Concept

Molecular imprinting

Résumé
Molecular imprinting is a technique to create template-shaped cavities in polymer matrices with predetermined selectivity and high affinity. This technique is based on the system used by enzymes for substrate recognition, which is called the "lock and key" model. The active binding site of an enzyme has a shape specific to a substrate. Substrates with a complementary shape to the binding site selectively bind to the enzyme; alternative shapes that do not fit the binding site are not recognized. Molecularly imprinted materials are prepared using a template molecule and functional monomers that assemble around the template and subsequently get cross-linked to each other. The monomers, which are self-assembled around the template molecule by interaction between functional groups on both the template and monomers, are polymerized to form an imprinted matrix (commonly known in the scientific community as a molecular imprinted polymer (MIP)). The template is subsequently removed in part or entirely, leaving behind a cavity complementary in size and shape to the template. The obtained cavity can work as a selective binding site for the templated molecule. In recent decades, the molecular imprinting technique has been developed for use in drug delivery, separations, biological and chemical sensing, and more. Taking advantage of the shape selectivity of the cavity, use in catalysis for certain reactions has also been facilitated. The first example of molecular imprinting is attributed to M. V. Polyakov in 1931 with his studies in the polymerization of sodium silicate with ammonium carbonate. When the polymerization process was accompanied by an additive such as benzene, the resulting silica showed a higher uptake of this additive. By 1949, the concept of instructional theory molecular imprinting was used by Dickey; his research precipitated silica gels in the presence of organic dyes and showed imprinted silica had high selectivity towards the template dye.
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