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Capoferri D, Del Carlo M, Ntshongontshi N, Iwuoha EI, Sergi M, Di Ottavio F, Compagnone D. MIP-MEPS based sensing strategy for the selective assay of dimethoate. Application to wheat flour samples. Talanta 2017; 174:599-604. [PMID: 28738628 DOI: 10.1016/j.talanta.2017.06.062] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2017] [Revised: 06/19/2017] [Accepted: 06/22/2017] [Indexed: 11/17/2022]
Abstract
The aim of this work was to demonstrate the potentialities of the use of a molecularly imprinted (MIP) sensor coupled to a microextraction by packed sorbent (MEPS) strategy for the selective and sensitive detection of dimethoate in real samples. A dimethoate-polypyrrole MIP film was realised by cyclic voltammetry (CV) on the surface of a glassy carbon electrode (GCE). Being dimethoate electro-inactive, K3[Fe(CN)6] was used as probe for the indirect quantification of the analyte via the decrease of redox peaks observed upon binding of the target analyte. Detection of dimethoate at low nanomolar range was achieved with linearity in the 0.1-1nM range. Relative standard deviation calculated for different electrodes at 0.5nM of dimethoate was < 3% and selectivity was very satisfactory being the response for omethoate only 23% of dimethoate. A MEPS strategy for the extraction of dimethoate from a challenging matrix as wheat flour was then used in conjunction with the MIP electrochemical sensor. The procedure applied to flour samples spiked with dimethoate at 0.5 MRL, MRL, and 1.5 MRL gave very favourable comparison with a validated UHPLC-MS/MS method with deviations in the -21% /+17% range, demonstrating the feasibility of the approach as screening assay. This work clearly shows that the sequential use of a microextraction based procedure and electrochemical sensing system is low cost, easy to realise and use and can open new perspectives for the development of selective sensing system to be used in field or decentralised lab testing for the selective screening of target analytes.
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Affiliation(s)
- D Capoferri
- Faculty of Biosciences and Technologies for Food, Agriculture and Environment, University of Teramo, via R. Balzarini 1, 64100 Teramo, Italy
| | - M Del Carlo
- Faculty of Biosciences and Technologies for Food, Agriculture and Environment, University of Teramo, via R. Balzarini 1, 64100 Teramo, Italy
| | - N Ntshongontshi
- SensorLab, Department of Chemistry, University of the Western Cape, Bellville 7535, South Africa
| | - E I Iwuoha
- SensorLab, Department of Chemistry, University of the Western Cape, Bellville 7535, South Africa
| | - M Sergi
- Faculty of Biosciences and Technologies for Food, Agriculture and Environment, University of Teramo, via R. Balzarini 1, 64100 Teramo, Italy
| | - F Di Ottavio
- Faculty of Biosciences and Technologies for Food, Agriculture and Environment, University of Teramo, via R. Balzarini 1, 64100 Teramo, Italy
| | - D Compagnone
- Faculty of Biosciences and Technologies for Food, Agriculture and Environment, University of Teramo, via R. Balzarini 1, 64100 Teramo, Italy.
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Mavundla SE, Malgas GF, Motaung DE, Iwuoha EI. Synthesis of flower-like zinc oxide and polyaniline with worm-like morphology and their applications in hybrid solar cells. Cryst Res Technol 2012. [DOI: 10.1002/crat.201100537] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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Ignaszak A, Hendricks N, Waryo T, Songa E, Jahed N, Ngece R, Al-Ahmed A, Kgarebe B, Baker P, Iwuoha EI. Novel therapeutic biosensor for indinavir-a protease inhibitor antiretroviral drug. J Pharm Biomed Anal 2008; 49:498-501. [PMID: 19056199 DOI: 10.1016/j.jpba.2008.10.025] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2008] [Revised: 10/19/2008] [Accepted: 10/20/2008] [Indexed: 11/26/2022]
Abstract
An amperometric drug metabolism biosensor consisting of cytochrome P450-3A4 (CYP3A4) encapsulated in a didodecyldimethylammonium bromide (DDAB) vesicular system on a Pt disk electrode was developed for the determination of indinavir, a protease inhibitor antiretroviral drug. Cyclic, square wave and pulse voltammetric responses of the bioelectrode showed quasi-reversible electrochemistry of the Fe(3+)/Fe(2+) redox species of the heme thiolate CYP3A4 enzyme under aerobic and anaerobic conditions. The biosensor exhibited excellent response to indinavir with a detection limit and response time of 6.158 x 10(-2)mgL(-1), and 40s, respectively. The detection limit is well below the plasma concentration of indinavir (8h after intake) which range from 0.13 to 8.6mgL(-1).
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Affiliation(s)
- A Ignaszak
- Department of Chemistry, University of Western Cape, Bellville, Cape Town 7535, South Africa
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Iwuoha EI, Wilson A, Howel M, Mathebe NGR, Montane‐Jaime K, Narinesingh D, Guiseppi‐Elie A. Cytochrome P4502D6(CYP2D6) Bioelectrode for Fluoxetine. ANAL LETT 2007. [DOI: 10.1081/al-120030288] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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Iwuoha EI, Williams-Dottin AR, Hall LA, Morrin A, Mathebe GN, Smyth MR, Killard A. Electrochemistry and application of a novel monosubstituted squarate electron-transfer mediator in a glucose oxidase-doped poly(phenol) sensor. PURE APPL CHEM 2004. [DOI: 10.1351/pac200476040789] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Electrosynthetic poly(phenol) nanofilms were deposited in situ on platinum electrodes in the presence and absence of glucose oxidase. The synthesis charges and currents of the nonconducting polymer films were recorded at various applied potentials for films grown from 25 –100 mM phenol concentrations. Film parameters such as the standard rate constant for film deposition, film thickness, and surface concentration of the poly(phenol) films were evaluated from the cyclic and step voltammograms of the polymerization process. A novel electron-transfer mediator consisting of monosubstituted 4-hydroxycyclobut-3-ene-1,2-dione (squarate) was used as a mediator for Pt/poly(phenol) nanofilm/GOx amperometric glucose biosensors. Amperometric responses for 3-diphenylamino-4-hydroxycyclobut-3-ene-1,2-dione (diphenylaminosquarate: E°'=of +328 mV/Ag-AgCl at pH 7.0)-mediated systems were measured by both steady-state amperometric and cyclic voltammetry. The sensor sensitivity was calculated to be 558 nA cm−2 (µM)−1.
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Affiliation(s)
- E. I. Iwuoha
- 1Department of Chemistry, University of the Western Cape, Belleville 7535, South Africa; Department of Chemistry, The University of the West Indies, St.Augustine, Trinidad; School of Chemical Sciences, Dublin City University, Dublin 9, Ireland
| | - A. R. Williams-Dottin
- 1Department of Chemistry, University of the Western Cape, Belleville 7535, South Africa; Department of Chemistry, The University of the West Indies, St.Augustine, Trinidad; School of Chemical Sciences, Dublin City University, Dublin 9, Ireland
| | - L. A. Hall
- 1Department of Chemistry, University of the Western Cape, Belleville 7535, South Africa; Department of Chemistry, The University of the West Indies, St.Augustine, Trinidad; School of Chemical Sciences, Dublin City University, Dublin 9, Ireland
| | - A. Morrin
- 1Department of Chemistry, University of the Western Cape, Belleville 7535, South Africa; Department of Chemistry, The University of the West Indies, St.Augustine, Trinidad; School of Chemical Sciences, Dublin City University, Dublin 9, Ireland
| | - G. N. Mathebe
- 1Department of Chemistry, University of the Western Cape, Belleville 7535, South Africa; Department of Chemistry, The University of the West Indies, St.Augustine, Trinidad; School of Chemical Sciences, Dublin City University, Dublin 9, Ireland
| | - M. R. Smyth
- 1Department of Chemistry, University of the Western Cape, Belleville 7535, South Africa; Department of Chemistry, The University of the West Indies, St.Augustine, Trinidad; School of Chemical Sciences, Dublin City University, Dublin 9, Ireland
| | - Anthony Killard
- 1Department of Chemistry, University of the Western Cape, Belleville 7535, South Africa; Department of Chemistry, The University of the West Indies, St.Augustine, Trinidad; School of Chemical Sciences, Dublin City University, Dublin 9, Ireland
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Iwuoha EI, Joseph S, Zhang Z, Smyth MR, Fuhr U, Ortiz de Montellano PR. Drug metabolism biosensors: electrochemical reactivities of cytochrome P450cam immobilised in synthetic vesicular systems. J Pharm Biomed Anal 1998; 17:1101-10. [PMID: 9884200 DOI: 10.1016/s0731-7085(98)00076-4] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Biosensors containing cytochrome P450cam in a didodecyldimethylammonium bromide vesicular system were prepared by cross-linking onto a glassy carbon electrode (GCE) with glutaraldehyde in the presence of bovine serum albumin. Cyclic voltammetric responses of the sensor in air-free buffer solution showed that the sensor exhibited reversible electrochemistry due to direct electron exchange between the haem Fe(3+/2+) redox system and the GCE surface. In air-saturated solution containing camphor, the biosensor gave an irreversible electrocatalytic current which is compatible with the monooxygenation of the substrate. Steady state amperometric experiments with camphor, adamantanone and fenchone were performed with a biosensor prepared by cross-linking P450cam with glutaraldehyde onto a Pt disc electrode. The sensor was characterised by fast amperometric responses, attaining steady-state in about 20 s in a cobalt sepulchrate mediated electrochemical system. The kinetic parameters of the biosensor were analysed using the electrochemical Michaelis Menten equation. The estimated apparent Michaelis-Menten constant, Km, values for the biosensors were in the range of 1.41-3.9 mM.
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Affiliation(s)
- E I Iwuoha
- Biomedical and Environmental Sensor Technology Centre, School of Chemical Sciences, Dublin City University, Ireland
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Abstract
The effects of the water-miscible organic solvent acetonitrile on the enzymatic activity of horseradish peroxidase (HRP) and on HRP-anti-HRP binding have been investigated. Results showed that both the catalytic activity of HRP and the binding ability of the antibody were affected on increasing the concentration of the organic solvent. The activity of HRP varied with the organic composition of the solvent, indicating that the conformation of the enzyme was affected. The binding ability of the antibody also decreased significantly with an increase of the organic composition of the solvent, and in absolute acetonitrile, the activity of the antibody is about 500 times lower than that in aqueous medium. Binding reversibility experiments indicated that the antibody was not irreversibly damaged in solutions with acetonitrile composition greater than 80% and below 40%; however, an irreversible decrease in the binding was observed in solutions with an acetonitrile composition between 40 and 80%. The reduction in the binding ability is probably due to the irreversible conformation changes in the antibody.
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Affiliation(s)
- B Lu
- BEST Centre, Dublin City University, Ireland
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McGrath MJ, Iwuoha EI, Diamond D, Smyth MR. The use of differential measurements with a glucose biosensor for interference compensation during glucose determinations by flow injection analysis. Biosens Bioelectron 1995; 10:937-43. [PMID: 8652108 DOI: 10.1016/0956-5663(95)99231-9] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
A novel detection system for the determination of glucose in the presence of clinically important interferents, based on the use of dual sensors and flow-injection analysis (FIA), is described. The normalisation methodology involves measurement of the interference signal at a reference sensor; this signal can then be subtracted from the glucose sensor signal (post-run) to give a corrected measurement of the glucose concentration. The detection system consists of a thin layer with dual glassy carbon working electrodes. One electrode was surface modified to act as a glucose biosensor by immobilisation of glucose oxidase (GOx) (from Aspergillus niger) with 1% glutaraldehyde and bovine serum albumin. The second electrode (glucose oxidase omitted) was utilised to measure the interference signal responding only to electroactive species present in the injected sample. A computer controlled multichannel potentiostat was used for potential application and current monitoring duties. The sensor responses were saved in ASCII format to facilitate post-run analysis in Microsoft Excel. Cyclic voltammetry (CV) was utilised to investigate the manner in which the interference signal contributed to the total signal obtained at the biosensor in the presence of glucose. The kinetics parameters Imax and the apparent Michaelis-Menten constant, K'm, were calculated for the sensor operating under flow-injection conditions.
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Affiliation(s)
- M J McGrath
- School of Chemical Sciences, Dublin City University, Glasnevin, Ireland
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Abstract
On the basis of a reaction scheme in which the ligand binding steps are preceded by fast iron spin transitions (Okonjo, K.O. (1980) Eur. J. Biochem. 105, 329-334; Iwuoha, E.I. and Okonjo, K.O. (1985) Biochim. Biophys. Acta 829, 327-334), the spin equilibrium constants of methemoglobin subunits are calculated from kinetic and equilibrium binding parameters with azide ion as ligand. The results demonstrate the existence of thermodynamic spin heterogeneity within the tetramer.
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Iwuoha EI, Okonjo KO. Relaxation amplitude analysis of thiocyanate and formate binding to human aquomethemoglobin A. Biochim Biophys Acta 1985; 829:327-34. [PMID: 4005266] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
The kinetics of the reaction of thiocyanate and formate ions with aquomethemoglobin can be adequately accounted for by a scheme in which the ligand-binding step in both the alpha and beta subunits is preceded by a fast transition of the iron atom from high to low spin (Okonjo, K.O. (1980) Eur. J. Biochem. 105, 329-334). Amplitude expressions derived from this scheme are used to analyse the relaxation amplitude data for alpha and beta subunits within the methemoglobin tetramer. The mean of the reaction enthalpies for ligand binding by the subunits within the tetramer is in good agreement with the reaction enthalpy for ligand binding by the methemoglobin tetramer obtained from a Van't Hoff plot of equilibrium titration data.
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