丝网印刷电极在食品安全检测中的应用进展

食品安全问题一直以来都是被广泛关注的热点,选择成本低、使用方便、灵敏度高的检测手段也就成为了食品安全检测领域中研究的焦点。丝网印刷电极因具有可批量生产、成本低、灵敏度高和一次性可抛等特点,已被广泛应用到食品安全检测中。因此,近年来,关于丝网印刷电极在食品安全检测中的应用研究日益增多,建立了多种类型的电化学传感器。依据电化学传感器的不同类型,综述了丝网印刷电极在食品安全检测中的应用,并对丝网印刷电极的应用前景进行了展望。     

Electrochemical Determination of Methotrexate at a Disposable Screen-Printed Electrode and Its Application Studies

Methotrexate is widely used for treatment of various neoplastic diseases. The present work details the voltammetric analysis of Methotrexate at a multi-walled carbon nanotube (MWNT) modified screen-printed electrode (SPE). The fabrication and evaluation of MWNT-derived screen-printed electrochemical sensors based on a MWNT ink are reported. The fabricated MWNT strips combine the attractive advantages of CNT materials and disposable screen printed electrodes. The anodic voltammetric behavior of methotrexate was studied using cyclic and square-wave voltammetric techniques in tris-HCl (pH = 7.5) solution. The oxidation of methotrexate was an irreversible adsorptive-driven process. The experimental conditions such as carbon ink, MWNT, pH, the concentration, and nature of buffer were investigated to optimize the determination of methotrexate. Under optimum conditions, the square-wave voltammetric peak currents were in a linear relationship to methotrexate concentrations in the range of 5.0 × 10^?7M–1.0 × 10^?4 M with a detection limit of 1.0 × 10^?7 M. The MWNT/SPE showed good stability, selectivity, and was successfully used to quantify methotrexate in pharmaceutical formulations.     

Disposable Screen-Printed Electrodes (Spe) Mercury-Free for Lead Detection

ABSTRACT

Strategies to modify screen-printed electrodes (SPE) for lead determination are reported. Dithizone was mixed with graphite ink to obtain a modified screen-printed strip to detect ppb levels of lead(II) (detection limit 12 μg/l) using square wave anodic stripping voltammetry (SWASV). In addition, screen-printed electrodes were also modified by casting a few μl of a Nafion® solution onto the working electrode surface. In this case, ppb levels of lead were detected (detection limit 15 μg/1), using potentiometric stripping analysis (PSA). The addition of an ionophore to Nafion® polymer was also investigated, but this did not yield a significant improvement.     

Carbon nanotube screen-printed electrochemical sensors

The fabrication, and evaluation of carbon-nanotube (CNT)-derived screen-printed (SP) electrochemical sensors based on a CNT ink are reported. The fabricated CNT strips combine the attractive advantages of CNT materials and disposable screen-printed electrodes. Such thick-film CNT sensors have a well-defined appearance, are mechanically stable, and exhibit high electrochemical reactivity.     

Stacked graphene nanofibers doped polypyrrole nanocomposites for electrochemical sensing

This publication shows a single-step electropolymerization which has been carried out by the incorporation of an anionic stacked graphene nanofiber (SGNF) dopant into a polypyrrole (PPy) film, at a disposable screen-printed electrode. The incorporation of the SGNFs into the polymer does not affect their electrochemical properties, shown through cyclic voltammetry by the earlier oxidation of guanine, when compared with that at the graphite doped PPy electrode. The SGNF/PPy composite shows a high selectivity when used in the oxidation of guanine and hydrogen peroxide, both of which are important biomarkers used for biosensing. Disposable screen-printed electrodes provide an inexpensive, sensitive and portable substitute to glassy carbon electrodes, while giving a reproducible surface; qualities essential for effective bionsensing. The production of this single-step disposable SGNF/PPy composite electrode allows for further applications in the detection of biomedically important compounds and DNA sensing.     

Carbon nanotube wiring for signal amplification of electrochemical magneto immunosensors: application to myeloperoxidase detection

In this work, chronoamperometric myelo-peroxidase (MPO) detection was accomplished using immunofunctionalized magnetic microparticles (MPs), disposable carbon screen-printed electrodes (C-SPEs), and a ready-to-use commercially available tetramethylbenzidine (TMB)-based enzymatic substrate. In order to reach the limit of detection (LOD) needed to study real blood serum samples, assay performance was additionally improved by exploiting CNT wiring, which amplified the signal and decreased the LOD. The optimized assay can be performed in 30 min and yields LODs of 6 and 55 ng mL^?1 in PBS and undiluted human serum, respectively, making it useful for the identification of patients at risk of cardiovascular disease. These results demonstrate that electrode nanostructuring can be accomplished “post-assay,” which favors the development of enhanced magneto immunosensors based on the exploitation of cheap and simple SPE devices.     

Electrochemical DNA biosensor for analysis of wastewater samples

The application of a disposable electrochemical DNA biosensor to wastewater samples is reported. The DNA biosensor is assembled by immobilising double-stranded calf thymus DNA on the surface of a disposable, carbon screen-printed electrode (SPE). The oxidation signal of the guanine base, obtained by a square wave voltammetric scan, is used as analytical signal. The presence of compounds with affinity for DNA is measured by their effect on the guanine oxidation. The comparison of the results with a toxicity test based on bioluminescent bacteria has confirmed the applicability of the method to real samples.     

Screen-printed biosensors for the control of wine quality based on lactate and acetaldehyde determination

Biosensors for d-lactate and acetaldehyde were developed, based on screen-printed electrodes and NAD⁺-dependent dehydrogenases. Modification of screen-printed electrodes with the mediator Meldola Blue or with Meldola Blue-Reinecke salt resulted in sensitive, low cost and reliable NADH detectors. The biosensors were realised in two configurations, as disposable and reusable devices. Single-use sensors were obtained by simple deposition of enzyme and cofactor on the surface of mediator-modified electrodes. Chronoamperometry was used for the detection of substrates in small volumes of samples (25 μl). Immobilisation of dehydrogenases by entrapment in poly(vinyl alcohol) bearing styrylpyridinium groups (PVA-SbQ) allowed sensors to be obtained with sufficient operational stability. Amperometry in stirred solutions was the detection technique with biosensors for multiple use. The 3σ detection limits for acetaldehyde were 1 μM by amperometry and 6 μM by chronoamperometry and for d-lactate-0.03 μM and 0.05 μM for reusable and disposable biosensors respectively. The biosensors were applied in the analysis of some French and Romanian wines.     

Highly sensitive disposable nucleic acid biosensors for direct bioelectronic detection in raw biological samples

The development of rapid, low-cost and reliable diagnostic methods is crucial for the identification and treatment of many diseases. Screen-printed gold electrodes (Au/SPEs), coated with a ternary monolayer interface, involving hexanedithiol (HDT), a specific thiolated capture probe (SHCP), and 6-mercapto-1 hexanol (MCH) (SHCP/HDT/MCH) are shown here to offer direct and sensitive detection of nucleic acid hybridization events in untreated raw biological samples (serum, urine and crude bacterial lysate solutions). The composition of the ternary monolayer was modified and tailored to the surface of the Au/SPE. The resulting SHCP/HDT/MCH monolayer has demonstrated to be extremely useful for enhancing the performance of disposable nucleic acid sensors based on screen-printed electrodes. Compared to common SHCP/MCH binary interfaces, the new ternary self-assembled monolayer (SAM) resulted in a 10-fold improvement in the signal (S)-to-noise (N) ratio (S/N) for 1 nM target DNA. The SHCP/HDT/MCH-modified Au/SPEs allowed the direct quantification of the target DNA down to 25 pM (0.25 fmol) and 100 pM (1 fmol) in undiluted/untreated serum and urine samples, respectively, and of 16S rRNA Escherichia coli (E. coli) corresponding to 3000 CFU μL⁻¹ in raw cell lysate samples. The new SAM-coated screen-printed electrodes also displayed favorable non-fouling properties after a 24 h exposure to raw human serum and urine samples, offering great promise as cost-effective nucleic acid sensors for a wide range of decentralized genetic tests.     

Characterisation of Screen-Printed Electrodes for Detection of Heavy Metals

 The characterisation of disposable screen-printed electrodes for stripping analysis is described. The graphite surface of the working electrode is used as substrate for plating a thin mercury film, which allows the electrochemical preconcentration of heavy metals. Optimisation procedures and experimental results are presented. Detection limits around the ppb level were obtained for different metals [Pb(II), Cd(II), Cu(II)]. Received June 6, 1998. Revision November 10, 1988.     

Polishing of screen-printed electrodes improves IgG adsorption

The screen-printing technology has several advantages over the others for industrial sensor production. In fact, it has the advantage of its heterogeneic nature, which is very similar to carbon paste electrodes, combined with the properties of solid electrodes. Carbon ink may be modified with metallic particles, mediators, biocomponents, etc. Carbon screen-printed electrode (SPE) may be coated with additional layers by again screen-printing, adsorption, electropolymerization, etc. The aim of this work is to investigate the effect of polishing the carbon SPE for the active electrode area, for adsorption properties, and for reproducibility. Two polishing methods were investigated, a gentle method using an office paper, and an aggressive one using an emery paper (SiC 240 mum). The adsorption of rabbit immunoglobulin (IgG) was significantly enhanced in the order, emery paper>office paper>original. The reproducibility between electrodes was found to be in this order, office paper>emery paper>original. The electrode area was not significantly affected by any polishing.     

Carbon black as successful screen-printed electrode modifier for phenolic compound detection

We report a miniaturized and disposable electrochemical sensor for phenolic compound detection. The sensor was constructed by modifying the working electrode surface of screen-printed electrode (SPE) with carbon black (CB) dispersion. This new probe showed higher sensitivity and better resistance to fouling than the bare SPE, displaying the suitability of CB as an excellent nanomodifier of SPE for phenolic compound detection. Catechol, gallic acid, caffeic acid, and tyrosol were detected by square wave voltammetry with a detection limit of 0.1 μM, 1 μM, 0.8 μM, and 2 μM, respectively. The sensor was able to selectively discriminate the mono-phenols and ortho-diphenols with rapid and easy measurement, paving the way to use a cost-effective device for quality control of foods and beverages containing phenolic compounds.     

Disposable integrated bismuth citrate-modified screen-printed immunosensor for ultrasensitive quantum dot-based electrochemical assay of C-reactive protein in human serum

A novel immunosensor based on graphite screen-printed electrodes (SPEs) modified with bismuth citrate was developed for the voltammetric determination of C-reactive protein (CRP) in human serum using quantum dots (QDs) labels. The sandwich-type immunoassay involved physisorption of CRP capture antibody on the surface of the sensor, sequential immunoreactions with CRP and biotinylated CRP reporter antibody and finally reaction with streptavidin-conjugated PbS QDs. The quantification of the target protein was performed with acidic dissolution of the PbS QDs and anodic stripping voltammetric detection of the Pb(II) released. Detection was performed at bismuth nanodomains formed on the sensor surface during the electrolytic preconcentration step, as bismuth citrate was reduced to metallic bismuth simultaneously with the deposition of Pb on the surface of the immunosensor. Under optimal conditions, the response was linear over the range 0.2–100 ng mL⁻¹ CRP and the limit of detection was 0.05 ng mL⁻¹ CRP. Since the modified SPE serves as both the biorecognition element and the QDs reader, the analytical procedure is simplified, the drawbacks of existing electroplated immunosensors are minimized while the proposed disposable sensing platform provides convenient, low-cost and ultrasensitive detection of proteins and wider scope for mass-production.     

Dendrimer modified graphite sensors for detection of anticancer drug Daunorubicin by voltammetry and electrochemical impedance spectroscopy

The development of amino-terminated G4 PAMAM dendrimer (PDR) modified disposable electrodes were developed as the first time in our study by using the dendrimer modified disposable graphite (PDR-PGE) and multiwalled carbon nanotube based screen-printed graphite (PDR-MWCNT-SPE) electrodes. Firstly, the microscopic characterization of bare PGEs and PDR modified PGEs was performed. These sensors were then applied for electrochemical monitoring of an anticancer drug, Daunorubicin (DNR). The enhanced oxidation signal of DNR was measured at +0.50 V by using differential pulse voltammetry (DPV) in combination with the PDR-PGEs. The detection limit, estimated from S/N = 3, corresponds accordingly to 317 nM and 128 nM for DNR respectively at the PGE and PDR-PGE. The voltammetric results were consistent with electrochemical impedance spectroscopy (EIS) that was used to characterize the successful modification of PDR onto the surface of PGE and MWCNT-SPE.     

Evaluation of different mediator-modified screen-printed electrodes used in a flow system as amperometric sensors for NADH

This work presents a comparative study between two different methods for the preparation of mediator-modified screen-printed electrodes, to be used as detectors in a reliable flow injection system for the determination of the nicotinamide adenine dinucleotide (NADH) coenzyme. The best strategy was selected for the final development of compact biosensors based on dehydrogenase enzymes. For the first immobilisation strategy, different redox mediators were electropolymerised onto the SPE surface. The second immobilisation strategy was carried out using polysulfone–graphite composites, which were deposited by screen-printing technology onto the screen-printed electrode (SPE) surface. Both methods achieved an effective and reliable incorporation of redox mediators to the SPE configuration. Finally, a flow system for ammonium determination was developed using a glutamate dehydrogenase (GlDH)-Meldola's Blue (MB)-polysulfone-composite film-based biosensor.

The stability of the redox mediators inside the composite films as well as the negligible fouling effect observed on the electrode surface improve the repeatability and reproducibility of the sensors, important features for continuous analysis in flow systems. Furthermore, the optimised bio/sensors, incorporated in a flow injection system, showed good sensitivities and short response times. Such a good analytical performance together with the simple and fast sensor construction are interesting characteristics to consider the polysulfone-composite films as attractive electrochemical transducer materials for the development of new dehydrogenase-based SPEs.     

Carbon nanotube/polysulfone composite screen-printed electrochemical enzyme biosensors

The fabrication, evaluation and attractive performance of multiwall carbon nanotube(MWCNT)/polysulfone biocomposite membrane modified thick-film screen-printed electrochemical biosensors are reported. The fabricated carbon nanotube/polysulfone (CNT/PS) strips combine the attractive advantages of carbon nanotube materials, polysulfone matrix and disposable screen-printed electrodes. Such thick-film carbon nanotubes/polysulfone sensors have a well defined performance, are mechanically stable, and exhibit high electrochemical activity. Furthermore, biocompatibility of CNT/PS composite allows easy incorporation of biological functional moiety of horseradish peroxidase by phase inversion technique. The comparison of graphite with MWCNT as conductor material is described in this paper. The proposed H(2)O(2) biosensor exhibited a linear range (applied potential, -0.2 V) from 0.02 to 0.5 mM and a K(M)(app) of 0.71 mM.     

Electrochemical Characterization of and Stripping Voltammetry at Screen Printed Electrodes Modified with Different Brands of Multiwall Carbon Nanotubes and Bismuth Films

A screen-printed electrode sensor has been fabricated by modifying the carbon ink surface with different brands of multiwall carbon nanotubes (MWCNTs) and bismuth film (BiF) for the determination of traces of lead, cadmium and zinc ions by square wave anodic stripping voltammetry. The MWCNTs, from three different sources, were functionalized and dispersed in Nafion (MWCNT-Nafion) solution and placed on screen printed electrodes (MWCNT-Nafion/SPE); bismuth films were then prepared by ex-situ plating of bismuth onto the MWCNT-Nafion/SPE electrodes. The electrochemical characteristics of BiF/MWCNT-Nafion/SPE/ were examined by electrochemical impedance spectroscopy and showed differences; the charge transfer resistance tends to decrease with negative applied potentials. After optimizing the experimental conditions, the square-wave peak current signal is linear in the nmol L^?1 range. The lowest limit of detection found for the separate determination of lead, cadmium and zinc were 0.7 nmol L^?1, 1.5 nmol L^?1, and 11.1 nmol L^?1, respectively, with a 120 s deposition time.     

Bioelectrochemical immunoassay of polychlorinated biphenyl

A simple, rapid, and highly sensitive bioelectrochemical immunoassay method based on magnetic beads (MBs) and disposable screen-printed electrodes (SPE) has been developed to detect polychlorinated biphenyls (PCBs). The principle of this bioassay is based on a direct competitive enzyme-linked immunosorbent assay using PCB-antibody-coated MBs and horseradish peroxidase (HRP)-labeled PCB (HRP-PCB). A magnetic process platform was used to mix and shake the samples during the immunoreactions and to separate free and unbound reagents after the liquid-phase competitive immunoreactions among PCB-antibody-coated MBs, PCB analyte, and HRP-PCB. After a complete immunoassay, the HRP tracers attached to MBs were transferred to a substrate solution containing o-aminophenol and hydrogen peroxide for electrochemical detection. The different parameters, including the amount of HRP-PCB conjugates, immunoreaction time, and the concentration of substrate that governs the analytical performance of the immunoassay have been studied in detail and optimized. The detection limit of 10 pg mL⁻¹ was obtained under optimum experimental conditions. The performance of this bioelectrochemical immunoassay was successfully evaluated with untreated river water spiked with PCBs, and the results were validated by commercial PCB enzyme-linked immunosorbent assay kit, indicating that this convenient and sensitive technique offers great promise for decentralized environmental application and trace PCBs monitoring.     

Sensitive and selective cocaine electrochemical detection using disposable sensors

This paper describes the voltammetric determination of cocaine in presence of three different interferences that could be found in street samples using disposable sensors. The electrochemical analysis of this alkaloid can be affected by the presence of codeine, paracetamol or caffeine, whose oxidation peaks may overlap and lead to false positives. This work describes two different solutions to this problem. On one hand, the modification of disposable carbon sensors with carbon nanotubes allows the voltammetric quantification of cocaine by using ordinary least squares regressions in the concentration range from 10 to 155 μmol L⁻¹, with a reproducibility of 5.6% (RSD, n = 7. On the other hand, partial least squares regressions are used for the resolution of the overlapped voltammetric signals when using screen-printed carbon electrodes without any modification. Both procedures have been successfully applied to the evaluation of the purity of cocaine street samples.     

Construction and performance characterization of screen printed and carbon paste ion selective electrodes for potentiometric determination of naphazoline hydrochloride in pharmaceutical preparations

This paper describes the development of screen-printed (SPE) and carbon paste (CPE) sensors for the rapid and sensitive quantification of naphazoline hydrochloride (NPZ) in pharmaceutical formulations. This work compares the electroactivity of conventional carbon paste and screen-printed carbon paste electrodes towards potentiometric titration of NPZ. The repeatability and accuracy of measurements performed in the analysis of these pharmaceutical matrices using new screen printed sensors were evaluated. The influence of the electrode composition, conditioning time of the electrode and pH of the test solution, on the electrode performance were investigated. The drug electrode showed Nernstain responses in the concentration range from 1 × 10(-6) to 1 × 10(-2) mol L(-1) with slopes of 57.5 ± 1.3 and 55.9 ± 1.6 mV per decade for SPE and CPE, respectively, and was found to be very precise and usable within the pH range 3-8. These sensors exhibited a fast response time (about 3 s for both SPE and CPE, respectively), a low detection limit (3.5 × 10(-6) and 1.5 × 10(-6) M for SPE and CPE, respectively), a long lifetime (3 and 2 months for SPE and CPE, respectively) and good stability. The selectivity of the electrode toward a large number of inorganic cations, sugars and amino acids was tested. It was applied to potentiometric determination of NPZ in pure state and pharmaceutical preparation under batch conditions. The percentage recovery values for the assay of NPZ in tablets (relative standard deviations ≤0.3% for n = 4) were compared well with those obtained by the official method.