Enhanced stability of enzyme organophosphate hydrolase interfaced on the carbon nanotubes.
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 micromolL(-1) with a detection limit of 0.01 micromolL(-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.
Department of Materials Engineering, Auburn University, AL 36849, USA.
Valber A
VA
Pedrosa
Sheetal
S
Paliwal
Shankar
S
Balasubramanian
Dhriti
D
Nepal
Virginia
V
Davis
James
J
Wild
Erlan
E
Ramanculov
Aleksandr
A
Simonian
D055162:Biocatalysis; D015374:Biosensing Techniques; D004563:Electrochemistry; D004795:Enzyme Stability; D006868:Hydrolysis; D057230:Limit of Detection; D008855:Microscopy, Electron, Scanning; D046529:Microscopy, Electron, Transmission; D037742:Nanotubes, Carbon; D010261:Paraoxon / Q000378:metabolism; D010744:Phosphoric Monoester Hydrolases / Q000378:metabolism*
D037742:Nanotubes, Carbon; C045290:phosphorylphosphatase; D010744:Phosphoric Monoester Hydrolases; D010261:Paraoxon