A novel potential application for Tc-99m-HMPAO: Endothelial cell labeling for in vitro investigation of cell-biomaterial interactions

Good adherence of endothelial cells (ECs) seeded on vascular prostheses and cell retention under flow conditions are important factors to consider in the use of functionalized prostheses in vascular surgery. Because (111)ln-o xine radiolabeling presents disadvantages, we wondered whether, because of its well-known physical properties, Tc-99m-hexamethyl propyleneamine oxime (HMPAO or exametazime) could be used. Methods: The cytotoxicity of unlabele d HMPAO and Tc-99m-HMPAO at increasing concentrations and activities was te sted on monolayers of the EC line EA-hy-926. The influence of temperature a nd time on tracer incorporation into cells was also tested. The optimal lab eling conditions were applied to evaluate the retention of ECs seeded on po lyester grafts under flow conditions by gamma camera detection. Results: Th e activity of 10 MBq/10(6) cells corresponding to 4.5 mu g/10(6) cells of u nlabeled HMPAO, applied for 3 h at 37 degrees C (cellular uptake = 18%), wa s the best compromise between the maintenance of cell viability and metabol ic activity and efficient detection by the gamma camera. Spontaneous leakag e was observed and analyzed by high-performance liquid chromatography. A ce ll loss of 13% after 180-min exposure to shear stress was obtained. Conclus ion: Our data thus indicate the feasibility of using such a radiolabeling t echnique to investigate EC-biomaterial interactions.