INITIAL HEMOCOMPATIBILITY STUDIES OF TITANIUM AND ZIRCONIUM ALLOYS - PREKALLIKREIN ACTIVATION, FIBRINOGEN ADSORPTION, AND THEIR CORRELATIONWITH SURFACE ELECTROCHEMICAL PROPERTIES

Two novel metal alloys, Ti-13Nb-13Zr and Zr-2.5Nb, have been engineere d for applications in orthopedic implants because of their favorable m echanical properties, corrosion resistance, and compatibility with bon e and tissue. These alloys also have the ability to form a hard, abras ion-resistant, ceramic surface layer upon oxidative heat treatment (di ffusion hardening, DH). Previous studies have indicated that these and other ceramics cause limited hemolysis and exhibit remarkable structu ral integrity after extended exposure to physiological environments. S uch observations suggest that DH Ti-13Nb-13Zr and ZrO2/Zr-2.5Nb could be used successfully as components in blood-contacting devices. Materi als intended for such applications must possess properties that do not elicit adverse physiological responses,such as the initiation of the coagulation cascade or thrombus formation. In the present study measur ements of prekallikrein activation, fibrinogen adsorption from diluted human plasma, and the strength of fibrinogen attachment as judged by residence-time experiments were performed to evaluate the potential he mocompatibility of these materials. The results of the prekallikrein a ctivation and fibrinogen-retention studies correlated well with two el ectrochemical properties of the alloys, the open circuit potential and reciprocal polarization resistance. The results indicate that both th e original and treated Ti and Zr alloys activate prekallikrein and ads orb as well as retain fibrinogen in amounts similar to other materials used as components of blood-contacting devices. On the basis of these studies, these alloys appear to be promising candidates for cardiovas cular applications and merit further investigation. (C) 1996 John Wile y & Sons, Inc.