M. Dąbrowski, A. Ziminska, J. Kalecki, M. Cieplak, W. Lisowski, R. Maksym, S. Shao, F. D’Souza, A. Kuhn, P. S. Sharma
We present an improved approach for the preparation of highly selective and homogeneous molecular cavities in molecularly imprinted polymers (MIP) via the combination of surface imprinting and semi-covalent imprinting. Towards that, first a colloidal crystal mold was prepared via the Langmuir-Blodgett technique. Then, human chorionic gonadotropin (hCG) template protein was immobilized on the colloidal crystal mold. Later, hCG derivatization with electroactive functional monomers via amide chemistry was performed. In a final step, optimized potentiostatic polymerization of 2,3′-bithiophene enabled depositing an MIP film as macroporous structure. This synergistic strategy resulted in the formation of molecular imprinted cavities exclusively on the internal surface of the macropores, which were accessible after dissolution of silica molds. The recognition of hCG by the macroporous MIP film was transduced with the help of electric transducers, namely extended-gate field-effect transistors (EG-FET) and capacitive impedimetry (CI). These readout strategies offer the ability to create chemosensors for the label-free determination of hCG hormone. Other than the simple confirmation of pregnancy, hCG assay is a common tool for the diagnosis and follow-up of ectopic pregnancy or trophoblast tumors. Concentration measurements with these EG-FET and capacitive impedimetry based devices allowed real-time measurements of hCG in the range of 0.8 to 900 fM and 0.17 to 2.0 fM, respectively in 10 mM carbonate buffer (pH = 10). Moreover, the selectivity of the chemosensors with respect to protein interferences was very high.