Molecular imprinted gels

Stable polymer phases (e.g. molecularly imprinted gels) and non-porous materials have the best chances for a broader use. However, especially for non-porous materials the high price is an issue. 

Gel materials are utilized in a variety of technological appUcations and are currently investigated for advanced exploitations such as the formulation of intelligent gels and the synthesis of molecularly imprinted polymers. 

Molecularly imprinting sol-gel using a sacrificial spacer was successful in creating a material that could bind DDT82 with a moderate degree of... 

The scientists from Hong Kong reported83 on a sol-gel derived molecular imprinted polymers (MIPs) based luminescent sensing material that made use of a photoinduced electron transfer (PET) mechanism for a sensing of a non-fluorescent herbicide - 2,4-dichlorophenoxyacetic acid. A new organosilane, 3 - [N,V-bis(9-anthrylmethyl)amino]propyltriethoxysilane, was synthesized and use as the PET sensor monomer. The sensing MIPs material was fabricated by a conventional sol-gel process. 

Graham A., Carlson C., Edmiston P., Development and characterization of molecularly imprinted sol-gel materials for the selective detection of DDT, Anal. Chem. 2002 74 458-467. 

Leung M., Chow C., Lam M., A sol-gel derived molecular imprinted luminescent PET sensing material for 2,4-dichlorophenoxyacetic acid, J. Mater. Chem. 2001 11 2985-2991. 

The concept of thin films of a molecularly imprinted sol-gel polymer with specific binding sites for a target analyte is general and can be applied also to electrochemical sensors. For example, a sensor to detect parathion in aqueous solutions is based on films cast on glass substrates and on glassy carbon electrodes (Figure 6.14).12... 

S. Marx, A. Zaltsman, I. Turyan and D. Mandler, Parathion sensor based on molecularly imprinted sol-gel films, Anal. Chem., 2004, 76, 120. 

Silica particles surface-imprinted with a TSA of a-chymotrypsin were applied for the enantio-selective hydrolyzation of amides. Surprisingly, the particles showed reverse enantio-selectivity, i. e., the sol-gel imprinted with the L-isomer of the enzyme s TSA showed a higher selectivity for the D-isomer of the substrate [125]. Also Ti02 gels have been imprinted, e.g., with 4-(4-propyloxypheny-lazo)benzoic acid. QCM coated with ultrathin films of this gel were prepared by an immersion process and showed selective binding of the template [ 126]. These examples demonstrate once more the broad applicability of the concept of molecular imprinting. 

Investigations of enzyme-catalyzed direct electron transfer introduce the basis for a future generation of electrocatalysts based on enzyme mimics. This avenue could offer new methods of synthesis for nonprecious metal electrocatalysts, based on nano-structured (for example, sol—gel-derived) molecular imprints from a biological catalyst (enzyme) with pronounced and, in some cases, unique electrocatalytic properties. Computational approaches to the study of transition state stabilization by biocatalysts has led to the concept of theozymes . " ... 

Dlaz-Garcia ME Badia Laino R, Molecular imprinting in sol-gel materials Recent developments and applications, Microchim. Acta, 2005,149, 19-36. 

Figure 6.14. Two different approaches of molecular imprinting by the surface sol-gel process the pre-mixing approach (a), and the layer-by-layer approach (b).

The application of molecular imprinting to biologically active substances such as amino acids and proteins is extremely important. As the first trial, we examined molecular imprinting of protected amino acids in a Ti02-gel thin film [35]. 

The method of choice in the preparation of inorganic matrices for molecular imprinting has been the sol-gel technique. A number of excellent reviews and books are available for those interested in a more detailed understanding of the method... 

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