Journal
COLLOIDS AND SURFACES B-BIOINTERFACES
Volume 77, Issue 1, Pages 69-74Publisher
ELSEVIER SCIENCE BV
DOI: 10.1016/j.colsurfb.2010.01.009
Keywords
Carbon nanotubes; Covalent immobilization; Organophosphate
Funding
- NSF [CTS-0330189]
- USDA-CSREES [2006-34394-16953]
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In this paper we demonstrate that SWNTs and a covalent immobilization strategy enable very sensitive sensors with excellent long term stability. Organophosphorus hydrolase (OPH) functionalized single and multi-walled carbon nanotube (CNT) conjugates were exploited for direct amperometric detection of paraoxon, a model organophosphate. The catalytic hydrolysis of paraoxon produces equimoles of p-nitrophenol; oxidation was monitored amperometrically in real time under flow-injection (FIA) mode. OPH covalently immobilized on single-walled carbon nanotubes (SWNTs) demonstrated much higher activity than OPH conjugated to multi-walled carbon nanotubes (MWNTs). The dynamic concentration range for SWNT-OPH was 0.5-8.5 mu mol L-1 with a detection limit of 0.01 mu mol L-1 (S/N = 3). In addition to this high sensitivity, the immobilized OPH retained a significant degree of enzymatic activity, and displayed remarkable stability with only 25% signal loss over 7 months. These results suggest that covalent immobilization of OPH on CNTs can be used for specific immobilization with advantages of long term stability, high sensitivity, and simplicity. Published by Elsevier B.V.
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