μA μM Research Articles

Nanofloral BiVO4/rGO composites for sensitive electrochemical detection of furazolidone in water

Antibiotics are widely used in agriculture, animal husbandry, and aquaculture, and the development of efficient, sensitive, and convenient antibiotic trace detection techniques is beneficial for tracking their transfer behavior in the environment. Electrochemical sensors have recently shown significant promise in the detection of antibiotics, however, the complex composition of the aqueous environment may interfere with the sensitivity and accuracy of the electrodes during electrochemical detection, and the selection of appropriate nanocomposites for modifying the electrodes has been considered as an effective solution. Nanofloral BiVO4/rGO electrocatalysts were developed for the electrochemical detection of furazolidone (FZD) based on a robust green sonochemical approach. the large specific surface area and excellent electrical conductivity of the BiVO4/rGO composites efficiently catalyzed the electrochemical reaction of FZD, which led to the improvement in the detection sensitivity and stability of the sensors. It exhibits current amplification and electrocatalytic effects in the reduction reaction of furazolidone. The assay exhibited a wide linear range, low detection limit, good reproducibility, stability and anti-interference properties, and a simple and convenient preparation process. The effects of conditions such as scanning rate (v), electrolyte pH, and electrode loading on the detection effect were investigated, developed BiVO4/rGO composites exhibited detection limits of 1.46 and 22.4 nM and sensitivities of 24.4 and 1.94 μA μM−1 cm−2, respectively, for FZD. The objective of the study is to provide a novel, low-cost, convenient and highly sensitive assay for the detection of antibiotics in the aqueous environment. BiVO4/rGO electrocatalysts are ideal candidates for low-cost, convenient and highly sensitive detection of antibiotics in aqueous environments, promoting the technological development and application in this field.

Preparation of unique corn-stalk-like MnO₂/CoNi nanowires via in situ epitaxial attachment growth for monitoring environmental pollutant hydrazine

This paper presents the synthesis of a novel corn-stalk-like MnO₂/CoNi oxide composite using an in situ epitaxial attachment growth strategy, in which CoNi oxide nanosheets are anchored onto MnO₂ nanowires. The one-dimensional MnO₂ nanowires, with their large specific surface area, serve as a support to enhance the electronic conductivity of the CoNi oxides. Hexamethylenetetramine (HMTA) is employed as an alkaline linking agent, playing a key role in shaping the CoNi oxide nanosheets and ensuring their successful growth on the MnO₂ nanowires. The MnO₂/CoNi oxide composite-based electrochemical sensor exhibits excellent synergistic and interfacial effects, promoting electron transfer and charge migration. This composite material shows outstanding electrocatalytic performance for hydrazine detection, with a broad linear range (0.48−6106.58 μM), low detection limit (0.286 μM, S/N = 3), and high sensitivity (0.037 μA μM⁻1). Moreover, when tested for hydrazine detection in water samples, the sensor achieved a recovery rate of 95.7–105 %, highlighting its high sensitivity and rapid response in practical applications.

Novel cobalt-based aerogels for uric acid detection in fluids at physiological pH

A sensor for uric acid (UA) based on the urate oxidase enzyme (UOx) immobilized in novel Co-based aerogels with transition metals synthesized by the sol-gel method was developed and evaluated. The Co-based aerogels: Co, Ni-Co and Pd-Co were physicochemically characterized by XRD and HR-TEM. The surface area values of 53, 57 and 66 m2 g-1 were determined for Co, Ni-Co and Pd-Co, respectively by N2 adsorption-desorption technique. Co-based aerogels were mixed by cross-linking with UOx enzymes and electrochemically characterized in buffers at pH 7.4 and 5.6 (pH values reported for biological fluids such as blood and sweat) in the presence of different uric acid concentrations. Co-based aerogels with UOx showed improved performance as a uric acid biosensor compared to using the enzyme alone. At a pH of 7.4, a higher sensitivity of 11 μA μM−1 was obtained with Pd-Co/UOx, 1.6 times higher than with UOx. At a pH value of 5.6, the highest sensitivity is achieved with Ni-Co/UOx. Stability and selectivity tests were performed in the presence of biological interferents without significant changes in the sensor. These results indicate a pleasing synergistic activity between Co-based aerogels and the enzyme.

Copper-decorated covalent organic framework covalently modified 3D-printed nanocarbon electrodes for the determination of methotrexate

3D printing has emerged as a popular topic in electrochemistry due to its high flexibility in production. In this work, we used graphene/polylactic acid materials for the fabrication of 3D printed electrodes (3DEs) via fused deposition modeling (FDM). Subsequently, the synthesized novel copper-decorated covalent organic framework (Cu(II)@S-COF) was covalently bound on the 3DE by the Au-S bonding to construct the Cu(II)@S-COF@Au@3DE sensor. Scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and contact angle experiments were used to characterize the prepared 3DEs. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were used to investigate the electrochemical performance of the prepared 3DEs. The sensor exhibited good electrocatalytic performance for detecting methotrexate (MTX). It was capable of accurately determining MTX in the range from 0.5 to 100 μM with a limit of detection (LOD) of 0.07 μM and a sensitivity of 0.1489 μA μM−1 cm−2. In addition, the sensor has recoveries from 97.33% to 101.09% for the detection of MTX in commercial tablets and urine samples, so it can be used to detect MTX in real samples successfully. This work opens a novel avenue for using metal-decorated COF materials in the field of electrochemistry.

Fast preparing bioelectrode with conductive bioink for nitrite detection in high sensitivity and stability

Electrochemically active biofilms (EABs) for nitrite detection have high specificity, rapid response, operational simplicity, and extended lifespan advantages. However, their scale production remains challenging due to time-consuming and uniform preparation. In this study, a novel approach was proposed to fast fabricate an EAB biosensor with a synthetic biofilm electrode for nitrite detection. The biofilm electrode was prepared by coating bioinks with varying conductive materials onto the surface of the graphite sheets, showing short incubation time and good reproducibility. Incorporating conductive materials into the bioinks remarkably enhanced the maximum voltage of the first cycle of bioelectrode incubation, with an increase of up to 633% for carbon nanofibers. The nitrite reduction current was amplified by a factor of 2.97, due to the enhancement of extracellular electron transfer (EET). The developed nitrite biosensor exhibited a detection range of 0.1–15 mg NO2--N L−1, with a high sensitivity of 610.8 μA mM−1 cm−2, and a stabilization operation time of at least 280 cycles. This study not only provided valuable insights into conductive materials for synthetic biofilms but also presented a practical approach for the rapid preparation, scale production, and optimization of highly sensitive and stable EAB sensors.

Electrochemical Detection of H2O2 Using Bi2O3/Bi2O2Se Nanocomposites.

The development of high-performance hydrogen peroxide (H2O2) sensors is critical for various applications, including environmental monitoring, industrial processes, and biomedical diagnostics. This study explores the development of efficient and selective H2O2 sensors based on bismuth oxide/bismuth oxyselenide (Bi2O3/Bi2O2Se) nanocomposites. The Bi2O3/Bi2O2Se nanocomposites were synthesized using a simple solution-processing method at room temperature, resulting in a unique heterostructure with remarkable electrochemical characteristics for H2O2 detection. Characterization techniques, including powder X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM), confirmed the successful formation of the nanocomposites and their structural integrity. The synthesis time was varied to obtain the composites with different Se contents. The end goal was to obtain phase pure Bi2O2Se. Electrochemical measurements revealed that the Bi2O3/Bi2O2Se composite formed under optimal synthesis conditions displayed high sensitivity (75.7 µA µM-1 cm-2) and excellent selectivity towards H2O2 detection, along with a wide linear detection range (0-15 µM). The superior performance is attributed to the synergistic effect between Bi2O3 and Bi2O2Se, enhancing electron transfer and creating more active sites for H2O2 oxidation. These findings suggest that Bi2O3/Bi2O2Se nanocomposites hold great potential as advanced H2O2 sensors for practical applications.

Highly Specific Non-Enzymatic Electrochemical Sensor for the Detection of Uric Acid Using Carboxylated Multiwalled Carbon Nanotubes Intertwined with GdS-Gd2O3 Nanoplates in Human Urine and Serum.

Herein, the electrochemical sensing efficacy of carboxylic acid functionalized multiwalled carbon nanotubes (C-MWCNT) intertwined with coexisting phases of gadolinium monosulfide (GdS) and gadolinium oxide (Gd2O3) nanosheets is explored for the first time. The nanocomposite demonstrated splendid specificity for nonenzymatic electrochemical detection of uric acid (UA) in biological samples. It was synthesized using the coprecipitation method and thoroughly characterized. The presence of functional groups and disorder in the as-synthesized nanocomposite are confirmed using Fourier transform infrared spectroscopy and Raman spectroscopy. Furthermore, field emission scanning electron microscopy, high-resolution transmission electron microscope, X-ray powder diffraction, and X-ray photoelectron spectroscopy provides a clear understanding of the morphology, coexisting phases, and elemental composition of the as-synthesized nanocomposites. The differential pulse voltammetry technique was utilized to elaborate the electrochemical sensing of UA using a GdS-Gd2O3/C-MWCNT modified glassy carbon electrode (GCE), The sensor showed an enhanced current response by more than 2-fold compared to bare GCE. Also, the sensor's performance was further improved by dispersing the nanocomposite in an ionic liquid with the exceptional reproducibility (SD = 0.0025, n = 3). The fabricated UA sensor GdS-Gd2O3/C-MWCNT/IL/GCE demonstrated a wide linear detection range from 0.5-30 μM and 30-2000 μM, effectively covering the entire physiological range of UA in biological fluids with a limit of detection (LOD) of 0.380 μM (+3SD of blank) and a sensitivity of 356.125 μA mM-1 cm-2. Moreover, the electrodes exhibited storage stability for 2 weeks with decrease in zero-day current by only 4.5%. The sensor was validated by quantifying UA in 12 unprocessed clinical human urine and serum samples, and its comparison with the gold standard test yielded remarkable results (p < 0.05). Hence, the proposed nonenzymatic electrochemical UA sensor is selective, sensitive, reproducible, and stable, making it reliable for point-of-care diagnostics.

Electrochemical biosensing of cerium with a tyrosine‐functionalized EF‐hand loop peptide

AbstractThe significance of easily detecting rare earth elements (REEs) has increased due to the growing demand for REEs. Addressing this need, we present an innovative electrochemical biosensor, focusing on cerium as a model REE. This biosensor utilizes a modified EF‐hand loop peptide sequence, incorporating cysteine for covalent attachment to a gold working electrode and tyrosine as an electrochemically active amino acid. The sensor was designed such that binding to cerium induces a conformational change in the peptide, affecting tyrosine's proximity to the electrode surface, modulating the current. A calibration curve was generated from cyclic voltammetry current peaks at ~0.55–0.65 V versus a silver pseudo‐reference electrode, with cerium concentrations ranging from 0 to 67 μM in artificial urine. The sensor exhibited a biologically relevant limit of detection of 35 μM and a sensitivity of −0.0024 ± 0.002 (μA μM)−1. These findings offer insights into designing peptide sequences for electrochemical biosensing.

Reusable gallium-based electrochemical sensor for efficient glucose detection

Among wearable sensing devices, electrochemical sensors are overwhelming in biochemical detection due to their simple design but high sensitivity. Most electrochemical sensors are disposable, which significantly impairs the service life. Here we present a reusable gallium (Ga)-based multi-layer electrochemical glucose biosensor to extend noninvasive monitoring of glucose in the interstitial fluid. This multilayer sensor includes Ga as a conductive interconnector, poly(3,4-ethylenedioxythiophene) as an electrode layer to prevent oxidation and metal leakage, a nano-Pt layer to enhance the electrochemical properties, and a nano-Prussian blue layer for reducing the hydrogen peroxide reduction potential. Most importantly, the biosensors can be renewed by automatically removing the modified nanocomposites via the electrolysis-induced bubbles and by electroplating without impairing the whole structure of the biosensor. The biosensor showed high sensitivity (24.6 μA mM-1 cm-2), wide linear range (0.01-26 mM), excellent stability (i.e., pH, long-term use) and superior selectivity, that is comparable to those of the current electrochemical tools for glucose detection. More importantly, incorporated with the reverse iontophoresis (RI), the Ga-based hybrid sensor was applied as a skin patch on mice for the in vivo noninvasive and continuous monitoring of ISF-borne glucose. The results showed a good correlation with that measured by blood glucometer. As a whole, this Ga-based electrochemical biosensor should endow new functions like biochemical analysis in biofluids for Ga-based soft bioelectronic sensing devices, in which almost are physical sensors. We believe that the reusability of electrochemically controllable processes may further inspire the development of more integrated and long-term stable gallium-based biosensing devices.

Dual-functional carbon nanotube yarn supercapacitor for real-time reactive oxygen species monitoring and sustainable energy supply in implantable device

Smart stents integrate embedded sensors and advanced technology, providing a real-time diagnostic feedback, particularly for detection of thrombotic events. A continuous monitoring reactive oxygen species (ROS) in blood vessels is crucial for cardiovascular disease. The provision of a continuous power supply to sensors integrated within blood vessels is challenging. This study introduces a novel device that combines a sensor and supercapacitor, functioning as a ROS sensor and enabling continuous charging and discharging within blood vessels. This device uses yarn-shaped electrodes integrated with cytochrome c and carbon nanotubes (Cyt.c/CNT). The Cyt.c/CNT electrode exhibits a high specificity to ROS with an sensitivity (49.02 μA μM−1 cm−2), as a real-time biosensor for monitoring of cellular ROS levels in living cells. In addition, it exhibited an energy storage performance of 257.95 mF cm−2 as a supercapacitor and maintained a stable performance during 10,000 repeated cycles in various biofluids. Notably, the integration of the Cyt.c/CNT electrode with an enzymatic biofuel cell enables continuous charging and discharging in a biofluid, making it a promising system for in-vivo applications. This study presents the potential of Cyt.c for ROS sensing as well as its potential as an energy storage system, showing new possibilities for implantable devices for cardiovascular diseases.

Evaluation of electrodeposition synthesis of gold nanodendrite on screen-printed carbon electrode for nonenzymatic ascorbic acid sensor

Gold nanodendrite (AuND) is a type of gold nanoparticles with dendritic or branching structures that offers advantages such as large surface area and high conductivity to improve electrocatalytic performance of electrochemical sensors. AuND structures can be synthesized using electrodeposition method utilizing cysteine as growth directing agent. This method can simultaneously synthesize and integrate the gold nanostructures on the surface of the electrode. We conducted a comprehensive study on the synthesis of AuND on screen-printed carbon electrode (SPCE)-based working electrode, focusing on the optimization of electrodeposition parameters, such as applied potential, precursor solution concentration, and deposition time. The measured surface oxide reduction peak current and electrochemical surface area from cyclic voltammogram were used as the optimization indicators. We confirmed the growth of dendritic gold nanostructures across the carbon electrode surface based on FESEM, EDS, and XRD characterizations. We applied the SPCE/AuND electrode as a nonenzymatic sensor on ascorbic acid (AA) and obtained detection limit of 16.8 μM, quantification limit of 51.0 μM, sensitivity of 0.0629 μA μM−1, and linear range of 180–2700 μM (R2 value = 0.9909). Selectivity test of this electrode against several interferences, such as uric acid, dopamine, glucose, and urea, also shows good response in AA detection.

Development of smart molecularly imprinted tetrahedral amorphous carbon thin films for in vitro dopamine sensing

This study investigates how varying the thickness of tetrahedral amorphous carbon (ta-C) thin films and incorporating a titanium adhesion layer influences the structural and electrochemical properties of molecularly imprinted ta-C thin film-based sensing platforms, aiming to develop a molecularly imprinted ta-C electrochemical sensor for dopamine (DA) detection with physiologically relevant sensitivity. This electrochemical sensing platform was designed by integrating ta-C with molecularly imprinted polymers (MIPs). The process involved depositing a ta-C thin film onto boron-doped p-type silicon wafers through a filtered cathodic vacuum arc (FCVA) system. Subsequently, the ta-C sensing platforms were electrochemically coated with the MIP layer (DA-imprinted polypyrrole). We evaluated three configurations: (i) a 15 nm ta-C layer, (ii) a 7 nm ta-C layer with a 20 nm titanium adhesion layer, and (iii) a 15 nm ta-C layer with a 20 nm titanium adhesion layer. Comprehensive structural and electrochemical characterization was performed to understand how these modifications affect sensor performance. The optimized MIP/ta-C sensor demonstrated a sensitivity of 0.16 μA μM−1 cm−2 and a limit of detection (LOD) of 48.6 nM, suitable for detecting DA at physiological levels. Leveraging the synergistic effects of ta-C coatings and molecular imprinting, as well as its compatibility with common complementary metal–oxide–semiconductor (CMOS) processes underlines its potential for integration into microanalytical systems, paving the way for miniaturized and high-throughput sensing platforms.

Uniform nickel nanoparticles decorated porous carbon nanofibers for efficient electrochemical nitrite sensing

One-dimensional carbonaceous materials exhibit significant promise for sensing applications driven by their attractive properties. Herein, nickel/nitrogen-doped carbon (Ni/N–C) nanofibers were fabricated via a novel electrospinning-carbonization strategy. The distribution of Ni nanoparticles (NPs) in the carbon nanofibers was crucially affected by the carbonization temperatures. Various techniques were employed to characterize the fabricated Ni/N–C-X (X = 700, 800, and 900 °C, representing the carbonization temperatures) nanofibers, followed by an evaluation of their electrochemical sensing response to nitrite. The Ni/N–C-800-based sensor outperformed those based on the Ni/N–C-700 and Ni/N–C-900 catalysts in detecting nitrite, by merits of the relatively superior conductivity and more exposed active sites. The Ni/N–C-800-based sensor, delivered detected concentrations of 0.2–7000 μM, along with a sensitivity value of 0.991 μA μM−1 cm−2, and a detection limit of 0.1 μM. Furthermore, this Ni/N–C-800-based sensor demonstrated notable selectivity and stability, affirming its practicality in nitrite detection within sausage samples. The findings of this research illustrate that Ni/N–C materials hold great promise for monitoring nitrite.

Three-dimensional flower-like strontium doped zinc oxide decorated with carbon black modified glassy carbon electrode for the detection of strychnine

The widespread use of Strychnine (STN) pesticides has sparked considerable concerns regarding their impact on human health, underscoring the urgent need for a reliable STN detection system to ensure both environmental and human safety. To address this need, a simple hydrothermal technique was employed to synthesize three-dimensional flower-like Strontium doped Zinc oxide (Sr-ZnO) nanomaterials integrated with Carbon Black (CB) to form a composite, which was then utilized for selective STN detection. The prepared Sr-ZnO/CB nanocomposite has been utilized to decorate a glassy carbon electrode (GCE), providing a cost-effective and simplified platform for STN detection. Hence, the structural confirmation of the composite formation was achieved through appropriate microscopic and spectroscopic methods. In terms of electrochemical STN detection, the Sr-ZnO/CB/GCE exhibited superior sensitivity compared to previous sensors. Notably, it demonstrated a broad linearity response range from 0.01 to 145 μM, a low detection limit of 0.02 μM, and a high sensitivity of 5.541 μA μM−1 cm−2 under optimal conditions for STN detection. Hence, the proposed approach showed promise for analyzing STN in biological samples, with satisfactory results obtained when applied to real samples using the Sr-ZnO/CB. Additionally, the Sr-ZnO/CB modified electrode displayed appealing qualities such as stability, repeatability, and suitability for practical applications.

Sensitive detection of Hg(II) on MoS2/NiS2 based on interfacial engineering to accelerate the Ni2+/Ni3+ cycle: Identification the role of atomic-level heterojunction-induced electron transfer in electroanalysis

The valence change of transition metal ions in nanomaterials can highly enhance the electrochemical detection performance toward heavy metal ions (HMIs), and how to further promote the valence change calls enormous concerns in electroanalysis. In this work, an interfacial engineering that combing the MoS2 and NiS2 together to form the MoS2/NiS2 complex is proposed. The density functional theory (DFT) results reveals that the novel atomic-level heterojunction between MoS2 and NiS2 will build an internal electric field (IEF), which leads to an enhanced conductivity and valence change behavior of Ni atoms in MoS2/NiS2 complex, resulting in a superior detection performance. In detail, the formation of atomic-level heterojunctions in the MoS2/NiS2 complex accelerates electron transfer due to the valence changes associated with Ni2+/Ni3+ cycling. The active Mo4+ species on MoS2 act as electron donors, facilitating the reduction of Ni3+ to Ni2+ on NiS2, thereby promoting Ni2+/Ni3+ cycling. As anticipated, the MoS2/NiS2 complex exhibits exceptional detection performance for Hg(II), with a sensitivity of 459.13 μA μM−1 cm−2, surpassing even that of other composite materials. In general, these findings are expected to significantly advance the application of electron transfer acceleration in electroanalysis based on the construction of heterojunction.

Development of metal oxide Nanocomposite-Coated electrospun nanofibers for highly sensitive xanthine monitoring

Developing a durable, cost-effective, and readily available electroactive sensor that doesn’t depend on noble metals is crucial for the selective and sensitive monitoring of xanthine (Xn) to overcome the risks linked to metabolic disorders like gout, xanthinuria, and renal failure. Thus, to meet these requirements, herein we have designed a noble-metal-free highly sensitive and selective electrochemical sensor for Xn. We have developed an electrochemical sensor by depositing Co3O4-NiO nanoblossoms on the surface of cellulose acetate (CA) and polyaniline (PANI) based electrospun nanofibers. These electrospun nanofibers facilitate rapid diffusion of Xn molecules to the sensing interface via amine and imine groups, leading to fast response by providing a smooth pathway for transportation of electrons. Moreover, synergistic characteristics of CNNB with electrospun nanofibers contribute to the selective binding of Xn with quick response as well. Our findings reveal that fabricated material exhibits high sensitivity (5 μA μM−1), a response range (0.1–42 µM) with remarkably low limit of detection (0.03 µM). Additionally, our designed electrode demonstrates more selectivity towards Xn in the presence of other interfering species. The designed electrochemical sensor has shown greater reliability in terms of reproducibility and reusability with robust response in human serum samples.

Non-enzymatic detection of versatile anti-oxidant in diverse media using 3D spinel nickel cobalt oxide with 2D tungsten carbide nanohybrid heterostructure electrocatalyst

Diphenylamine (DPA), an organic amine derivative compound widely used in agriculture and polymer industries as an anti-scaling and anti-oxidising agent. The excessive and prolonged usage of DPA in agricultural products would result in the accumulation of it. The poor degradation ability and associated health hazards marked it as a “contaminant of emerging concern”. Since DPA is not completely banned in many countries, measuring the trace levels of DPA is essential to ensure the safety of the ecosystem. Therefore, the electrochemical sensing method was applied for the precise detection of an infinitesimal concentration of this component. In this work, we have prepared a spinel nickel cobalt oxide with a tungsten carbide (NCO/WC) electrocatalyst-based electrochemical sensor for the accurate detection of DPA. The structural, and morphological details were examined with Powder X-ray diffraction (PXRD), Fourier transform infrared spectroscopy (FT-IR), Field emission scanning electron microscope (FE-SEM), Transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS), and Brunauer-Emmett-Teller (BET) analyses. The electrochemical properties were evaluated with impedance and voltammetric measurements. Various voltammetric techniques were utilized to assess the efficiency of NCO/WC towards DPA. Significantly, our sensor displayed a low detection (0.001 µM), and low quantification (0.0048 µM) limits, good linear range (0.01 to 147 µM), optimal sensitivity (1.716 µA µM−1 cm−2), remarkable selectivity, appreciable repeatability, reproducibility, and stability performance outcomes. Then, the sensor was employed to monitor the DPA in various matrices like agricultural, environmental, and human samples and conquered astonishing results. These findings suggest that our NCO/WC-based electrochemical sensor is a promising platform for the enhanced detection of DPA.

Electrochemical sensors for sensitive and selective detection of nitrite based on flexible gold microneedle like nanodendrites modified electrode

In this study, we present a new approach utilizing Au nanodendrites (Au NDs) to modify flexible screen-printed carbon electrodes (FSPCEs), offering an efficient platform for voltammetric sensing of nitrite ions in food samples. The FSPCEs are created with gold leaf-like nanodendrites through a simple, one-step electrochemical deposition process. The direct growth of these Au NDs occurs efficiently on the carbon-paste electrode, eliminating the need for binders or additional reducing agents and organic solvents, owing to the aforementioned matrix. The modified electrodes serve as promising sensing platforms for nitrite detection. The outcomes demonstrated that a significant amount of AuNPs with dendritic morphologies were dispersed throughout the FSPCE.These novel flexible electrodes act as effective electrocatalyst for NO2− oxidation due to their large electrochemical active surface area (ECSA), well-dispersed Au nanostructures, and high electrical conductivity. The optimized sensor exhibits a wide linear response range from 0.02 to 5.8 µM, with 1.0 nM limit of detection, an impressive sensitivity of 52.529 µA µM−1 cm−2 and a quick current response time (< 3 s) towards nitrite ions. Additionally, the suggested sensor demonstrates high selectivity, reproducibility, and stability. Furthermore, the FSPCEs are evaluated for their ability to selectively detect nitrite ions in various food samples such as tap water, drinking water, milk, and fruit juices, comparing the results with standard methods in real sample analysis. The fabricated sensors show promising potential for practical applications in food and environmental analysis. Consequently, Au NDs@FSPCE electrode emerged to be a novel platform for NO2− electrochemical detection. Because of their great affinity for analytical substances in solutions, gold nanodendrites supported on flexible screen-printed carbon electrodes (FSPCEs) are very useful for electrode modifications. Their increased effective surface area, which greatly raises the electrode's sensitivity and specificity for a range of analytical applications, is responsible for their high affinity.

Highly sensitive biosensors for real-time monitoring of histamine at acupoint PC6 in rats based on graphene-modified acupuncture needles.

Acupoints are the local initial response sites of acupuncture therapeutic effects. As a biomarker, histamine is released into the acupoint region and plays its role concurrently as acupuncture needles are inserted into acupoints. Hence, real-time monitoring of histamine at acupoints is important to elucidate the effectiveness of the acupoint-activation process in acupuncture. Therefore, we developed highly sensitive acupuncture/Au particles/graphene biosensors by electrodeposition, brushing, and annealing methods based on bare acupuncture needles. We achieved a histamine detection limit of approximately 4.352 (±3.419) × 10-12 mol L-1 and good sensitivity of approximately 6.296 (±3.873) μA μM-1, with satisfactory specificity, repeatability, and stability in vitro, rendering them more competitive and suitable for real-time monitoring in vivo without causing additional damage. Subsequently, we conducted real-time histamine monitoring at non-acupoint and acupoint PC6 in rats, respectively. Our results showed minimal changes at the non-acupoint, whereas a trend of initial increase followed by a decrease was observed at acupoint PC6. The change in histamine concentration at acupoint PC6 reflected its involvement in the acupoint-activation procedure. Moreover, its peak position at ∼18 min could provide guidance for optimizing needle retaining time for maximum therapeutic effect. This work presents the first real-time in vivo monitoring of histamine at acupoints with high sensitivity and underscores the specificity of histamine release between non-acupoint and acupoint PC6, demonstrating great potential for elucidating the acupoint-activation mechanisms in acupuncture. Additionally, this work expands the application of nanomaterials in the integration of medicine and engineering, which is an important aspect of the future development of materials science.

Brewer's Spent Grain-Cellulose-Coated Copper Electrode-Based Extended Gate Field-Effect Transistor for Nonenzymatic Glucose Detection toward Diagnosis of Diabetes Mellitus.

The demand for environmentally friendly, reliable, and cost-effective electrodes for glucose sensor technology has become a major research area in the paradigm shift toward green electronics. In this regard, cellulose has emerged as a promising flexible biopolymer solution with unique properties such as biocompatibility, biodegradability, nontoxicity, renewability, and sustainability. Because of their large surface area and porous structure, fibrous cellulose substrates quickly adsorb and disperse analytes at detection sites. This work focuses on utilizing glyoxal-treated cellulose (derived from brewer's spent grain (BSG)) for the fabrication of extended gate field-effect transistor (EGFET)-based glucose sensors. This investigation extends to the utilization of BSG-cellulose for glucose detection in biomimicking electrolytes (phosphate buffer saline) to facilitate glucose detection in human blood samples. The fabricated electrode demonstrates a linear range of glucose detection from 1 to 13.5 mM with a Langmuir adsorption coefficient (K) of 0.102. Also, its selectivity toward glucose over interfering molecules such as sucrose, fructose, ascorbic acid, and uric acid under physiological conditions has been demonstrated. This cellulose-based EGFET electrode exhibits a sensitivity of 6.5 μA mM-1 cm-2 with a limit of detection (LOD) of 0.135 mM. Computational studies by density functional theory calculations confirmed the higher binding affinity of glucose molecules with glyoxal-modified cellulose (-0.95 eV) than with pristine cellulose (-0.46 eV). Here, the novelty lies in the fabrication of electrodes with biodegradable catalysts and their integration into the EGFET configuration.