Preparation of Template Synthetic Nanobiocomposites by the Sol-Gel

Active enzymes were encapsulated into a sol-gel matrix for the first time in 1990 719 About 60 different types of hybrid bioceramic materials with inotganic matrices made from silicon, titanium, and zirconium oxides Ti02-cellulose composites etc. were described. Recentiy, bioceramic sensors, solid electrolytes, electrochemical biosensors, etc. have been surveyed in a review. The moderate temperatures and mild hydrolytic and polymerization conditions in sol-gel reactions of alkoxides make it possible to trap proteins during matrix formation. This prevent proteins denaturation. The high stability of the trapped biomolecules, the inertness, the large specific surface, the porosity, and the optical transparency of the matrix facilitate use of sol-gel immobilization. The principal approaches ate considered below. 

Antibodies bound by sol-gel encapsulation are used in medicine, immunochro-matography, immunosensors, etc. Immimoglobulins that are trapped retain their ability to bind external antigens from solutions. Antibodie 14D9 catalyze hydrolysis of cyclic acetals, ketals, epoxides, etc. when incorporated in sol-gel matrices. The ability of a sol-gel matrix containing 10% PEG and antiatrazine antibodies to bind atrazine was studied. This matrix recogni2es and binds atrazine and widely distributed herbicides. In this case, neither leaching of antibodies nor nonspecific physical sorption of atrazine on the ceramic matrix occurs. The activity did not decrease 

Enzymes, which act as bioreactors, were immobilized according to such sol-gel procedures (Sections VI and VII). Certain chemically active terminal groups of enzymes and ceramic dopants such as Sn-Cl, were used (scheme 34).  

For example, alcohol dehydrogenase has been immobilized into nanotubes of Ti02, which were prepared by sol-gel template synthesis. This enzyme retained its ability to oxidize ethanol for more than 4 days (NAD cofactor, phosphate bulfer, pH Since these Ti02 nanotubes were open at both ends, this configuration allowed their use as a flow reactor. Examples of boimd enzymes acting as bioreactor are large in number. They also involve covalent binding of antibodies to functionalize sol-gel films.  

This fact is most pronounced in the reproduction of hierarchic macrostructured organized silica gels. Multicellular fibers from Bacillus subtilis (Fig. 24) can serve as an example of scaled organic 3D templates. Nanosize magnetic (Fc304), semiconducting (CdS) or Ti02 particles were prepared first and then incorporated into 

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