Proving the automatic benchtop electrochemical station for the development of dopamine and paracetamol sensors.

The introduced work represents an implementation of the automatic benchtop electrochemical station (BES) as an effective tool for the possibilities of high-throughput preparation of modified sensor/biosensors, speeding up the development of the analytical method, and automation of the analytical procedure for the determination of paracetamol (PAR) and dopamine (DOP) as target analytes. Within the preparation of gold nanoparticles modified screen-printed carbon electrode (AuNPs-SPCE) by electrodeposition, the deposition potential EDEP, the deposition time tDEP, and the concentration of HAuCl4 were optimized and their influence was monitored on 1 mM [Ru(NH3)6]3+/2+ redox probe and 50 µM DOP. The morphology of the AuNPs-SPCE prepared at various modification conditions was observed by SEM. The analytical performance of the AuNPs-SPCE prepared at different modification conditions was evaluated by a construction of the calibration curves of DOP and PAR. SPCE and AuNPs-SPCE at modification condition providing the best sensitivity to PAR and DOP, were successfully used to determine PAR and DOP in tap water by "spike-recovery" approach. The BES yields better reproducibility of the preparation of AuNPs-SPCE (RSD = 3.0%) in comparison with the case when AuNPs-SPCE was prepared manually by highly skilled laboratory operator (RSD = 7.0%).

Label-free electrochemical aptasensor for the detection of HepG2 hepatocellular carcinoma cells.

Hepatocellular carcinoma (HCC) is the most common liver malignancy and is characterized by increasing incidence and high mortality rates. Current methods for the screening and diagnosis of HCC exhibit inherent limitations, highlighting the ever-growing need for the development of new methods for the early diagnosis of HCC. The aim of this work was to develop a novel electrochemical aptasensor for the detection of HepG2 cells, a type of circulating tumor cells that can be used as biomarkers for the early detection of HCC. A carbon screen-printed electrode was functionalized with a composite suspension containing graphene oxide, chitosan, and polyaniline nanoparticles to increase the electrode surface and provide anchoring sites for the HepG2 cell-specific aptamer. The aptamer was immobilized on the surface of the functionalized electrode using multipulse amperometry, an innovative technique that significantly reduces the time required for aptamer immobilization. The innovative platform was successfully employed for the first time for the amplification-free detection of HepG2 cells in a linear range from 10 to 200,000 cells/mL, with a limit of detection of 10 cells/mL. The platform demonstrated high selectivity and stability and was successfully used for the detection of HepG2 cells in spiked human serum samples with excellent recoveries.

Ti3C2/Ni/Sm-based electrochemical glucose sensor for sweat analysis using bipolar electrochemistry.

An innovative electrochemical sensor is introduced that utilizes bipolar electrochemistry on a paper substrate for detecting glucose in sweat. The sensor employs a three-dimensional porous nanocomposite (MXene/NiSm-LDH) formed by decorating nickel-samarium nanoparticles with double-layer MXene hydroxide. These specially designed electrodes exhibit exceptional electrocatalytic activity during glucose oxidation. The glucose sensing mechanism involves enzyme-free oxidation of the analyte within the sensor cell, achieved by applying an appropriate potential. This leads to the reduction of K3Fe(CN)6 in the reporter cell, and the resulting current serves as the response signal. By optimizing various parameters, the measurement platform enables the accurate determination of sweat glucose concentrations within a linear range of 10 to 200 µM. The limit of detection (LOD) for glucose is 3.6 µM (S/N = 3), indicating a sensitive and reliable detection capability. Real samples were analysed  to validate the sensor's efficiency, and the results obtained were both promising and encouraging.

Point-of-care testing device platform for the determination of creatinine on an enzyme@CS/PB/MXene@AuNP-based screen-printed carbon electrode.

Screen-printed carbon electrodes (SPCE) functionalized with MXene-based three-dimensional nanomaterials are reported for rapid determination of creatinine. Ti3C2TX MXene with in situ reduced AuNPs (MXene@AuNP) were used as a coreactant accelerator for efficient immobilization of enzymes. Creatinine could be oxidized by chitosan-embedded creatinine amidohydrolase, creatine amidinohydrolase, or sarcosine oxidase to generate H2O2, which could be electrochemically detected enhanced by Prussian blue (PB). The enzyme@CS/PB/MXene@AuNP/SPCE detected creatinine within the range 0.03-4.0 mM, with a limit of detection of 0.01 mM, with an average recovery of 96.8-103.7%. This indicates that the proposed biosensor is capable of detecting creatinine in a short amount of time (4 min) within a ± 5% percentage error, in contrast with the standard clinical colorimetric method. With this approach, reproducible and stable electrochemical responses could be achieved for determination of creatinine in serum, urine, or saliva. These results demonstrated its potential for deployment in resource-limited settings for early diagnosis and tracking the progression of chronic kidney disease (CKD).

A renewable screen-printed electrode based on magnetic NiCo@N-doped carbon nanotubes derived from Co-MOF for ractopamine detection.

A renewable electrochemical screen-printed electrode (SPE) is proposed based on magnetic bamboo-like nitrogen-carbon (N-C) nanotubes loaded with nickel-cobalt alloy (NiCo) nanoparticles (NiCo@N-CNTs) for the determination of ractopamine (RAC). During the preparation of NiCo@N-CNTs, Co-MOF-67 (ZIF-67) was firstly synthesized, and then blended with dicyandiamide and nickel acetate, followed by a one-step pyrolysis procedure to prepare NiCo@N-doped carbon nanotubes. The surface morphology, structure, and chemical composition of NiCo@N-CNTs were characterized by SEM, TEM, XRD, XPS, and EDS. The electrocatalytic and electrochemical behavior of NiCo@N-CNTs were investigated by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The results demonstrated that NiCo@N-CNTs possessed remarkable conductivity and electrocatalysis to the oxidation of ractopamine (RAC). By using screen-printed electrode (SPE), NiCo@N-CNTs, and a designed base support, a magnetic RAC sensor (NiCo@N-CNTs/SPE) was successfully constructed. It presented a detection linear range of 0.05-80 µM with a detection limit of 12 nM (S/N = 3). It also exhibited good sensitivity, reproducibility, and practicability in spiked real pork samples. Since the adhesion of NiCo/N-CNTs on SPE was controlled by magnet, the NiCo@N-CNTs was easily detached from the SPE surface by magnetism and thus displayed excellent renewability. This work broadened insights into portable devices for on-site and real-time analysis.

A novel potentiometric screen-printed electrode based on crown ethers/nano manganese oxide/Nafion composite for trace level determination of copper ion in biological fluids.

Copper levels in biological fluids are associated with Wilson's, Alzheimer's, Menke's, and Parkinson's diseases, making them good biochemical markers for these diseases. This study introduces a miniaturized screen-printed electrode (SPE) for the potentiometric determination of copper(II) in some biological fluids. Manganese(III) oxide nanoparticles (Mn2O3-NPs), dispersed in Nafion, are drop-casted onto a graphite/PET substrate, serving as the ion-to-electron transducer material. The solid-contact material is then covered by a selective polyvinyl chloride (PVC) membrane incorporated with 18-crown-6 as a neutral ion carrier for the selective determination of copper(II) ions. The proposed electrode exhibits a Nernstian response with a slope of 30.2 ± 0.3 mV/decade (R2 = 0.999) over the linear concentration range 5.2 × 10-9 - 6.2 × 10-3 mol/l and a detection limit of 1.1 × 10-9 mol/l (69.9 ng/l). Short-term potential stability is evaluated using constant current chronopotentiometry (CP) and electrochemical impedance spectroscopy (EIS). A significant improvement in the electrode capacitance (91.5 µF) is displayed due to the use of Mn2O3-NPs as a solid contact. The presence of Nafion, with its high hydrophobicity properties, eliminates the formation of the thin water layer, facilitating the ion-to-electron transduction between the sensing membrane and the conducting substrate. Additionally, it enhances the adhesion of the polymeric sensing membrane to the solid-contact material, preventing membrane delamination and increasing the electrode's lifespan. The high selectivity, sensitivity, and potential stability of the proposed miniaturized electrode suggests its use for the determination of copper(II) ions in human blood serum and milk samples. The results obtained agree fairly well with data obtained by flameless atomic absorption spectrometry.

Atomically Co-dispersed nitrogen-doped carbon for sensitive electrochemical immunoassay of breast cancer biomarker CA15-3.

The development of an ultrasensitive and precise measurement of a breast cancer biomarker (cancer antigen 15-3; CA15-3) in complex human serum is essential for the early diagnosis of cancer in groups of healthy populations and the treatment of patients. However, currently available testing technologies suffer from insufficient sensitivity toward CA15-3, which severely limits early large-scale screening of breast cancer patients. We report a versatile electrochemical immunoassay method based on atomically cobalt-dispersed nitrogen-doped carbon (Co-NC)-modified disposable screen-printed carbon electrode (SPCE) with alkaline phosphatase (ALP) and its metabolite, ascorbic acid 2-phosphate (AAP), as the electrochemical labeling and redox signaling unit for sensitive detection of low-abundance CA15-3. During electrochemical detection by differential pulse voltammetry (DPV), it was found that the Co-NC-SPCE electrode did not have a current signal response to the AAP substrate; however, it had an extremely favorable response current to ascorbic acid (AA). Based on the above principle, the target CA15-3-triggered immunoassay enriched ALP-catalyzed AAP produces a large amount of AA, resulting in a significant change in the system current signal, thereby realizing the highly sensitive detection of CA15-3. Under the optimal AAP substrate concentration and ALP catalysis time, the Co-NC-SPCE-based electrochemical immunoassay demonstrated a good DPV current for CA15-3 in the assay interval of 1.0 mU/mL to 10,000 mU/mL, with a calculated limit of detection of 0.38 mU/mL. Since Co-NC-SPCE has an excellent DPV current response to AA and employs split-type scheme, the constructed electrochemical immunoassay has the merits of high preciseness and anti-interference, and its clinical diagnostic results are comparable to those of commercial kits.

Sandwich-type supersensitive electrochemical aptasensor of glypican-3 based on PrGO-Hemin-PdNP and AuNP@PoPD.

A new sandwich-type electrochemical biosensing platform was developed by gold @polyphthalenediamine nanohybrids (AuNP@PoPD) as the sensing platform and phosphorus doped reduced graphene oxide-hemin-palladium nanoparticles (PrGO-Hemin-PdNP) as the signal amplifier for phosphatidylinositol proteoglycan 3 (GPC3). AuNP@PoPD, co-electrodeposited into the screen printed electrode with high conductivity and stability, is dedicated to assembling the primary GPC3 aptamer (GPC3Apt). The second GPC3Apt immobilized on the high conductivity and large surface area of PrGO-Hemin-PdNP was utilized as an electrochemical signal reporter by hemin oxidation (PrGO-Hemin-PdNP-GPC3Apt). In the range 0.001-10.0 ng/mL, the hemin oxidation current signal of the electrochemical aptasensor increased log-linearly with the concentration of GPC3, the lowest detection limit was 0.13 pg/mL, and the sensitivity was 2.073 µA/µM/cm2. The aptasensor exhibited good sensing performance in a human serum sample with the relative error of 4.31-8.07%. The sandwich sensor showed good selectivity and stability for detection GPC3 in human serum samples, providing a new efficient and sensitive method for detecting HCC markers.

First Acyclovir Determination Procedure via Electrochemically Activated Screen-Printed Carbon Electrode Coupled with Well-Conductive Base Electrolyte.

In this work, a new voltammetric procedure for acyclovir (ACY) trace-level determination has been described. For this purpose, an electrochemically activated screen-printed carbon electrode (aSPCE) coupled with well-conductive electrolyte (CH3COONH4, CH3COOH and NH4Cl) was used for the first time. A commercially available SPCE sensor was electrochemically activated by conducting cyclic voltammetry (CV) scans in 0.1 mol L-1 NaOH solution and rinsed with deionized water before a series of measurements were taken. This treatment reduced the charge transfer resistance, increased the electrode active surface area and improved the kinetics of the electron transfer. The activation step and high conductivity of supporting electrolyte significantly improved the sensitivity of the procedure. The newly developed differential-pulse adsorptive stripping voltammetry (DPAdSV) procedure is characterized by having the lowest limit of detection among all voltammetric procedures currently described in the literature (0.12 nmol L-1), a wide linear range of the calibration curve (0.5-50.0 and 50.0-1000.0 nmol L-1) as well as extremely high sensitivity (90.24 nA nmol L-1) and was successfully applied in the determination of acyclovir in commercially available pharmaceuticals.

A Convenient Strategy for the Voltammetric Direct Determination of Ce(III) in Environmental Waters Using a Multi-Walled Carbon Nanotubes Modified Screen-Printed Carbon Electrode.

A simple and fast stripping voltammetric procedure for trace determination of Ce(III) in environmental water samples has been developed. The procedure of cerium determination in the presence of Alizarin S and acetate buffer was employed as the initial method. The adsorption material, multi-walled carbon nanotubes, was used as a screen-printed electrode modifier ensuring efficient accumulation of the Ce(III)-Alizarin S complex. The calibration graph for Ce(III) for an accumulation time of 60 s was linear in the range from 1 × 10-8 to 7 × 10-7 mol L-1 with the linear correlation coefficient r = 0.997. The detection limit was estimated from three times the standard deviation of low Ce(III) concentration and an accumulation time of 60 s was about 3.5 × 10-9 mol L-1. The proposed method was successfully applied to Ce(III) determination at trace levels in environmental water samples, such as river, lake and rain water with recoveries ranged from 93% to 98%.

Rapid integration of screen-printed electrodes into thermoplastic organ-on-a-chip devices for real-time monitoring of trans-endothelial electrical resistance.

Trans-endothelial electrical resistance (TEER) is one of the most widely used indicators to quantify the barrier integrity of endothelial layers. Over the last decade, the integration of TEER sensors into organ-on-a-chip (OOC) platforms has gained increasing interest for its efficient and effective measurement of TEER in OOCs. To date, microfabricated electrodes or direct insertion of wires has been used to integrate TEER sensors into OOCs, with each method having advantages and disadvantages. In this study, we developed a TEER-SPE chip consisting of carbon-based screen-printed electrodes (SPEs) embedded in a poly(methyl methacrylate) (PMMA)-based multi-layered microfluidic device with a porous poly(ethylene terephthalate) membrane in-between. As proof of concept, we demonstrated the successful cultures of hCMEC/D3 cells and the formation of confluent monolayers in the TEER-SPE chip and obtained TEER measurements for 4 days. Additionally, the TEER-SPE chip could detect changes in the barrier integrity due to shear stress or an inflammatory cytokine (i.e., tumor necrosis factor-α). The novel approach enables a low-cost and facile fabrication of carbon-based SPEs on PMMA substrates and the subsequent assembly of PMMA layers for rapid prototyping. Being cost-effective and cleanroom-free, our method lowers the existing logistical and technical barriers presenting itself as another step forward to the broader adoption of OOCs with TEER measurement capability.

Electrodeposited copper nanoparticles for creatinine detection via the in situ formation of copper-creatinine complexes.

Creatinine is an important biomarker of kidney diseases. In this work, a fast and facile electrochemical sensor was developed for creatinine detection based on the use of copper nanoparticle-modified screen-printed electrodes. The copper electrodes were prepared by simple electrodeposition of Cu2+ (aq). The electrochemically inactive creatinine was detected reductively via the in situ formation of copper-creatinine complexes. Two linear detection ranges, 0.28-3.0 mM and 3.0-20.0 mM, were achieved using differential pulse voltammetry, with the sensitivities of 0.824 ± 0.053 µA mM-1 and 0.132 ± 0.003 µA mM-1, respectively. The limit of detection was determined to be 0.084 mM. The sensor was validated in synthetic urine samples to yield 99.3% recovery (%RSD = 2.8), demonstrating high tolerance to possible interfering species. Finally, the stability of creatinine and its degradation kinetics at different temperatures were evaluated using our developed sensor. The loss of creatinine was found to be a first-order reaction with the activation energy of 64.7 kJ mol-1.

Aptamers dimerization inspired biomimetic clamp assay towards impedimetric SARS-CoV-2 antigen detection.

Antigen-detecting rapid diagnostic testing (Ag-RDT) has contributed to containing the spread of SARS-CoV-2 variants of concern (VOCs). In this study, we proposed a biomimetic clamp assay for impedimetric SARS-CoV-2 nucleocapsid protein (Np) detection. The DNA biomimetic clamp (DNA-BC) is formed by a pair of Np aptamers connected via a T20 spacer. The 5'- terminal of the DNA-BC is phosphate-modified and then anchored on the surface of the screen-printed gold electrode, which has been pre-coated with Au@UiO-66-NH2. The integrated DNA-material sensing biochip is fabricated through the strong Zr-O-P bonds to form a clamp-type impedimetric aptasensor. It is demonstrated that the aptasensor could achieve Np detection in one step within 11 min and shows pronounced sensitivity with a detection limit of 0.31 pg mL-1. Above all, the aptasensor displays great specificity and stability under physiological conditions as well as various water environments. It is a potentially promising strategy to exploit reliable Ag-RDT products to confront the ongoing epidemic.

Disposable electrochemical platform based on solid-binding peptides and carbon nanomaterials: an alternative device for leishmaniasis detection.

Neglected tropical diseases are those caused by infectious agents or parasites and are considered endemic in low-income populations. These diseases also have unacceptable indicators and low investment in research, drug production, and control. Tropical diseases such as leishmaniasis are some of the main causes of morbidity and mortality around the globe. Electrochemical immunosensors are promising tools for diagnostics against these diseases. One such benefit is the possibility of assisting diagnosis in isolated regions, where laboratory infrastructure is lacking. In this work, different peptides were investigated to detect antibodies against Leishmania in human and canine serum samples. The peptides evaluated (395-KKG and 395-G) have the same recognition site but differ on their solid-binding domains, which ensure affinity to spontaneously bind to either graphene oxide (GO) or graphene quantum dots (GQD). Cyclic voltammetry and differential pulse voltammetry were employed to investigate the electrochemical behavior of each assembly step and the role of each solid-binding domain coupled to its anchoring material. The graphene affinity peptide (395-G) showed better reproducibility and selectivity when coupled to GQD. Under the optimized set of experimental conditions, negative and positive human serum samples responses were distinguished based on a cut-off value of 82.5% at a 95% confidence level. The immunosensor showed selective behavior to antibodies against Mycobacterium leprae and Mycobacterium tuberculosis, which are similar antibodies and potentially sources of false positive tests. Therefore, the use of the graphene affinity peptide as a recognition site achieved outstanding performance for the detection of Leishmania antibodies.

Graphene oxide-manganese oxide composite as an electrocatalyst for simultaneous detection of manganese- and chromium-contaminated water.

The development of a sensitive and selective electrochemical sensor for simultaneous quantification of manganese (Mn(II)) and chromium (Cr(VI)) using composite of graphene oxide (GO) and manganese oxide modified screen printed carbon electrode (GO-Mn2O3/SPCE) is reported for the first time. The good sensing performance is achieved by mixing GO prepared by modified Hummer's method (GO-H) with proper particle size of Mn2O3 (241 nm). The mechanism of this sensor is based on the formation of Mn-O and Cr-O on the modified electrode with assistance of oxygen moieties provided by both Mn2O3 NPs and GO. The analytical performances were investigated by measuring electrochemical signal of Mn(II) and Cr(VI) by using square-wave cathodic stripping voltammetry (SWCSV). This sensor holds low electrode-to-electrode variation (relative standard deviation (RSD) < 4%) with a good limit of detection (LOD) at about 6.67 and 11.20 µg⋅L-1 for Mn(II) and Cr(VI), respectively. Applicability of this sensor was demonstrated by measuring Mn(II) and Cr(VI) in tap water samples with recovery of 90.77-103.45% and 82.34-103.73% for Mn(II) and Cr(VI) determinations, respectively. With the contribution of both GO and Mn2O3 as electrocatalysts, this developed sensor is capable to be used for water quality monitoring in real samples.

Microfluidic paper-based analytical devices for simultaneous detection of oxidative potential and copper in aerosol samples.

The potential reach of point-of-care (POC) diagnostics into daily routines for exposure to reactive oxygen species (ROS) and Cu in aerosolized particulate matter (PM) demands that microfluidic paper-based analytical devices (µPADs) take into consideration the simple detection of these toxic PM components. Here, we propose µPADs with a dual-detection system for simultaneous ROS and Cu(II) detection. For colorimetric ROS detection, the glutathione (GSH) assay with a folding design to delay the reaction yielded complete ROS and GSH oxidation, and improved homogeneity of color development relative to using the lateral flow pattern. For electrochemical Cu(II) determination, 1,10-phenanthroline/Nafion modified graphene screen-printed electrodes showed ability to detect Cu(II) down to pg level being low enough to be applied to PM analysis. No intra- and inter-interference affecting both systems were found. The proposed µPADs obtained LODs for 1,4-naphthoquinone (1,4-NQ), used as the ROS representative, and Cu(II) of 8.3 ng and 3.6 pg, respectively and linear working ranges of 20 to 500 ng for ROS and 1 × 10-2 to 2 × 102 ng for Cu(II). Recovery of the method was between 81.4 and 108.3% for ROS and 80.5-105.3% for Cu(II). Finally, the sensors were utilized for simultaneous ROS and Cu(II) determination in PM samples and the results statistically agreed with those using the conventional methods at 95% confidence.

Nanostructured poly(thiophene acetic acid)/Au/poly(methylene blue) interface for electrochemical immunosensing of p53 protein.

A poly(thiophene acetic acid)/Au/poly(methylene blue) nanostructured interface was electrochemically assembled step-by-step on screen-printed carbon electrodes (SPCE) for label-free detection of p53 protein. The initial electrical conductive properties of the polymeric interface were increased with an additional layer of poly(methylene blue) electropolymerized in the presence of gold nanoparticles. The nano-immunosensing architecture was prepared by covalent immobilization of anti-p53 antibodies as bioreceptors through the poly(thiophene acetic acid) moieties. The nano-immunosensor assembly was extensively characterized by ultraviolet-visible spectrophotometry, dynamic and electrophoretic light scattering, scanning electron microscopy, X-ray photoelectron spectroscopy, Raman spectroscopy, atomic force microscopy, cyclic voltammetry, and electrochemical impedance spectroscopy. Under optimal conditions, p53 was specifically and selectively detected by square wave voltammetry in a linear range between 1 and 100 ng mL-1 with a limit of detection of 0.65 ng mL-1. In addition, the electrochemical nano-immunosensor detected p53 in spiked human serum samples and colorectal cancer cell lysates, and the results were validated with a standard spectrophotometric method using a paired samples t test, which did not exhibit significant differences between both methods. The resultant p53 nano-immunosensor is simple to assemble, robust, and has the potential for point-of-care biomarker detection applications.

Zirconium copper oxide microflowers based non-enzymatic screen-printed electrochemical sensor for the detection of glucose in saliva, urine, and blood serum.

Zirconium copper oxide microflowers (Zr/CuO MF) based non-enzymatic sensor was developed for glucose detection in saliva, urine, and blood. An easy urea hydrolysis method was employed for the synthesis of the metal oxide and further calcined to improve the catalytic property. The flower-like morphology of the Zr/CuO was confirmed by SEM analysis and the presence of copper and zirconium was examined using energy dispersive X-ray analysis (EDAX). The Zr/CuO MF modified screen-printed electrodes exhibited excellent glucose sensing performance in 0.15 M NaOH medium and could quantify glucose in the range from 10 µM to 27 mM. A high sensitivity of 1.815 ± 0.003 mA mM-1 cm-2 was obtained for lower glucose concentration from 15 µM to 3 mM and 1.250 ± 0.006 mA mM-1 cm-2 for higher concentration glucose from 3 to 27 mM. The limit of detection of the fabricated sensor was found to be 0.8 µM. The sensor displayed high selectivity and stability towards glucose in different body fluids like saliva, urine, and blood serum at a working potential of 0.6 V (vs. Ag/AgCl). In saliva, urine, and serum samples, the sensor exhibited excellent recovery of 95-108, 92-108, and 93-101% in saliva, urine, and serum, respectively, with a relative standard deviation of less than 10%, demonstrating high accuracy and reliability of the sensor. The developed sensor is promising for developing an invasive and non-invasive point-of-care testing device for glucose detection.

Portable Device for Potentiometric Determination of Antioxidant Capacity.

For the first time, a prototype of a portable device for the potentiometric determination of antioxidant capacity based on a new measurement principle is proposed. A feature of the approach is the use of an electrochemical microcell with separated spaces and two identical electrodes with immobilized reagents. An antioxidant solution is introduced into one half-cell, and the antioxidants interact with the reagents. The other half-cell contains only reagents. The potential difference between the electrodes is due to the change in the ratio of the oxidized and reduced form of the reagents, which occurs as a result of the reaction with the antioxidants in one of the half-cells and is related to their concentration. The range of linearity of the microcell with immobilized reagents is 40-4000 µM-eq, and the limit of detection is 20 µM-eq. The device was successfully tested in the analysis of standard antioxidant solutions. The recoveries were (92-113)%, and the relative standard deviation did not exceed 15%. A good correlation was found between the data obtained by the approach and the potentiometric method in a macrocell for fruit juice analysis. Pearson's coefficient for the obtained experimental data was 0.9955. The proposed portable device is promising and can be used in field conditions.

Using Sparfloxacin-Capped Gold Nanoparticles to Modify a Screen-Printed Carbon Electrode Sensor for Ethanol Determination.

Alcohol is a dangerous substance causing global mortality and health issues, including mental health problems. Regular alcohol consumption can lead to depression, anxiety, cognitive decline, and increased risk of alcohol-related disorders. Thus, monitoring ethanol levels in biological samples could contribute to maintaining good health. Herein, we developed an electrochemical sensor for the determination of ethanol in human salivary samples. Initially, the tetra-chloroauric acid (HAuCl4) was chemically reduced using sparfloxacin (Sp) which also served as a stabilizing agent for the gold nanoparticles (AuNPs). As-prepared Sp-AuNPs were comprehensively characterized and confirmed by UV-visible spectroscopy, X-ray diffraction, field emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectroscopy (EDS), and elemental mapping analysis. The average particle size (~25 nm) and surface charge (negative) of Sp-AuNPs were determined by using dynamic light scattering (DLS) and Zeta potential measurements. An activated screen-printed carbon electrode (A-SPE) was modified using Sp-AuNPs dispersion, which exhibited greater electrocatalytic activity and sensitivity for ethanol (EtOH) oxidation in 0.1 M sodium hydroxide (NaOH) as studied by cyclic voltammetry (CV) and differential pulse voltammetry (DPV). DPV showed a linear response for EtOH from 25 µM to 350 µM with the lowest limit of detection (LOD) of 0.55 µM. Reproducibility and repeatability studies revealed that the Sp-AuNPs/A-SPEs were highly stable and very sensitive to EtOH detection. Additionally, the successful electrochemical determination of EtOH in a saliva sample was carried out. The recovery rate of EtOH spiked in the saliva sample was found to be 99.6%. Thus, the incorporation of Sp-AuNPs within sensors could provide new possibilities in the development of ethanol sensors with an improved level of precision and accuracy.