Fluorescence methods for detecting the kinetics of photosensitizer release from nanosized carriers

Three approaches to analyzing the rate of release of the photosensitizer meta-tetrahydroxyphenylchlorin (mTHPC) from unilaminar lipid vesicles (ULV) in model biological systems are studied: by excitation energy transfer from probe diphenylhexatriene to mTHPC, by the fluorescence anisotropy of mTHPC, and by photoinduced quenching of the fluorescence of mTHPC. Each of these methods has its characteristic range of sensitivity for measurements of the local concentration of mTHPC in ULV. Fluorescence anisotropy can be used for quantitative determination of the mTHPC yield from ULV for mTHPC:lipid ratios of 1:100 to 1:1000, determining the efficiency of fluorescence quenching of diphenylhexatriene for ratios <1:200, and photoinduced quenching for ratios of 1:10–1:500.