Cationic carbon dot-silver nanohybrids with enhanced stability and redox control

Silver nanoparticles (AgNPs) show promise for biomedical applications, but their functional stability remains a major challenge. Here, the photochemical synthesis of hybrid AgNPs using carbon dots (CDs) as both reducing and capping agents (CDs-AgNPs) is described, producing highly stable nanostructures under physiological conditions. Comparisons with traditionally synthesized AgNPs, using Irgacure-2959 photoreduction and sodium borohydride methods, indicate that CDs-AgNPs have better colloidal stability across a range of pH levels (4.5-8), ionic strengths (up to 500 mM in NaCl), and oxidative conditions, especially against peroxyl radicals for at least 2 h, whereas other AgNP formulations destabilize within minutes. Spectroscopic analysis confirmed the presence of CDs on the AgNP surface, forming a protective shell rich in amino groups. This shell prevents nanoparticle clumping and oxidation, while also enhancing antioxidant capacity compared to gallic acid and BHT standards, outperforming other standard AgNPs. In vitro cytotoxicity tests on cancerous and non-cancerous cell lines showed toxicity toward MCF cell lines at the highest concentration used, with CDs-AgNPs showing increased activity likely due to a pro-oxidant cellular mechanism. These findings demonstrate a green and reproducible method for creating carbon-silver nanohybrids with improved stability and redox control. This hybrid structure offers a platform to reduce instability and potential side effects associated with metallic nanomaterials, supporting their advancement in therapeutic applications.