Molecular imprinting
Encyclopedia
In chemistry
, molecular imprinting is a technique to create template-shaped cavities in polymer
matrices with memory of the template molecule
s to be used in molecular recognition
. This technique is based on the system used by enzyme
s for substrate
recognition, which is called the "lock and key" model. The active binding site of an enzyme has a unique geometric structure that is particularly suitable for a substrate. A substrate that has a corresponding shape to the site is recognized by selectively binding to the enzyme, while an incorrectly shaped molecule that does not fit the binding site is not recognized.
In a similar way, molecularly imprinted materials are prepared using a template molecule and functional monomer
s that assemble around the template and subsequently get crosslinked to each other. The functional monomers, which are self-assembled
around the template molecule by interaction between functional group
s on both the template and monomers, are polymerized to form an imprinted matrix (commonly known in the scientific community as a molecular imprinted polymer
i.e. MIP). Then the template molecule is removed from the matrix under certain conditions, leaving behind a cavity complementary in size and shape to the template. The obtained cavity can work as a selective binding site for a specific template molecule.
In recent decades, the molecular imprinting technique has been developed for use in receptor
s, chromatographic separations
, fine chemical sensing, etc. Taking advantage of the shape selectivity of the cavity, use in catalysis
for certain reactions has also been facilitated.
with ammonium carbonate
. When the polymerization process was accompanied by an additive such as benzene, the silica particles ultimately formed showed a higher uptake of this additive .
Chemistry
Chemistry is the science of matter, especially its chemical reactions, but also its composition, structure and properties. Chemistry is concerned with atoms and their interactions with other atoms, and particularly with the properties of chemical bonds....
, molecular imprinting is a technique to create template-shaped cavities in polymer
Polymer
A polymer is a large molecule composed of repeating structural units. These subunits are typically connected by covalent chemical bonds...
matrices with memory of the template molecule
Molecule
A molecule is an electrically neutral group of at least two atoms held together by covalent chemical bonds. Molecules are distinguished from ions by their electrical charge...
s to be used in molecular recognition
Molecular recognition
The term molecular recognition refers to the specific interaction between two or more molecules through noncovalent bonding such as hydrogen bonding, metal coordination, hydrophobic forces, van der Waals forces, π-π interactions, electrostatic and/or electromagnetic effects...
. This technique is based on the system used by enzyme
Enzyme
Enzymes are proteins that catalyze chemical reactions. In enzymatic reactions, the molecules at the beginning of the process, called substrates, are converted into different molecules, called products. Almost all chemical reactions in a biological cell need enzymes in order to occur at rates...
s for substrate
Substrate (biochemistry)
In biochemistry, a substrate is a molecule upon which an enzyme acts. Enzymes catalyze chemical reactions involving the substrate. In the case of a single substrate, the substrate binds with the enzyme active site, and an enzyme-substrate complex is formed. The substrate is transformed into one or...
recognition, which is called the "lock and key" model. The active binding site of an enzyme has a unique geometric structure that is particularly suitable for a substrate. A substrate that has a corresponding shape to the site is recognized by selectively binding to the enzyme, while an incorrectly shaped molecule that does not fit the binding site is not recognized.
In a similar way, molecularly imprinted materials are prepared using a template molecule and functional monomer
Monomer
A monomer is an atom or a small molecule that may bind chemically to other monomers to form a polymer; the term "monomeric protein" may also be used to describe one of the proteins making up a multiprotein complex...
s that assemble around the template and subsequently get crosslinked to each other. The functional monomers, which are self-assembled
Self-assembly
Self-assembly is a term used to describe processes in which a disordered system of pre-existing components forms an organized structure or pattern as a consequence of specific, local interactions among the components themselves, without external direction...
around the template molecule by interaction between functional group
Functional group
In organic chemistry, functional groups are specific groups of atoms within molecules that are responsible for the characteristic chemical reactions of those molecules. The same functional group will undergo the same or similar chemical reaction regardless of the size of the molecule it is a part of...
s on both the template and monomers, are polymerized to form an imprinted matrix (commonly known in the scientific community as a molecular imprinted polymer
Molecular imprinted polymer
A Molecularly Imprinted Polymer , or plastic antibody is a polymer that is formed in the presence of a molecule that is extracted afterwards, thus leaving complementary cavities behind. These polymers show a certain chemical affinity for the original molecule and can be used to fabricate sensors,...
i.e. MIP). Then the template molecule is removed from the matrix under certain conditions, leaving behind a cavity complementary in size and shape to the template. The obtained cavity can work as a selective binding site for a specific template molecule.
Receptor (biochemistry)
In biochemistry, a receptor is a molecule found on the surface of a cell, which receives specific chemical signals from neighbouring cells or the wider environment within an organism...
s, chromatographic separations
Chromatography
Chromatography is the collective term for a set of laboratory techniques for the separation of mixtures....
, fine chemical sensing, etc. Taking advantage of the shape selectivity of the cavity, use in catalysis
Catalysis
Catalysis is the change in rate of a chemical reaction due to the participation of a substance called a catalyst. Unlike other reagents that participate in the chemical reaction, a catalyst is not consumed by the reaction itself. A catalyst may participate in multiple chemical transformations....
for certain reactions has also been facilitated.
Early history
The first example of molecular imprinting is attributed to M.V. Polyakov in 1931. He studied the polymerization of sodium silicateSodium silicate
Sodium silicate is the common name for a compound sodium metasilicate, Na2SiO3, also known as water glass or liquid glass. It is available in aqueous solution and in solid form and is used in cements, passive fire protection, refractories, textile and lumber processing, and automobiles...
with ammonium carbonate
Ammonium carbonate
Ammonium carbonate is a commercial salt with the chemical formula 2CO3. It is used when crushed as a smelling salt. It can be crushed when needed in order to revive someone who has fainted...
. When the polymerization process was accompanied by an additive such as benzene, the silica particles ultimately formed showed a higher uptake of this additive .