Hydrophobic sol-gel materials

Adsorption on solid matrices, which improves (at optimal protein/support ratios) enzyme dispersion, reduces diffusion limitations and favors substrate access to individual enzyme molecules. Immobilized lipases with excellent activity and stability were obtained by entrapping the enzymes in hydrophobic sol-gel materials [20]. Finally, in order to minimize substrate diffusion limitations and maximize enzyme dispersion, various approaches have been attempted to solubilize the biocatalysts in organic solvents. The most widespread method is the one based on the covalent linking of the amphiphilic polymer polyethylene glycol (PEG) to enzyme molecules [21]. 

Reetz, M.T. (1997) Entrapment of biocatalysts in hydrophobic sol-gel materials for use in organic chemistry. Advanced Materials, 9, 943-953. 

Reetz, M.T., Zonta, A., Simpelkamp, J. andKonen, W. (1996) In situ fixation of lipase-containing hydrophobic sol-gel materials on sintered glass - Highly efficient heterogeneous biocatalysts. Chemical Communications, 1397-1398. 

M.T. Reetz, A. Zonta, and J. Simpelkamp, Efficient heterogeneous biocatalysts by entrapment of lipases in hydrophobic sol-gel materials. Angew. Chem. Int. Ed. 34, 301-303 (1995). 

Figure 6.2 A bifurcated optical fibre is used to carry light to a probe. The hose tip consists of a thin layer of hydrophobic sol-gel material doped with a ruthenium complex which senses oxygen and reveals its content. (Image courtesy of Ocean Optics.)...

Reetz, M.T. and Dugal, M., Entrapment of Nanostructured Palladium Clusters in Hydrophobic Sol-Gel Materials, Catal. Lett., 58, 207, 1999. 

Recently, an efficient way to encapsulate lipases in hydrophobic sol-gel materials has been pubfished [42]. By introducing methyltrimethoxysilane/poly-dimethylsilane in water/lipase/polyvinyl alcohol mixtures, gel formation occurs as catalyzed by sodium fluoride. The gels were dried and washed with organic solvents. For Pseudomonas lipase the esterification activity in organic solvents was dependent on the methyltrimethoxysilane content with activity yields up to 93 %. 

Meter F, Zarcula C, Kiss C et al. (2007) Enhancement of lipases enantioselectivity by entrapment in hydrophobic sol-gel materials influence of sdane precursors and immobilization parameters. J Biotechnol 131(2) S109... 

Przybyt M, Biaikowska B (2002) Enzyme electrodes constructed on the basis of oxygen electrode with oxidases immobilised by sol-gel technique. Mater Sci 20(2) 63-79 Reetz MT (1997) Entrapment of biocatalysts in hydrophobic sol-gel materials for use in organic chemistry. Adv Mater 9(12) 943-954... 

Reetz MT, Zonta A, Simpelkamp J (1996) Efficient immobUzation of lipases by entrapment in hydrophobic sol-gel materials. Biotechnol Bioeng 49 527—534 Reetz MT (2001) Combinatorial and evolution-based methods in the creation of enantioselective catalyst. Angew Chem Int Ed 40 284-310... 

Reetz, M. T., A. Zonta, and J. SimpeUcamp. 1996a. Efficient Immobilization of Lipases by Entrapment in Hydrophobic Sol-Gel Materials. Biotechnology and Bioengineering 49 (5) 527-534. 

Reetz, M. T., R. Wenkel, and D. Avnir. 2000. Entrapment of Lipase in Hydrophobic Sol-Gel-Materials Efficient Heterogeneous Biocatalysts in Aqueous Medium. Synthesis 6 781-783. 

Yang, G., J. Wu, G. Xu, and L. Yang. 2009. Improvement of Catalytic Properties of Lipase from Arthrobacter Sp. By Encapsulation in Hydrophobic Sol-Gel Materials. Bioresource Technology 100 (19) 4311-4316. 

Pope E.J.A., Braun K., Petersen C.M. Bioartificial organs. I Sihca gel encapsulated pancreatic islets for the treatment of diabetes meUitus. J. Sol-Gel Sci. Technol. 1997 8 635-639 Reetz M.T., Zonta A., Simpelkamp J., Rufinska A., Tesche B. Characterization of hydrophobic sol-gel materials containing entrapped lipase. J. Sol-Gel Sci. Technol. 1996 7 35-43 Reisfeld R. Spectroscopy and application of molecules in glasses. J. Non-Cryst. Sol. 1990 121 254-266... 

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