Non-enzymatic Electrochemical Sensor Research Articles

NiNP/Cu-MOF-C/GCE for the the noninvasive detection of glucose in natural saliva samples

This study presents the preparation of a novel electrochemical non-enzymatic sensor for the detection of glucose in natural saliva based on a metal organic framework (MOF) derivative (Cu-MOF-C) and nickel nanoparticle (NiNP) composite modified glassy carbon electrodes (GCE). The morphology and structural evolution were thoroughly characterized using scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), ultraviolet and visible spectrum (UV) and Fourier transform infrared spectrum (FTIR). Moreover, the electrocatalytic activity of the NiNPs/Cu-MOF-C/GCE for glucose was investigated using cyclic voltammetry (CV) and the amperometric i-t technique. The NiNPs/Cu-MOF-C/GCE sensor exhibits a wide linear range of 0.3–1150 μM and low detection limit (DL) of 0.090 μM at a signal/noise ratio (S/N) of 3. The average recovery rate of this method is satisfactory between 97.3% and 108.4%. Furthermore, the sensor exhibited excellent repeatability, good stability and reproducibility for glucose detection. Compared with traditional invasive measurement, the detection of glucose in natural saliva can reduce the pain caused by continuous blood collection, which is an ideal method for patients requiring continuous monitoring of glucose.

Fabrication non-enzymatic electrochemical sensor based on methyl red and graphene oxide nanocomposite modified carbon paste electrode for determination of nitrite in food samples

The purpose of this work was to create a non-enzymatic electrochemical sensor based on methyl red and modified carbon paste electrodes (MR/GO/CPE) that can measure nitrite in food samples. FE-SEM images showed that the assembly of MR on the surface of GO nanosheets caused the combination of GO nanosheets and MR particles to form a MR/GO nanocomposite with a high density of holes and crevasses. Amperometry, CV, and DPV techniques were used to study the electrochemical responses of MR/GO/CPE to the determination of nitrite. The results revealed that the MR/GO/CPE demonstrated sensitive, selective, and stable responses to determination nitrite. According to amplitude studies, the proposed nitrite sensor should have a sensitivity value of 0.12735 μA/μM, a large linear range of 0–7000 μM, and a low detection limit value of 0.011 μM. In the current study, the accuracy and applicability of the proposed nitrite electrochemical sensor for the determination of nitrite in prepared meat specimens were examined. The results showed good recovery values (more than 96.00 %) and appropriate precision (RSD less than 5.10 %), as well as good agreement between the amperometric measurements and the Test Kit for Nitrate assays. These findings demonstrated that MR/GO/CPE can be used as trustworthy nitrite sensors for tracking nitrite levels in food specimens.

Highly Sensitive Electrochemical Non-Enzymatic Uric Acid Sensor Based on Cobalt Oxide Puffy Balls-like Nanostructure

Early-stage uric acid (UA) abnormality detection is crucial for a healthy human. With the evolution of nanoscience, metal oxide nanostructure-based sensors have become a potential candidate for health monitoring due to their low-cost, easy-to-handle, and portability. Herein, we demonstrate the synthesis of puffy balls-like cobalt oxide nanostructure using a hydrothermal method and utilize them to modify the working electrode for non-enzymatic electrochemical sensor fabrication. The non-enzymatic electrochemical sensor was utilized for UA determination using cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The puffy balls-shaped cobalt oxide nanostructure-modified glassy carbon (GC) electrode exhibited excellent electro-catalytic activity during UA detection. Interestingly, when we compared the sensitivity of non-enzymatic electrochemical UA sensors, the DPV technique resulted in high sensitivity (2158 µA/mM.cm2) compared to the CV technique (sensitivity = 307 µA/mM.cm2). The developed non-enzymatic electrochemical UA sensor showed good selectivity, stability, reproducibility, and applicability in the human serum. Moreover, this study indicates that the puffy balls-shaped cobalt oxide nanostructure can be utilized as electrode material for designing (bio)sensors to detect a specific analyte.

3D Nanocomposite with High Aspect Ratio Based on Polyaniline Decorated with Silver NPs: Synthesis and Application as Electrochemical Glucose Sensor.

In this paper, we present a new methodology for creating 3D ordered porous nanocomposites based on anodic aluminum oxide template with polyaniline (PANI) and silver NPs. The approach includes in situ synthesis of polyaniline on templates of anodic aluminum oxide nanomembranes and laser-induced deposition (LID) of Ag NPs directly on the pore walls. The proposed method allows for the formation of structures with a high aspect ratio of the pores, topological ordering and uniformity of properties throughout the sample, and a high specific surface area. For the developed structures, we demonstrated their effectiveness as non-enzymatic electrochemical sensors on glucose in a concentration range crucial for medical applications. The obtained systems possess high potential for miniaturization and were applied to glucose detection in real objects-laboratory rat blood plasma.

Copper(II)-Incorporated Porphyrin-Based Porous Organic Polymer for a Nonenzymatic Electrochemical Glucose Sensor.

To date, the fabrication of multifunctional nanoplatforms based on a porous organic polymer for electrochemical sensing of biorelevant molecules has received considerable attention in the search for a more active, robust, and sensitive electrocatalyst. Here, in this report, we have developed a new porous organic polymer based on porphyrin (TEG-POR) from a polycondensation reaction between a triethylene glycol-linked dialdehyde and pyrrole. The Cu(II) complex of the polymer Cu-TEG-POR shows high sensitivity and a low detection limit for glucose electro-oxidation in an alkaline medium. The characterization of the as-synthesized polymer was done by thermogravimetric analysis (TGA), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectroscopy, and 13C CP-MAS solid-state NMR. The N2 adsorption/desorption isotherm was carried out at 77 K to analyze the porous property. TEG-POR and Cu-TEG-POR both show excellent thermal stability. The Cu-TEG-POR-modified GC electrode shows a low detection limit (LOD) value of 0.9 μM and a wide linear range (0.001-1.3 mM) with a sensitivity of 415.8 μA mM-1 cm-2 toward electrochemical glucose sensing. The interference of the modified electrode from ascorbic acid, dopamine, NaCl, uric acid, fructose, sucrose, and cysteine was insignificant. Cu-TEG-POR exhibits acceptable recovery for blood glucose detection (97.25-104%), suggesting its scope in the future for selective and sensitive nonenzymatic glucose detection in human blood.

Pt/MXene-Based Flexible Wearable Non-Enzymatic Electrochemical Sensor for Continuous Glucose Detection in Sweat.

Wearable non-invasive sensors facilitate the continuous measurement of glucose in sweat for the treatment and management of diabetes. However, the catalysis of glucose and sweat sampling are challenges in the development of efficient wearable glucose sensors. Herein, we report a flexible wearable non-enzymatic electrochemical sensor for continuous glucose detection in sweat. We synthesized a catalyst (Pt/MXene) by the hybridization of Pt nanoparticles onto MXene (Ti3C2Tx) nanosheets with a broad linear range of glucose detection (0-8 mmol/L) under neutral conditions. Furthermore, we optimized the structure of the sensor by immobilizing Pt/MXene with a conductive hydrogel to enhance the stability of the sensor. Based on Pt/MXene and the optimized structure, we fabricated a flexible wearable glucose sensor by integrating a microfluidic patch for sweat collection onto a flexible sensor. We evaluated the utility of the sensor for the detection of glucose in sweat, and the sensor could detect the glucose change with the replenishment and consumption of energy by the body, and a similar trend was observed in the blood. An in vivo glucose test in sweat indicated that the fabricated sensor is promising for the continuous measurement of glucose, which is essential for the treatment and management of diabetes.

A Conductive Metal−Organic Framework Based on Triptycene Ligand: An Effective Electrochemical Sensor for Glucose and H2O2 Detection in Food and Human Serum

Triptycenes (TT) scaffolds have emerged as attractive organic ligands for the synthesis of MOF electrocatalytic materials because their characteristic rigid trigonal topology interferes with close molecular packing, thus favoring the formation of open structures with significant volume available for the inclusion of guests. In this work, a novel conductive metal-organic framework based on 2, 3, 6, 7, 14, 15-hexahydroxytriptycene (Cu-HHTT) is synthesized in situ by a simple hydrothermal method. As an bifunctional electrocatalyst for efficient glucose electrooxidation and H2O2 electroreduction in alkaline and neutral electrolytes, the non-enzymatic electrochemical sensor has a sensitivity of 47200 mA μM−1 cm−2 and 5170 mA μM−1 cm−2 to glucose and H2O2 with detection limits of 0.16 μM and 0.54 μM (S/N = 3) respectively, and successfully used in the detection of actual serum, orange juice and milk samples. The method provides a new idea for the preparation and application of MOF materials based on triptycene scaffolds.

Ultra-sensitive smartphone assisted-colorimetric and non-enzymatic electrochemical sensor behaviors of zinc doped MnO2 nanocomposite: a comparative study on highly selective sensor design against dopamine, ascorbic acid, gallic acid, and tannic acid

Ultra-sensitive smartphone assisted-colorimetric and non-enzymatic electrochemical sensor behaviors of zinc doped MnO2 nanocomposite: a comparative study on highly selective sensor design against dopamine, ascorbic acid, gallic acid, and tannic acid

Fabrication of Efficient and Non-Enzymatic Electrochemical Sensors for the Detection of Sucrose.

Molecularly imprinted polymers have been used for the creation of an electrochemical sensor for the detection of sucrose, which are modified by using functionalized graphene (fG). Using AIBN as the free radical initiator and sucrose as the template, imprinted polymers are synthesized. The monomer, 4,4'-diisocyanatodiphenylmethane (DPDI), has both proton donor groups (N-H or O-H) and lone-pair donor groups (C=O). By creating H-bonds with electron donor groups (C=O), the proton donor group in this polymer may interact with the sugar molecule serving as its template. The sensor signals have improved as a result of the interaction between the monomer and the template. Thermogravimetric and differential thermal analysis (TGA/DTA) curves, scanning electron microscopy (SEM), and FT-IR spectroscopy have been employed to characterize the fabricated receptors. The fabricated sensor has exhibited a limit of detection of 16 ppb for the target analyte that is highly sensitive, linear, reversible, regenerative, and selective. Moreover, the sensor's stability, reproducibility, and reusability have been evaluated for six months, following the device's manufacturing, and the results revealed similar responses with the percentage error of less than 1%. Most importantly, this sensor has demonstrated a quick response time, which is very sensitive, stable, and selective.

Nonenzymatic Electrochemical Glutamate Sensor Using Copper Oxide Nanomaterials and Multiwall Carbon Nanotubes.

Glutamate is an important neurotransmitter due to its critical role in physiological and pathological processes. While enzymatic electrochemical sensors can selectively detect glutamate, enzymes cause instability of the sensors, thus necessitating the development of enzyme-free glutamate sensors. In this paper, we developed an ultrahigh sensitive nonenzymatic electrochemical glutamate sensor by synthesizing copper oxide (CuO) nanostructures and physically mixing them with multiwall carbon nanotubes (MWCNTs) onto a screen-printed carbon electrode. We comprehensively investigated the sensing mechanism of glutamate; the optimized sensor showed irreversible oxidation of glutamate involving one electron and one proton, and a linear response from 20 μM to 200 μM at pH 7. The limit of detection and sensitivity of the sensor were about 17.5 μM and 8500 μA·mM-1·cm-2, respectively. The enhanced sensing performance is attributed to the synergetic electrochemical activities of CuO nanostructures and MWCNTs. The sensor detected glutamate in whole blood and urine and had minimal interference with common interferents, suggesting its potential for healthcare applications.

Eco-friendly fabrication of nonenzymatic electrochemical sensor based on cobalt/polymelamine/nitrogen-doped graphitic-porous carbon nanohybrid material for glucose monitoring in human blood

The design and development of eco-friendly fabrication of cost-effective electrochemical nonenzymatic biosensors with enhanced sensitivity and selectivity are one of the emerging area in nanomaterial and analytical chemistry. In this aspect, we developed a facile fabrication of tertiary nanocomposite material based on cobalt and polymelamine/nitrogen-doped graphitic porous carbon nanohybrid composite (Co-PM-NDGPC/SPE) for the application as a nonenzymatic electrochemical sensor to quantify glucose in human blood samples. Co-PM-NDGPC/SPE nanocomposite electrode fabrication was achieved using a single-step electrodeposition method under cyclic voltammetry (CV) technique under 1 M NH4Cl solution at 20 constitutive CV cycles (sweep rate 20 mV/s). Notably, the fabricated nonenzymatic electroactive nanocomposite material exhibited excellent electrocatalytic sensing towards the quantification of glucose in 0.1 M NaOH over a wide concentration range from 0.03 to 1.071 mM with a sensitive limit of detection 7.8 μM. Moreover, the Co-PM-NDGPC nanocomposite electrode with low charge transfer resistance (Rct∼81 Ω) and high ionic diffusion indicates excellent stability, reproducibility, and high sensitivity. The fabricated nanocomposite materials exhibit a commendable sensing response toward glucose molecules present in the blood serum samples recommends its usage in real-time applications.

A review on the recent advancements in nanomaterials for nonenzymatic lactate sensing

AbstractLactate is one of the major biomarkers to assess the physical fitness of human in clinical or sports medicine. The proper and well‐timed lactate determination can avoid some exigent conditions including hemorrhage, respiratory distress, sepsis, and hypoxia. Therefore, rapid, facile, selective, and reliable detection of lactate have gained appreciation lately. Among the various lactate detection methods, electrochemical method is the most rapid, convenient, and sensitive technique. Specifically, nanomaterial‐based nonenzymatic electrochemical lactate sensors are much desirable to solve the demerits and stability issues of enzymatic lactate sensors. Numerous materials including metal and metal oxide nanoparticles, metal–organic frameworks, molecularly imprinted polymers, and carbons were used as electrocatalysts to achieve highly sensitive lactate sensors. This present review mainly focuses on the recent developments of these materials for enzyme‐free lactate oxidation and the future prospective of electrode modification catalysts for lactate sensors.

A Non-Enzymatic Electrochemical Sensor for Glyphosate Adopting Surface Modified Screen-Printed Electrodes

In this study, a lab-on-chip electrochemical sensor was developed for ultratrace determination of glyphosate. A single-step approach was adopted for the surface modification of screen-printed electrodes using reduced graphene oxide. Cyclic voltammetry and electrochemical impedance spectroscopy were employed to characterize the electrochemical behavior of the modified electrode. The modified electrode exhibited lowered electron transfer resistance, improved current response, and demonstrated selectivity and sensitivity toward glyphosate. Differential pulse voltammetry was employed to quantify glyphosate. The detection limit for glyphosate was achieved up to 0.144 nmol L–1 for a wide concentration range of 1 to 1000 nM. The proposed sensor presents the advantage of nonenzymatically and specifically determining glyphosate and offers exceptional stability with a relative standard deviation of 3.3% for 10 days. Finally, the applicability of the developed technique was assessed by quantification of glyphosate in tap water and garden soil samples. The ease of fabrication and implementation of the proposed sensor can contribute to the quest for on-site determination of the ecological contaminants.

A non-enzymatic electrochemical sensor based on polyaniline/borophene nanocomposites for dopamine detection

A non-enzymatic electrochemical sensor based on polyaniline/borophene nanocomposites for dopamine detection

Hybridization of Co3S4 and Graphitic Carbon Nitride Nanosheets for High-performance Nonenzymatic Sensing of H2O2.

The development of efficient H2O2 sensors is crucial because of their multiple functions inside and outside the biological system and the adverse effects that a higher concentration can cause. This work reports a highly sensitive and selective non-enzymatic electrochemical H2O2 sensor achieved through the hybridization of Co3S4 and graphitic carbon nitride nanosheets (GCNNS). The Co3S4 is synthesized via a hydrothermal method, and the bulk g-C3N4 (b-GCN) is prepared by the thermal polycondensation of melamine. The as-prepared b-GCN is exfoliated into nanosheets using solvent exfoliation, and the composite with Co3S4 is formed during nanosheet formation. Compared to the performances of pure components, the hybrid structure demonstrates excellent electroreduction towards H2O2. We investigate the H2O2-sensing performance of the composite by cyclic voltammetry, differential pulse voltammetry, and amperometry. As an amperometric sensor, the Co3S4/GCNNS exhibits high sensitivity over a broad linear range from 10 nM to 1.5 mM H2O2 with a high detection limit of 70 nM and fast response of 3 s. The excellent electrocatalytic properties of the composite strengthen its potential application as a sensor to monitor H2O2 in real samples. The remarkable enhancement of the electrocatalytic activity of the composite for H2O2 reduction is attributed to the synergistic effect between Co3S4 and GCNNS.

High-Performance, non-Enzymatic Glucose Sensor Based on Fe and Cu Doped ZnO/rGO Based Nanocomposite

In the present work, the fabrication and performance of glucose sensor based on zinc oxide (ZnO) nanoparticles (NPs) and their composite is demonstrated. ZnO nanostructures possess fascinating properties like large surface area, superior crystal nature and good electrical as well as optical properties. Co-precipitation method was used to fabricate ZnO NPs, iron doped and copper doped ZnO NPs and their composite with reduced graphene oxide (rGO). The structural parameters of pure and doped samples were investigated by X-ray diffraction method. Functional group study of the sample was carried out by fourier transform infrared spectroscopy. Morphological study of bare ZnO, iron doped ZnO, copper doped ZnO and their composite with rGO were studied by SEM. XRD pattern showed that ZnO had hexagonal wurtzite structure. The studies of electrochemical properties of the electrode using cyclic voltammetry showed that prepared samples were promising for the development of cost effective and non-enzymatic electrochemical based glucose sensor with excellent characteristics. The prepared iron doped ZnO/rGO based composite signify greater sensitivity and greater electrocatalytic activity than rest of the composition considered in current study.

Nickel Hydroxide Nanoflake/Carbon Nanotube Composites for the Electrochemical Detection of Glutamic Acid using In Vitro Stroke Model

The significance of glutamic acid in healthcare as a neurotransmitter and food additive has prompted the scientific community to develop cost-effective non-enzymatic sensors with improved sensitivity, selectivity, and stability. Herein, we propose a non-enzymatic electrochemical sensor based on low-cost transition metal hydroxides to detect glutamic acid efficiently. An n-butanol/water interface-assisted synthesis strategy was employed as an initial step to tailor two-dimensional nickel hydroxide nanoflakes. To further improve electrical conductivity, nickel hydroxide nanoflakes were composited with a small amount of highly conductive multiwalled carbon nanotubes to form NH/MWCNT composite. The NH/MWCNT composite-modified sensor demonstrated excellent detection of glutamic acid with a detection limit of 72 nM, even in the presence of many interfering groups. The practicality of the sensor in medical technology was established by its ability to detect glutamic acid released by SH-SY5Y neural cells in both normal and oxygen–glucose deprivation-stressed conditions. As an extended application, the proposed sensor was also demonstrated to detect monosodium glutamate, a food additive found in commercially available food products. Finally, as a proof of concept, an in-house flexible sensor was fabricated to monitor glutamic acid released by human neural cells and monosodium glutamate in food samples. We anticipate that the present work will contribute to the development of cutting-edge third-generation non-enzymatic sensors for glutamic acid monitoring.

Laser-induced graphene (LIG)-based Au@CuO/V2CTx MXene non-enzymatic electrochemical sensors for the urine glucose test

Glucose monitoring is of great significance for the health management of diabetic patients. Herein, non-enzymatic glucose sensors were developed by modifying Au@CuO or Au@CuO/V2CTx MXene nanocomposites (NCs) on the surface of disposable laser-induced graphene (LIG) electrode. The structures and morphologies were confirmed by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and elemental analysis. The electrochemical performances of NCs were investigated by electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV) and chronoamperometry (CA). The results demonstrated that both Au@CuO/LIG and Au@CuO/V2CTx MXene/LIG have excellent electrocatalytic activity for glucose oxidation in an alkaline medium. However, it was found that Au@CuO/V2CTx MXene/LIG was easily oxidized. Hence, the combination of Au@CuO/LIG was preferred for glucose test. Under optimized conditions, the electrochemical sensor achieved a detection range of 0.005 to 5.0 mM with a sensitivity of 1.124 × 106 μA mM−1 cm−2. The response time was 1.5 s and the limit of detection (LOD) was as low as 1.8 μM. The sensor has good selectivity and stability (84.12 % activity retained after 6 weeks). Its affordable price, disposable usage and portable essence are suitable for clinical application. Our study presented a novel strategy to the field of non-enzymatic glucose sensing.

Advances in nanostructured material-based non-enzymatic electrochemical glucose sensors.

Non-enzymatic electrochemical sensors that use functional materials to directly catalyze glucose have shown great promise in diabetes management, food control, and bioprocess inspection owing to the advantages of high sensitivity, long-term stability, and low cost. Recently, in order to produce enhanced electrochemical behavior, significant efforts have been devoted to the preparation of functional materials with regular nanostructure, as it provides high specific surface area and well-defined strong active sites for electrochemical sensing. However, the structure-performance correlation in this field has not been reviewed thoroughly in the literature. This review aims to present a comprehensive report on advanced zero- to three-dimensional nanostructures based on the geometric feature and to discuss in depth their structural effects on enzyme-free electrochemical detection of glucose. It starts by illustrating the sensing principles of nanostructured materials, followed by a detailed discussion on the structural effects related to the features of each dimension. The structure-performance correlation is explored by comparing the performance derived from diverse dimensional architectures, which is beneficial for the better design of regular nanostructure to achieve efficient enzyme-free sensing of glucose. Finally, future directions of non-enzymatic electrochemical glucose sensors to solve emerging challenges and further improve the sensing performance are also proposed.

A sensitive non-enzymatic electrochemical glucose sensor based on a ZnO/Co3O4/reduced graphene oxide nanocomposite

A novel sensitive and selective ZnO/Co3O4/rGO nanocomposite was fabricated using a hydrothermal method and used as a non-enzymatic electrochemical sensor for the detection of glucose.