Commercial Screen-printed Electrodes Research Articles

Low-cost inkjet-printed nanostructured biosensor based on CRISPR/Cas12a system for pathogen detection

The escalating global incidence of infectious diseases caused by pathogenic bacteria, especially in developing countries, emphasises the urgent need for rapid and portable pathogen detection devices. This study introduces a sensitive and specific electrochemical biosensing platform utilising cost-effective electrodes fabricated by inkjet-printing gold and silver nanoparticles on a plastic substrate. The biosensor exploits the CRISPR/Cas12a system for detecting a specific DNA sequence selected from the genome of the target pathogen. Upon detection, the trans-activity of Cas12a/gRNA is triggered, leading to the cleavage of rationally designed single-strand DNA reporters (linear and hairpin) labelled with methylene blue (ssDNA-MB) and bound to the electrode surface. In principle, this sensing mechanism can be adapted to any bacterium by choosing a proper guide RNA to target a specific sequence of its DNA. The biosensor's performance was assessed for two representative pathogens (a Gram-negative, Escherichia coli, and a Gram-positive, Staphylococcus aureus), and results obtained with inkjet-printed gold electrodes were compared with those obtained by commercial screen-printed gold electrodes. Our results show that the use of inkjet-printed nanostructured gold electrodes, which provide a large surface area, in combination with the use of hairpin reporters containing a poly-T loop can increase the sensitivity of the assay corresponding to a signal variation of 86%. DNA targets amplified from various clinically isolated bacteria, have been tested and demonstrate the potential of the proposed platform for point-of-need applications.

Gold leaf electrochemical flow cell for determination of iodide in nuclear emergency tablets

This work introduces an innovative gold-leaf flow cell for electrochemical detection in flow injection (FI) analysis. The flow cell incorporates a hammered custom gold leaf electrochemical sensor. Hammered gold leaves consist of pure gold and are readily available in Thailand at affordable prices (approximately $0.085 for a sheet measuring 40 mm × 40 mm). Four sensing devices can be made from a single sheet of this gold leaf, resulting in a production cost of approximately $0.19 per sensor. Each electrochemical sensor has the gold leaf as the working electrode, together with a printed carbon strip, and a printed silver/silver chloride strip as the counter and reference electrodes, respectively. Initial investigations using cyclic voltammetry of a standard 1000 μmol L⁻1 iodide solution in 60 mmol L⁻1 phosphate buffer (PB) solution at pH 5, demonstrated performance comparable to that of a commercial screen-printed gold electrode. The hammered gold leaf electrode was then installed in a commercial flow cell as part of an FI system. A sample or standard iodide solution (100 μL) is injected into the first carrier stream of phosphate buffer (PB) solution, which then merges to mix with the second stream of the same buffer solution before flowing into the flow cell for amperometric detection of iodide. The optimized operating conditions include a fixed potential of +0.39 V (vs Ag/AgCl), and a total flow rate of 3 mL min⁻1. A linear calibration is obtained in the concentration range of 1 to 1000 μmol L⁻1 I− with a typical equation of μA = (0.00299 ± 0.00004) × (μmol L−1 I−) + (0.021 ± 0.020), and R2 = 0.9994. Analysis of iodide using this gold leaf-FI system is rapid with sample throughput of 86 samples h⁻1 and %RSD of a sample of 100 μmol L⁻1 I⁻ of 1.2 (n = 29). The limit of detection, (calculated as 2.78 × SD of regression line/slope), is 27 μmol L⁻1 I−. This method was successfully applied to determine iodide in nuclear emergency tablets.

Ultrasensitive electrochemical sensors based on Cu and Cu@Ag nanorods for simultaneous heavy metal detection

This work reports the development of ultrasensitive miniaturized electrochemical device for heavy metal sensing. A laser engraver based patterning of fluorine-doped tin oxide (FTO) sheet was done to draw an etched pattern forming a miniaturized 3-electrode configuration. A layer of Ag/AgCl ink served as pseudo-reference electrode. The sensing electrode was coated using low-cost Cu nanorods (CuNRs) grown radially along the {110} surface with aspect ratio of 8.0 and Cu@Ag core-shell nanorods (Cu@AgNRs) formed via galvanic displacement for simultaneous electrocatalytic detection of heavy metal ions (Pb(II), Cd(II), Hg(II), and Zn(II)) present in water. The electroactive surface area of the prepared devices is 0.026, 0.093 and 0.125 cm2 for bare FTO, CuNRs/FTO and Cu@AgNRs/FTO, respectively. Bimetal Cu@AgNRs/FTO sensor exhibited the lowest limit of detection of 1, 2, 5 and 6 nM, respectively, detecting Cd(II), Pb(II), Zn(II), and Hg(II) ions, and it was 2, 2, 3 and 4 nM, respectively, for simultaneous detection of Zn(II), Pb(II), Cd(II) and Hg(II). The Cu@AgNRs/FTO based device showed distinct peak-to-peak separation by 0.40, 0.25 and 0.51 V for Zn(II)-Cd(II), Cd(II)-Pb(II) and Pb(II)-Hg(II), respectively. This device was highly sensitive (583.6–1261.8 μA․μM−1․cm−2) for heavy metal detection over CuNRs/FTO (15.9–107.4 μA․μM−1․cm−2). The Cu@AgNRs/FTO based sensors demonstrated good reproducibility (relative standard deviation ≤ 5%) with recovery (>90%) in the case of all target heavy metals simultaneously present in environmental water samples. Hence, the Cu nanorods based miniaturized sensing platforms developed in the present study for simultaneous heavy metal detection are potential low-cost alternatives providing a repeatability of upto 4 cycles unlike the commercial screen-printed electrodes.

Comparison of Faradaic and Non-Faradaic Impedance Biosensors Using 2-Electrode and 3-Electrode Configurations for the Determination of Bovine Serum Albumin (BSA)

This paper presents a study on the impedance spectroscopy methods applied to 2-electrode and 3-electrode biosensors. While 3-electrode electrochemical biosensors have been extensively studied and applied in various applications, the 2-electrode configuration of electrochemical biosensors still lacks comprehensive investigation for real-world applications. In particular, the miniaturization of the 3-electrode configuration for integration into microfluidic devices has been explored due to the relatively limited number of previous studies. A commercial screen-printed gold electrode was employed to develop immunosensors for bovine serum albumin (BSA) detection. The comparisons were performed on non-Faradaic and Faradic immunosensors corresponding to 2-electrode and 3-electrode configurations through impedance measurements. The results show the performance of both types of sensors in detecting BSA protein. While the 2-electrode configuration-based sensor can detect the BSA protein with a sensitivity of 12 Ω/µM, the 3-electrode configuration-based sensor shows superior results with a sensitivity of 7.2 kΩ/µM. Besides, the results also indicate that the 2-electrode configuration-based sensor can easily be miniaturized to integrate into a microfluidic channel to develop lab-on-a-chip systems. Although the 3-electrode configuration demonstrates advancements compared to the 2-electrode configuration, the 2-electrode system based on non-Faradaic processes still shows high potential for future applications.

Improving design features and air bubble manipulation techniques for a single-step sandwich electrochemical ELISA incorporating commercial electrodes into capillary-flow driven immunoassay devices.

Integrating electrochemistry into capillary-flow driven immunoassay devices provides unique opportunities for quantitative point-of-care testing. Although custom electrodes can be inexpensive and are tunable, they require skilled fabrication. Here, we report the incorporation of a commercial electrode into a capillary-flow driven immunoassay (iceCaDI) device for a single end-user step sandwich electrochemical enzyme-linked immunosorbent assay (ELISA). The iceCaDI device is a pump-free portable microfluidic device with an integrated commercial screen-printed electrode and flow driven by capillary action. The iceCaDI device is composed of alternating polyester transparency film and double-sided adhesive film layers that are patterned with a laser cutter. This platform was designed to address known limitations of laminated device fabrication methods and operation. First, we developed a foldable laminated device fabrication using hinges for easy assembly and precise alignment. Second, reagent dispersing was achieved by incorporating a 1 mm wide arrow-shaped notch in the middle of the channel that trapped an air bubble and formed a baffle that facilitated reagent spreading to cover the detection area. Third, small vent holes were added to the top layer of the channels to prevent air bubbles from blocking flow. Finally, we fabricated a CRP immunosensor with a detection range of 0.625 to 10.0 μg mL-1 as a proof-of-concept to demonstrate an automatically driven sandwich electrochemical ELISA using the iceCaDI device. Three concentrations of CRP were successfully measured under flow conditions within 8 min. Our proposed device is a promising approach and a step forward in the development of point-of-care (POC) devices for techniques that traditionally require multiple user steps.

An advanced miniature fluidic system in multilayer ceramic technology with precise temperature and flow control for in situ pollution monitoring

Rapid, on-site, water-quality monitoring is necessary to prevent and remediate environmental pollution. This study aims to develop a miniature, portable, fluidic system (MFS) designed for the easy insertion of disposable, screen-printed electrodes (SPEs) and the measurement of an electrochemical response (EC) under controlled temperature and flow conditions. The three-dimensional MFS, realised in low-temperature, cofired ceramic and multilayer ceramic technology, consist of three distinct cavities, each with separate inlet and outlet channels. These channels are designed to maintain an equivalent flow rate across all three cavities. The MFS allows simultaneous measurements at three measuring sites, temperature control of the fluid from room temperature to 125 °C via integrated heaters and temperature sensors, and flow regulation up to 20 mL/min via an external fluid pump. The EC values obtained from the SPEs in a standard solution of potassium ferrocyanide/potassium ferricyanide at room temperature and under stagnant conditions were consistent with measurements conducted in the MFS, droplet and conventional electrochemical cells, confirming the accuracy and reliability of the MFS. The EC response was confirmed in the MFS under flow conditions of 4 mL/min and temperatures of 25 °C, 35 °C, and 45 °C. This shows that multilayer ceramic technology enables the fabrication of a miniature, three-dimensional MFS with integrated fluidic and electronic components that provide reliable and accurate electrochemical measurements using a commercial SPE under controlled flow and temperature conditions.

G-Quadruplex/Hemin-Mediated Polarity-Switchable and Photocurrent-Amplified System for Escherichia coli O157:H7 Detection.

The contamination of food by pathogens is a serious problem in global food safety, and current methods of detection are costly, time-consuming, and cumbersome. Therefore, it is necessary to develop rapid, portable, and sensitive assays for foodborne pathogens. In addition, assays for foodborne pathogens must be resistant to interference resulting from the complex food matrix to prevent false positives and negatives. In this study, hemin and reduced graphene oxide-MoS2 sheets (GMS) were used to design a near-infrared (NIR)-responsive photoelectrochemical (PEC) aptasensor with target-induced photocurrent polarity switching based on a hairpin aptamer (Hp) with a G-quadruplex motif. A ready-to-use analytical device was developed by immobilizing GMS on the surface of a commercial screen-printed electrode, followed by the attachment of the aptamer. In the presence of Escherichia coli O157:H7, the binding sites of Hp with the G-quadruplex motif were opened and exposed to hemin, leading to the formation of a G-quadruplex/hemin DNAzyme. Crucially, after binding to hemin, the charge transfer pathway of GMS changes, resulting in a switch of the photocurrent polarity. Further, G-quadruplex/hemin DNAzyme enhanced the cathodic photocurrent, and the proposed sensor exhibited a wide linear range ((25.0-1.0) × 107 CFU/mL), a low limit of detection (2.0 CFU/mL), and good anti-interference performance. These findings expand the applications of NIR-responsive PEC materials and provide versatile PEC methods for detecting biological analytes, especially for food safety testing.

An amperometric method for the determination of cystine in urine samples and pharmaceutical tablets using screen-printed silver electrodes

Elevated urinary cystine levels are closely associated with the development of cystine stone. Therefore, the ability to rapidly and efficiently determine urinary cystine levels is crucial for physicians to manage patients with cystinuria or those undergoing cystine medication. In this study, an amperometric method employing a commercial screen-printed silver electrode was successfully established. The resulting calibration curve indicated a detection limit of 0.65 mg/dL. Satisfactory recoveries ranging from 89% to 109% were obtained for urine samples. The method was also effective for the quality control analysis of cystine in pharmaceutical tablets. The recovery of cystine from pharmaceutical tablets ranged from 98% to 101% using the developed method. This method enables the rapid and accurate determination of cystine in both urine samples and pharmaceutical tablets and provides valuable information for clinical diagnosis and pharmaceutical quality control.

Laser-Induced Graphene Electrodes for Electrochemistry Education and Research

Many aspects of electrochemical education, such as electroanalysis demonstrations, require three-electrode-cell experimental setups. Many researchers and educators use screen-printed electrochemical electrodes, which are miniature and disposable but are relatively expensive and use proprietary fabrication components. The present article describes how to laser-scribe complete three-electrode graphene-based electrodes that can compete with (and, in some regards, even rival) commercial screen-printed electrodes. The process of optimization of the lasing procedure to produce laser-induced graphene using almost any laser cutter available to the reader is described. A way to form a Ag/AgCl pseudoreference electrode on the graphene trace to complete the three-electrode cell, without usage of commercial inks or complicated printing technologies, is demonstrated. Electrochemical characterization of the electrode surface, reference electrode stability, and student practice demonstration of analytic applications of the produced cells (determination of dopamine concentration and coffee polyphenols) are described. These experiments and procedures act both as a method of fabrication of laser-scribed electrodes and as an educational material for introduction to electrodeposition, voltammetry, and electroanalysis.

An Impedimetric Biosensing Strategy Based on BicyclicPeptides as Bioreceptors for Monitoring h-uPA Cancer Biomarkers

In the era of liquid biopsies, the reliable and cost-effective detection and screening of cancer biomarkers has become of fundamental importance, thus paving the way for the advancement of research in the field of point-of-care testing and the development of new methodologies and technologies. Indeed, the latter ones can help designing advanced diagnostic tools that can offer portability, ease of use with affordable production and operating costs. In this respect, impedance-based biosensing platforms might represent an attractive alternative. In this work, we describe a proof-of-concept study aimed at designing portable impedimetric biosensors for the monitoring of human urokinase-type plasminogen activator (h-uPA) cancer biomarker by employing small synthetic receptors. Aberrant levels of h-uPA were correlated with different types of cancers. Herein, we report the use of two bicyclic peptides (P2 and P3) which have been engineered to bind h-uPA with high affinity and exquisite specificity. The synthetic receptors were immobilized via biotin-streptavidin chemistry on the surface of commercial screen-printed electrodes. The impedimetric changes in the electrode/solution interface upon incubation of spiked h-uPA samples in the presence of a redox probe were followed via electrochemical impedance spectroscopy. The P3-based impedimetric assay showed the best outcomes in terms of dynamic range and linearity (0.01–1 μg mL−1) and sensitivity (LOD = 9 ng mL−1). To fully assess the performances of P3 over P2, and to compare the label-free architecture vs. labelled architecture, a voltammetric assay was also developed.

Functionalization of Screen-Printed Electrodes with Grape Stalk Waste Extract-Assisted Synthesized Silver and Gold Nanoparticles: Perspectives of Electrocatalytically Enhanced Determination of Uranyl Ion and Other Heavy Metals Ions.

Recently, nanotechnology and nanoparticles (NPs) such as AgNPs and AuNPs have become important in analytical chemistry due to their great potential to improve the performance of electrochemical sensors. In this work, Ag and Au nanoparticles have been synthesized using a green route in which a grape stalk waste extract is used as a reducing agent to obtain metallic nanoparticles. These NPs were used to customize the surface of commercial screen-printed electrodes (SPCNFEs). The spin-coating method was used to modify commercial SPCNFEs under a nitrogen atmosphere. The resulting electrodes were used in a determination study of Cd(II), Pb(II), and U(VI) with differential pulse anodic stripping voltammetry (DPASV). The customized green AgNPs and AuNPs electrodes presented higher sensitivity and electroanalytical performance than the non-modified SPCNFE. The results showed that the best analytical parameters were obtained with the green, silver nanoparticle SPCNFEs, with a LOD of 0.12 μg L-1 for Pb(II), which is a lower value compared to the most restrictive regulation guidelines. Additionally, the U(VI) ion was successfully determined using the developed G-AgNPs-SPCNFE in spiked tap water, showing comparable results with the ICP-MS technique.

Effect of microfluidic channel integration onto gold microelectrode on its redox electrochemistry.

Microfluidic systems have attracted significant interest in recent years as they are extensively employed in lab-on-chip and organ-on-chip research. Their combination with electrochemical platforms offers many advantages, promising a high potential for sensing applications, still the microfluidic-channel integration onto electrodes might induce challenges related to changes in signal-to-noise ratios and mass transport conditions. In this study, we investigated the effect of microfluidic channel integration in redox behavior of thermally deposited gold thin film microelectrodes by voltammetric (CV and SWV) electrochemical measurements. Using different dimensions of PDMS microfluidic channels (i.e. widths of 50, 100, 250, and 500 μm) and a constant electrode dimension (200 μm), we analyzed the relationship between altered electroactive area and electrochemical response against target redox molecules. The increases in electroactive area which were determined by the microfluidic channel sizes were in well-correlation with the obtained CV and SWV redox currents as expected. There was no significant decrease in signal-to-noise ratio in microchannel-integrated electrodes. AFM and SEM characterization demonstrated that thermally deposited thin film electrodes had significantly lower (approximately 25 fold) surface roughness in comparison to commercial screen-printed electrodes. Additionally, we have observed a clear microelectrode-to-macroelectrode transition, from hemispherical to linear (planar) diffusion in other terms, with the increasing channel size.

A customizable cost-effective design for printed circuit board-based nanolayered gold screen-printed electrode: From fabrication to bioapplications.

Screen-printed electrodes (SPEs) are promising candidates for fabricating biosensing platforms in the laboratory and industry due to the various advantages they involve. The primary method for fabricating SPEs is 2D printing. However, commercial SPEs have some limitations due to the specific ports and connections they require, inflexible design, high prices, and decreased efficiency after a short time. This article introduces high performance, feasible, and cost-effective gold SPEs based on the combination of printed circuit board substrate (PCBs) and sputtering methods for electrochemical biosensing platforms. First, we discuss a general gold SPE development procedure that helps researchers to develop specific designs. The final developed version of SPEs was characterized in the second step, showing positive performance in electrochemical parameters because of the optimization of design and fabrication steps. In the study's final phase, SPEs were used to fabricate a simple platform for breast cancer cell detection as a proof of concept without using any linker or labeling step. The designed immunosensor is very simple and cost-effective, showing a linear calibration curve in the range of 10 - 2× 102 cellsmL-1 (R 2 = 0.985, S/N = 3). This research can be used as a reference for future studies in SPEs-based biosensors because of the flexibility of its design and the accessibility of the manufacturing equipment required.

UV-vis Spectroelectrochemical In situ Study During the Electrochemical Oxidation of 2-Thiazolamine and 2-Oxazolamine

Oxazoles and thiazoles are useful organic compounds in the pharmaceutical industry and agricultural chemistry. For example, the aminothiazole heterocycle system is a useful structural element in medical chemistry and has found wide applications. [1] In previous studies, our group has reported that he electroactivity of 2-aminothiazole and 2-aminooxazole derivate resides on the primary amine group in C-2 position in thiazolic and oxazolic ring respectively and the electron donor ability is mainly governed by 2-aminothiazole and 2-aminooxazole chemistry. [2] Preliminary results, however, have not described or reported the electrochemical behavior of these heterocyclic compounds using in situ coupled techniques. One of the most interesting tools in the characterization of materials is the spectroscopy in the UV-Vis region, because it gives an idea of the compounds present. [3] This interesting technique has been coupled to electrochemicals methods, giving the possibility to in-situ information.In this work, the electrochemical oxidation of 2-Thiazolamine and 2-Oxazolamine is performed utilizing cyclic voltammetry purely electrochemical technique, coupled to UV-vis spectroscopy in situ. The UV–Vis spectra were collected simultaneously while potentiostatic electrolysis was performed. Cyclic voltammetry was carried out using a PalmSens4 potentiostat and Spectroelectrochemical experiments were performed using a quartz curvet of 1 cm path length by placing a commercial screen-printed electrode (IS-1, Italsens), which included a three-electrode configuration printed on the same strip. The preliminary results show the important information provided by UV-Visible spectroscopy coupled with electrochemical techniques.Bibliographic Yichao Wan, Jiabing Long, Han Gao, Zilong Tang, 2021, Eur. J. Med. Chem 210, 15, 112953J A Morales-Morales, A F Villamarin, E Florez-López, J J Rios-Acevedo, 2018 Phys.: Conf. Ser. 1119 012006Noelia González-Diéguez, Alvaro Colina, Jesús López-Palacios, and Aránzazu Heras 2012, Chem. 84, 21, 9146–9153

Polyimide adhesive tapes as a versatile and disposable substrate to produce CO2 laser-induced carbon sensors for batch and microfluidic analysis

The laser scribing technique produced disposable electrochemical devices with Kapton adhesive tape as a polyimide substrate. The approach consisted of carbonizing the polyimide substrate with a CO2 laser source, generating the 3-electrode electrochemical system based on carbon conductive tracks. The materials were characterized by Raman spectroscopy, scanning electron microscopy, and electrochemical techniques. The laser processing parameters were submitted to the optimization process, demonstrating a strong impact on the electrochemical properties of the sensors. The sensors were initially fabricated in a chip format, providing satisfactory electrochemical responses compared to commercial screen-printed electrodes. In addition, they showed reproductivity, repeatability, and storage stability. Once characterized, the sensors were combined with paper devices to show the versatility of the electrochemical system. Paper was chosen because of its ubiquity and ability to generate flow without external pumps, resulting in portable analytical platforms. This combination can be advantageous for point-of-need applications. The analytical performance of the devices was evaluated for voltammetric determination of 3-nitrotyrosine, uric acid, and dopamine, demonstrating attractive features for analytical applications.

Electrochemical Detection and Spectrophotometry of Dopamine using Commercial Screen-Printed Electrodes

Lab-on-chip is miniaturized devices integrated into a chip which can run one or several analyses which are usually done in laboratory settings, such as biochemical detection. Dopamine is an important neurotransmitter which regulates hormones, control of movement, emotion, attention, and motivation. Excess, lack, and dysregulation of dopamine could cause numbers of diseases and disorders. The technique used to measure and evaluate dopamine usually are expensive to run, require longer time to run, require some technical qualification to run, require expensive equipments, and some are invasive to do. These are the reasons why a lab-on-chip system is needed to make the detection of dopamine concentration faster, easier, and more portable. This paper studied the accuracy of using electrochemical detection to measure the concentration of liquid specimens of dopamine compared to uv/vis spectrophotometry. Electrochemical detection method named cyclic voltammetry was chosen for this study. The hypothesis for this study is that both peak current (ip) and absorbance positively correlate to concentration, therefore both could be used with minimal error margin. For this study, the peak current (ip) and absorbance of different concentrations of liquid specimen of dopamine are measured, and its regression were observed. It was shown that the concentration of liquid specimens of dopamine is linear to both anodic peak current (ipa) and absorbance. Due to the high R2 values of 0.9883, electrochemical detection could be used and implemented to detect dopamine concentration for application of lab-on-chip, as it is more portable and requires less volume of sample compared to spectrophotometry.

Commercial Screen-Printed Electrode Decorated with Carbonaceous Binary Sulfides for Direct Glucose Detection in Human Fluid Samples

We hereby demonstrate a highly controllable, green, and rapid synthesis strategy for the production of binary metal sulfides on carbon nano-horns (CNHs) for the fabrication of non-enzymatic glucose sensor using commercial graphite screen-printed electrodes (GSPEs). CNHs were synthesized using the submerged arc discharge method as described elsewhere. In the next step, one droplet (50 µL) of the well-dispersed CNHs was carefully cast on the surface of the GCE (and GSPE). In the final step of preparing the modified electrodes, CNH/GCEs were covered by a thin layer of nickel cobalt sulfide by a simple electrochemical deposition procedure.Following the structural examination of the prepared electrocatalyst were examined. In this regard, several microscopic methods like FE-SEM or TEM were used to know more regard the morphology of the material. The FE-SEM images confirmed the successful formation of sponge like nanosheets of NiCo-S on carbonaceous material. Since CNHs are prepared from graphene sheets with open ends in horn-like shapes, they can be considered as being formed from the origami-like or crushing contortion of a single graphene sheet. According to the FE-SEM images, the agglomeration of CNHs establishes discrete nano-sphere structures with diameters in the range of 50 to 150 nm. The TEM images also confirm this nano-sphere strictures.Following detailed structural characterization, the electrocatalytic activity of the fabricated NiCo-S/CNH electrodes toward electro-oxidation of glucose is examined in detail. The cyclic voltammetry was also used for glucose electro-oxidation mechanism investigation. In addition, parameter optimization was also done by utilizing cyclic voltammetry technique. These include medium pH, deposition cycles, and metals mole ration. Moreover, the effect of the presence and absence of CNH on the electrochemical performance of glucose oxidation were also examined. It shows that in the presence of CNH the peak current density for glucose oxidation is higher that is perfect for analytical purposes and increase the analytical sensitivity. The structural properties and electrochemical response of the fabricated electrodes were also compared to their corresponding mono-metallic counterparts.The amperometric method was utilized as one of the most prevalent and momentous techniques for the quantitative determination of glucose. The applied potential in amperometric tests was optimized to be +0.5 V (vs. Ag/AgCl). The proposed electrodes were operated within two distinct linear dynamic ranges of 0.001- 0.330 mM and 0.330 - 4.53 mM of standard glucose with sensitivities of 1842 µA.mM-1.cm-2, and 854 µA.mM-1.cm-2, respectively. On the other hand, an analytical sensitivity of 467 µA.mM-1.cm-2, within the linear dynamic range of 0.5 - 6 mM was obtained for the static chronoamperometric measurements for modified commercial screen-printed electrode (GSPE). The proposed sensor showed outstanding selectivity against iso-structures and co-existing interferences, long-term durability, rapid response (1.7 s), excellent poisoning resistance against chloride ions, good repeatability, and reproducibility. The tested interferences were 0.1 mM solutions of fructose, galactose, sucrose, lactose, ascorbic acid, uric acid, dopamine hydrochloride, and NaCl. In order to demonstrate the capability of the fabricated electrodes and to evaluate their potential for glucose measurements in real physiological specimens, the glucose level was successfully measured in human blood serum, urine, and saliva samples, without any sample pre-treatment. All in all, the encouraging results make NiCo-S/CNH electrodes immensely promising for clinical and physiological glucose-level measurements.Figure 1. (a) FE-SEM image of CNH. (b) FE-SEM image of NiCo-S/CNH. (c) TEM image of CNHs. (d) Cyclic voltammogarm of NiCo-S/CNH in the absence and presence of various concentration of glucose. (e) The amperometric responses of the NiCo-S/CNH/GCEs after addition of 1 mM glucose followed by successive injection of 0.1 mM fructose, galactose, sucrose, lactose, AA, UA, DA, and NaCl. (f) Chrono amperograms of the NiCo-S/CNH/GSPEs in the presence of the different glucose concentration ranging from 0.5 ~ 10.0 mM under applying +0.5 V. Amperogram of the NiCo-S/GCEs current response obtained from the addition of (g) 50 µL human blood serum, (h) 200 µL urine, and (i) 100 µL saliva followed by injection of 400 µM standard glucose solutions under the optimum potential of +0.5 V, the amperograms of five successive glucose addition. Figure 1

Electricity, chemistry and biomarkers: an elegant and simple package: The potential of electrochemical biosensors for developing novel point-of-care diagnostics: The potential of electrochemical biosensors for developing novel point-of-care diagnostics.

Electrochemical sensors to measure biomarkers from complex samples are a tried and tested technology with large untapped potential for addressing important public health needs.

Inkjet-Printed Three-Electrode System on Flexible Substrate for Low-Cost Electrochemical Analysis

Inkjet printing (IJP) has emerged as a promising additive manufacturing technique for fabrication of electrodes and sensors due to its cost-effectiveness compared to the traditional techniques, such as screen-printing. In this work, we present a planar, three-electrode system fabricated by inkjet printing on a polyethylene naphthalate (PEN) flexible substrate for rapid voltametric electrochemical analysis. An in-house formulation of aqueous-based gold ink with low temperature-sintering was used in printing the working and counter electrodes. The reference electrode was also inkjet-printed using a commercial silver ink and chlorinated to form an AgCl layer. Cyclic voltammetry studies using the ferri/ferrocyanide redox couple showed that the inkjet-printed electrode system has a comparable electrochemical performance to a commercial screen-printed electrode. Fabrication of a single inkjet-printed electrochemical 3-electrode platform consumes only about 0.5 mg Au and 0.2 mg Ag loading of ink with minimal waste during fabrication because of the additive nature of the printing technique. The 3-electrode platform operates with a microliter sample volume for analysis and can be used in aqueous media without delamination.

Simple Melatonin Determination Using Disposable and Low-Cost Lab-Made Screen-Printed Carbon Electrode

This work describes the preparation and application of a screen-printed electrode (SPE) for direct melatonin (MT) determination in samples of saliva and urine. The low-cost SPE was obtained using a simple and feasible 2D printing methodology and a lab-made conductive ink based on graphite powder and colorless nail polish. The proposed electrode showed similar electrochemical performance compared to a commercial SPE towards melatonin oxidation. Based on electrooxidation of melatonin recorded at +0.62 V an electroanalytical method was developed using the lab-made SPE under square wave voltammetric conditions. Repeatability and reproducibility studies showed that the relative peak current values did not show significant differences between them. Under optimized parameters inherent to the methodology and voltammetric technique, the proposed SPE presented a linear dynamic range (LDR) between 0.25 to 75.0 μmol L−1 (R2 = 0.99), and calculated limit of detection (LOD) and limit of quantification (LOQ) of 25.8 and 83.3 nmol L−1, respectively, were obtained. The effect of other biologically relevant compounds such as glucose, urea, and estradiol was investigated, and non-significative signal interference was observed. The method proposed was successfully applied to MT determination in spiked samples providing good recovery values between 95.6 to 104%.