Smart molecularly imprinted hydrogels for protein recognition

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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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