Mechanistic approach to laser-induced oxidative stress and apoptosis in breast cancer cells using BSA-functionalized gold nanoparticles.

Photothermal therapy (PTT) using gold nanoparticles (AuNPs) offers a promising platform for targeted cancer treatment due to its minimally invasive nature and potential for spatial precision. However, achieving selective cytotoxicity while preserving healthy tissue remains a critical challenge. In this study, we developed a biocompatible photothermal platform using bovine serum albumin-functionalized gold nanoparticles (AuNPs@BSA) to selectively induce apoptosis in MDA-MB-231 breast cancer cells. The successful synthesis and surface modification of AuNPs were confirmed through UV-Vis spectroscopy, Fourier-transform infrared spectroscopy (FTIR), dynamic light scattering (DLS), and zeta potential analysis. The results of FTIR confirmed functionalization of AuNPs by BSA and zeta potential results showed that after binding BSA to gold nanospheres, the amount of surface charge decreases, which is a confirmation of the successful binding of BSA to nanospheres. Under optimized conditions (5 min laser irradiation), the AuNPs@BSA, despite a high biocompatibility (IC50 ~ 800 µg/mL), induced a profound oxidative stress. This was evidenced by a significant reduction in total antioxidant capacity and the activity of key antioxidant enzymes (SOD and CAT). This oxidative insult directly led to characteristic apoptotic events: chromatin condensation, DNA fragmentation, and ultimately, apoptotic cell death as confirmed by flow cytometry. Our results establish that laser-irradiated AuNPs@BSA induce oxidative stress, leading to membrane damage, metabolic disruption, and ultimately, caspase-dependent apoptosis in MDA-MB-231 cells. Future studies should explore its in vivo efficacy and long-term safety to advance clinical translation.