The synergistic effect and mechanism of doxorubicin-ZnO nanocomplexes as a multimodal agent integrating diverse anticancer therapeutics

BACKGROUND Nanomaterials have emerged as ideal multimodal nanomedicine platforms, each one combining different designs and therapeutic approaches in a single system against cancer. The aim of the current study was to explore the synergistic effect and mechanism of a doxorubicin (Dox)-ZnO nanocomplex as a multimodal drug delivery system, integrating Dox chemotherapy and ZnO-mediated photodynamic therapy, in anticancer therapeutics. METHODS Dox was loaded onto ZnO nanomaterials, forming complexes with the transition metal Zn to yield the Dox-ZnO nanocomplexes. After culture with SMMC-7721 hepatocarcinoma cells, the cellular uptake was quantitatively detected by flow cytometry and visualized by fluorescence microscopy. The synergistic effects of the different anticancer therapeutic modalities on the proliferation of SMMC-7721 hepatocarcinoma cells were evaluated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. The expression of B-cell lymphoma 2 protein (Bcl-2), Bcl-2 associated X protein (Bax), caspase 9, and caspase 3 were examined by Western blot, to elucidate the possible molecular mechanisms involved. RESULTS Our observations demonstrated that Dox-ZnO nanocomplexes could act as an efficient drug delivery system for importing Dox into SMMC-7721 cells, enhancing its potential chemotherapy efficiency by increasing the intracellular concentration of Dox. With the addition of ultraviolet (UV) illumination, the ZnO nanomaterials showed excellent photodynamic therapeutic properties, attacking the cancer cells further. Thus the caspase-dependent apoptosis was synergistically induced, resulting in distinct improvement in anticancer activity. CONCLUSION The Dox-ZnO nanocomplex presents a promising multimodal agent for comprehensive cancer treatment.