Fabrication And Characterization Of The Phosphate Biosensor

A biosensor which can detect and quantify of phosphate ion with high sensitivity, selectivity and accuracy is required in various areas, such as laboratory analysis, clinical medicine, bio-fermentation, food inspection and environmental monitoring. In our study the maltose phosphorylase (MP) and glucose oxidase (GOD) enzyme membranes which are fixed on platinum electrode for the measurement of phosphate have been developed. Developing relevant methods of immobilizing enzyme and researching suited test solution environment are important in the development of novel phosphate electrochemical biosensors. Therefore, it is very important to find an effective immobilization strategy and appropriate matrixes to retain high activity of the immobilized maltose MP and GOD and to develop suitable test environment. In this work, the enzyme membranes of phosphate electrochemical biosensors based on immobilizing MP and GOD on nitrocellulose membrane (effective diameter 6.4 mm) using the method of cross linking have been developed, and also its performance on the detection of phosphate has been studied. The main contents of the thesis are given as follows:An enzyme membrane of phosphate electrochemical biosensor developed based on immobilizing MP and GOD on a nitrocellulose membrane using the glutaraldehyde vapor as a cross linking agent. In Different preparation conditions measuring the enzyme membrane for phosphate responses help to determine the best enzyme preparation conditions of the membrane. The optimum enzyme amount is dropping 6 U MP 5 U GOD solution, and the pH of the phosphate buffer solution (PBS) is 6.5. The optimum buffer solution contains 10 mmol/L maltose and 400 mmol/L 2-hydroxypyridine. The resulting phosphate biosensor exhibited a fast response of 3 min, high sensitivity of 4.24 nA/(mmol-L-1) and wide linear range from 0.5 mmol/L to 6.0 mmol/L. The proposed MP-GOD membrane performs high selectivity, reproducibility and operation stability.