A colorimetric assay for determination of methyl parathion using recombinant methyl parathion hydrolase

Abstract

A simple, rapid and sensitive colorimetric dipstick assay for the detection of the organophosphorous insecticide methyl parathion (MPT) residue in vegetables was developed. The assay was based on the hydrolysis of MPT by a recombinant methyl parathion hydrolase (recMPH), the encoding gene of which was isolated from Burkholderia cepacia, a soil bacterium indigenous to Thailand. This reaction generates protons leading to a change in pH that correlates with the amount of MPH present. Hence, the pH indicator bromothymol blue was used to monitor the MPH hydrolysis as the associated color changes can be observed by the naked eye. The recMPH was immobilized on a PVDF membrane to establish a dipstick assay format. The assays could detect MPT residues in spiked vegetable samples at the concentration of 1 mg/L without using analytical instrumentation. The test is reusable and stable for up to 3 months in the absence of any preservatives.

A sensitive tapered-fiber optic biosensor for the label-free detection of organophosphate pesticides

“…Carbon paste electrodes modified by HNC-CNP 1.55×10 -9 -3.67×10 -6 4.7×10 −10 [42] Amperometric biosensor based on AuNPs/CNT 1.9×10 -8 -7.6×10 -7 3.8×10 −9 [43] Electrochemical sensor with ZrO 2 nanoparticles 1.9×10 -8 -11.4×10 -6 2.16×10 −8 [44] Electrochemical sensor using MWCNT/MIP 2×10 −7 -1×10 −5 6.7×10 −8 [45] Nanocomposite biosensor 3.8×10 -9 -1.9×10 -5 1.14×10 -9 [46] Colorimetric sensor 0.5×10 -9 -0.5×10 -6 0.1×10 -9 [47] Colorimetric dipstick assay by recMPH 3.8×10 −8 -3.8×10 −4 3.8×10 −6 [48] Enzyme-linked immunosorbent assay (ELISA) 1.67×10 −7 -5.24×10 −6 7.18×10 −8 [49] Indirect competitive ELISA 3.8×10 -10 -3.8×10 -6 3×10 −10 [50] Direct competitive ELISA 19×10 -9 -3.8×10 -6 1.9×10 −9 [50] Fluorescence polarization immunoassay (FPIA) 9.5×10 -8 -3.8×10 -5 5.7×10 −8 [50] Fluoroimmunochromatography by CdTe QD 3.8×10 -10 -3.8×10 -9 3.8×10 -10 [51] Fluorescent sensor based on CdTe QDs/CTAB 9.5×10 −8 -11.4×10 −6 6.84×10 −8 [10] Fluorescent sensor based on carbon dots 1×10 -10 -1×10 -4 0.48×10 −10 [11] Optofluidic SERS not specified 19×10 −6 [52] Optical microbial biosensor 4×10 -6 -80×10 -6 3×10 −7 [53] Optical absorbance-based biosensor 0 -1×10 -4 4×10 −6 [54] Optofluidic WGM ring resonator 0.4×10 -10 -4×10 -6 0.4×10 -10 [23] Tapered fiber optical biosensor 2.1×10 −9 -4.7×10 −5 2.4×10 −10 present study …”

Acetylcholinesterase-Free Colorimetric Detection of Chlorpyrifos in Fruit Juice Based on the Oxidation Reaction of H2O2 with Chlorpyrifos and ABTS2− Catalyzed by Hemin/G-Quadruplex DNAzyme

“…According to the report risk assessments and maximum residue limit of CP (10 ppb) (Zhang et al 2010), our results show that the colorimetric method could be used as an effective detection technology for CP. Moreover, a comparison of the various detection methods for OPs detection is summarized in Table 1 (Anh et al 2011;Fu et al 2013;Li et al 2011Li et al , 2014Namera et al 2000;No et al 2007). Compared with nanomaterial-based CP detection methods which always need a complicated label and operation steps, although the detection limit of the present method is a little lower than that of nanomaterialbased detection methods, the present method is more simple and cost-effective because the main reagents used in the present system are label-free and cost-effective.…”

Microbial Phosphotriesterase: Structure, Function, and Biotechnological Applications

“…Moreover, the techniques require trained technicians to perform the analysis competently [41]. Thus, portable and specific enzymatic biosensors (especially for use in field OP monitoring), with high selectivity and sensitivity, would be very beneficial [42,43].…”