Water-Soluble Ammonium BODIPYs: Synthesis, Photophysics, Photogelation, and Antimicrobial Activity.

A family of cationic ammonium BODIPY-NMe2Et complexes were developed as water-soluble multifunctional antimicrobial photoinitiators for the generation of biocompatible hydrogels. The BODIPY compounds were characterized using 1H, 19F, and 13C{1H} nuclear magnetic resonance (NMR) spectroscopy and electrospray ionization mass spectrometry. Additionally, the majority of synthesized complexes were new and were structurally characterized using X-ray crystallography. The electronic properties of the new water soluble BODIPYs were examined using UV-vis and emission spectroscopy and density functional theory (DFT) calculations. Several water insoluble electronically tuned BODIPYs were found to photoinitiate the cross-linking of poly(vinyl alcohol)-methacrylate (PVA-MA) in mixed solvent systems (water/ethanol or water/dimethyl sulfoxide). The water-soluble cationic ammonium BODIPYC6H4NMe2Et chromophore was shown to photoinitiate the formation hydrogels with visible light from either gelatin methacrylate (Gel-MA) or PVA-MA in biocompatible conditions (water/aqueous phosphate-buffered saline(PBS)). However, the current BODIPY system is not as effective as the known [Ru(bipy)3]2+ (where bipy = 2,2'-bipyridine) gelation photocatalysts. The antibacterial properties of the cationic ammonium BODIPY compounds were examined against Gram positive (Staphylococcus aureus) and Gram negative (Escherichia coli) bacteria. Several of the more hydrophobic compounds were bactericidal and highly active against S. aureus with more modest activity against E. coli.