Screening of biomedical polymer biocompatibility in NMRI-mice peritoneal cavity: a comparison between ultra-high-molecular-weight polyethylene (UHMW-PE) and polyethyleneterephthalate (PET).

The peritoneal resident cell population is influenced by various inflammatory and immunogenic stimuli. The influence of intraperitoneal application of polyethyleneterephthalate (PET) (group A) and ultra-high-molecular-weight polyethylene (UHMW-PE) (group B) powders on peritoneal cell count and macrophage activity was investigated. Powders were tested to mimic wear particles from solid implant devices as these particles often cause chronic granulomatous inflammation. The results were compared with the inflammatory response following an abdominal midline incision (group C) and untreated animals (group D). On days 1, 7, 14 and 30 peritoneal cells were quantified and the number of active macrophages was assessed. Groups A and C mice showed a significant loss of macrophages in the peritoneal lavage at day 1 but this returned to normal values (group D) on day 7. In contrast, group B animals remained at low peritoneal cell counts but showed the highest number of active macrophages. Only in this latter group was adhesion formation and granulomatous clustering of polymer powder observed. Applying the parameters macrophage count and the number of active macrophages it can be concluded that PET elicits a weaker inflammatory reaction than UHMW-PE in mice peritoneal cavity. Thus this animal model may be used as a screening test for biomedical materials, especially their wear products.