Estrone Linked BODIPYs: Assessing Their Role as Sonosensitizers for Antimicrobial Applications

Sonodynamic therapy (SDT) is a promising modality for anticancer and antimicrobial applications for deep seated wounds and infections. The boron-dipyrromethene based photosensitizers can be activated by ultrasound (US) for therapeutic applications of SDT. The estrone linked BODIPY were synthesized and characterized. The linker between estrone unit and boron-dipyrrin unit was varied from phenyl to thiophene rings. Estrone substituted BODIPYs exhibited noticeable red shifts (12-36 nm) in the absorption and emission maxima as compared to the meso-phenyl BODIPY (standard reference BODIPY), with relatively larger Stokes shifts (719-2095 cm^-1). TD-DFT calculation indicated significant intramolecular charge transfer from estrone linker unit to the boron dipyrrin unit. This study demonstrates the feasibility of using estrone linked BODIPYs sonosensitizers for antimicrobial sonodynamic therapy (SDT). Among them, EBD-1 exhibited the highest singlet oxygen quantum yield (∼90%) and demonstrated potent antibacterial activity, achieving ≥ 3 log₁₀ reduction (≥ 99.9%) in Escherichia coli (E. coli) viability under microbubble assisted sonodynamic therapy.