Enhanced electrochemical performance at screen-printed carbon electrodes by a new pretreating procedure

An Electrochemical o-Phthalaldehyde Sensor Using a Modified Disposable Screen-Printed Electrode with Polyacrylate Hydrogel for Concentration Verification of Clinical Disinfectant

The study proposes an o-phthalaldehyde (OPA) sensor for rapid and reliable detection of OPA in healthcare disinfection practices, based on a hydrogel-modified screen-printed carbon electrode strip. The hydrogel film, which contains glycine and N-acetylcysteine, reacts with OPA to produce a reductive isoindole derivative. The derivative is then oxidized for OPA determination using cyclic voltammetry. The proposed sensor achieves an optimal detection time of 20-30 s and requires only a small analyte volume of 5 µL. It exhibits good precision (10%) and sensitivity (3.3 μA/cm² mM) in a phosphate-buffered solution (pH 7.6), with excellent linearity (R² > 0.97) and precision (<3%) in the detection range (0.2-0.6%) required for clinical OPA solutions. Moreover, the sensor demonstrates good concentration verification of Cidex-OPA disinfection in healthcare institutes, with high sensitivity (18.28 μA/cm² mM) and precision around the minimum effective concentration (0.3%). Overall, the proposed sensor offers a promising and practical solution for accurate and reliable OPA detection in clinical disinfection practices.

Electrochemical Sensing of Lead in Drinking Water Using Copper Foil Bonded with Polymer

Levels of lead (Pb) in tap water that are well below established guidelines are now considered harmful, so the detection of sub-parts-per-billion (ppb) Pb levels is crucial. In this work, we developed a two-step, facile, and inexpensive fabrication approach that involves direct bonding of copper (Cu) and liquid crystal polymer (LCP) followed by polyester resin printing for masking onto Cu/LCP to fabricate Cu thin-film-based Pb sensors. The oxygen plasma-treated surfaces resulted in strongly bonded Cu/LCP with a high peel strength of 500 N/m due to the highly hydrophilic nature of both surfaces. The bonded specimen can withstand wet etching of the electrode and can address delamination of the electrode for prolonged use in application environments. The Cu-foil-based electrochemical sensor showed sensitivity of ~11 nA/ppb/cm² and a limit of detection (LOD) of 0.2 ppb (0.2 µg/L) Pb ions in water. The sensor required only 30 s and a 100 µL sample to detect Pb. To date, this is the most rapid detection of Pb performed using an all-Cu-based sensor. The selectivity test of Cu to Pb with interferences from cadmium and zinc showed that their peaks were separated by a few hundred millivolts. This approach has strong potential towards realizing low-cost, highly reliable integrated water quality monitoring systems.

Reactive argon-plasma activation of screen-printed carbon electrodes for highly selective dopamine determination

Dopamine (DA) deficiency has been linked to several psychiatric disorders. Electrochemical determination of the level of DA suffers from abundant ascorbic acid (AA) and uric acid (UA) in body fluids. In this work, a facile argon (Ar) plasma treatment was utilized to enhance the electrocatalytic reactivity of screen-printed carbon electrodes (SPCEs) for selective DA detection. Surface characterization of the Ar-treated SCPEs verified that the carbon paste binders were successfully removed and single-bonded oxygenated moieties (-OH and C-O-C) were generated. Interestingly, the sharper D* and D'' Raman interbands were new key evidence of a higher exposure of carbon defect sites. Electrochemical studies further revealed that the Ar-treated SPCEs possessed faster heterogeneous electron-transfer rates, larger electroactive surface areas, and much higher conductivity when compared with untreated electrodes. As a result, the oxidation potentials of AA, DA, and UA in the mixture could be well-resolved and the current responses were significantly increased. The selective determination of DA in the presence of AA and UA by differential pulse voltammetry gave two linear responses with the limit of detection of 0.27 μM (0.15-10 μM range). Moreover, this Ar-treated SPCE had high reproducibility and good storage stability. These results suggest that Ar-plasma treatment could be a promising method to enhance the electrocatalytic properties of SPCEs for the detection of biomolecules.

Electrochemically Pretreated Sensor Based on Screen-Printed Carbon Modified with Pb Nanoparticles for Determination of Testosterone

Testosterone (TST), despite its good properties, may be harmful to the human organism and the environment. Therefore, monitoring biological fluids and environmental samples is important. An electrochemically pretreated screen-printed carbon sensor modified with Pb nanoparticles (pSPCE/PbNPs) was successfully prepared and used for the determination of TST. The surface morphology and electrochemical properties of unmodified and modified sensors were characterized by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), scanning and transmission electron microscopy (SEM and TEM), and energy-dispersive X-ray spectroscopy (EDS). Selective determinations of TST at the pSPCE/PbNPs were carried out by differential pulse adsorptive stripping voltammetry (DPAdSV, E_{Pb dep.and TST acc.} of −1.1 V, t _{Pb dep.and TST acc.} of 120 s, ΔE_A of 50 mV, ν of 175 mV s⁻¹, and t_m of 5 ms) in a solution containing 0.075 mol L⁻¹ acetate buffer of pH = 4.6 ± 0.1, and 7.5 × 10⁻⁵ mol L⁻¹ Pb(NO₃)₂. The analytical signal obtained at the potential around −1.42 V (vs. silver pseudo-reference electrode) is related to the reduction process of TST adsorbed onto the electrode surface. The use of pSPCE/PbNPs allows obtaining a very low limit of TST detection (2.2 × 10⁻¹² mol L⁻¹) and wide linear ranges of the calibration graph (1.0 × 10⁻¹¹–1.0 × 10⁻¹⁰, 1.0 × 10⁻¹⁰–2.0 × 10⁻⁹, and 2.0 × 10⁻⁹–2.0 × 10⁻⁸ mol L⁻¹). The pSPCE/PbNPs were successfully applied for the determination of TST in reference material of human urine and wastewater purified in a sewage treatment plant without preliminary preparation.

Screen-Printed Voltammetric Sensors-Tools for Environmental Water Monitoring of Painkillers

The dynamic production and usage of pharmaceuticals, mainly painkillers, indicates the growing problem of environmental contamination. Therefore, the monitoring of pharmaceutical concentrations in environmental samples, mostly aquatic, is necessary. This article focuses on applying screen-printed voltammetric sensors for the voltammetric determination of painkillers residues, including non-steroidal anti-inflammatory drugs, paracetamol, and tramadol in environmental water samples. The main advantages of these electrodes are simplicity, reliability, portability, small instrumental setups comprising the three electrodes, and modest cost. Moreover, the electroconductivity, catalytic activity, and surface area can be easily improved by modifying the electrode surface with carbon nanomaterials, polymer films, or electrochemical activation.

Silver Nanoparticles Coupled with Graphene Nanoplatelets Modified Screen-Printed Carbon Electrodes for Rhodamine B Detection in Food Products

A rapid, simple, and sensitive voltammetric sensor has been fabricated to determine Rhodamine B (RhB), a textile coloring agent. Silver nanoparticles (AgNPs) were synthesized by the chemical reduction method of silver nitrate and sodium citrate. Graphene nanoplatelets (GPLs) and AgNPs were drop-casted on the surface of a working electrode of a screen-printed carbon electrode (SPCE), forming the SPCE-GPLs/AgNPs samples. Scanning electron microscopy-energy dispersive X-ray and cyclic voltammetry confirmed the altered surface of the SPCE. The square wave voltammetry was used for the electrochemical determination of RhB. The SPCE-GPLs/AgNPs demonstrated electrochemical responses to detect RhB with a linear range of 2-100 μM, and the limit of detection was 1.94 μM. The SPCE-GPLs/AgNPs demonstrated a selective detection of RhB in the presence of common interfering compounds present in the food samples, including sucrose and monosodium glutamate. Furthermore, the sensor presented good reproducibility as well as repeatability in the detection of RhB. When the sensor was used to determine RhB in an actual food sample, similar results were shown as suggested by UV-vis spectroscopy analysis. Hence, the fabricated sensor can be applied for the detection of RhB in food samples.

Optimisation of an Electrochemical DNA Sensor for Measuring KRAS G12D and G13D Point Mutations in Different Tumour Types

Circulating tumour DNA (ctDNA) is widely used in liquid biopsies due to having a presence in the blood that is typically in proportion to the stage of the cancer and because it may present a quick and practical method of capturing tumour heterogeneity. This paper outlines a simple electrochemical technique adapted towards point-of-care cancer detection and treatment monitoring from biofluids using a label-free detection strategy. The mutations used for analysis were the KRAS G12D and G13D mutations, which are both important in the initiation, progression and drug resistance of many human cancers, leading to a high mortality rate. A low-cost DNA sensor was developed to specifically investigate these common circulating tumour markers. Initially, we report on some developments made in carbon surface pre-treatment and the electrochemical detection scheme which ensure the most sensitive measurement technique is employed. Following pre-treatment of the sensor to ensure homogeneity, DNA probes developed specifically for detection of the KRAS G12D and G13D mutations were immobilized onto low-cost screen printed carbon electrodes using diazonium chemistry and 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride/N-hydroxysuccinimide coupling. Prior to electrochemical detection, the sensor was functionalised with target DNA amplified by standard and specialist PCR methodologies (6.3% increase). Assay development steps and DNA detection experiments were performed using standard voltammetry techniques. Sensitivity (as low as 0.58 ng/μL) and specificity (>300%) was achieved by detecting mutant KRAS G13D PCR amplicons against a background of wild-type KRAS DNA from the representative cancer sample and our findings give rise to the basis of a simple and very low-cost system for measuring ctDNA biomarkers in patient samples. The current time to receive results from the system was 3.5 h with appreciable scope for optimisation, thus far comparing favourably to the UK National Health Service biopsy service where patients can wait for weeks for biopsy results.

Exploring carbon particle type and plasma treatment to improve electrochemical properties of stencil-printed carbon electrodes

Stencil-printing conductive carbon inks has revolutionized the development of inexpensive, disposable and portable electrochemical sensors. However, stencil-printed carbon electrodes (SPCEs) typically suffer from poor electrochemical properties. While many surface pretreatments and modifications have been tested to improve the electrochemical activity of SPCEs, the bulk composition of the inks used for printing has been largely ignored. Recent studies of other carbon composite electrode materials show significant evidence that the conductive carbon particle component is strongly related to electrochemical performance. However, such a study has not been carried out with SPCEs. In this work, we perform a systematic characterization of SPCEs made with different carbon particle types including graphite particles, glassy carbon microparticles and carbon black. The relationship between carbon particle characteristics including particle size, particle purity, and particle morphology as well as particle mass loading on the fabrication and electrochemical properties of SPCEs is studied. SPCEs were plasma treated for surface activation and the electrochemical properties of both untreated and plasma treated SPCEs are also compared. SPCEs displayed distinct analytical utilities characterized through solvent window and double layer capacitance. Cyclic voltammetry (CV) of several standard redox probes, FcTMA+, ferri/ferrocyanide, and pAP was used to establish the effects of carbon particle type and plasma treatment on electron transfer kinetics of SPCEs. CV of the biologically relevant molecules uric acid, NADH and dopamine was employed to further illustrate the differences in sensing and fouling characteristics of SPCEs fabricated with different carbon particle types. SEM imaging revealed significant differences in the SPCE surface microstructures. This systematic study demonstrates that the electrochemical properties of SPCEs can be tuned and significantly improved through careful selection of carbon particle type and plasma cleaning with a goal toward the development of better performing electrochemical point-of-need sensors.

Electrochemical immunosensor based on gold-labeled monoclonal anti-LipL32 for leptospirosis diagnosis

Leptospirosis is a critical human health problem in the tropical area, thus, a precise technique that can be used for point-of-care analysis is greatly required. This is the first report on electrochemical immunosensor based on gold-labeled monoclonal anti-LipL32 for rapid, simple and sensitive determination of LipL32. The sensor consisted of two LipL32-specific antibodies: an unlabeled capture primary antibody (Anti-1°Ab) and an electrochemically detectable gold-conjugated secondary antibody (Au-2°Ab). The Anti-1°Ab was immobilized onto the modified screen-printed graphene electrode (SPGE) to form the anti-LipL32 surface. The electrochemical signal response was determined by differential pulse voltammetry (DPV). In the presence of LipL32, the sensor displayed a significant increase in current response in a concentration-dependent manner, but no observable signal was detected in the absence of LipL32. The linearity between LipL32 concentration and the measured current was found in a range of 1-100 ng/mL, and the limit of detection (LOD) (3SD_blank/Slope) and limit of quantitation (LOQ) (10SD_blank/Slope) were found to be 0.28 and 0.93 ng/mL, respectively. This sensor was successfully applied to detect pathogenic Leptospira whole cell lysates samples with the satisfactory results. The promissing results suggested that this immunosensor might be an alternative tool for diagnosis of leptospirosis.

Hemin immobilized into metal-organic frameworks as an electrochemical biosensor for 2,4,6-trichlorophenol

Hemin immobilized into copper-based metal-organic frameworks was successfully prepared and used as a new electrode material for sensitive electrochemical biosensing. X-ray diffraction patterns, Fourier transform infrared spectra, scanning electron microscopy, UV-vis absorption spectroscopy, and cyclic voltammetry were used to characterize the resultant composites. Due to the interaction between the copper atom groups and hemin, the constrained environment in Cu-MOF-74 acts as a matrix to avoid the dimerization of enzyme molecules and retain its biological activity. The hemin/Cu-MOF composites demonstrated enhanced electrocatalytical activity and high stability towards the oxidation of 2,4,6-trichlorophenol. Under optimum experimental conditions, the sensor showed a wide linear relationship over the range of 0.01-9 μmol L^-1 with a detection limit (3σ) of 0.005 μmol L^-1. The relative standard deviations were 4.6% and 3.5% for five repeated measurements of 0.5 and 5 μmol L^-1 2,4,6-trichlorophenol, respectively. The detection platforms for 2,4,6-trichlorophenol developed here not only indicate that hemin/Cu-MOF-74 possesses intrinsic biological reactivity, but also enable further work to be conducted towards the application of enzyme-containing metal-organic frameworks in electrochemical biosensors.

Screen-Printed Graphite Electrodes as Low-Cost Devices for Oxygen Gas Detection in Room-Temperature Ionic Liquids

Screen-printed graphite electrodes (SPGEs) have been used for the first time as platforms to detect oxygen gas in room-temperature ionic liquids (RTILs). Up until now, carbon-based SPEs have shown inferior behaviour compared to platinum and gold SPEs for gas sensing with RTIL solvents. The electrochemical reduction of oxygen (O₂) in a range of RTILs has therefore been explored on home-made SPGEs, and is compared to the behaviour on commercially-available carbon SPEs (C-SPEs). Six common RTILs are initially employed for O₂ detection using cyclic voltammetry (CV), and two RTILs ([C₂mim][NTf₂] and [C₄mim][PF₆]) chosen for further detailed analytical studies. Long-term chronoamperometry (LTCA) was also performed to test the ability of the sensor surface for real-time gas monitoring. Both CV and LTCA gave linear calibration graphs-for CV in the 10-100% vol. range, and for LTCA in the 0.1-20% vol. range-on the SPGE. The responses on the SPGE were far superior to the commercial C-SPEs; more instability in the electrochemical responses were observed on the C-SPEs, together with some breaking-up or dissolution of the electrode surface materials. This study highlights that not all screen-printed ink formulations are compatible with RTIL solvents for longer-term electrochemical experiments, and that the choice of RTIL is also important. Overall, the low-cost SPGEs appear to be promising platforms for the detection of O₂, particularly in [C₄mim][PF₆].

Carbon functionalized metal organic framework/Nafion composites as novel electrode materials for ultrasensitive determination of dopamine

Carbon functionalized metal organic frameworks (C/Al-MIL-53-(OH)₂) were successfully prepared for the first time by a solvothermal technique and characterized by Fourier transform infrared spectroscopy, X-ray diffraction spectrometry, and scanning electron microscopy. This composite was coated with a Nafion film so as to form a Nafion/C/Al-MIL-53-(OH)₂ modified glassy carbon electrode. The modified electrode was then used as a novel electrocatalyst for dopamine (DA) oxidation in phosphate buffer solution. Due to the synergistic effects of the different materials, including the high conductivity of carbon, the large surface area of Al-MIL-53-(OH)₂, and the film-forming ability of a cation-exchange polymer, the modified electrode exhibited a remarkable enhancement effect on voltammetric response of DA. Under the optimal conditions, the response peak currents had a linear relationship with the DA concentration in the range from 3.0 × 10^-8 to 1.0 × 10^-5 mol L^-1. The limits of detection and quantitation for DA were found to be 0.8 × 10^-8 mol L^-1 and 2.6 × 10^-8 mol L^-1, respectively. The analytical utilities of the proposed biosensor were achieved by analyzing the content of DA in biological fluids.

Clinical evaluation of bionime rightest GM310 biosensors with a simplified electrode fabrication for alternative-site blood glucose tests

BACKGROUND

Most processes for fabricating biosensors applied to screen-printed carbon electrodes (SPCEs) are complex. This study presents a novel one-step process for manufacturing electrodes for injection-molding biosensors.

METHODS

During the sensor-fabrication process, barrel-plated gold electrodes were inserted into an injection-molded base. The electrode directly touched the electrical contact of a meter. We analyzed technical measurements for this biosensor, including tests of the measurement range, within-run imprecision, and between-meter imprecision. In clinical trials, experienced technicians tested 3 alternative sites (fingertip, palm, and arm). The results were simultaneously compared with plasma values obtained with the hexokinase method on the Olympus AU640 instrument. Analytical results were evaluated according to International Standards Organization 15197 (ISO 15197:2003) criteria and by Clarke error grid analysis (EGA), and CVs were calculated to evaluate within-run imprecision.

RESULTS

The glucose measurement range was 0.6- 33.3 mmol/L (y = 0.96x + 0.07 mmol/L; r(2) = 0.9977). The CVs in the within-run imprecision test were 1.7%-3.5%, and the overall CV was 2.1%, indicating good reproducibility of results. The Student t-tests of mean values from 5 meters revealed statistically insignificant differences (P > 0.05). In clinical trials, the agreement of the Rightest GM310 meter results with those of a laboratory method complied with ISO 15197:2003 criteria. In the EGA, 100% of the values were within the acceptable zones (A + B), and the proportion of values within zone A exceeded 95%.

CONCLUSIONS

The Bionime Rightest GM310 meter applied a simplified process for biosensor fabrication and displayed acceptable performance for monitoring glucose concentrations at alternative test sites.