Detection of paraoxon by immobilized organophosphorus hydrolase in a Langmuir-Blodgett film

Xihui Cao, Sarita V. Mello, Roger M. Leblanc, Vipin K. Rastogi, Tu Chen Cheng, Joseph J. DeFrank

Research output: Contribution to journalArticlepeer-review

22 Scopus citations


Langmuir-Blodgett (LB) film deposition technique was employed for the immobilization of organophosphorus hydrolase (OPH). OPH enzyme was covalently bonded to a fluorescent probe, fluorescein isothiocyanate (FITC), and used as a biological recognition element. Under optimal experimental conditions, OPH monolayers were deposited onto the surface of silanized quartz slides as LB film and utilized as a bioassay for the detection of paraoxon. Two different methods were employed for detection of paraoxon: the fluorescence quenching of the fluorescence probe (FITC) covalently bonded to OPH and the UV-vis absorption spectrum of the paraoxon hydrolysis product. The UV-vis absorption measurement demonstrated a linear relationship between the absorbance at 400 nm and the concentration of paraoxon solutions over the range of 1.0 × 10 -7-1.0 × 10 -5 M (0.27-27 ppm). By observing the FITC fluorescence quenching, the concentration of paraoxon can be detected as low as 10 -9 M (S/N = 3). The research described herein showed that the LB film bioassay had high sensitivity, rapid response time and good reproducibility.

Original languageEnglish (US)
Pages (from-to)349-356
Number of pages8
JournalColloids and Surfaces A: Physicochemical and Engineering Aspects
Issue number1-3 SPEC. ISS.
StatePublished - Dec 10 2004


  • Fluorescein isothiocyanate
  • Organophosphorus hydrolase
  • UV-vis absorption

ASJC Scopus subject areas

  • Colloid and Surface Chemistry
  • Physical and Theoretical Chemistry


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