INTRODUCTION: diseases caused by antibiotic-resistant bacteria pose a growing global health challenge. Photodynamic Therapy (PDT), which uses light-activated photosensitizers to kill bacteria, offers a promising alternative. This study evaluates the antibacterial efficacy of gold nanoparticles synthesized from mangosteen peel extract (AuNPs-GML) combined with blue diode laser irradiation against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus), two common pathogens.MATERIALS AND METHODS: Four treatments were applied: control (no treatment), AuNPs-GML alone, blue laser irradiation alone (405 nm), and a combination of AuNPs-GML with laser irradiation. Samples were incubated at 37 °C for 24 h before bacterial viability was assessed. Statistical analysis was performed using Two-Way ANOVA and Tukey's post hoc test (p