STRUCTURAL ALTERATIONS INDUCED BY PHOTODYNAMIC-ACTION OF HEMATOPORPHYRIN DERIVATIVE (HPD) IN PLASMA-MEMBRANE OF GLIOBLASTOMA (U-87MG) CELLS- TIME-DEPENDENT FLUORESCENCE SPECTROSCOPIC STUDY

Photodynamic action of hematoporphyrin derivative (HpD) on the plasma membrane of human glioblastoma U-87MG cells was investigated using lip id and protein specific fluorescent probes trimethylammonium-1,6-diphe nyl 1,3,5-hexatriene (TMA-DPH) and N-(1-pyrene)-maleimide (PM) respect ively. Steady state anisotropy, decay time and time dependent anisotro py of these probes in U-87MG cells were measured. Light irradiation ca used an increase in the steady state anisotropy of TMA-DPH in cells tr eated with HpD; however, no change in decay time was observed. Time de pendent anisotropy measurements were performed and the data were analy zed using wobbling in cone model. A decrease in the rotational relaxat ion time (phi) as well as the cone angle (theta(c)) and an increase in the order parameter (S) of TMA-DPH were observed on photosensitizatio n of cells. A decrease in the steady state anisotropy and the rotation al relaxation time (phi) of PM and enhancement in the lipid peroxidati on were also observed. Our results show that the photodynamic action o f HpD increases the order in the lipid bilayer and the mobility of the proteins in the plasma membrane of cells.