Nanoparticle-Mediated Photodynamic Therapy for Mixed Biofilms

Wounds associated with diabetes are difficult to heal and often stay unhealed, leading to higher morbidity and mortality in the diabetic population. A major barrier to the successful healing of chronic diabetic wounds is the presence of biofilm-mediated infections. In recent years, photodynamic therapy (PDT) has emerged as a promising treatment modality for the management of chronic wounds. The objective of the present study was to evaluate the effectiveness of toluidine blue- (TB-) loaded nanoparticle-mediated PDT in eradicating antibiotic-resistant polymicrobial biofilms of Pseudomonas aeruginosa and methicillin-resistant Staphylococcus aureus in an in vitro model. Dioctyl sodium sulfosuccinate (aerosol OT, AOT)-alginate nanoparticles with high TB loading (10.8 ± 2.2 %) were formulated using a double emulsification cross-linking method. TB nanoparticles induced effective killing of planktonic P. aeruginosa (3.5 log₁₀ CFU) and S. aureus (>5 log₁₀ CFU) and their combined biofilms (2.8 log₁₀ CFU for P. aeruginosa versus 3.4 log₁₀ CFU for S. aureus). While P. aeruginosa biofilm was more resistant when compared to that of S. aureus, our results demonstrated effective eradication of complex biofilms of dual bacterial strains in vitro.