Highly-sensitive cholesterol biosensor based on well-crystallized flower-shaped ZnO nanostructures

This paper reports the fabrication of highly-sensitive cholesterol biosensor based on cholesterol oxidase (ChOx) immobilization on well-crystallized flower-shaped ZnO structures composed of perfectly hexagonal-shaped ZnO nanorods grown by low-temperature simple solution process. The fabricated cholesterol biosensors reported a very high and reproducible sensitivity of 61.7 mu A mu M-1 cm(-2) with a response time less than 5s and detection limit(based on S/N ratio) of 0.012 mu M. The biosensor exhibited a linear dynamic range from 1.0-15 mu M and correlation coefficient of R=0.9979. A lower value of apparent Michaelis-Menten constant (K-m(aPP)), of 2.57 mM,exhibited a high affinity between the cholesterol and ChOx immobilized on flower-shaped ZnO structures. Moreover, the effect of pH on ChOx activity on the ZnO modified electrode has also been studied in the range of 5.0-9.0 which exhibited a best enzymatic activity at the pH range of 6.8-7.6. To the best of our knowledge. this is the first report in which such a very high-sensitivity and low detection limit has been achieved for the cholesterol biosensor by using ZnO nanostructures modified electrodes. (c) 2008 Elsevier B.V. All rights reserved.