Aluminum phthalocyanines with asymmetrical lower sulfonation and with symmetrical higher sulfonation: A comparison of localizing and photosensitizing mechanism in human tumor LOX xenografts

A comparison of time‐dependent localization patterns between lower, asymmetrical (AIPCS 2a ) and higher, symmetrical (AIPCS 4 ) sulfonates of aluminum phthalocyanines in human malignant melanoma LOX transplanted to athymic nude mice from 1 to 120 hr after i. v. administration was made by means of laser scanning fluorescence microscopy. The lipophilic AIPCS 2a was distributed mainly in tumor cells, while the hydrophilic AIPCS 4 , localized only in the vascular stroma of the tumor tissue. Concomitantly, comparative observations on the killing mechanism of photodynamic effects after treatment with a much lower i. v. dose of AIPCS 2a and AIPCS 4 plus laser light on the human tumor LOX were also made by morphological studies. Light and electron microscopy showed that there was a direct, extensive, photo‐damaging action on all organelles and nuclear structure in the tumor cells after PDT with AIPCS 2a ; whereas the photo‐induced injury to the tumor tissue after treatment with AIPCS 4 and light was largely the consequence of initial functional vasogenic response and ultimate damage to vascular structure. These findings correlate well with the different localization patterns of the 2 dyes observed in human tumor tissues.