Enhanced stability of enzyme organophosphate hydrolase interfaced on the carbon nanotubes

Valber A. Pedrosa, Sheetal Paliwal, Shankar Balasubramanian, Dhriti Nepal, Virginia Davis, James Wild, Erlan Ramanculov, Aleksandr Simonian

Research output: Contribution to journalArticlepeer-review

100 Citations (Scopus)


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 μmol L-1 with a detection limit of 0.01 μmol 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.

Original languageEnglish
Pages (from-to)69-74
Number of pages6
JournalColloids and Surfaces B: Biointerfaces
Issue number1
Publication statusPublished - May 1 2010
Externally publishedYes


  • Carbon nanotubes
  • Covalent immobilization
  • Organophosphate

ASJC Scopus subject areas

  • Biotechnology
  • Surfaces and Interfaces
  • Physical and Theoretical Chemistry
  • Colloid and Surface Chemistry

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