Superhydrophobic Dressing for Singlet Oxygen Delivery in Antimicrobial Photodynamic Therapy against
Fernanda V Cabral1, QianFeng Xu2, Alexander Greer2,3,4
1Wellman Center for Photomedicine, Massachusetts General Hospital and Harvard Medical School, 40 Blossom Street, Boston, Massachusetts 02114, United States.
Abstract:
The rise of antimicrobial resistance poses a critical public health threat worldwide. While antimicrobial photodynamic therapy (aPDT) has demonstrated efficacy against multidrug-resistant (MDR) bacteria, its effectiveness can be limited by several factors, including the delivery of the photosensitizer (PS) to the site of interest and the development of bacterial resistance to PS uptake. There is a need for alternative methods, one of which is superhydrophobic antimicrobial photodynamic therapy (SH-aPDT), which we report here. SH-aPDT is a technique that isolates the PS on a superhydrophobic (SH) membrane, generating airborne singlet oxygen (1O2) that can diffuse up to 1 mm away from the membrane. In this study, we developed a SH polydimethylsiloxane dressing coated with PS verteporfin. These dressings contain air channels called a plastron for supplying oxygen for aPDT and are designed so that there is no direct contact of the PS with the tissue. Our investigation focuses on the efficacy of SH-aPDT on biofilms formed by drug-sensitive and MDR strains of Gram-positive (Staphylococcus aureus and S. aureus methicillin-resistant) and Gram-negative bacteria (Pseudomonas aeruginosa and P. aeruginosa carbapenem-resistant). SH-aPDT reduces bacterial biofilms by approximately 3 log with a concomitant decrease in their metabolism as measured by MTT. Additionally, the treatment disrupted extracellular polymeric substances, leading to a decrease in biomass and biofilm thickness. This innovative SH-aPDT approach holds great potential for combating antimicrobial resistance, offering an effective strategy to address the challenges posed by drug-resistant wound infections.
Insights
Superhydrophobic antimicrobial photodynamic therapy (SH-aPDT) effectively eradicates bacterial biofilms, including drug-resistant strains. This novel approach uses a photosensitizer on a superhydrophobic membrane to generate airborne singlet oxygen, offering a promising solution for antimicrobial resistance.
Area of Science:
- Biomedical Engineering
- Photochemistry
- Microbiology
Background:
- Antimicrobial resistance (AMR) is a global health crisis.
- Antimicrobial photodynamic therapy (aPDT) shows promise against multidrug-resistant (MDR) bacteria but faces challenges in photosensitizer delivery and bacterial resistance.
- Existing methods require improvement for effective AMR treatment.
Purpose of the Study:
- To develop and evaluate a novel superhydrophobic antimicrobial photodynamic therapy (SH-aPDT) method.
- To assess the efficacy of SH-aPDT against bacterial biofilms, including drug-sensitive and MDR strains.
- To investigate the mechanism of SH-aPDT in disrupting biofilms and reducing bacterial viability.
Main Methods:
- Development of a superhydrophobic polydimethylsiloxane dressing incorporating the photosensitizer verteporfin.
- Design of dressings with air channels (plastron) for oxygen supply, ensuring no direct tissue contact.
- Testing SH-aPDT efficacy on biofilms of *Staphylococcus aureus* (including MRSA) and *Pseudomonas aeruginosa* (including carbapenem-resistant strains).
Main Results:
- SH-aPDT achieved approximately a 3-log reduction in bacterial biofilms.
- Treatment led to a significant decrease in bacterial metabolism, as measured by MTT assays.
- Extracellular polymeric substances were disrupted, reducing biofilm biomass and thickness.
Conclusions:
- SH-aPDT is a highly effective strategy for combating bacterial biofilms, including those formed by MDR pathogens.
- The technique's ability to generate airborne singlet oxygen and avoid direct tissue contact offers advantages over conventional aPDT.
- This innovative approach presents a promising new avenue for addressing the critical challenge of antimicrobial resistance in wound infections.
