Abstract
We have developed a novel optical biosensor device using recombinant methyl parathion hydrolase (MPH) enzyme immobilized on agarose by metal-chelate affinity to detect organophosphorus (OP) compounds with a nitrophenyl group. The biosensor principle is based on the optical measurement of the product of OP catalysis by MPH (p-nitrophenol). Briefly, MPH containing six sequential histidines (6× His tag) at its N-terminal was bound to nitrilotriacetic acid (NTA) agarose with Ni ions, resulting in the flexible immobilization of the bio-reaction platform. The optical biosensing system consisted of two light-emitting diodes (LEDs) and one photodiode. The LED that emitted light at the wavelength of the maximum absorption for p-nitrophenol served as the signal light, while the other LED that showed no absorbance served as the reference light. The optical sensing system detected absorbance that was linearly correlated to methyl parathion (MP) concentration and the detection limit was estimated to be 4 μM. Sensor hysteresis was investigated and the results showed that at lower concentration range of MP the difference got from the opposite process curves was very small. With its easy immobilization of enzymes and simple design in structure, the system has the potential for development into a practical portable detector for field applications.
Highlights
Organophosphorus (OP) compounds, such as methyl parathion (MP), are among the most widely used pesticides in the agricultural industry, home hygiene, garden management and veterinary practice as an alternative to organochlorine chemicals [1,2,3]
The present study focused on optical biosensors based on methyl parathion hydrolase (MPH)
An optical biosensor for MP detection based on MPH immobilization by metal-chelate affinity was developed
Summary
Organophosphorus (OP) compounds, such as methyl parathion (MP), are among the most widely used pesticides in the agricultural industry, home hygiene, garden management and veterinary practice as an alternative to organochlorine chemicals [1,2,3]. Two types of enzyme-based analytical methods have been widely studied: indirect quantitative detection of OP compounds using AChE and direct monitoring of OP compounds using organophosphorus hydrolase (OPH). These enzyme activities are not affected by substrates and could be used repeatedly This method is more applicable and convenient in field analysis and several studies have reviewed the progress of biosensor development for OP compound analysis [22,23,24]. Some studies have reported previously developed biosensors using AChE for the detection of OP compounds with metal-chelate NTA affinity [6,12] These methods are indirect and are based on electrochemical or piezoelectric analysis. Few studies have focused on metal-chelate biosensors based on MPH until now, which is used as direct analysis
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