Smart molecularly imprinted hydrogels for protein recognition
The direct application
of molecularly imprinted polymers (MIPs) for the selective recognition and
isolation of proteins has some limitations. As we described in a recent post,
the tridimensional structure of the protein can be modified during the MIP
synthesis due to the solvents or the monomers employed. On the other hand, the
huge molecular size of biomolecules restricts their diffusion through the
polymeric network making difficult their extraction and/or final elution.
Smart hydrogels can
substitute conventional polymeric materials in molecularly imprinting due to
their peculiar characteristics. A smart hydrogel is a porous polymeric network
that may respond to external stimulus (mainly pH, ionic strength or
temperature) with a change in its structure or dimension. This change can be
used to control the uptake and release of the templates with a negligible
effect on the polymeric network which memorizes the imprinting state. This
polymeric network is synthesized using three general building elements: a
monomer which responds to the external stimuli, a monomer which interacts with
the protein allowing its selective recognition and a cross-linker which
provides stability to the structure.
Researchers from the
Hunan University at China have recently evaluated the potential of smart
hydrogels in the recognition of bovine serum albumin (BSA). The proposed
hydrogel is synthesized using N-isopropylacrylamide as stimuli-sensitive
monomer, acryilamide as recognition monomer (since it establishes electrostatic
interaction with the negative charged groups of the protein) and
N,N-methylenebisacryilamide as cross-linker. The role of the temperature in the synthesis of the hydrogel is really interesting since at low temperatures (-20 ºC) the hydrogels present a higher porosity which is ascribed to the porogenic effect of crystal ice.
Some of the properties of the
hydrogel, such as the swelling ratio and the adsorption capacity, respond to
the working temperature. The evaluation of this molecularly imprinted hydrogel shows
a high adsorption capacity toward BSA (68 mg/g, three fold better than the
non-imprinted gel) and reproducibility (4.7 %, expressed as relative standard deviation).
Moreover, the imprinted gel allows the selective extraction of BSA in the
presence of other proteins.
The article, published
in Analytica Chimica Acta, is highly recommendable. The readers will find the optimal synthesis conditions of the hydrogel, the chemical characterization
of the polymer and its selectivity evaluation.
Reference
Link to the article: Bovine serum albumin recognition via
thermosensitive molecular imprinted macroporous hydrogels prepared at two
different temperatures
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