A molecularly imprinted copolymer designed for enantioselective recognition of glutamic acid

A newly designed molecularly imprinted polymer (MIP) material was developed and successfully used as recognition element to fabricate a capacitive sensor for enantioselective recognition of glutamic acid (Glu). The MIP with a well-defined structure was synthesized on a gold electrode in one step by electrochemical copolymerization of o-phenylenediamine (o-PD) and dopamine (DA) in the presence of template molecule Glu. The resulting MIP material was characterized with a potentiostatic frequency scan method, cyclic voltammetry, capacitance measurements, atomic force microscopy, and X-ray photoelectron spectroscopy. The structure and recognition behaviour of the copolymer film to template molecule depended on its composition. The optimal composition was at the o-PD to DA molar ratio of 3:2. With a potentiostatic time scan method the copolymer displayed high enantioselectivity and sensitivity to the stereoselective rebinding of L- or D-Glu to their corresponding artificial receptor due to the exact definition of the imprint cavity. The capacitance response of the sensor for L-Glu or D-Glu was proportional to their concentration in the range of 16.7 to 250 mu M. The enantiometric selectivity coefficients for L-Glu and D-Glu imprinted films against their respective enantiomers are 24 and 15, respectively. The resulting MIP capacitive sensors showed good reproducibility, stability and repeatability. This strategy opened a convenient way for preparation of enantioselective MIPs and recognition of enantiotropic molecules.