs by carbodiimide chemistry. The MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] cell proliferation assay indicated that these hydrophilic PMAO-coated AgInS₂/ZnS QDs exhibited negligible cytotoxicity. Human cervical (HeLa) cancer cells had >80% cell viability after 24 h at concentrations of up to 300 μg/mL. Confocal laser scanning microscopy revealed that the AgInS₂/ZnS QDs conjugated with MTX were taken up effectively by HeLa cells. In addition, this nanomaterial was shown to have a dose-dependent antiproliferative effect in cancer cells by the MTT assay. These important features suggest that AgInS₂/ZnS QDs conjugated with MTX might be a novel candidate for cancer therapeutics and diagnosis in future.