An electrochemical sensor for L-tryptophan using a molecularly imprinted polymer film produced by copolymerization of 1, 4 phenylenediamine and resorcinol

Tryptophan ((2S)-2-amino-3-(1H-indol-3-yl) propionic acid), is well known as a kind of an essential amino acid [1], that effects on regulating the physiological function of body [2], because it is the metabolic precursor for serotonin, melatonin, and niacin [3]. In this paper, we combined the use of MIPs electropolymerization to produce a sensor which was capable of detecting tryptophan. The MIP electrode was obtained by electrocopolymerization of 1, 4-phenylenediamine and resorcinol in the presence of the template molecular tryptophan.Their retention and molecular-recognition properties were investigated by means of three instrumental techniques: cyclic voltammetry (CV), differential pulse voltammetry (DPV) and electrochemical impedance spectroscopy (EIS). The obtained results indicate that the MIP electrode exhibited a much higher current response compared with the non-imprinted electrode. Moreover the MIP had specific recognition ability for tryptophan, while other structurally related compounds could not be recognized on the MIP.The response of the imprinted sensor to tryptophan was linearly proportional to its concentration over the range 4.5×10−8-2×10−7M. The detection limit of tryptophan is 0.015 μM (S/N=3). These results revealed that such a sensor provides a promising strategy to fabricate sensor devices based on MIPs with highly selective recognition ability, simplicity of operation, small size and low cost for tryptophan detection.