Bare Screen-printed Electrode Research Articles

High performance electrochemical sensor based on modified screen-printed electrodes with cost-effective dispersion of nanostructured carbon black

Abstract A novel sensor based on a screen-printed electrode (SPE) modified with a stable dispersion of commercially available carbon black (CB) N220 was developed. This probe showed significantly enhanced electrochemical activity relative to a bare SPE when tested with ferricyanide, epinephrine, norepinephrine, benzoquinone and NADH. When challenged in amperometric batch mode with NADH, the response was stable and revealed a linear dependence up to 2·10−4 mol L−1 with a detection limit of 3·10−7 mol L−1. The analytical performance, coupled with the low cost of the CB nanomaterial, suggests that this sensor holds promise for electrochemical applications.

Flexible thick-film glucose biosensor: Influence of mechanical bending on the performance

The influence of the bending-induced mechanical stress of flexible Nafion/GOx/carbon screen-printed electrodes (SPEs) upon the performance of such glucose biosensors has been examined. Surprisingly, such flexible enzyme/polymer-SPEs operate well following a severe bending-induced mechanical stress (including a 180 degrees pinch), and actually display a substantial sensitivity enhancement following their mechanical bending. The bending-induced sensitivity enhancement is observed only for the amperometric detection of the glucose substrate but not for measurements of hydrogen peroxide, catechol or ferrocyanide at coated or bare SPEs. These (and additional) data indicate that the bending effect is associated primarily with changes in the biocatalytic activity. Such sensitivity enhancement is more pronounced at elevated glucose levels, reflecting the bending-induced changes in the biocatalytic reaction. Factors affecting the bending-induced changes in the performance are examined. While our data clearly indicate that flexible enzyme/polymer-SPEs can tolerate a severe mechanical stress and hold promise as wearable glucose biosensors, delivering the sample to the active sensor surface remains the major challenge for such continuous health monitoring.

Highly Sensitive Amperometric Immunosensor for Detection of Plasmodium falciparum Histidine-Rich Protein 2 in Serum of Humans with Malaria: Comparison with a Commercial Kit

A disposable amperometric immunosensor was developed for the detection of Plasmodium falciparum histidine-rich protein 2 (PfHRP-2) in the sera of humans with P. falciparum malaria. For this purpose, disposable screen-printed electrodes (SPEs) were modified with multiwall carbon nanotubes (MWCNTs) and Au nanoparticles. The electrodes were characterized by cyclic voltammetry, scanning electron microscopy, and Raman spectroscopy. In order to study the immunosensing performances of modified electrodes, a rabbit anti-PfHRP-2 antibody (as the capturing antibody) was first immobilized on an electrode. Further, the electrode was exposed to a mouse anti-PfHRP-2 antibody from a serum sample (as the revealing antibody), followed by a rabbit anti-mouse immunoglobulin G-alkaline phosphatase conjugate. The immunosensing experiments were performed on bare SPEs, MWCNT-modified SPEs, and Au nanoparticle- and MWCNT-modified SPEs (Nano-Au/MWCNT/SPEs) for the amperometric detection of PfHRP-2 in a solution of 0.1 M diethanolamine buffer, pH 9.8, by applying a potential of 450 mV at the working electrode. Nano-Au/MWCNT/SPEs yielded the highest-level immunosensing performance among the electrodes, with a detection limit of 8 ng/ml. The analytical results of immunosensing experiments with human serum samples were compared with the results of a commercial Paracheck Pf test, as well as the results of microscopy. The specificities, sensitivities, and positive and negative predictive values of the Paracheck Pf and amperometric immunosensors were calculated by taking the microscopy results as the "gold standard." The Paracheck Pf kit exhibited a sensitivity of 79% (detecting 34 of 43 positive samples; 95% confidence interval [CI], 75 to 86%) and a specificity of 81% (correctly identifying 57 of 70 negative samples; 95% CI, 76 to 92%), whereas the developed amperometric immunosensor showed a sensitivity of 96% (detecting 41 of 43 positive samples; 95% CI, 93 to 98%) and a specificity of 94% (correctly identifying 66 of 70 negative samples; 95% CI, 92 to 99%). The developed method is more sensitive and specific than the Paracheck Pf kit.

Electrocatalysis and sensitive determination of cysteine at poly(3,4-ethylenedioxythiophene)-modified screen-printed electrodes

The electrocatalytic oxidation of cysteine at screen-printed electrode (SPE) modified with electrogenerated poly(3,4-ethylenedioxythiophene) film (PEDOT) was investigated. Cyclic voltammetric studies showed that the SPE/PEDOT electrode lowers the overpotentials and improves electrochemical behavior of cysteine oxidation, as compared to the bare SPE. The catalytic oxidation responses were studied and the reaction mechanisms were discussed. Excellent analytical features, including high sensitivity, low detection limit and satisfactory dynamic range, were achieved by flow-injection amperometry under optimized conditions.

Amperometric detection in TMB/HRP-based assays

3,3',5,5'-Tetramethylbenzidine (TMB) is the most commonly used chromogen for horseradish peroxidase (HRP) and so its performance as an electrochemical substrate was evaluated. Measurements of HRP activity in solution were carried out by using an amperometric detector coupled to a flow injection analysis (FIA) system. The enzymatic product was easily detected at a potential of +0.1 V (vs. Ag-pseudoreference electrode) at a bare screen-printed electrode placed in a homemade electrochemical flow cell. A high flow rate (4.3 mL min(-1)) of 0.5 M H2SO4 was used to obtain repeatable signals and a short analysis time. The detection limit achieved after 15 min of incubation was 2x10(-14) M of HRP. The applicability of the amperometric detector to ELISAs was demonstrated by using a commercially available kit for the quantification of interleukin-6 (IL-6) without modifying the kit manufacturer's protocol or the reagents for this test.

Indirect determination of alkaline phosphatase based on the amperometric detection of indigo carmine at a screen-printed electrode in a flow system.

Amperometric analysis of indigo carmine at a bare screen-printed electrode placed in an FIA system is reported. This compound is easily detected at a potential of -0.3 V (vs. Ag pseudo-reference electrode) without observing any fouling of the electrode surface, thus allowing the repetitive use of the same electrode in a reproducible manner (coefficients of variation down to 7% for more than 20 consecutive determinations). A linear range of three orders of magnitude and a limit of detection in the sub-micromolar range were attained for this molecule. Based on these studies, indirect amperometric measurements of alkaline phosphatase (ALP) activity in solution were easily carried out using 3-indoxyl phosphate substrate. Its hydrolysis catalyzed by ALP gave rise to indigo product. This product is insoluble in aqueous solutions but it was easily converted into its soluble parent compound, indigo carmine, by addition of fuming sulfuric acid to the reaction media. Using this approach, we achieved a linear range of more than one order of magnitude and a limit of detection of 1 U/l ALP, for an enzymatic reaction time of 60 min.