A STUDY ON THE CHARACTERISTICS OF CHITOSAN AS AN IMMOBILIZATION MATRIX FOR BIOSENSORS

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Date
2007-11
Authors
ANG, LEE FUNG
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Abstract
Two chitosan samples (FCHIT and SCHIT) were investigated as an enzyme immobilization matrix for the fabrication of glucose biosensor. The viscosityaverage molecular weight of FCHIT and SCHIT were determined to be 981.80 kD and 398.61 kD respectively. Their degree of deacetylation determined by FDUV spectrophotometry were 82.44% and 77.20% respectively. The physical properties of chitosan solution and membrane were studied by dissolving the chitosan in different organic acids (acetic acid, lactic acid and maleic acid). Both the chitosan samples were most soluble in aqueous acetic acid, followed by lactic acid and maleic acid. Chitosan membranes prepared from acetic acid were flexible, transparent, smooth and quick-drying. They exhibited good mechanical strength and elongation at break and the values were significantly higher than those prepared in lactic acid and maleic acid. FTIR spectra and SEM micrographs showed the existence of intermolecular interactions between chitosan and glucose oxidase (GOD). Higher catalytic activities were observed on GOD-FCHIT than GOD-SCHIT and for those crosslinked with glutaraldehyde than through the adsorption technique. Enzyme loading higher than 0.6 mg could decrease its activity. The highest response for glucose was observed at 0.21 mllcm2 membrane thickness for GOD-FCHIT/PT and 0.35 mllcm2 membrane thickness for GOD-SCHIT/PT. The optimum experimental conditions for analyzing glucose at pH 6.0 using the biosensors were found to be at 35 DC with an applied potential of 0.6 V. Under such conditions, response times of 85 sand 65 s were observed for GOD-FCHIT/PT and GOD-SCHIT/PT respectively. The apparent Michaelis-Menten constant (K;:P) was found to be 12.7370 mM for GOD-FCHIT/PT and 17.6920 mM for GOD-SCHIT/PT. This indicated that the GOD-FCHIT/PT had greater affinity for the enzyme. Moreover, GOD-FCHIT/PT showed higher sensitivity (52.3666 nAlmM glucose) when compared with GOD-SCHIT/PT (9.8579 nAlmM glucose) at S/N>3. A better repeatability and reproducibility were achieved by GOD-FCHIT/PT than GOD-SCHIT/PT in the glucose measurement. GOD-FCHIT/PT was found to give the highest enzymatic activity among the electrodes under investigation. The extent of interference encountered by GOD-FCHIT/PT and GODSCHIT/ PT was not significantly different. Although the Nafion coated biosensor significantly reduced the signal due to the interferents under study, it also significantly reduced the response to glucose. The performance of the biosensors in the determination of glucose in rat serum was evaluated. Comparatively better accuracy and recovery results were obtained for GODFCHIT/ PT. Hence, GOD-FCHIT/PT showed a better performance when compared with GOD-SCHIT/PT. In conclusion, chitosan membrane has the potential to be a suitable matrix in the development of glucose biosensor.
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CHARACTERISTICS , BIOSENSORS
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