The Synthesis Of 111In. Tetraphenyl Porphyrine (TPP InCl.) And Its Use In Platelet Labelling

Abstract

The synthesis of TPP InCl was realized using a modified method of A.D. Dunn previously reported (1979).In order to optimize the labeling conditions we performed a study of different parameters: incorporation of carrier-free Indium (InCl) into tetraphenyl porphyrine (TPPH2), kinetic of insertion, different concentrations of TPPH2 and InCl.The most reproducible yield (88%) was obtained using 8.108M.TTPH2 (50μg) and 3.25 × 1010M. InCl (50μCi) heated to reflux in acetic acid (250μl) for 20 hours. The purification was performed by a chloroform extraction followed by sterilisation. This radiochemical compound was used for in vitro labeling of human platelets.A comparative study with In-oxine exhibited a higher labeling efficiency, even in 10 ml of pure plasma medium (95% for 1.6 × 1010 cells).The optimal concentration of TTP InCl for which we observed no functional alteration by in vitro tests (aggregation with ADP or collagen, hypotonic stress) was 15μg/10ml suspension.The absolute number of platelets necessary for an acceptable labeling efficiency (40%) was 5×l07 cells.TPP InCl has a good platelet labeling efficiency in pure plasma medium and appears to be an interesting tracer. However further studies (elution from labeled cells, kinetics and distribution of labeled platelets) are necessary before introducing TPP InCl as a physiological platelet label.