Avaliação do uso de nano carreadores de ramnolipídeos associados ao fotossensibilizador azul de Taylor na terapia fotodinâmica antimicrobiana contra Staphylococcus aureus: estudo in vitro

Abstract

The increase in bacterial resistance to antibiotics has driven the search for alternative therapies, such as Antimicrobial Photodynamic Therapy (PDT). With the advancement of science, nanotechnology techniques are increasingly present, promoting the enhancement of existing techniques. This study evaluated, in vitro, the efficacy of PDT coupled with carrier nanotechnology against Staphylococcus aureus (ATCC 25923) in planktonic cultures, using the photosensitizer 1,9-dimethylmethylene blue (DMMB, λ ≈ 656 nm) and rhamnolipid nanocarriers (RL-NPs) produced by Pseudomonas aeruginosa. Seven experimental groups were established: Control (no treatment); LED (irradiation only, 20 J/cm²); DMMB (300 ng/mL); RL-NPs (300 ng/mL); RL-NPs/DMMB (300 ng/mL); PDT (DMMB + LED); and PDT+RL-NPs/DMMB (nanocarrier + LED). Photodynamic activation was performed with a prototype red LED (λ = 630 nm, power of 45.2 mW/cm²). Statistical analysis (one-way ANOVA with Tukey's post-hoc test) demonstrated that PDT promoted a significant reduction of ~2 logs (99.1%, p<0.0001) in bacterial viability. Notably, the group containing PDT+RL-NPs/DMMB nanotechnology showed a marked reduction of ~3 logs (99.9%, p<0.0001), significantly exceeding the standard PDT. The results indicate that the encapsulation of DMMB in rhamnolipid nanostructures enhances the antimicrobial efficacy of PDT. The characterizations performed on the nanocarrier elucidated in more detail the nature of the particles formed, including size, surface charge, and shape, which contributed to the enhanced effect, thus representing a promising strategy for the development of innovative clinical protocols against bacterial infections.