Hematoporphyrin derivative binding and photosensitization in human glioblastoma cells: comparison of exponential and plateau phase cells.

Plateau phase glioblastoma (U 87MG) cells were found more photosensitive than the exponentially growing cells. In both phases of growth, the photosensitivity showed further enhancement on incubating the cells with HpD for longer duration. Plateau phase cells accumulated more HpD than exponential phase cells for shorter duration of incubation with HpD, however, for longer duration of incubation, the amount of drug uptake was almost the same in both phases of growth. Fluorescence spectra of cell bound HpD showed a difference in spectral intensity distribution in exponential and plateau phase cells. In exponential phase cells, the fluorescence maximum of cell bound HpD was at 615 nm whereas in plateau phase cells the same was at 636 nm.