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.