In vitro and in vivo spectrofluorometry of a water-soluble meta-(tetrahydroxyphenyl)chlorin (m-THPC) derivative

The pharmacokinetics of a water-soluble derivative obtained from meta-(tetrahydroxyphenyl) chlorin (m-THPC) was evaluated in in vitro and in vivo studies, Cytoplasm fluorescence was measured in two cell models (L1210 and HT29) using a flow cytometer and a confocal microspectrofluorometer. Cells were incubated with the compound at several doses (0-150 mu g ml(-1) for flow cytometry) and for several time periods (0-6 h for microspectrofluorometry). For in vivo studies, nude mice were grafted with human adenocarcinoma 15 days before intraperitoneal injection of polyethylene glycol-m-THPC (PEG-m-THPC). Fluorescence was recorded through an optical fibre spectrofluorometer using the 660 nm peak for detection. In in vitro studies, the fluorescence was found to be proportional to the dose. Maximum fluorescence was recorded in L1210 cells earlier and more intensely than in HT29 cells (3 h at 202 +/- 14 counts s(-1) and 5 h at 43 +/- 2.15 counts s(-1) respectively). Concerning in vivo studies, maximum tumour fluorescence was observed 24 h after injection (3568 +/- 178 counts s(-1)). Selectivity was expressed by the calculated tumour-to-skin and tumour-to-muscle ratios. The time taken to observe the maximum ratios (2.95 +/- 0.16 for tumour-to-skin and 6.61 +/- 0.3 for tumour-to-muscle) was almost the same as the time taken to observe the maximum fluorescence in the tumour. Studies are in progress to correlate these results with photodynamic effects. (C) 1997 Elsevier Science S.A.