Superhydrophobic\nDressing for Singlet Oxygen Delivery\nin Antimicrobial Photodynamic Therapy against Multidrug-Resistant\nBacterial Biofilms

The rise of antimicrobial resistance poses a critical\npublic health\nthreat worldwide. While antimicrobial photodynamic therapy (aPDT)\nhas demonstrated efficacy against multidrug-resistant (MDR) bacteria,\nits effectiveness can be limited by several factors, including the\ndelivery of the photosensitizer (PS) to the site of interest and the\ndevelopment of bacterial resistance to PS uptake. There is a need\nfor alternative methods, one of which is superhydrophobic antimicrobial\nphotodynamic therapy (SH-aPDT), which we report here. SH-aPDT is a\ntechnique that isolates the PS on a superhydrophobic (SH) membrane,\ngenerating airborne singlet oxygen (<sup>1</sup>O<sub>2</sub>) that\ncan diffuse up to 1 mm away from the membrane. In this study, we developed\na SH polydimethylsiloxane dressing coated with PS verteporfin. These\ndressings contain air channels called a plastron for supplying oxygen\nfor aPDT and are designed so that there is no direct contact of the\nPS with the tissue. Our investigation focuses on the efficacy of SH-aPDT\non biofilms formed by drug-sensitive and MDR strains of Gram-positive\n(Staphylococcus aureus and S. aureus methicillin-resistant) and Gram-negative\nbacteria (Pseudomonas aeruginosa and P. aeruginosa carbapenem-resistant). SH-aPDT reduces\nbacterial biofilms by approximately 3 log with a concomitant decrease\nin their metabolism as measured by MTT. Additionally, the treatment\ndisrupted extracellular polymeric substances, leading to a decrease\nin biomass and biofilm thickness. This innovative SH-aPDT approach\nholds great potential for combating antimicrobial resistance, offering\nan effective strategy to address the challenges posed by drug-resistant\nwound infections.