Development Of Molecularly Imprinted Electrochemical Sensor

MIPs as a recognition element for sensors, which possess several advantages, such as robustness and stability under a harsh physical and chemical conditions, easiness of preparation, used repeatedly and ability to'tailor'recognition material for target analytes, have increasingly attracted considerable attention recently. Limitations, such as difficult to control the thickness of film, long response time, incomplete template removal, high detection limit, bad reversibility and repeatability, et.al, are existing in traditional imprinting technique and materials, which introduce difficulties for the application on the electrochemical sensor. Studies are encouraged to find new imprinting materials and new methods to meet to the requirements of electrochemical sensor.Thereby, in this paper the applications of new materials and methods in MIT are investigated, and some new MIPs electrochemical sensors are constructed successfully by coupling these imprinted matrices with electric transducers. The main contents are listed as follows:1. A novel voltammetric sensor based on molecularly imprinted polymers (MIPs) by a kind of photo-sensitive amphiphilic copolymer was developed for determination of glucose in this work. Without the cross-linker and the initiator, a MIPs film on the surface of a gold electrode was easily formed by in-situ cross-link within 10 min under UV light irradiation. In alkaline medium, electrochemical oxidation behaviors of glucose on the MIPs sensor, as well as on a bare gold electrode have been investigated with square wave voltammetry (SWV). At oxidation potential of -0.50 V (vs. SCE), the peak currents on the MIPs sensor were proportional to the concentration of glucose in the range of 5.0μmol/L～120μmol/L with the detection limit of 0.2μg ml-1 (S/N=3), whereas the extremely small responses of the control electrode were observed and independent of the analyte concentration. MIPs sensor displayed specific selectivity toward glucose in comparison to structurally similar analogues. The selective coefficient of glucose MIPs sensor with respect to maltose, arabinose and mannose was 9.17, 1.51 and 1.25, respectively. Fructose and inositol would not interfere with the determination of glucose because they could not be electrochemically oxidized at the potential of -0.50 V. Relative rapid response of the MIPs sensor was obtained within 7 min, and the RSD of peak currents was 5.0% (n=5). MIPs sensor was applied to determine glucose in the simulative blood serum samples, the average recoveries was 92.6%.2. A voltammetric sensor based on MIPs, which was constructed on the surface of a glassy carbon electrode with the ethylparaben (EP) as template and methacrylic acid as functional monomer, was developed for determination of paraben in this work. Electrochemical oxidation behaviors of EP on the imprinted electrode have been investigated with SWV. When the incubation time was 15min, the peak currents at oxidation potential of 0.95 V were proportional to the concentration of EP in the range of 2.0×10-6～2.0×10-4 mol/L with the detection limit of 1.0×10-6mol/L (S/N=3) and the relative standard deviation (RSD) of peak current was 4.3% (n=10), whereas the extremely small responses of the control electrode were observed and independent of the analyte concentration. On the other hand, the voltammogram of EP recorded with imprinted electrode was different from that with the bare electrode at the same conditions, with a positive shift of oxidation potential. The imprinted electrode displayed substantially specific binding of paraben, which the selective coefficient of imprinted electrode with respect to MP, PP and BP was 1.89,1.70 and 2.01, respectively. And only small responses of structural analogs such as phenol, p-hydroxybenzoic acid and p-aminobenzoic acid were observed. Moreover, structural unanalog vitamin C had almost no response. The imprinted electrode was used for analysis of parabens in actual samples, the recoveries were between 91% and 95%.On the basis of that, paraben sensor based on MIPs using MP and PP as dual-template was researched preliminarily. In order to obtain the same sensitivity on MIPs sensor for both the MP and PP, the ratio of the MP to PP as the dual-template was investigated. The imprinted electrode was used for analysis of parabens in actual sample, the recoveries were between 98% and 114%. The experimental results showed that the sensor for parabens was simpler to construct and operate, and provided an adequate sensitivity, good repeatability and acceptable accuracy.