Fabrication of electrochemical sensor based on nano-sized molecularly imprinted polymer for detection of L-Tryptophan

During the past decade, molecular imprinting technology has become a well-established analytical tool. Non-covalent imprinting, in particular, has found a wide range of applications because of the theoretical lack of restrictions on size, shape, or chemical character of the imprinted molecule. The possibility of tailor-made, highly selective artificial receptors at low cost, with good mechanical, thermal, and chemical properties, makes these synthetic materials appear as ideal chemoreceptors. There are new horizons for the development of a new generation of chemical sensors using these novel synthetic materials as recognition elements [1, 2]. In this study an electrochemical sensor for selective detection of L-tryptophan (L-Tryp) based on nano-sized molecularly imprinted polymer was synthesized at the surface of glassy carbon electrode (GCE). This sensor was created by polymerization of dopamine (DA) as functional monomer and cross linking agent, and L-Tryp as the template. For preparation of molecularly imprinted polymer (MIP), the requred precursors including L-Tryp, DA, and phosphate buffer solution were mixed and stirred at room temperature. After centrifugation, it was dried at room temperature for one night. Then it was dispersed in ultrapure water and ultrasonicated for 10 min. Then GCE was coated with 3 μL of the composite and dried at room temperature for 30 min. The obtained product was washed with hydrochloric acid solution and methanol to remove the template L-Tryp [3]. Determination of L-Tryp was directly performed by electro-oxidation process. The surface features of the modified electrode was characterized by cyclic voltammetry (CV), differential pulse voltammetry (DPV). The morphology of the MIP film modified electrode characterized by Fourier transform infrared spectrometer (FT-IR) and X-ray diffraction (XRD). Some important experimental conditions such as adsorption time, removal time, preconcentration solution pH, were investigated and optimized. Under the optimized conditions the proposed sensor showed a wide calibration range 10-14 – 10-8 M with improved LOD value of 5×10-15 M. Also the MIP-based sensor exhibited good selectivity and repeatability.