Metal center ion effects on photoinactivating rapidly growing mycobacteria using water-soluble tetra-cationic porphyrins.

Rapidly growing mycobacteria (RGM) are pathogens that belong to the mycobacteriaceae family and responsible for causing mycobacterioses, which are infections of opportunistic nature and with increasing incidence rates in the world population. This work evaluated the use of six water-soluble cationic porphyrins as photosensitizers for the antimicrobial photodynamic therapy (aPDT) of four RGM strains: Mycolicibacterium fortuitum, Mycolicibacterium smeagmatis, Mycobacteroides abscessus subs. Abscessus, and Mycobacteroides abscessus subsp. massiliense. Experiments were conducted with an adequate concentration of photosensitizer under white-light irradiation conditions over 90 min and the results showed that porphyrins 1 and 2 (M = 2H or Zn ion) were the most effective and significantly reduced the concentration of viable mycobacteria. The present work shows the result is dependent on the metal-center ion coordinated in the cationic porphyrin core. Moreover, we showed by atomic force microscopy (AFM) the possible membrane photodamage caused by reactive oxygen species and analyzed the morphology and adhesive force properties. Tetra-positively charged and water-soluble metalloporphyrins may be promising antimycobacterial aPDT agents with potential applications in medical clinical cases and bioremediation.