ACTIVITY OF ENZYME IMMOBILIZED ON SILANIZED CO-CR-MO

The surface of an orthopedic biomaterial was modified by the covalent immobilization of biomolecules. Derivatization of Co-Cr-Mo samples wit h organic and aqueous solutions of gamma-aminopropyltriethoxysilane (A PS) resulted in a concentration-dependent number of reactive NH2 group s on the surface available for coupling to protein. The enzyme trypsin was used as a model biomolecule to investigate the effect of immobili zation on proteolytic activity. Trypsin was coupled to the silanized s amples by formation of Schiffs base linkages via glutaraldehyde. The n ature of the interaction between trypsin and biomaterial was then prob ed by treatment with concentrated guanidine hydrochloride (GuHC1) and urea. Residual activity (following treatment with chaotropic agents) o f trypsin immobilized on silanized Co-Cr-Mo was dependent both on the nature of the silane solution and on the type of chaotropic agent. Org anic silanization with APS required a minimum density of approximately 49 NH2 per nm(2) of nominal surface area (> 0.021 M APS) for residual activity of immobilized trypsin. For aqueous silanization, approximat ely 5.4 NH2/nm(2) (0.51 M APS) resulted in maximal residual trypsin ac tivity. Treatment with GuHCI removed more trypsin activity from Co-Cr- Mo samples silanized with organic solutions of APS than did treatment with urea. On the contrary, with aqueous silanization the samples poss essed greater residual activity following treatment with GuHCI than fo llowing urea. Compared to simple adsorption with protein onto Co-Cr-Mo , both methods of silanization with APS resulted in superior residual immobilized enzyme activity. (C) 1995 John Wiley and Sons, Inc.