(a). Cellular uptake of phthalocyanine as a function of time and concentration. Uptake of AlPcS2 in exponentially growing glioma (BMG-1) cells as a function of incubation time at 37°C in HBSS containing the photosensitizer (1 μM) as determined by fluorescence image analysis (40-50 cells were examined from 2 experiments). The intensity of the background was subtracted from the values obtained for each cell from the same image. (b) Cellular uptake of AlPcS2 after incubation (2 h) of BMG-1 cells at different concentrations of AlPcS2 in HBSS. Measurements of absorbance and fluorescence were made in cell suspensions (n = 2).