The stability of methacrylate biomaterials when enzyme challenged: Kineticand systematic evaluations

This study addressed whether methacrylate monomers and polymers used in den tistry might degrade from enzymolysis by acetylcholinesterase (ACHE), chole sterol esterase (CHE), porcine liver esterase (PRLE), and a pancreatic lipa se (PNL). Short (hour) and long-term (day) exposures were performed. Produc t ratios were used to determine surface hydrolysis of the polymeric materia ls. Enzyme kinetics were studied for the monomers when challenged by ACHE, CHE, and PRLE. In the case of PRLE, the V-max for the dimethacrylate substr ates varied slightly, but amounted to as much as 10% of that of p-nitrophen ylacetate. The K-m for triethylene glycol dimethacrylate (TEGDMA) was 197 m uM for ACHE and 1107 muM for CHE. The V-max was 2.7 nmol/min for ACHE and 3 .5 nmol/min for CHE. TEGDMA was converted by CHE at 2% the rate of choleste ryl oleate. Long-term incubations of monomers with CHE and ACHE produced de grees of hydrolysis that evidenced structure dependency in the ability of t he enzymes to effect hydrolysis. Particularly resistant were aromativ deriv atives and those with branching in methacrylate linkages. Overall, the stud y confirms the ability of physiologically important esterases to catalyze t he hydrolysis of biomaterial methacrylates. (C) 2001 John Wiley & Sons, Inc .