QUANTIFICATION OF THE INFLAMMATORY RESPONSE IN EXUDATES TO 3 POLYMERSIMPLANTED IN-VIVO

Flow cytometry was used to quantify an inflammatory reaction in vivo a s a new approach to evaluating the biocompatibility of biomaterials. T he exudate formed inside cylindrical tubes composed of polyvinyl chlor ide (PVC), silicone elastomer (SIL), or polyurethane (PU) implanted su bcutaneously in the dorsal region of rats was collected over a S-week period. The volume, number of cells, and concentration of fibrinogen w ere determined in the exudate for the three biomaterials. The exudate was analyzed using a flow cytometry technique after labeling of the le ukocytes with a monoclonal anti-CD45 antibody. Fibrinogen rose progres sively over the 3-week period for the three polymers. After the differ ent leukocyte lines were identified in rat blood samples, their determ ination in the exudate revealed differences among the three biomateria ls. At day 2, PVC induced a predominantly neutrophilic inflammatory re action whereas PU and SIL gave a mixture of monocytes and neutrophils. At day 9, the aspect of the cytograms was different, but the identifi cation of the subpopulations was still possible. At day 23, the number of cell events became too low to distinguish the subpopulations. An e ven more detailed approach might be possible using specific labeling f or each leukocyte line to establish a comparison among the three bioma terials. Flow cytometry associated with histomorphometric assessment m ight provide a precise quantitative in vivo test for determining the b iocompatibility of materials. (C) 1998 John Wiley & Sons, Inc.