Molecularly imprinted polymer based sensor directly responsive to attomole bovine serum albumin.

Through years of extensive research and development, molecularly imprinted polymers (MIPs) are still inferior to their biological rivals such as antibodies, enzymes etc. In this study we report a protein-imprinted cryogel, showing antibody-like affinity and selectivity against the protein template (bovine serum albumin, BSA). The MIP was synthesized from the co-polymerization of acrylamide, N,N-methylenebisacrylamide, acrylic acid and diallylamine. Due to the participation of the ionizable monomers (acrylic acid and diallylamine), imprinted cavities with inner surface-clung charged groups were created to recognize BSA. Therefore each cavity appears like a molecular capacitor charged by carboxyl and amino groups. As the cavities are all of a molecule-size volume, a membrane made of the MIP contains a huge array of the molecular capacitors. This will produce a synergistic effect and greatly amplify the impedance signal deviations when template sorption/desorption takes place on the sensor. When the MIP was used as an artificial antibody to make an electrochemical sensor, high sensitivity and selectivity were achieved at the same time. Results indicate that BSA could be determined in a linear range of 1.5 × 10-16-10-12 mol-L-1. Meanwhile a low limit of detection was achieved at 7.2 × 10-18 mol L-1. Conclusively protein-imprinted amphoteric polyacrylamide cryogels are materials of a great potential to sense and determine charged objects like molecules, cells, microorganisms or other particles.

Synthesis of Molecularly Imprinted Cryogels to Deplete Abundant Proteins from Bovine Serum.

Molecularly imprinted polyacrylamide cryogels were synthesized with pending templates (bovine serums of different concentrations). As the serum concentrations increased in the monomer solutions, the resulting cryogels could adsorb and deplete more proteins from serum samples. Due to the addition of vinyltriethoxysilane (VTEOS) in the prepolymerizing solutions, the polymers came as organic⁻inorganic hybrid materials. It endued the silica-modified amphoteric polyacrylamide cryogels with improved mechanical strengths. Scanning electron micrography (SEM), Infrared (IR) spectrometry, thermogravimetry-differential thermal analysis (TG-DTA), and X-ray photoelectron spectroscopy (XPS) were carried out to characterize these macroporous polymers. Amphoteric cryogels proved to be favorable materials recognizing and binding proteins. When used as liquid chromatography stationary phases, they were capable of simultaneously adsorbing various serum proteins. Electrophoresis showed that abundant proteins were gradually depleted by the cryogels prepared from increased ratios of bovine serums in the monomer solutions. As abundant proteins are always imprinted first, this sample per se imprinting method provides an effective and convenient way to deplete abundant proteins from complex samples such as serums, meanwhile concentrating and collecting scarce species therein.

Ice Squeezing Induced Multicolor Fluorescence Emissions from Polyacrylamide Cryogels.

Being short of conventional chromophores, polyacrylamide is generally not regarded as a fluorescent material. Exactly the polymerization of dilute solutions of acrylamide and N,N'-methylenebisacrylamide led to thick liquids at 60 °C, showing no fluorescence. Things changed when the phase transition of water was involved. The squeezing effect of ice crystals not only created polymeric solids (cryogels) at - 20 °C, but also endowed them unexpected fluorescence emissions. The macroporous cryogels are mainly blue fluorescent polymers. However yellow and red fluorescence were also achieved by changing the ingredient ratios. A series of instrumental detections revealed that the multicolor fluorescence were based on exquisite amido stacking induced from ice squeezing. If people make good use of the squeezing effect of the heaven-sent molecule to manipulate the interactions of monomer functionalities, cryogenic polymerization can be a promising method to produce diverse polymeric materials.

Depletion of abundant human serum proteins by per se imprinted cryogels based on sample heterogeneity.

Macroporous cryogels were prepared and used to deplete abundant proteins. It was accomplished based on the sample heterogeneity rather than any exogenous assistance. Human serum was added in monomer solutions to synthesize molecularly imprinted polymers; therein some abundant proteins were imprinted in the polyacrylamide cryogels. Meanwhile the rare components remained aqueous. Chromatography and electrophoresis showed that albumin, serotransferrin, and most globulins were depleted by columns packed with the molecularly imprinted polymers. After the depletion, lower abundance proteins were revealed by SDS-PAGE, peptide fingerprint analysis, and identified by MALDI-TOF-MS. This is an example that a "per se imprint" protocol enables to gradually dimidiate proteomes, simplify sample complexities, and facilitate further proteome profiling or biomarker discovery.