This study addressed whether methacrylate monomers and polymers used in dentistry might degrade from enzymolysis by acetylcholinesterase (ACHE), cholesterol esterase (CHE), porcine liver esterase (PRLE), and a pancreatic lipase (PNL). Short (hour) and long-term (day) exposures were performed. Product ratios were used to determine surface hydrolysis of the polymeric materials. 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 substrates varied slightly, but amounted to as much as 10% of that of p-nitrophenylacetate. The K(m) for triethylene glycol dimethacrylate (TEGDMA) was 197 microM for ACHE and 1107 microM 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 cholesteryl oleate. Long-term incubations of monomers with CHE and ACHE produced degrees of hydrolysis that evidenced structure dependency in the ability of the enzymes to effect hydrolysis. Particularly resistant were aromativ derivatives and those with branching in methacrylate linkages. Overall, the study confirms the ability of physiologically important esterases to catalyze the hydrolysis of biomaterial methacrylates.
The composition of whole human and sheep cortical bone tissue, and of a synthetic hydroxyapatite (P120), were compared using Fourier transform Raman (FT-Raman) spectroscopy. Deproteination procedures to remove the bulk of the collagen present in bone tissue allowed isolation of the mineral phase. A comparison of the spectra obtained from both whole and deproteinated bone with those of synthetic hydroxyapatite showed direct correlation only in the region of 952 cm-1 (symmetric P-O mode). In contrast, human and sheep bone were very closely matched in both, the organic and inorganic structures. The results demonstrate that deproteination of bone is not a necessary precursor to obtain spectral information.
Specimens of 14C-labeled poly(ethylene terephthalate), nylon 66, and poly(methyl methacrylate) have been synthesized and exposed, in vitro, to a number of enzyme solutions. Poly(ethylene terephthalate) was found to be affected by esterase and papain, although in different ways, but not by trypsin or chymotrypsin. Nylon 66 was unaffected by esterase but degraded by the other three. Poly(methyl methacrylate) was not affected by any of these enzymes. This indicates that some nominally stable polymers are susceptible to degradation by enzymes under some circumstances. The amount of degradation is small, but could have significant sequelae should it be reproduced in vivo.
We have concluded preliminary investigations concerning the composition of human cortical bone tissue, and of a number of samples of synthetic hydroxyapatite, using Fourier transform Raman (FT-Raman) spectroscopy. Deproteination procedures to remove the bulk of the collagen present in the tissue have allowed isolation of the mineral phase, and a comparison of the spectra obtained from the latter with those of synthetic hydroxyapatites has highlighted a number of discrepancies. FT-Raman spectra obtained for whole, wet bone samples have produced a degree of spectral detail that is much improved upon that available from existing studies. This has mainly been achieved by the successful elimination of fluorescence from the tissue, a problem which has dogged the Raman analysis of bone in particular.
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