BINDING OF MONOMERIC AND OLIGOMERIC PORPHYRINS TO HUMAN GLIOBLASTOMA (U-87MG) CELLS AND THEIR PHOTOSENSITIVITY

The binding of monomeric (Hp) and oligomeric (PI-IE) forms of porphyri n to glioblastoma (U-87MG) cells and the photosensitization of these c ells have been studied. Upon binding to U-87MG cells, Hp and PHE exhib ited fluorescence bands at 615 and 636 nm, respectively. The fluoresce nce and absorption spectra of Hp, HpD and PHE, measured in different s olvents, suggest that the 615 nm band may arise due to the binding of monomeric as well as aggregated forms of porphyrin to the hydrophilic sites in the cells whereas the 636 nm band may be due to the binding o f an aggregated form of porphyrin to the hydrophobic sites. The photos ensitivity of cells and photo-induced lipid peroxidation were measured as a function of light dose. Cells were found most photosensitive to PHE followed by HpD and Hp. The photosensitivity of cells correlates w ell with the fluorescence intensity of cell bound dye at 636 nm. These results suggest that the binding of the oligomeric component of HpD t o hydrophobic sites in the cells is responsible for the enhancement in the photosensitivity. (C) 1997 Elsevier Science Ireland Ltd.