Stress-induced neoplasia detection in the lower part of gastrointestinal tract of rats using phthalocyanines

Abstract

In this study, phthalocyanine (ZnPc, AlPc, LuPc – Pcs) compounds were employed as exogenous fluorescent markers for diagnostics of GIT adenocarcinoma in laboratorial animals (adult male rats, n = 40) after application of an experimental model of adenocarcinoma formation with metastases. The neoplastic lesions were developed under the influence of social stress and chemical stress using nitrosamines during a 9-month period of application. A significant fluorescence signal in the region of 670 – 720 nm was observed from the neoplastic lesions, which was absent in the normal mucosa. This signal is related to the fluorescence of phthalocyanines accumulated in the tumor area. The autofluorescence background covered the region of 450 – 650 nm with a maximum at 480 – 520 nm and originated mainly from protein cross-links and co-enzymes – NADH and flavins. Endogenous porphyrins fluorescence was also observed in the lesions with a maximum at 630 – 640 nm. Visually, the presence of accumulation sites of Pcs in the form of bright pink patches was observed after excitation at 405 nm, as opposed to a healthy tissue, which remained blue-violet due to the autofluorescence signal. This allows one to use the Pcs fluorescence discrimination not only in a spectroscopic mode of detection, but for imaging of the lesions investigated, which is preferable in clinical applications during endoscopic observations in humans.