Subcellular localization, redistribution and photobleaching of sulfonated aluminum phthalocyanines in a human melanoma cell line

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Abstract
Intracellular localization, intracellular translocation and photobleaching following non‐lethal laser microirradiation of the fluorescing derivatives of sulfonated aluminum phthalocyanines (A1‐PcSn, n = 1‐4) in a human melanoma cell line (LOX) were studied by means of confocal laser scanning microxopy (LSM) and image processing. Use of confocal microscopy allowed 3‐dimensional information to be obtained. Both A1‐PcS1, and A1‐PcS2, localized diffusely in the cytoplasm of the cells, while A1‐PcS3, and A1‐PcS4, exhibited a granular pattern in the extranuclear fraction of the cells. None of the A1‐PcSn, family was observed in the nuclei of the cells except that a small fraction of fluorescence was occasionally detected in nuclei of some cells treated with A1‐PcS1, and A1‐PcS2. Furthermore, exactly the same granular localization patterns and positions in the same cells were found after incubation initially with A1‐PcS3, (or A1‐PcS4,) followed by acridine orange (AO) which emits red fluorescence from lysosomes of cells. Thus, the granular fluorescence of A1‐PcS3, and A1‐PcS4, is confined to the lysosomes of the LOX cells. Non‐lethal laser exposure of cells incubated with high concentrations of the 2 dyes resulted in a translocation of the dyes from the lysosomes to the whole cytoplasm and an increase in total intracellular fluorescence intensity. Finally, a small fraction of the dyes localized into the nuclei of the cells. The laser exposure of cells incubated with low concentrations of the lysosomally localized dyes resulted in an increase in the intracellular fluorescence intensity with no translocation of the dyes. Under all conditions, high laser exposure resulted in a decrease in the total intracellular fluorescence intensity.