Disposable Electrodes Research Articles

From waste to resource: Hydrogen generation and antimicrobial activity of Ag-based photocatalysts recovered from biomedical waste

Electrocardiogram (ECG) disposable electrodes contain a substantial amount of silver (Ag), which can be extracted and recycled. Most current methods for recovering Ag from waste are expensive and environmentally harmful. This study investigated a sustainable chemical process for extracting Ag from discarded medical electrodes using a simple Cu(II) solution under moderately acidic conditions. Using response surface methodology (RSM) based on a three-level, full-factorial design, the optimized extraction conditions were determined as pH = 4.78, T = 80°C, [Cu(II)]₀ = 8.0 × 10⁻³ M, and [NaCl]₀ = 3.72 M. Under these conditions, a process efficiency approaching 100 % was achieved. Moreover, the recovery of metallic silver exceeded 85 %, even when using real matrices. (i.e., discarded ECG electrodes). As a result, the Ag-containing leachate solutions were utilized to synthesize silver-based materials with varying Ag content. These materials demonstrated (i) excellent photocatalytic activity for hydrogen production in aqueous solutions containing organic compounds and (ii) significant antipathogenic properties. In summary, effective Ag/TiO₂ photocatalytic materials with high efficiency for hydrogen production and antimicrobial activity were successfully prepared through a novel, sustainable, and cost-effective chemical recovery process of silver from discarded ECG electrodes.

Electrochemical behavior and L-tyrosine sensing properties of nanostructured Cr, Sn and La-doped α-Fe2O3 interfaces

L-tyrosine (Tyr) is a promising biomarker for the diagnosis and monitoring of metabolic disorders and neurodegenerative diseases. This study reports on the electrochemical properties of α-Fe2O3 nanostructures doped with Cr, Sn and La, referred to as CrFeOx, SnFeOx and LaFeOx, respectively, and their application in the enzyme-free electrochemical Tyr sensors. These disposable sensors offer accurate Tyr concentration analysis at room temperature, addressing the limitations of current point-of-care diagnostic methods. The CrFeOx, SnFeOx, and LaFeOx nanostructures serve as selective agents for binding and recognizing Tyr, deposited onto disposable graphite pencil electrodes to form the electrochemical interface. The interfacial resistance, charge-transfer kinetics, mechanism, and reversibility are studied via extensive electrochemical measurements employing electro¬chemical impedance spectroscopy and cyclic voltammetry. Furthermore, differen¬tial pulse voltammetry demonstrates excellent Tyr sensing performance in the concen¬tration range of 0 to 80 μM with 2.65 µA µM-1 cm-2 sensitivity and 360 nM thres¬hold detection limit for the best-performing CrFeOx sensors. Hence, these α-Fe2O3-based sensor systems are practical and efficient for selective Tyr detection, offering potential advancements in personalized healthcare and early disease diagnosis.

Electrochemical Sensing/Biosensing ‐ Bench to Market

The proposition of new sensors based on carbon (nano)structures as well as metal (nano)particles is a great alternative for electroanalysis. In this context, graphite, carbon nanotubes, graphene, carbon black and fullerene, as well as gold, silver, platinum, copper are the most common materials employed [1]. Also, biomolecules such as antibodies, DNA sequences, enzymes and aptamers can be promising molecular recognition elements and enable specific sensor/biosensor designs, with interferent species [2]. Since the pioneering works from Professor Joseph Wang [3,4], the screen‐printed and disposable electrodes have been reported in the literature as options to be used in point‐of‐care and point‐of use sites. Also, the evolution of 3D printing [5] and wearable devices have led to an increase in the number of papers reporting on their use.. The “Achilles heel” is that the laboratory creations don't make it to the market place [6]. Therefore, academia needs to think more about in the validation, demonstration and promotion of the laboratory developed technology with of new companies based on startups, for example, to attract investments and promote these sensors to commercial ones. In this context, the special issue “Electrochemical Sensing/Biosensing ‐ Bench to Market” brings the discussion and advances of electrochemical sensors, which can be used in many areas, such as medical, environmental, food safety, pharmaceutical, and forensic. For this purpose, the preparation, characterization, and application of these devices have attracted interest. Studies of the production, shelf‐life as well as reproducibility, and repeatability have been highlighted for mass production. Important subjects such as screen printing, and 3D printing are welcome for submissions. Therefore, we expect you to enjoy this Special Issue published in Electroanalysis.

Graphene quantum dots modified electrodes as electrochemical sensing tool towards the detection of codeine in biological fluids and soft drinks.

An electroanalytical method based on disposable screen-printed carbon electrodes modified with non-toxic carbonaceous nanodots is proposed as a reliable and effective device for codeine determination in biological fluids and soft drinks. Graphene quantum dots (GQDs), carbon quantum dots (CQDs) and carbon nanodots (CNDs) were evaluated as electrode modifiers for the determinationof the drug. The electroactive areas of the modified electrodes were assessed by cyclic voltammetry using potassium ferricyanide. Results demonstrated that GQDs provided the best analytical response for codeine, displaying an intense and well-defined anodic wave approximately 0.9V vs reference electrode. The method exhibits an acceptable linear dynamic range, low limits of detection and quantification (0.21 and 0.73µM, respectively), and satisfactory precision (below 3.9% expressed as relative standard deviation (RSD)) in saliva. Only the analysis of biofluids requires a simple extraction protocol. The feasibility and applicability of this novel approach were assessed by determining codeine in different matrices, with recoveries ranging from 69 to 112%. This cost-effective, simple, easily miniaturised and portable method was applied not only to biofluids but also for the direct detection of codeine in soft drinks combined with a codeine-enriched syrup, a medication that is being used to adulterate beverages, particularly at specific events (drinking and nightclub parties). There is no need forany sample treatment, demonstrating its versatility in analysing beverages for potential adulteration as well.

Diffusive ex situ galvanic growth of metal nanocrystals on transmission electron microscopy grid

The uniform modification of commercial and standardized objects features considerable potential, as in the case of dip-pen lithography, biosensor kits, and disposable electrodes. In this study, we devised a dense nanoparticle array formation using the metallic mesh of a transmission electron microscopy (TEM) grid, which was formerly solely employed as a sampling stage. Incompletely oxidized cationic species generated from the galvanic replacement reaction of the metallic support mesh at the opposite side of the carbon layer diffused to the exposed top side and led to ex situ nanostar formation. A uniform nanoparticle array was obtained by immersion in an aqueous solution of replacing metal cations without reducing agents or surface energy-controlling compounds. Moreover, the array density was exclusively regulated by the incubation time. The straightforward nanoparticle array formation was successfully extended to various metal mesh TEM grids and different transition metal cations capable of spontaneous redox reactions. Cu mesh TEM grid and Mo grids could be utilized as sacrificial templates, and the growth of Au, Pd, Pt, Ag, and Rh nanostructures was confirmed.

Electrochemical investigation of the antimicrobial agent daptomycin utilizing disposable pencil graphite electrode and DNA interaction with green techniques

Electrochemical investigation of the antimicrobial agent daptomycin utilizing disposable pencil graphite electrode and DNA interaction with green techniques

A three-components-based disposable electrochemical sensor for the detection of heavy metal ions in water

The development of an efficient sensor based on a novel three-components nanocomposite is presented for the detection of heavy metal ions (Cd2+ and Pb2+) in water. For the preparation of three-components nanocomposite surface, the polydopamine reduced graphene oxide (PyDA/RGO) composite was initially prepared by a one-step polymerization of dopamine (DA) on RGO followed by surface modification of the prepared composite with cysteine (Cys). The formation of three-components nanocomposite surface (i.e., Cys/PyDA/RGO) was initially confirmed through physical characterization techniques, including X-ray diffraction and infrared spectroscopy, whereas scanning electron microscopy revealed the surface morphology after each step of sensor fabrication. The electrochemical properties of the sensing platform were evaluated through electrochemical techniques, including cyclic voltammetry and electrochemical impedance spectroscopy with an external ferri‐−/ferrocyanide redox probe. The prepared three-components nanocomposite on disposable pencil graphite electrode (Cys/PyDA/RGO/PGE) showed an improved charge transfer rate as compared to PyDA/RGO/PGE and bare PGE electrode. Targeted heavy metal ions were detected on the sensor surface using differential pulse voltammetry with greater sensitivity, showing detection limits of 0.77 and 1.13 ppb for Cd+2 and Pb+2 ions in citrate buffer solution, respectively. The sensor demonstrated comparable performance in the tap water samples.

Development of graphene oxide-based biosensing platforms for label-free bioelectronic detection of pathogenic microorganisms.

A novel electrochemical nanogenosensor devoted to clinical analysis is reported for label-free detection of pathogenic microorganisms in the present work. The designed biosensor is composed of graphene oxide-modified disposable pencil graphite electrodes as a sensing platform. Escherichia coli is used as a model case. A 5'-aminohexyl-linked 22-base sequence probe representing the E. coli amplicon is immobilized onto sensor surfaces via carbodiimide chemistry. Hybridization is performed with denatured PCR amplicons of the bacteria. Detection is realized by transduction with the electrochemical impedance spectrometry technique. The selectivity of the designed genosensor is measured using Mycobacterium tuberculosis and Klebsiella pneumoniae sequences. Outstanding sensitivity is achieved with this genosensor array platform with a detection limit of 102 nM. This platform offers promise for rapid, simple, and cost-effective detection of various pathogenic microorganisms.

Enhancing Sensitivity and Selectivity: Current Trends in Electrochemical Immunosensors for Organophosphate Analysis.

This review examines recent advancements in electrochemical immunosensors for the detection of organophosphate pesticides, focusing on strategies to enhance sensitivity and selectivity. The widespread use of these pesticides has necessitated the development of rapid, accurate, and field-deployable detection methods. We discuss the fundamental principles of electrochemical immunosensors and explore innovative approaches to improve their performance. These include the utilization of nanomaterials such as metal nanoparticles, carbon nanotubes, and graphene for signal amplification; enzyme-based amplification strategies; and the design of three-dimensional electrode architectures. The integration of these sensors into microfluidic and lab-on-a-chip devices has enabled miniaturization and automation, while screen-printed and disposable electrodes have facilitated on-site testing. We analyze the challenges faced in real sample analysis, including matrix effects and the stability of biological recognition elements. Emerging trends such as the application of artificial intelligence for data interpretation and the development of aptamer-based sensors are highlighted. The review also considers the potential for commercialization and the hurdles that must be overcome for widespread adoption. Future research directions are identified, including the development of multi-analyte detection platforms and the integration of sensors with emerging technologies like the Internet of Things. This comprehensive overview provides insights into the current state of the field and outlines promising avenues for future development in organophosphate pesticide detection.

Cuprospinel decorated biopolymer functionalized CNFs based electrocatalytic platform integrated with grid search optimized neural network for detection of vital amino acid in beverages

An electrocatalytic platform based on a novel nanocomposite integrated with a grid search-optimized neural network (GSNN) was proposed for intelligent sensing of tryptophan. The cuprospinel-decorated chitosan-functionalized carbon nanofibers (CuFe2O4/Chit-CNFs) fabricated on a disposable electrode revealed exceptional electrocatalytic activity with a low detection limit (2 nM) and good sensitivity (79.18 μAμM−1 cm−2) over a broad linear range (0.05–152.55 μM). Cyclic voltammetry and differential pulse voltammetry were employed, and the sensing mechanism of tryptophan entails its electrocatalytic oxidation, where the synergistic impact of CuFe2O4 and Chit-CNFs boosts electrochemical response owing to their high surface area and conductivity. GSNN-based intelligent sensing returned a root mean square error (RMSE) of 2.76 and a mean absolute error (MAE) of 1.12. Moreover, the sensor's performance was tested on samples from apple juice, tomato juice, pineapple juice, and milk for assessing practicality, demonstrating recovery between 96.93 and 101.06 % and maximum relative standard deviation of 2.63 %. The proposed sensor showcased excellent selectivity, repeatability, reproducibility, and stability.

Production of Ag nanowires with high yield and narrow size distribution by promoting nucleation through hot injection and their application to disposable paper electrodes

The polyol method has been the most commonly used technique for fabricating silver nanowires (Ag NWs), wherein additive reagents facilitate precise control over their morphology. In this work, we introduced a straightforward approach to synthesize Ag NWs with minimal impurities and uniform diameter by using hot injection method. The underlying mechanism and final product are evaluated, and the scalable process was optimized to achieve a high yield (∼87.8 %). It was found that the hot injection of a Ag precursor at 170 °C significantly accelerated the reduction of Ag ions. The issue of the uniformity of Ag NWs was addressed by adding an organic halide to control the nucleation rate of Ag. The resulting Ag NWs solution was used to impregnated cellulose paper, forming an enhanced electrical network compared to other substrates. Given the low commercial cost of paper, this approach holds significant potential for widespread use in disposable electrodes. Furthermore, after subjecting the fabricated paper electrodes to various forms of damage, the connected LED bulbs consistently maintained their brightness. This demonstrates the network stability and suitability of these electrodes for flexible applications.

Scalp surface Laplacian potential monitoring system based on novel hydrogel active tri-polar concentric ring electrodes

Electroencephalography is valued in brain research for its high temporal resolution and user-friendly nature. However, limitations in spatial resolution and susceptibility to biological artifacts restrict its broader application. The surface Laplacian potential obtained through tri-polar concentric ring electrodes offers a solution by mitigating biological artifact interference and enhancing spatial resolution while preserving essential information. In this study, an active tri-polar concentric ring electrode based on conductive hydrogel and a 3-lead surface Laplacian potential monitoring system designed for use with the electrode were proposed. The part of the electrode that came into contact with the human body was the hydrogel with high electrical conductivity. The contact surface curvature was designed based on the real forehead curvature of 22 subjects, resulting in a normalized electrode-skin contact impedance of 30.95±16.76KΩ*cm2 at 10 Hz, which was lower than commercial disposable wet electrodes and remained stable over a 10-hour period of long-term wear. And the electrode still exhibited excellent performance after being left for 20 days. Additionally, the internal noise of the system was about 1.9μV, which was comparable to that of the FDA-approved equipment. The signal analysis results demonstrated that the surface Laplacian potential collected by the proposed electrode and system had better signal-to-noise ratio and spatial resolution, and had a good suppression effect on biological artifacts.

Optimized aptamer-based next generation biosensor for the ultra-sensitive determination of SARS-CoV-2 S1 protein in saliva samples

COVID-19 is an infectious disease caused by the SARS-CoV-2 virus, which rapidly spread worldwide and resulted in a pandemic. Efficient and sensitive detection techniques have been devised since the onset of the epidemic and continue to be improved at present. Due to the crucial role of the SARS-CoV-2 S1 protein in facilitating the virus's entry into cells, efforts in detection and treatment have primarily centered upon this protein. In this study, a rapid, ultrasensitive, disposable, easy-to-use, cost-effective next generation biosensor based on optimized aptamer (Optimer, OPT) was developed by using a disposable pencil graphite electrode (PGE) and applied for the impedimetric determination of SARS-CoV-2 S1 protein. The S1 protein interacted with the OPT in the solution phase and then immobilized onto the PGE surface. Subsequently, measurements using electrochemical impedance spectroscopy (EIS) were conducted in a solution containing a redox probe of 1 mM [Fe(CN)6]3−/4−. Under optimum conditions, the limit of detection (LOD) for the S1 protein in buffer medium at concentrations ranging from 101 to 106 ag/mL was calculated as 8.80 ag/mL (0.11 aM). The selectivity of the developed biosensor was studied against MERS-CoV-S1 protein (MERS) and Influenza Hemagglutinin antigen (HA). Furthermore, the application of the biosensor in artificial saliva medium is demonstrated. The LOD was also calculated in artificial saliva medium in the concentration range of 101–105 ag/mL and calculated as 2.01 ag/mL (0.025 aM). This medium was also used to assess the selectivity of optimized-aptamer based biosensor.

Voltammetric determination of uric acid using a miniaturized platform based on screen-printed electrodes modified with platinum nanoparticles

Disposable and sensitive screen-printed carbon electrodes (SPCE) modified with multi-walled carbon nanotubes (MWCNT) and platinum nanoparticles (PtNPs) were constructed to analyse uric acid (UA) in biological samples using a miniaturized smartphone potentiostat system. Combining the nanomaterials with Nafion® yielded a stable dispersion that could be successfully used as an electroactive layer. Transmission electron microscopy (TEM) and energy dispersive scanning (EDS) were used to characterize the morphology of PtNPs. These revealed approximately spherical shapes with emission lines characteristics of platinum. Furthermore, PtNPs/MWCNT/SPCE film was characterized by scanning electron microscopy (SEM), which demonstrated the tubular characteristic of MWCNT distributed and covered by carbon black (CB) spheres present in the screen-printed ink. An enhanced current response was observed for UA voltammetric analysis, especially due to the synergism effect of PtNPs and MWCNT, which reduced the Rct value. The values of Dapp (1.6 × 10−6 cm−2 s−1) and kcat (2.76 × 103 mol−1 L/s) were determined for UA using the proposed sensor. The sensor displayed linear response for UA in the range from 5.0 × 10−6 mol/L to 6.9 × 10−4 mol/L, with a detection limit of 4.9 × 10−7 mol/L. Along with detectability, excellent performances were verified in terms of repeatability, anti-interference features, and analysis of UA in the biological samples.

Fabrication of a disposable electrode based on recordable gold compact disc modified with Bi-Bi2O2CO3@ graphitic carbon nitride nanocomposite for the simultaneous detection of mesalazine and uric acid in biological fluids

Fabrication of a disposable electrode based on recordable gold compact disc modified with Bi-Bi2O2CO3@ graphitic carbon nitride nanocomposite for the simultaneous detection of mesalazine and uric acid in biological fluids

Green Voltammetric Detection of Ophthalmic Drug Nepafenac Using Pencil Graphite Electrode as a Responsive Disposable Electrochemical Sensor

AbstractIn this study, the electrochemical properties of nepafenac, used after eye surgery operations, were investigated on a disposable pencil graphite electrode. Cyclic and square wave voltammetry techniques were used to investigate the electrochemical properties of nepafenac. Two peaks at potentials of approximately +0.33 V and +1.03 V in the anodic direction and two peaks at potentials of approximately +0.29 V and +0.08 V in the cathodic direction were observed on the surface of the disposable pencil electrode in acetate (pH 4.8) medium with the cyclic voltammetry technique. The analytical performance of the developed voltammetric technique had good linearity in the concentration range of 0.30 µM to 3.5 µM at pH 4.8. The LOD value of this voltammetric method in acetate (pH 4.8) medium was calculated as 0.035 µM (8.90 ng mL−1). For reproducibility, the relative standard deviation (RSD) values for Ia and IIa anodic peak current/potential were found to be 1.45%/0.43% and 1.28%/0.25%, respectively. The voltammetric method was successfully applied to urine and pharmaceutical preparations and the results were compared with the spectrophotometric method.

A Self-Powered Enzymatic Glucose Sensor Utilizing Bimetallic Nanoparticle Composites Modified Pencil Graphite Electrodes as Cathode.

Enzymatic biofuel cells (EBFC) are promising sources of green energy owing to the benefits of using renewable biofuels, eco-friendly biocatalysts, and moderate operating conditions. In this study, a simple and effective EBFC was presented using an enzymatic composite material-based anode and a nonenzymatic bimetallic nanoparticle-based cathode respectively. The anode was constructed from a glassy carbon electrode (GCE) modified with a multi-walled carbon nanotube (MWCNT) and ferrocene (Fc) as a conductive layer coupled with the enzyme glucose oxidase (GOx) as a sensitive detection layer for glucose. A chitosan layer was also applied to the electrode as a protective layer to complete the composite anode. Chronoamperometry (CA) results show that the MWCNT-Fc-GOx/GCE electrode has a linear relationship between current and glucose concentration, which varied from 1 to 10mM. The LOD and LOQ were calculated for anode as 0.26mM and 0.87mM glucose, respectively. Also the sensitivity of the proposed sensor was calculated as 25.71 A/mM. Moreover, the studies of some potential interferants show that there is no significant interference for anode in the determination of glucose except ascorbic acid (AA), uric acid (UA), and dopamine (DA). On the other hand, the cathode consisted of a disposable pencil graphite electrode (PGE) modified with platinum-palladium bimetallic nanoparticles (Nps) which exhibit excellent conductivity and electron transfer rate for the oxygen reduction reaction (ORR). The constructed EBFC was optimized and characterized using various electroanalytical techniques. The EBFC consisting of MWCNT-Fc-GOx/GCE anode and Pt-PdNps/PGE cathode exhibits an open circuit potential of 285.0mV and a maximum power density of 32.25µWcm-2 under optimized conditions. The results show that the proposed EBFC consisting of an enzymatic composite-based anode and bimetallic nanozyme-based cathode is a unique design and a promising candidate for detecting glucose while harvesting power from glucose-containing natural or artificial fluids.

Determinationof indole-3-acetic acid using disposable molecularly imprinted electrochemical sensors based on bifunctional monomers.

Stainless steel sheets were coated with carbon ink to obtain disposable carbon electrodes, which were used as supports for moleculary imprinted polymer (MIP) electrochemical sensors by electropolymerizing o-phenylenediamine and o-aminophenol along with indole-3-acetic acid (IAA) as the template. After optimization, the MIP biosensors could be used for sensitive and selective detection of IAA with the limit of quantification of 0.1µM. Our experimental results showed that stable and reproducible electrochemical responses could be achieved for the disposable MIP biosensors. This approach wassuccessfully used for detection of IAA in different tissues of pea sprouts. This study reveals the potential of MIP electrochemical sensors in practical applications and shrinks the trench between the research and the real world.

A 3D printed dual screen-printed electrode separation device for twin electrochemical mini-cell establishment.

We describe a tiny 3D-printed polymethyl-methacrylate-based plastic sleeve that houses two disposable screen-printed electrodes (SPE) and enables each of the working electrodes (WEs) to work independently, on a different side of a thin barrier, in its own electrochemical (EC) mini-cell, while the SPE counter and reference units are shared for electroanalysis. Optical and EC performance tests proved that the plastic divider between WE1 and WE2 efficiently inhibited solution mixing between the mini-cells. The two neighboring, independently operating mini-cells enabled matched differential measurements in the same sample solution, a tactic designed for elimination of electrochemical interference in complex samples. In a proof-of-principle glucose biosensor trial, a glucose oxidase-modified WE2 and an unmodified WE1 delivered the EC data for the removal of anodic ascorbic acid (AA) interference simply by subtracting the WE1 (background) current from the analyte-specific WE2 current (from buffered sample solution supplemented with glucose/AA), at an anodic H2O2 detection potential of +1 V. The microfabricated SPE accessory is cheap and easy to make and use. For the many dual electrode SPE strips on the market for multiple analytical targets the new device widens the options for their exploitation in assays of biological and environmental samples with complex matrix compositions and significant risks of interference.

Portable Electrochemical Immunosensor Based on a Gold Microblobs-Optimized Screen-Printed Electrode for SARS-CoV-2 Diagnosis

The development of biosensors for determining the most diverse biomolecules is a constant focus of many research groups. There is a latent need to propose sensors that combine portability, simple measurements, and good analytical performance. Here, we propose an electrochemical immunosensor that is fully portable and energy-independent for diagnosing antibodies against SARS-CoV-2 (the virus that causes COVID-19). Initially, disposable screen-printed carbon electrodes (SPEs) were covered by gold microblobs (AuMBs), which were synthesized amperometrically from Au3+ ions. Then, the SPE-AuMBs were coated with cysteamine, which allowed the N-hydroxysuccinimide-activated SARS-CoV-2 antigen (spike protein) to be immobilized. The antigen-activated electrode was used to detect COVID-19 antibodies from current measurements obtained by differential pulse voltammetry. The AuMBs synthesis time was optimized, and the presence of gold structures improved the electrochemical responses of the SPE. It was possible to quantitatively determine antibodies in the concentration range of 0.25 to 10 µg mL−1. This range includes concentrations found in biological fluids from patients at any stage of the disease. An analysis took approximately the same time as traditional rapid nasal tests (20 min) and costed less, considering all the steps necessary to prepare a disposable antigen-functionalized SPE.