A New Type Of Electrochemical Biosensor Used For Glucose And Organic Pesticide Detection

Due to their excellent selectivity, high sensitivity, simplicity, rapid analysis response, easy to miniaturization and easy to used in vivo online detection etc., the biosensorshave important application prospect in pharmaceutical industry, food inspection, environmental monitoring and exploring information transfer in life. The research has become the frontier and hot spots in the field of analytical chemistry resrarch. This study mainly committed to the development of new materials for immobilized technology, adopted the composite materials which with good conductivity and biocompatibility, and can keep the fixed enzyme activity to the immobilized of the biological protein molecules, in order to improve the interface electron transfer and perfect the performance of the biosensor. In the experiment, we used new nanomaterials to build a new type of superior performance of electrochemical biosensor and studied the characteristics of the sensor and use simple and new research methods for biological sensor. The work was divided into the following three aspects:1. Nitrogen-doped porous carbon(N-DPC) was prepared via a simple and effective method. Direct electrochemistry of glucose oxidase(GOD) on the N-DPC modified electrode was investigated. The results showed that the N-DPC has a large specific surface area, which is favorable to immobilize the redox proteins for constructing biosensors. Electrochemical results indicated that the modified electrode exhibited effective direct electron transfer. A novel biosensor was developed by entrapping GOD in the N-DPC modified electrode for glucose detection and showed a stable, rapid and reproducible electrocatalytic response, a high sensitivity, a wide linear range of 0.025 m M-7.0 m M(R=0.9992, n=14)and a low detection limit of 2.5μM.2. A sensitive electrochemical biosensor for quantitative determination of carbaryl pesticide was developed based on a sensing interface of citrate-capped gold nanoparticles(Au NPs)/(3-mercaptopropyl)-trimethoxysilane(MPS)/gold electrode(Au). The negatively charged Au NPs/MPS/Au originated from the citrate coated on Au NPs repulsed the negatively charged [Fe(CN)6]3-/4- to produce a negative response.In the presence of acetylcholinesterase(ACh E) and acetylthiocholine(ATCl), the ACh E would catalyze the hydrolysis of ATCl into positively charged thiocholine which could replace the citrate on Au NPs based on the strong Au-S bond and exchange the surface from negatively charged into positively charged. The resulted positively charged Au NPs/MPS/Au then attracted the [Fe(CN)6]3-/4-to produce a positive response. Based on the inhibition of carbaryl on the activity of ACh E, the carbaryl pesticide could be accurately and sensitively determined at a very lowpotential, which was verified by cyclic voltammograms and electrochemical impedance spectroscopy. The sensor for carbaryl detection showed a wide linear range of 0.003-2.00 μM(R=0.9880, n=6)and a low detection limit of 1.0 n M.3. A novel glucose biosensor was developed based on a bi-enzyme bio-interphase of horseradish peroxidase(HRP) and glucose oxidase(GOD) constructed on11-mercaptoundecanoic acid(MUA)-6-mercapto-1-hexanol(MCH) modified gold(Au) electrode. The glucose could be oxidized into gluconic acid by GOD in the bio-interphase, followed by the reduction of O2 into H2O2. In the presence of HRP, the generated H2O2 from the reduction of O2 accompanying by the oxidation of glucose could catalyze the polymerization of aniline to form polyaniline(PANI) film. With the increasing of added glucose, more H2O2 were produced and then a growing number of polyaniline(PANI) were formed on the electrode surface, which resulted in the decrease of peak current of [Fe(CN)6]3-/4-because the formed PANI can act as the inert electron and mass transfer blocking layer to hinder the electron transfer of Fe(CN)63-/4-toward the electrode surface. Accordingly, the glucose biosensor could be carried out at a low working potential(about 0.25 V), which reduced the interferences of other organic compounds. Therefore, interference from UA and AA which coexist with glucose in human blood has been found to be negligible. The glucose biosensor showed a wide linear range of 0.015-10 m M, a low detection limit of 5 μM and a sensitivity of 61.85 μA m M-1 cm-2.