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Macromolecular nano composite membrane current glucose biosensor based on single-walled carbon nanotubes / redox

Author: GuoYanYan
Tutor: GaoQiang
School: Shaanxi Normal University
Course: Analytical Chemistry
Keywords: glucose biosensor redox polymer single-walled carbon nanotubes layer-by-layer assembly screen-printed electrode
CLC: TP212.3
Type: Master's thesis
Year: 2011
Downloads: 66
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Abstract

Diabetes is a world-wide public health problem. The diagnosis and management of diabetes mellitus requires a tight monitoring of blood glucose levels, thus the glucose has also become the most common analyte. The challenge of providing such tight and reliable glycemic control remains the subject of the worthiness of research. Electrochemical biosensors for glucose play a leading role in this direction. Amperometric enzyme electrodes, based on glucose oxidase (GOx) bound to electrode transducers, have thus been the target of substantial research.This thesis includes two parts, review and study.In the review, electrochemical biosensors including the history and the type are introduced. The main principle of electrochemical biosensors, immobilization strategies of the biocomponent and mediator involed in the biosensor methodology are extensively introduced. Nanotechology and the application of nanotechnology into biosensors are given, especially in the characteristics, preparation and application of the carbon nanotube.The second is the study including two parts.(1) Fabrication of glucose biosensor based on the GOx/SWNT/PVI-Os nanocompositIn this study,our fabricate glucose biosensor with a conventional three-electrode system with the screen-printed carbon electrode (SPCE) as working electrode, an Ag/AgCl (saturated potassium chloride) as reference electrode, and a platinum foil as counter electrode. First,the SPCE was functionalized with cationic PVI-Os by electrodeposition of a layer of PVI-Os onto the electrode surface. This was accomplished by applying a steady reducing potential (-1.4 V vs. Ag/AgCl) for 200 s on an SPCE in PBS (pH 7.1,0.020mol/L) containing PVI-Os (0.65 mg/mL). Followed by alternating immersions in SWNT solutions, PVI-Os solutions and GOx solutions. PVI-Os is highly cationic and can be electrostatically adsorbed to the negatively charged SWNT and GOx (GOx has an isoelectric point of about 3), by the LBL buildup of glucose biosensor based on the GOx/SWNT/PVI-Os nanocomposit. The modified electrode was characteristiced by the methods of cyclic voltammetry (CV) and environmental scanning electron microscope (SEM). The results show that this method will be successful to the printing of carbon nanotube modified electrode surface, and rise with the increase in the assembly, the number of carbon nanotube electrode surface increases. Preparation of modified electrode to detect 10 mmol/L glucose, results showed that: The electrocatalytic current for glucose oxidation was enhanced with an increase in the number of bilayers. With a five-bilayer electrode, the catalytic current was the largest. The glucose biosensor displayed a wide linear range from 0.5 to 6.0 mmol/L, a high sensitivity of 16.4μAmM-1cm-2, and the detection limit was 0.03mM. The long-term stability of the biosensor was evaluated by measuring its performance every 5 d in the course of 30 d. The sensing elements were found to be stable for at least one month and maintained 90% activity during the entire period, with storage at 4℃between measurements.(2) Fabrication of glucose biosensor based on the GOx-SWNT conjugates/PVI-Os nanocompositIn order to improve the sensitivity and simplify the preparation of the sensor, a glucose biosensor based on the GOx/SWNT/PVI-Os nanocomposit has been improved. This work prepared GOx-SWNT conjugates by adsorbing the redox enzyme GOx onto SWNT. First,the SPCE was functionalized by electrodeposition of a layer of PVI-Os on the electrode surface. Then the conjugates were incorporated into redox polymer hydrogels using the LBL method on SPCE to obtain a glucose biosensor. The modified electrode was characteristiced by the methods of cyclic voltammetry (CV) and flow injection nanalysis (FIA). Preparation of modified electrode to detect 10 mmol/L glucose, results showed that: The electrocatalytic current for glucose oxidation was enhanced with an increase in the number of bilayers. With a four-bilayer electrode, the catalytic current was the largest. The present glucose biosensor possessed a dynamic range of 0.5 to 8 mmol/L with a sensitivity of 32μAmM-1cm-2. Further, biosensors are promising amperometric detectors for the flow injection analysis of glucose.The long-term stability of the biosensor was evaluated by measuring its performance every 5 d in the course of 30 d. The sensing elements were found to be stable for at least one month and maintained 90% activity during the entire period, with storage at 4℃between measurements.Compares with the glucose biosensor based on the GOx/SWNT/PVI-Os nanocomposit, this kind of sensor is relatively simple, the linear range is wider and the sensitivity is higher.

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