Potential of Diiodo-BODIPY Meso-Acid and Its Esters for Photodynamic Therapy of Microbial Biofilms

Background. Nowadays, there is an increasing number of infectious diseases in humans and animals associated with formation of microbial biofilms, including fungal-bacterial consortia. Due to the diffusional barrier of the biofilm matrix, the biofilm-embedded cells are characterized by increased resistance to antimicrobials and the host immune system. In this study we assessed the ability of diiod derivatives of BODIPY luminophores to eradicate mono- and dual species communities of S. aureus and C. albicans. Results. The diiodo-BODIPY meso-butanoic acid, and its conjugate with isobornanethioethyl or pinanyl, were tested. The diiod derivative of BODIPY in the form of acid, when irradiated at 530 nm at concentrations of 2 μg/ml, resulted in complete cell death of planktonic staphylococci, and at 16 μg/ml completely eradicated its biofilm, but was non effective against Candida biofilms. Partial cell death was observed against S. aureus in mixed S. aureus and C. albicans biofilms at 8 μg/ml. The compound was able to penetrate biofilms as resolved by CLSM, but moderate antimicrobial activity was observed. Conclusion. The diiod-BODIPY acid of BODIPY luminophores are of interest for photodynamic therapy of staphylococcal biofilms. Their conjugation with terpenoids increases the rate of biofilm penetration, but the selection of a terpene radical is necessary to enhance antimicrobial activity.