An in vitro bovine pericardial hemocompatibility testing system

Bovine pericardium has been used as a biomaterial for heart valves since the late 1960s. Cross-linking agents have been applied routinely to reduce host-tissue response, including antigenicity, and to improve tissue leaflet durability. Evaluation of improvements in bovine pericardial valve leaflet calcification and flexibility require that in vitro systems be developed to correlate data with results from in vivo studies. This study describes an in vitro test system used to evaluate the effects of two surface-modifying treatments on pericardial tissue hemocompatibility.

Non-fixed and glutaraldehyde fixation-processed (GA) bovine pericardial tissues were exposed to anticoagulated whole blood for 60 min. Blood was then removed, and platelet-poor plasma prepared and frozen at -70 degrees C until analyzed for kallikrein activation and release of platelet factor 4 (PF4). Blood-exposed tissue samples were analyzed for fibrin (ogen) binding with an anti-fibrinogen antibody and for tissue cellular responsiveness (blood cell adherence and aggregation) by scanning electron microscopy.

Conditions were determined for minimum extent of pumping action by the minicam system required to allow for solution movement while not tearing or wearing the tissue. A blood-tissue exposure time of 60 min provided sufficient first-pass exposure to evaluate the acute blood-tissue response. The relative degree of both kallikrein activation and PF4 release was greater in the non-fixed tissue but a greater number of fibrin(ogen) molecules per cm2 was found on GA-treated tissue. Scanning electron microscopy showed a differential cell response of non-fixed tissue compared with GA-treated tissue.

This non-static test system demonstrated great promise for use in routine in vitro hemocompatibility testing of blood-contacting biological biomaterials.