Antimicrobial photodynamic activity of a BODIPY on an alternative preclinical model Galleria mellonella

Antimicrobial resistance is a major global threat to public health and development. To address it, novel antibiotic therapies must be evaluated as alternatives to classical treatments. In this regard, a novel therapy with potential applications in antibacterial field is antibacterial photodynamic therapy. It exploits the combined use of a photosensitizer, visible light, and molecular oxygen that together trigger a series of reactions that result in the death of microorganisms. In recent decades, pathogenicity and screening for novel antibiotic therapies have involved the use of various invertebrate animal models including Galleria mellonella. In this work, we evaluated the antimicrobial photodynamic efficacy of a photosensitizer belonging to the BODIPY family, previously tested on various bacterial species, on G. mellonella. Firstly, the optimal parameters to be used in the antibacterial efficacy assays of BODIPY with photoactivation, such as the molecular toxicity, uptake and kinetics on Micrococcus luteus, bacterial load, and BODIPY dose for G. mellonella administration were established. The in vivo photodynamic properties of BODIPY were evaluated on larvae infected with M. luteus, then treated with the photosensitizer and irradiated with green LED light for 60 or 90 min. Results showed that treatment significantly increase larval survival rate, confirming the antimicrobial properties of BODIPY combined with photodynamic therapy, as well as validity of this insect model for preclinical antimicrobial tests.