Red-Light Activable Oxovanadium(IV)-Gold Nanoparticles (VO@AuNPs) for Next-Generation Photodynamic Therapy: Design, Photophysics, and Therapeutic Evaluation.

Oxovanadium(IV) (VO) complexes have demonstrated considerable potential in photodynamic therapy (PDT). In this study, we report for the first time the conjugation of these VO complexes with gold nanoparticles (AuNPs), aiming to red-shift their absorption profile, and improve cellular uptake, solubility, and overall stability. The resulting VO@AuNPs nanoconjugates were extensively characterized by techniques like IR, UV-visible spectroscopy, DLS, PXRD, EDX, XPS, and TEM. The nanoconjugates exhibited excellent solubility and stability in physiological conditions (5% DMSO-PBS, pH 7.4), along with strong binding to serum albumin, suggesting good potential for systemic delivery. Biological studies revealed effective and selective cytotoxicity against cancer cells under PDT conditions. Cellular uptake assays showed rapid internalization in MDA-MB-231 cells within 2 h. Upon exposure to red light (620-750 nm), the VO@AuNPs displayed enhanced cytotoxic effects, driven by reactive oxygen species (ROS) generation. Specifically, IC₅₀ values were significantly lower upon light exposure compared to dark conditions in MDA-MB-231 and MCF-7 cells indicating their high phototoxicity, with phototoxicity indices of ∼6.0 and ∼2.5, respectively. Mechanistic studies confirmed light-induced apoptosis via caspase-3 activation, and elevated Bax levels. These results establish VO@AuNPs as promising metal complex functionalized gold nanoconjugate-based PDT agents for targeted cancer treatment.