Commercial Screen-printed Electrodes Research Articles

A new osmium-polymer modified screen-printed graphene electrode for fructose detection

This paper describes the development and performance of the first fructose biosensor based on a commercial screen-printed graphene electrode (SPGE). The electrode was modified with an osmium-polymer, which allowed the efficient wiring of the enzyme fructose dehydrogenase (FDH). The immobilization of both osmium-polymer and FDH was realized in an easy way. Aliquots of 10μL Os-polymer and 10μL FDH were thoroughly mixed with poly(ethylene glycol) (400) diglycidyl ether (PEDGE) and deposited on the electrode surface and left there to dry overnight. The biosensor exhibits a detection limit of 0.8μM, a linear range between 0.1 and 8mM, high sensitivity to fructose (2.15μAcm−2/mM), good reproducibility (RSD=1.9%), fast response time (3s) and a stability of 2 months when stored in the freezer.The proposed fructose biosensor was tested in real food samples and validated with a commercial spectrophotometric enzymatic kit. No significant interference was observed with the proposed biosensor.

Novel Impedimetric Immunosensor for Detection of Pathogenic Bacteria Streptococcus pyogenes in Human Saliva

Streptococcus pyogenes , also known as group A streptococcus (GAS), is a Gram positive human pathogen responsible for invasive and noninvasive human infections with a high incidence rate. Traditional detection methods involve cell culture and PCR, which are limited by long processing times or the need for high cost equipment. Impedance-based electrochemical immunosensors provide an alternative by which precise and rapid quantitative detection of the organism can help with rapid clinical decisions. To bring a biosensor for point-of-care applications to market, strict optimization of each level of construction and operation is required. In this paper, commercial screen-printed gold electrodes have been used to construct polytyramine (Ptyr)-based immunosensors. Biotin tagged whole antibodies against S. pyogenes were conjugated to Ptyr amine group via biotin-NeutrAvidin coupling. Sensors were optimized at each level of construction, particularly for Ptyr electrodeposition and antibody concentration, to optimize signal and specificity. Scanning electron microscopy, fluorescence microscopy, and on-sensor analysis (HRP conjugated enhanced chemiluminescence-based semiquantitative method) to detect Ptyr surface amine and bound antibody were performed as supporting techniques. Cumulative and single shot incubations had shown detection range of 100 to 10(5) cells per 10 μL and 100 to 10(4) cells per 10 μL of bacteria in PBS, respectively. Sensors were also able to specifically detect S. pyogenes in 50% (v/v) human saliva, with good selectivity and low cross-reactivity.

Insights into photo-electrochemical sensing of herbicides driven by Chlamydomonas reinhardtii cells

The unicellular green alga Chlamydomonas reinhardtii was exploited as bio-sensing element for the construction of an electrochemical whole-cell based biosensor to detect herbicides in water samples. To preserve the algal photosynthetic functionality, C. reinhardtii cells were entrapped in an alginate gel directly onto the surface of commercial screen-printed electrodes. Cyclic voltammetry (CV) measurements indicated the higher performance of screen-printed carbon nanotube electrodes compared to graphite and gold as working materials. Moreover, it provided insights into the electrochemical reactions occurring at the electrode/algal cells interface, and indicated the optimum buffer pH (pH 7.0) and potential values −(0.7±0.03)V vs. Ag/AgCl reference electrode to maximize current signals in chronoamperometry (CA) experiments. Electrodes with different number of cells and related chlorophyll content were tested by CA to optimize the electrochemical signal in terms of peak current intensity and signal to noise ratio. The oxygen reduction signal originated from the algal activity in response to red LEDs light exposure was monitored by amperometry, and the bio-sensing element response was expressed as a ratio between the current intensities registered in the absence and in the presence of herbicides. As competitive inhibitors of the plastoquinone (QB) binding to the reaction centre D1 protein, triazine and urea-type herbicides block the photosynthetic electron transport leading to a reduction of the biosensor output currents in a concentration-dependent manner. For linuron and simazine the limits of detection were 6×10−9 and 9×10−8M, respectively, while the inhibition constant values (I50) were (1.2±0.1)×10−7 and (2.3±0.2)×10−6M. The operational half-life of the bio-recognition element lasted approximately 9h, while room temperature storage stability tests indicated a 2 and 24% signal loss after 3 and 20 days, respectively. The inhibition of the biosensor photosynthetic activity was irreversible at low herbicide concentrations, and highly reversible at medium–high doses. These results were discussed considering the presence in the Photosystem II pigment–protein complex of two herbicide binding niches with different binding affinities. Beyond introducing a promising prototype for commercial applications, this research shed light on current functional issues related to the not yet fully explored plastoquinone/herbicide binding site.

Miniaturized voltammetric stripping on screen printed gold electrodes for field determination of copper in atmospheric deposition

The applicability of commercial screen-printed gold electrodes (SPGEs) connected to a portable potentiostat and a laptop has been explored to optimize a new square wave anodic stripping voltammetric method for on-site determination of soluble Cu(II) in atmospheric deposition samples taken around an industrial complex. Electrode conditioning procedures, chemical and instrumental variables have been optimized to develop a reliable method capable of measuring dissolved copper with a detection limit of 3.7ngmL−1, useful for pollution monitoring or screening purposes. The proposed method was tested with the SLRS-5 River Water for Trace Metals (recoveries 109.9–113.1%) and the SPS-SW2 Batch 121 Elements in Surface Waters (recoveries 93.2–97.6%). The method was applied to soluble Cu(II) measurement in liquid samples taken by a total atmospheric deposition collector modified with a quartz filter for soluble and insoluble elemental speciation. The voltammetric measurements on field samples were tested in the lab by a reference ICP-MS method, with good agreement. The proposed method proved capability for field operation during a two weeks monitoring campaign.

Comparison of Three Methods of Biocompatible Multi-Walled Carbon Nanotubes Confinement for the Development of Implantable Amperometric Adenosine-5′-Triphosphate Biosensors

An amperometric biosensor for adenosine 5 -triphosphate (ATP) was developed applying a competitive assay of two glucose converting enzymes: glucose oxidase (GOD) and hexokinase (HEX). Competition between GOD and HEX for glucose in presence of ATP, lead to a decrease in the current coming from the hydrogen peroxide generated by the GOD, and allows ATP detection. The biosensor was realized on commercial screen-printed electrodes modified with carbon nanotubes (CNTs). Confinement of CNTs in a polycarbonate membrane, Chitosan and Nafion polymers was investigated as possible solutions for implantable sensors. Nafion gave the best performances, with a sensitivity of 25 pA/μM mm-2, and a detection limit of 257 M. The sensor resulted able to measure ATP concentrations in the range of hundred of μmol/l.

Determination of mercury in ambient water samples by anodic stripping voltammetry on screen-printed gold electrodes

The applicability of commercial screen-printed gold electrodes (SPGEs) for the determination of Hg(II) in ambient water samples by square wave anodic stripping voltammetry has been demonstrated. Electrode conditioning procedures, chemical and instrumental variables have been optimized to develop a reliable method capable of measuring dissolved mercury in the low ng mL −1 range (detection limit 1.1 ng mL −1), useful for pollution monitoring or screening purposes. The proposed method was tested with the NIST 1641d Mercury in Water Standard Reference Material (recoveries 90.0–110%) and the NCS ZC 76303 Mercury in Water Certified Reference Material (recoveries 82.5–90.6%). Waste water samples from industrial origin and fortified rain water samples were assayed for mercury by the proposed method and by a reference ICP-MS method, with good agreement. Screen printing technology thus opens a useful way for the construction of reliable electrochemical sensors for decentralized or even field Hg(II) testing.

Design and adaptation of miniaturized electrochemical devices integrating carbon nanotube‐based sensors to commercial CE equipment

The design of new electrochemical devices integrating carbon nanotube sensors and their adaptation to commercial CE equipments are described. One of these designs was made for using commercial screen-printed electrodes, whereas the second was projected for coupling commercial glassy carbon electrodes. The electrochemical characterization of these devices revealed that their hydrodynamic behaviour is strongly influenced by the electrode modification with multi-wall carbon nanotubes that provided faster and/or more sensitive signals. The analytical applicability of these devices was illustrated for the CZE separation of chlorinated phenols and the MEKC separation of endocrine disruptors, where the use of carbon nanotube sensors has proved to be advantageous when compared with unmodified ones, with good electrocatalytic properties combined with acceptable background currents and a remarkable resistance to passivation.

Electrochemical characterization of screen-printed and conventional carbon paste electrodes

This work compares the electroactivity of a conventional carbon paste electrode and non-pretreated commercially available screen-printed carbon electrodes (from Alderon Biosciences, University of Florence and DropSens) towards some benchmark redox couples like hexaammineruthenium (III), ferricyanide, p-aminophenol and hydroquinone. While cyclic voltammograms of Ru 3+ did not show significative electron transfer reactivity differences between the electrodes tested, the other redox systems exhibited higher reversible behaviours on DropSens electrodes. Scanning electron microscopy and roughness analysis with a profilometer were applied to detect the surface morphology of the working electrodes. The roughness evaluated of the screen-printed carbon working electrodes increased in this order Alderon < University of Florence < DropSens. Finally, the most electrochemically active and rough unpretreated electrode (DropSens commercial screen-printed electrode) was used to study the electrochemical–chemical reaction mechanism of indigo carmine oxidation in 0.1 M sulphuric acid. This study showed that the adsorption of the oxidation product of indigo carmine is stabilized when it is adsorbed on the surface of the electrode.