Extracorporeal medical machines such as the pump oxygenator and artificial kidney rely on systemic heparinization to improve blood compatibility. However, heparin can lead to serious complications such as bleeding. The applicants propose a new method to control heparin levels using a blood filter containing immobilized heparinase. Such a filter might be used in situations where it is desired to heparinize the extracorporeal circuit without simultaneous heparinization of the patient. Alternatively, it could eliminate the use of neutralizing compounds such as protamine. Their research has focused not only on the development and testing of the filter, but on heparinase production and purification as well. The specific aims of the current proposal are: (1) to employ genetic engineering to produce high levels of heparinase, (2) to improve reactor design, (3) to develop comprehensive in vivo models to predict reactor performance, and (4) to conduct in vivo studies using hemodialysis and cardiovascular models in animals, to assess the safety and efficacy of the proposed approach.