Potentiation of photodynamic inactivation of staphylococcus aureus using inorganic salts

Antibiotics are used in the prevention and treatment of bacterial infections. However, unnecessary, misuse or overuse of antibiotics may cause drug-resistant bacteria, which pose a significant threat to human health. Photodynamic therapy (PDT) is researched as a bacterial infection treatment modality. In PDT, photosensitive molecules (photosensitizer, PS) are excited by light to create reactive oxygen species. PDT has advantages over antibiotics, including selectivity and low risk of resistance. PDT can also treat infections, including localized bacterial infections and viral infections. Besides the advantages, some situations limit the effectiveness of PDT. For example, the wavelength of the applied light that is used to excite the PS molecules may not penetrate deep tissues effectively, which makes it hard to treat deeper or internal infections. Another limitation of aPDT is that the effectiveness of aPDT may vary depending on the specific bacterium and the photosensitizing agent used. Therefore, strategies to increase the efficacy of antimicrobial photodynamic inactivation protocols are researched for the increased application of this method in clinics. A widely researched strategy for improving PDT efficacy is using drug delivery systems to increase the solubility and accumulation of PSs in the tumor tissue. Active targeting strategies using monoclonal antibodies are also researched to increase the selectivity of the treatment method. Another strategy shown to increase the aPDT efficacy is to use inorganic salts as potentiators. Building on the literature, this study aimed to increase the efficacy of aminolevulinic acid (ALA)- and chlorin e6 (Ce6)-mediated aPDT using potassium iodide (KI) and potassium chloride (KCl). Although the efficacy of ALA-mediated PDT did not increase with the studied concentrations of the inorganic salts, this study showed for the first time that Ce6-mediated PDT can be potentiated using KCl.