Molecular imprinting has been extensively reviewed in both the periodic press ( 7, 10– 13) and in a series of books ( 14– 17), and the number of original articles and patents have continued to increase ( 18). 1: formation of pre-polymerization complex 2: polymerization 3: template removal/rebinding. Schematic of molecular imprinting process adapted from Byrne ( 9). However, molecular imprinting on surfaces (2D imprinting) is gaining momentum especially when forming imprints against large macromolecules such as proteins and in sensor design ( 8). The nature of molecular imprinting lends itself to the generation of 3D imprint systems where binding sites are formed throughout a bulk material. Molecular imprinting is now a well-established technology in the field of synthetic molecular recognition, offering a generic, robust, and cost-effective alternative to existing techniques such as monoclonal antibodies ( 7). This complex is then preserved within a matrix to form an imprint that is chemically and sterically complementary to the template ( Figure 1). Compounds with functional groups reciprocal to those of a target molecule or template are selected and used to form a scaffold around the chosen template. This strategy is the basis for the process of molecular imprinting. Approaches that utilize naturally occurring macromolecules to act as selective recognition sites are well documented ( 6).Īn alternative strategy is to prearrange the recognition site around the target molecule or template. One drawback to the host-guest route is the lack of a generic process, meaning that each recognition problem requires a novel solution. Methods to synthesize these materials rely upon either “design and synthesis” or “coincidental fit” approach. Crown ethers ( 1), cyclophanes ( 2), phage display generated peptides ( 3), cyclodextrins ( 4), and dendrimers ( 5) are examples of these. Extending upon the natural systems, the production of artificial recognition elements (e.g., “plastic antibodies”) that mimic these highly selective agents is also a highly desirable research objective that may afford unique advantages over the biological counterparts.Ī number of divergent strategies, both natural and synthetic, have been described that operate as molecular structures and act as “host” sites for a ligand or “guest” moiety. Moreover, biological recognition in macromolecules, in particular antibodies, has led to development of highly useful and adaptable laboratory tools. The conceptionally simple “lock and key” hypothesis of protein-guest interaction is perhaps the most useful illustration of the principle. The binding process depends on the appropriate geometric organization of functional groups, including hydrophilic domains, within the host molecule that match or fit reciprocal functionality on the guest. These forces result in either entropy- or enthalpy-driven reduction in the free energy of the system. Therefore binding specificity is simply an indirect measure of the energy of the system. Binding of the host to the guest arises when these forces result in a host-guest complex leading to a decrease in the free energy of the system. The binding process arises as a result of attractive forces that exist between complimentary loci on the protein (or host) and ligand (or guest molecule). Proteins are complex macromolecule assemblies possessing sites that can controllably and specifically interact with and bind target molecules. This impressive and ubiquitous biological phenomenon is mediated, in the main, by proteins. Specific molecular recognition is the fundamental process governing control of both biological form and function.
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