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Sensors 2013, 13(12), 16851-16866; doi:10.3390/s131216851

Potentiometric Urea Biosensor Based on an Immobilised Fullerene-Urease Bio-Conjugate

1,* , 1
1 Faculty of Science and Technology/SEADPRI, LESTARI, University Kebangsaan Malaysia, Selangor 43600, Malaysia 2 Chemistry Department, Faculty of Science, K. N. Toosi University of Technology, Tehran 15418-49611, Iran 3 ACECR Mashhad Branch, Food Science and Technology Research Institute, Mashhad 91775-1376, Iran
* Author to whom correspondence should be addressed.
Received: 19 August 2013 / Revised: 21 September 2013 / Accepted: 23 September 2013 / Published: 6 December 2013
(This article belongs to the Section Biosensors)
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A novel method for the rapid modification of fullerene for subsequent enzyme attachment to create a potentiometric biosensor is presented. Urease was immobilized onto the modified fullerene nanomaterial. The modified fullerene-immobilized urease (C60-urease) bioconjugate has been confirmed to catalyze the hydrolysis of urea in solution. The biomaterial was then deposited on a screen-printed electrode containing a non-plasticized poly(n-butyl acrylate) (PnBA) membrane entrapped with a hydrogen ionophore. This pH-selective membrane is intended to function as a potentiometric urea biosensor with the deposition of C60-urease on the PnBA membrane. Various parameters for fullerene modification and urease immobilization were investigated. The optimal pH and concentration of the phosphate buffer for the urea biosensor were 7.0 and 0.5 mM, respectively. The linear response range of the biosensor was from 2.31 × 10−3 M to 8.28 × 10−5 M. The biosensor’s sensitivity was 59.67 ± 0.91 mV/decade, which is close to the theoretical value. Common cations such as Na+, K+, Ca2+, Mg2+ and NH4+ showed no obvious interference with the urea biosensor’s response. The use of a fullerene-urease bio-conjugate and an acrylic membrane with good adhesion prevented the leaching of urease enzyme and thus increased the stability of the urea biosensor for up to 140 days.
Keywords: fullerene; urease; urea biosensor; potentiometric fullerene; urease; urea biosensor; potentiometric
This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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Saeedfar, K.; Heng, L.Y.; Ling, T.L.; Rezayi, M. Potentiometric Urea Biosensor Based on an Immobilised Fullerene-Urease Bio-Conjugate. Sensors 2013, 13, 16851-16866.

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