Antimicrobial photodynamic therapy using gold nanoparticles conjugated with 1,9-dimethyl-methylene blue for treating...

This study aims to assess the effectiveness of Antimicrobial Photodynamic Therapy (aPDT) using phenothiazine photosensitizer (PS) combined with gold nanoparticles (DMMB-AuNPs) in treating S. aureus-contaminated wounds on the dorsum of rats. Twelve Wistar rats were divided into four groups: Control, LED, DMMB-AuNPs, and DMMB-AuNPs + LED. DMMB-AuNPs were prepared using DMMB (300 ng/mL) and 5 nm diameter AuNPs (~ 5.5E + 13 particles/mL). The light source was a red LED (12 J/cm², λ630 ± 20 nm, CW, 125 mW, 192s). Following the procedures, samples were plated on an agar medium specific to S. aureus to count the colony-forming units (CFU/mL). Statistical analysis using unidirectional ANOVA and Tukey's test revealed that the aPDT group (DMMB-AuNPs + LED) exhibited a 99.999% (5 log reduction) microbial reduction with a significant statistical difference (p < 0.0001) compared to the Control group, demonstrating a bactericidal effect. The in vivo findings unequivocally demonstrate the effectiveness of DMMB-AuNPs-mediated aPDT as an alternative therapy for staphylococcal infections.