Enhancement of photodynamic inactivation of planktonic cultures of Staphylococcus aureus by DMMB-AuNPs.

ABSTRACT

Photodynamic inactivation is a promising method for the treatment of infectious diseases. Nanotechnology through gold nanoparticles, as a tool to improve the delivery of photosensitizer is an attractive approach to enhance photodynamic inactivation of bacteria. Moreover, gold nanoparticles enchance the absorption of light due to their plasmon resonance. The aim of this study was to evaluate in vitro photodynamic inactivation effects of 1.9-Dimethyl-Methylene Blue (DMMB)-AuNPs associated with the red LED (λ630 ηm ± 20 ηm, 125 mW, 12 J / cm², 192 s) on S. aureus strain. Eight experimental groups were studied Control, LED, AuNPs, AuNPs + LED, DMMB, DMMB + LED, DMMB + AuNPs, DMMB + AuNPs + LED. After incubation, the number of bacteria surviving each treatment was determined and then enumerated by viable counting (CFU / mL). The logarithm of CFU / mL (CFU/mL log10) was calculated. All experiments realized in triplicate. The statistical analyses included one-way ANOVA tests, Tukey's multiple comparisons and nonlinear regression, p values <0.05 were considered statistically significant. According to results, the photodynamic inactivation of S. aureus on groups DMMB + LED and DMMB-AuNPs + LED, showed a significant reduction of the microbial load (p < 0.0001) when compared to the Control group. The decimal reduction (RD) of these groups were 99.96 % (RD = 3) and 99.994 % (RD = 4) respectively. In conclusion, these findings demonstrated that photodynamic inactivation is enhanced by using DMMB-AuNPs on S. aureus.