Photophysical Properties and Aggregation Behavior of Diethylene Glycol Substituted Pyropheophorbide-a in Cationic Surfactant Solutions

The aggregation behavior of a novel amphiphilic photosensitizer - pyropheophorbide-[Formula: see text] 17-diethylene glycol ester 1 was studied in aqueous and aqueous-organic mixtures by means of steady-state absorption and fluorescence emission spectroscopy. The formation of [Formula: see text]-aggregates with a bathochromic shift of the absorption bands, weak fluorescence and resonance enhancement of the light scattering was observed in the mixed water-organic solvents. Solubilization studies in micellar cationic surfactant solutions of alkyl trimethylammonium bromides (C[Formula: see text]TAB) and alkyl triphenylphosphonium bromides (C[Formula: see text]TPPB) resulted in the most effective stabilization of the fluorescent monomolecular form of 1 in C[Formula: see text]TPPB micelles. It was shown that [Formula: see text]-aggregate formation in submicellar surfactant solutions is the initial stage of the solubilization process, which significantly increases in phosphate buffer medium at pH 7.4. Fluorescence lifetime ([Formula: see text] of 1 in DMSO was found to be 7.4 ns, fluorescence quantum yield - 34% and singlet oxygen quantum yield - 62%. The results obtained indicate the need for further studies of compound 1 solubilized in C[Formula: see text]TPPB micelles as the most promising prototype of the drug formulation for mitochondria-targeted photodynamic therapy of cancer.