Preparation Of Electro-chemical Biosensors And Their Applications

This article described in detail the types, preparation methods and applications of electrochemical biosensors in the field of analytical chemistry. On the basis of different electrode material and lots of researches on immobilization of bio-material, some novel biosensors was fabricated. Electrochemical behaviors and their applications of the resulting modified electrodes were studied. The main research work was as follows: 1. Preparation of Glucose Oxidase Biosensors and Applications1.1 Glucose Biosensor Based on Poly(neutral red) Modified Glassy Carbon ElectrodeA novel glucoseoxidase biosensor was fabricated through crosslinking method. Neutral red, which was used as the electron mediator, electropolymerized on the Nafion modified glassy carbon electrode, forming NR/Nafion/GC electrode. Then glucose oxidase was immobilized on NR/Nafion/GC electrode by a cross-linker Glutaraldehyde. Lastly, additional Nafion membrane prevent the glucose oxidase dissipating from Glucose Biosensor. The biosensor kept a linear relationship with the concentration of glucose in the range of 1.0×10^-5～5.0×10^-3 mol·L-1 in pH 7.0 PBS at 30℃.1.2 Glucose Oxidase Biosensor Based on Carbon Nanotubes And Chitosan Through Electrostatic AdsorptionA novel glucose biosensor was fabricated by means of self-assembled technique to immobilize Glucose Oxidase (GOD). Neutral Red was electorpolymerized on glassy carbon electrode (GCE) modified with Nafion to form a positively charged surface, then Multi-walled Carbon Nanotubes (MWNT) and Chitosan (Cs) was linked by electrostatic adsorption step by step, finally GOD was electrostaticly absorbed in Cs film to prepare a glucose biosensor. The experiments showed a linear range to concentration of glucose was 5.0×10^-6～2.0×10^-3 mol/L with a detection limit of 1.0×10^-6 mol/L in PBS(pH 7.0) at 30℃, and response time was less than 10 s. The biosensor retained 84.3% of its original peak current after thirty days. Moreover, the biosensor exhibited good reproducibility, high selectivity and anti-interference ability to ascorbic acid, etc.2. Preparation of Horseradish Peroxidase Biosensors and Applications2.1 Hydrogen Peroxide Biosensor Based on Gelatin Immobilizing Horseradish PeroxidaseA novel Hydrogen Peroxide biosensor was obtained by successfully immobilizing horseradish peroxidase (HRP) on a glassy carbon (GC) electrode, which was modified with multi-walled carbon nanotubes (MWNT) and alizarin red(AR). Then the biosensor was immerged in 3% glutaraldehyde (GA) in order to overcome the swelling and improve the stability of the gelatin membrane. The experimental condition was optimized, and the electrochemistry behavior of the HRP/AR/MWNT/GC biosensor in PBS (pH 7.0) and H2O2 were discussed. The biosensor displayed rapid response and expanded linear response range from 5.0×10^-6 to 1.0×10^-3 mol/L (R=0.9932) with detection limit of 1.0×10-7 mol/L in PBS (pH 7.0), as well as acceptable preparation reproducibility and excellent stability.2.2 Horseradish Peroxidase Biosensor Based on Alizarin Red Modified Glassy Carbon ElectrodeA novel biosensor was fabricated by multi-walled carbon nanotubes (MWNT) modified glassy carbon (GC) electrode self-assembling Alizarin red (AR) coated with negative charge and staticly adsorbing with horseradish peroxidase (HRP) to fabricate amperometric biosensor (HRP/AR/MWNT/GC). The experimental condition was optimized, and the sensor showed a good catalytic behavior to H2O2. The linear response of the sensor to H2O2 is in the range of 1.0×10^-6～1.0×10^-3 mol/L with a correlation coefficient of 0.9953. The detection limit of the biosensor was 2.0×10-8 mol/L. Experiments showed that the sensor response rapidly with high sensitivity and good reproducibility, stability and longer service life, which possessed potential application value.3. Direct Electrochemistry of Cytochrome c at Nanohybrid Film Modified ElectrodeBeing novel favorite promoters, L-cysteine (L-Cys), gold nanoparticles (AuNPs) and multi-walled carbon nanotubes (MWNT), because of particular multi-absorbing sites, was immobilized on glassy carbon (GC) electrode surface by layer-by-layer self-assembly technique to form a robust and effective nanohybrid film. The film modified electrode (L-Cys/AuNPs/MWNT/GC) can promote the direct electron change reaction of cytochrome c (Cyt c). Experiments showed a pair of well-defined and nearly reversible peaks of Cyt c at about 0.121 V (vs.Ag/AgCl) was obtained. The sensor responded rapidly to Cyt c in the linear range from 4.037×10^-5 to 3.230×10^-4 mol/L with detection limit of 2.423×10^-5 mol/L in PBS(pH 7.0) .