Study On L-Tryptophan Molecularly Imprinted Films Modified Electrode

Molecular imprinting technology（MIT）is an antibody simulation technology, whichhas been developed in the past forty years. MIPs prepared by MIT could offer highsensitivity and selectivity comparable to biological entities, and could satisfy therequirements of sensing elements by overcoming the shortage of biological entities,which have variability and deactivation, limit in variety, high cost. Thechemically-modified electrodes（CME）are prepared by desigining the electrodes surfaceon the molecule level according to actual demand. With specific chemical andelectrochemical functional groups, the modified electrode showed great superiority onthe sensitivity and selectivity. Therefore, it has broad prospects and practical significanceto prepare molecular imprinted polymers modified electrode based on molecular design,control and optimization of the spatial structure, which could be acted as receptor mimicsof sensor interface. The L-Trp molecular imprinted polymers were synthesized on thesurface of electrode, and were characterizd by several methods. The main points of thisdissertation are summarized as follows:The number of binding sites formed by acrylamide as function monomer andL-tryptophan as template analyte were charactered by ultraviolet spectrum. Theinteraction force and association constant of template molecule and functional monomerwere discussed by fluorescence spectrum. The fluorescence characteristics of L-Trp andL-Trp-AM at different pH value were investigated.L-tryptophan imprinted membrane modified electrode was prepared bypotentiostatic method and cyclic voltammetry respectively. The performance of this twomodified electrodes was surveyed and compared by impedance-time andchronoamperometry. The effects of the type and amount of initiator, AM/L-Trp ratio, theamount of crosslinking agent, pH value, electropolymerization time on the sensitivity andadsorption property of MIPs modified electrode were discussed. Optimum conditions forpreparation of MIPs modified electrode have been obtained.The property of imprinted membrane modified electrode was studied by CV, DPVand AC impedance using potassium ferricyanide as an electro-active probe. A fast measurement upon L-Trp was carried out by chronoamperometry which exhibited a widelinear response range and a low detection limit. The reproducibility and reversibility wasconfirmed to be excellent after treated by strong acid, strong base, organic solvent andheat treatment. Fluorescence adsorption curve and selectivity experiment indicated thatthe imprinted membrane had specific recognization on L-Trp, a minor interference wasgenerated by L-Phe and L-Tyr whose space construction are similar to L-Trp, whileminimal interference for other amino acid. Kinetic study of the recognition processindicated two-step kinetic processes were happening sequentially between L-Trp and theimprint sites, which corresponds to a fast reaction and a slow reaction. The molecularrecognition betweeen the template and the imprint sites possessed fast response andexcellent specific recognization, meeting the demand of rapid detection by usingmodified electrodes.