Search Results (34)

Portable non-enzymatic electrochemical glucose sensors offer potential for decentralized healthcare and medical education; however, their integration into simulation-based teleconsultation training workflows remains limited. This study presents the functional integration of a portable copper-modified electrochemical glucose sensor into a web- and Android-based telemedicine platform within a simulation-based medical education framework. Screen-printed carbon electrodes were electrochemically activated and modified via copper electrodeposition. Surface and electrochemical characterization were performed using SEM-EDX and cyclic voltammetry, respectively, followed by chronoamperometry for quantitative detection. Glucose solutions in PBS (pH 10) were measured using 70 µL samples, and the resulting signals were converted into glucose values (mg/dL) through a calibration model and incorporated into simulated gynecological teleconsultation workflows. The sensor exhibited a stable amperometric response at +0.60 V, with a linear range of 3.125–50 mM (R² = 0.9822), an area-normalized sensitivity of 0.061 µA·mM⁻¹·cm⁻², and a limit of detection of 1.39 mM. Implementation within the simulation scenario (n = 26) demonstrated 69% high/very high perceived usability and 88% high/very high educational value. These results support the feasibility of functionally integrating portable electrochemical sensing into simulation-based teleconsultation training and provide a proof-of-concept framework for future technical refinement and broader educational validation. Full article

Two-dimensional Ti₃C₂O₂ MXene has emerged as a promising electrode material for non-enzymatic glucose sensing due to its metallic conductivity and biocompatibility. However, the atomic-scale sensing mechanism remains unclear. This DFT study uses the PBE functional with the D3(BJ) dispersion correction to elucidate glucose–MXene interactions under idealized vacuum conditions. Pristine Ti₃C₂O₂ shows metallic behavior with a density of states of about 8.2 states per electron volt at the Fermi level, dominated by Ti 3d states. β-d-glucose adsorbs onto the surface through hydrogen bonding, with an adsorption energy of −0.82 eV at a separation distance of 2.8 angstroms. Bader analysis indicates a transfer of about 0.15 electrons from MXene to glucose, resulting in a Fermi level shift of about −0.15 eV and an 18% reduction in the density of states at the Fermi level. These changes correspond to an estimated sensitivity of approximately 0.6 μA mM⁻¹ cm⁻² and a detection limit of about 17 µM, consistent with reported experimental performance of MXene-based sensors. Comparative adsorption calculations for common sweat interferents yield −0.45 eV for lactate and −0.25 eV for urea, indicating weaker interfacial affinity than glucose; these values reflect thermodynamic binding strength and possible surface occupation rather than definitive electrochemical selectivity, which additionally depends on redox potential, electron-transfer kinetics, and operating bias. We acknowledge three main limitations: first, the model considers only pure oxygen termination rather than mixed oxygen, hydroxyl, and fluorine terminations; second, the calculations are performed under vacuum rather than in aqueous conditions; third, the study is based on static zero kelvin structures rather than finite temperature dynamics. Despite these idealizations, the results provide baseline mechanistic insights to support rational design of MXene-based glucose sensors. Full article

Bifunctional materials present a promising route to develop advanced devices, yet the dual performance of CoNi₂S₄ nanosheets anchored on a porous scaffold is seldom reported. Herein, we propose a rational fabrication strategy to construct a three-dimensional hierarchical electrode via the in-situ growth of densely aligned CoNi₂S₄ nanosheets on a conductive fabric scaffold. This integrated porous architecture concurrently offers an ultrahigh specific surface area, efficient mass transport, and rapid electron conduction. As a supercapacitor, the electrode achieves a high areal capacitance of 3198 mF cm⁻² at 4 mA cm⁻² and retains 98.1% of its initial capacitance after 1000 cycles at 20 mA cm⁻². As a non-enzymatic glucose sensor, it exhibits outstanding selectivity (<4.1% interference), high sensitivity (1049 μA mM⁻¹ cm⁻²), a wide linear range (1–8 mM), and a low detection limit (1 μM). These results highlight the significant potential of this binder-free, scaffold-supported nanosheet design for advancing integrated energy storage and biosensing systems. Full article

Human organoids and organ-on-chip/microphysiological systems (OoC/MPS) are increasingly used as new-approach methodologies for biotoxin assessment. They retain human-relevant tissue organization and enable interpretable analysis of exposure geometry, barrier transport, perfusion, and (when needed) multi-organ coupling. In this review, we synthesize primary evidence across major toxin classes, including bacterial enterotoxins (e.g., cholera toxin, heat-stable enterotoxins, Shiga toxins), mycotoxins (e.g., aflatoxin B1, ochratoxin A, deoxynivalenol), and algal/cyanobacterial toxins (e.g., saxitoxin, domoic acid, microcystins, biliatresone). We emphasize studies that clearly define toxin identity and exposure context and that demonstrate mechanism-critical model competencies under assay conditions. We highlight decision-informative functional endpoints that align with the dominant pathophysiology. These include cystic fibrosis transmembrane conductance regulator (CFTR)-dependent secretion in human enteroids/colonoids, transporter-linked proximal tubular injury in kidney MPS, gut–kidney axis injury from Shiga toxin-producing E. coli in microfluidic systems, and multi-electrode array (MEA) network readouts in human 3D neural tissues. We then summarize best practices that improve cross-study comparability. These include reporting delivered versus nominal exposure, assessing recovery/mass balance and device/material interactions, applying proportional biological qualification (polarity, transporter/enzymatic competence, functional stability), defining a minimal comparable endpoint core, and preserving QIVIVE readiness in reporting. Finally, we outline near-term priorities for the field, including chronic low-dose and mixture designs, harmonized reference panels and acceptance criteria, and fit-for-purpose escalation to coupled OoC/MPS only when perfusion or organ–organ coupling is expected to change the interpretation. Full article

This study reports on the direct electron transfer (DET) ability of the enzyme spermidine dehydrogenase (SpDH) and its use in a DET-type enzymatic sensor for detecting spermine. SpDH was found to exhibit internal electron transfer from its cofactor, flavin adenine dinucleotide (FAD), to heme b. This was confirmed by observing the heme b-derived reduction peak at 560 nm in the presence of spermine, the substrate. SpDH was immobilized on a gold electrode via a dithiobis (succinimidyl hexanoate) self-assembled monolayer. The cyclic voltammetry analysis of the SpDH-immobilized gold electrode revealed an increased oxidation current in the presence of 0.1 mM spermine with an onset potential of −0.14 V vs. Ag/AgCl in the absence of an additional external electron acceptor. This result confirmed that SpDH is capable of DET. Chronoamperometric analyses were conducted using an SpDH-immobilized gold electrode with spermine as the substrate under a 0 V oxidation potential vs. Ag/AgCl using an artificial saliva matrix containing 10 µM ascorbic acid and 100 µM uric acid. The sensor exhibited good linear correlation between the current increase and spermine concentration from 0.2 to 2.0 µM, with a limit of detection of 0.084 µM, which encompasses the physiologically relevant spermine concentration found in the saliva. Primary structure alignments and 3D structure predictions revealed that all SpDH homologs possess two conserved histidine residues in the same location on the surface as the heme b ligand of SpDH. This indicates their potential for DET-ability with an electrode. Full article

Homogeneous aptasensors that eliminate the need for probe labeling or immobilization hold significant potential for the rapid detection of tumor biomarkers. Herein, a homogeneous aptasensor with electrochemical (EC) and electrochemiluminescence (ECL) dual detection channels was developed by integrating nanochannel-based probe enrichment and DNase I cleavage for selective detection of the tumor biomarker, carbohydrate antigen 125 (CA125). A two-dimensional (2D) composite probe was prepared by assembling the CA125-specific aptamer and the cationic probe tris(2,2′-bipyridyl)Ru(II) (Ru(bpy)₃²⁺), which exhibited both EC and ECL properties, onto graphene oxide (GO) nanosheets (Ru(bpy)₃²⁺/Apt@GO). A vertically ordered mesoporous silica film (VMSF) with ultrasmall, uniform, and vertically aligned nanochannel arrays was rapidly grown on the inexpensive and disposable indium tin oxide (ITO) electrode, forming the detection interface. Due to the size exclusion effect of the ultrasmall nanochannels in VMSF, the Ru(bpy)₃²⁺/Apt@GO probe was unable to penetrate the nanochannels, resulting in no detectable Ru(bpy)₃²⁺ signal on the electrode. Upon specific recognition of CA125 by the aptamer, an aptamer-CA125 complex was formed and subsequently detached from GO. DNase I then cleaved the aptamer-CA125 complex, releasing CA125 and allowing Ru(bpy)₃²⁺ to dissociate into the solution. This enzymatic cleavage enabled CA125 to re-enter the binding cycle, amplifying the release of Ru(bpy)₃²⁺ into the solution. The electrostatic adsorption of the cationic Ru(bpy)₃²⁺ by VMSF significantly enhanced both the EC and ECL signals. The constructed aptasensor exhibited a linear EC detection range for CA125 from 0.1 U/mL to 100 ng/mL, with a limit of detection (LOD) of 91 mU/mL. For ECL detection, CA125 was detected over a range from 0.001 to 100 U/mL, with a LOD as low as 0.4 mU/mL. The developed aptasensor demonstrated excellent selectivity and was successfully applied to the dual-mode EC/ECL detection of CA125 in fetal bovine serum samples. Full article

This research focuses on the rational design of porous enzymatic electrodes, using horseradish peroxidase (HRP) as a model biocatalyst. Our goal was to identify the main obstacles to maximizing biocatalyst utilization within complex porous structures and to assess the impact of various carbon nanomaterials on electrode performance. We evaluated as-synthesized carbon nanomaterials, such as Carbon Aerogel, Coral Carbon, and Carbon Hollow Spheres, against the commercially available Vulcan XC72 carbon nanomaterial. The 3D electrodes were constructed using gelatin as a binder, which was cross-linked with glutaraldehyde. The bioelectrodes were characterized electrochemically in the absence and presence of 3 mM of hydrogen peroxide. The capacitive behavior observed was in accordance with the BET surface area of the materials under study. The catalytic activity towards hydrogen peroxide reduction was partially linked to the capacitive behavior trend in the absence of hydrogen peroxide. Notably, the Coral Carbon electrode demonstrated large capacitive currents but low catalytic currents, an exception to the observed trend. Microscopic analysis of the electrodes indicated suboptimal gelatin distribution in the Coral Carbon electrode. This study also highlighted the challenges in transferring the preparation procedure from one carbon nanomaterial to another, emphasizing the importance of binder quantity, which appears to depend on particle size and quantity and warrants further studies. Under conditions of the present study, Vulcan XC72 with a catalytic current of ca. 300 µA cm⁻² in the presence of 3 mM of hydrogen peroxide was found to be the most optimal biocatalyst support. Full article

A flow-through biosensor system for the determination of uric acid was developed on the platform of flow-through electrochemical cell manufactured by 3D printing from poly(lactic acid) and equipped with a modified screen-printed graphite electrode (SPE). Uricase was immobilized to the inner surface of a replaceable reactor chamber. Its working volume was reduced to 10 μL against a previously reported similar cell. SPE was modified independently of the enzyme reactor with carbon black, pillar[5]arene, poly(amidoamine) dendrimers based on the p-tert-butylthiacalix[4]arene (PAMAM-calix-dendrimers) platform and electropolymerized 3,7-bis(4-aminophenylamino) phenothiazin-5-ium chloride. Introduction of the PAMAM-calix-dendrimers into the electrode coating led to a fivefold increase in the redox currents of the electroactive polymer. It was found that higher generations of the PAMAM-calix-dendrimers led to a greater increase in the currents measured. Coatings consisted of products of the electropolymerization of the phenothiazine with implemented pillar[5]arene and PAMAM-calix-dendrimers showing high efficiency in the electrochemical reduction of hydrogen peroxide that was formed in the enzymatic oxidation of uric acid. The presence of PAMAM-calix-dendrimer G2 in the coating increased the redox signal related to the uric acid assay by more than 1.5 times. The biosensor system was successfully applied for the enzymatic determination of uric acid in chronoamperometric mode. The following optimal parameters for the chronoamperometric determination of uric acid in flow-through conditions were established: pH 8.0, flow rate 0.2 mL·min⁻¹, 5 U of uricase per reactor. Under these conditions, the biosensor system made it possible to determine from 10 nM to 20 μM of uric acid with the limit of detection (LOD) of 4 nM. Glucose (up to 1 mM), dopamine (up to 0.5 mM), and ascorbic acid (up to 50 μM) did not affect the signal of the biosensor toward uric acid. The biosensor was tested on spiked artificial urine samples, and showed 101% recovery for tenfold diluted samples. The ease of assembly of the flow cell and the low cost of the replacement parts make for a promising future application of the biosensor system in routine clinical analyses. Full article

Metal–organic frameworks (MOFs) have broad potential applications in electrochemical glucose detection. Herein, a green ultrasonic synthesis process is presented for preparing two-dimensional (2D) copper–nickel metal–organic framework nanosheets (CuNi-MOFNs) for glucose detection. The synthesized CuNi-MOFNs were characterized using scanning electron microscopy (SEM), scanning transmission electron microscope (STEM), X-ray diffractometer (XRD), and X-ray photoelectron spectrometer (XPS). The CuNi-MOFN nanocomposites were used to cover the glassy carbon electrode (GCE) and the CuNi-MOFNs-modified electrode was studied in alkaline media. Cyclic voltammetry (CV) and amperometric i–t curves indicated that the CuNi-MOFNs-modified electrode revealed great electrochemical performances towards glucose oxidation. Due to the ease of access to active metal sites in large specific surface of nanosheets, the CuNi-MOFNs-modified electrode can effectively improve the electronic transfer rate and enhance electrocatalytic activity of the CuNi-MOFNs-modified electrode. The CuNi-MOFNs-modified electrode showed electrochemical performances for glucose detection with a linear range from 0.01 mM to 4 mM, sensitivity of 702 μAmM⁻¹cm⁻², and detection limit of 3.33 μΜ (S/N = 3). The CuNi-MOFNs-modified electrode exhibited excellent anti-interference ability and high selectivity in glucose measurements. Hence, the CuNi-MOFNs-modified electrode has good, promising prospects in non-enzymatic electrochemical glucose detection. Full article

A novel approach to surface modification, which consists of the adsorption of microgel–enzyme complexes preformed in solution, is highlighted. Accordingly, the microgel–enzyme complexes were formed due to the electrostatic interaction of the oppositely charged interacting components, that is, a cationic poly(N-isopropylacrylamide)-based microgel and glucose oxidase taken as a model enzyme. The spontaneous adsorption of the prepared microgel–enzyme complexes, examined by means of quartz crystal microbalance with dissipation monitoring and atomic force microscopy, was observed, resulting in the formation of well-adhered microgel–enzyme coatings. Further, the preformed microgel–enzyme complexes were adsorbed onto the modified graphite-based screen-printed electrodes, and their enzymatic responses were determined by means of amperometry, demonstrating a remarkable analytical performance toward the quantification of β-D-glucose in terms of high sensitivity (0.0162 A × M⁻¹ × cm⁻²), a low limit of detection (1 μM), and an expanded linear range (1–2000 μM). The fabricated microgel–enzyme biosensor constructs were found to be very stable against manifold-repeated measurements. Finally, the pH- or salt-induced release of glucose oxidase from the adsorbed preformed microgel–enzyme complexes was demonstrated. The findings obtained for the microgel–enzyme coatings prepared via adsorption of the preformed microgel–enzyme complexes were compared to those found for the microgel–enzyme coatings fabricated via a previously exploited two-stage sequential adsorption, which includes the adsorption of the microgel first, followed by the electrostatic binding of glucose oxidase by the adsorbed microgel. Full article

The authors present a novel sensing platform for a disposable electrochemical, non-enzymatic glucose sensor strip at physiological pH. The sensing material is based on dendritic gold nanostructures (AuNs) resembling feather branches, which are electrodeposited onto a laser-scribed 3D graphene electrode (LSGE). The LSGEs were fabricated via a one-step laser scribing process on a commercially available polyimide sheet. This study investigates several parameters that influence the morphology of the deposited Au nanostructures and the catalytic activity toward glucose electro-oxidation. The electrocatalytic activity of the AuNs-LSGE was evaluated using cyclic voltammetry (CV), linear sweep voltammetry (LSV), and amperometry and was compared to commercially available carbon electrodes prepared under the same electrodeposition conditions. The sensor demonstrated good stability and high selectivity of the amperometric response in the presence of interfering agents, such as ascorbic acid, when a Nafion membrane was applied over the electrode surface. The proposed sensing strategy offers a wide linear detection range, from 0.5 to 20 mM, which covers normal and elevated levels of glucose in the blood, with a detection limit of 0.21 mM. The AuNs-LSGE platform exhibits great potential for use as a disposable glucose sensor strip for point-of-care applications, including self-monitoring and food management. Its non-enzymatic features reduce dependence on enzymes, making it suitable for practical and cost-effective biosensing solutions. Full article

The functional significance of cytochrome P450s (CYP) enzymes is their ability to catalyze the biotransformation of xenobiotics and endogenous compounds. P450 enzymes catalyze regio- and stereoselective oxidations of C-C and C-H bonds in the presence of oxygen as a cosubstrate. Initiation of cytochrome P450 catalytic cycle needs an electron donor (NADPH, NADH cofactor) in nature or alternative artificial electron donors such as electrodes, peroxides, photo reduction, and construction of enzymatic “galvanic couple”. In our review paper, we described alternative “handmade” electron sources to support cytochrome P450 catalysis. Physical-chemical methods in relation to biomolecules are possible to convert from laboratory to industry and construct P450-bioreactors for practical application. We analyzed electrochemical reactions using modified electrodes as electron donors. Electrode/P450 systems are the most analyzed in terms of the mechanisms underlying P450-catalyzed reactions. Comparative analysis of flat 2D and nanopore 3D electrode modifiers is discussed. Solar-powered photobiocatalysis for CYP systems with photocurrents providing electrons to heme iron of CYP and photoelectrochemical biosensors are also promising alternative light-driven systems. Several examples of artificial “galvanic element” construction using Zn as an electron source for the reduction of Fe³⁺ ion of heme demonstrated potential application. The characteristics, performance, and potential applications of P450 electrochemical systems are also discussed. Full article

A disposable paper-based glucose biosensor with direct electron transfer (DET) of glucose oxidase (GOX) was developed through simple covalent immobilization of GOX on a carbon electrode surface using zero-length cross-linkers. This glucose biosensor exhibited a high electron transfer rate (ks, 3.363 s⁻¹) as well as good affinity (km, 0.03 mM) for GOX while keeping innate enzymatic activities. Furthermore, the DET-based glucose detection was accomplished by employing both square wave voltammetry and chronoamperometric techniques, and it achieved a glucose detection range from 5.4 mg/dL to 900 mg/dL, which is wider than most commercially available glucometers. This low-cost DET glucose biosensor showed remarkable selectivity, and the use of the negative operating potential avoided interference from other common electroactive compounds. It has great potential to monitor different stages of diabetes from hypoglycemic to hyperglycemic states, especially for self-monitoring of blood glucose. Full article

Porous carbon materials (PCs) were prepared via hydrothermal carbonization from calcium lignosulfonate (CL) based on enzymatic hydrolysis and alkali activation. The effects of enzymatic hydrolysis and different KOH feeding ratios on the structure and electrochemical properties of enzymatic hydrolysis CL (EHCL)-derived PCs were evaluated in detail. The results showed that the EHCL-derived PCs showed a higher SSA than that of CL. When the mass ratio of KOH/EHCL was 3/2, the PCs exhibited a honeycomb-like microscopic morphology with a specific surface area of up to 1771 m²/g and a 3D hierarchical porous structure composed of abundant micropores, mesopores, and macropores. As an electrode in a supercapacitor, the highest specific capacitance was 147 F/g at a current density of 0.25 A/g, and it maintained 78% of the initial value at a high current density of 10 A/g. The excellent electrochemical cycle and structural stability were confirmed on the condition of a higher capacitance retention of 95.2% after 5000 times of galvanostatic charge/discharge. This work provides a potential application of CL in high-performance supercapacitors. Full article

Owing to the high efficiency and specificity in moderate conditions, enzymatic biofuel cells (EBFCs) have gained significant interest as a promising energy source for wearable devices. However, the instability of the bioelectrode and the lack of efficient electrical communication between the enzymes and electrodes are the main obstacles. Herein, defect-enriched 3D graphene nanoribbons (GNRs) frameworks are fabricated by unzipping multiwall carbon nanotubes, followed by thermal annealing. It is found that defective carbon shows stronger adsorption energy towards the polar mediators than the pristine carbon, which is beneficial to improving the stability of the bioelectrodes. Consequently, the EBFCs equipped with the GNRs exhibit a significantly enhanced bioelectrocatalytic performance and operational stability, delivering an open-circuit voltage and power density of 0.62 V, 70.7 μW/cm², and 0.58 V, 18.6 μW/cm² in phosphate buffer solution and artificial tear, respectively, which represent the high levels among the reported literature. This work provides a design principle according to which defective carbon materials could be more suitable for the immobilization of biocatalytic components in the application of EBFCs. Full article