Quantitative fluorescence microscopy of photosensitisers: aluminium sulphonated phthalocyanine (AlSPc)

A quantitative technique based on fluorescence microscopic detection has been developed for measurements of AlSPc distributions in frozen sections of tissue and cultured cells. Imaging for AlSPc fluorescence was achieved with negligible interference from AlSPc photodegradation and tissue autofluorescence using laser excitation (at 633 nm) and detection with a highly sensitive CCD (charge-coupled device) camera system. Once the image is recorded the tissue section is stained for confirmation of histology. This has enabled pharmacokinetic studies of AlSPc distributions at the microscopic level: for example, in the case of rat bladder the authors have shown that uptake in the mucosa relative to the muscle layer is highest at 24 hours. Since the level of fluorescence should correlate with the AlSPc photoactivity these results are important in determining the optimal treatment time