Glucose Sensor Research Articles

One‐Step Laser Synthesis of Copper Nanoparticles and Laser‐Induced Graphene in a Paper Substrate for Non‐Enzymatic Glucose Sensing

AbstractThe synergy resulting from the high conductivity of graphene and catalytic properties of metal nanoparticle has been a resource to improve the activity and functionality of electrochemical sensors. This work focuses on the simultaneous synthesis of copper nanoparticles (CuNPs) and laser‐induced graphene (LIG) derived from paper, through a one‐step laser processing approach. A chromatography paper substrate with drop‐casted copper sulfate is used for the fabrication of this hybrid material, characterized in terms of its morphological, chemical, and conductive properties. Appealing conductive properties are achieved, with sheet resistance of 170 Ω sq−1 being reached, while chemical characterization confirms the simultaneous synthesis of the conductive carbon electrode material and metallic copper nanostructures. Using optimized laser synthesis and patterning conditions, LIG/CuNPs‐based working electrodes are fabricated within a three‐electrode planar cell, and their electrochemical performance is assessed against pristine LIG electrodes, demonstrating good electron transfer kinetics appropriate for electrochemical sensing. The sensor's ability to detect glucose through a non‐enzymatic route is optimized, to assure good sensing performance in standard samples and in artificial sweat complex matrix.

Schottky Interface Enabled Electrospun Rhodium Oxide Doped Gold for Both pH Sensing and Glucose Measurements in Neutral Buffer and Human Serum.

This study has focused on adjusting sensing environment from basic to neutral pH and improve sensing performance by doping electrodeposited gold (Au) with metal oxide for nonenzymatic glucose measurements in forming a Schottky interface for superior glucose sensing with detailed analysis for the sensing mechanism. The prepared sensor also holds the ability to measure pH with the identical electrospun metal oxide-electrodeposited Au, which composed a dual sensor (glucose and pH sensor) through applying chronoamperometry and open circuit potential methods. The rhodium oxide nanocoral structure was fabricated with an electrospinning precursor solution, followed by a calcination process, and it was mixed with electrodeposited nanocoral gold to form the Schottky interface by constructing a p-n type heterogeneous junction for improved sensitivity in glucose detection. The prepared materials were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray photoelectron spectrometry (XPS), etc. The prepared materials were used for both pH responsive testing and amperometric glucose measurements. The rhodium oxide nanocoral doped gold demonstrated a sensitivity of 3.52 μA mM-1 cm-2 and limit of detection of 20 μM with linear range up to 3 mM glucose concentration compared to solely electrodeposited gold for a sensitivity of 0.46 μA mM-1 cm-2 and a limit of detection of 450 μM. The Mott-Schottky method was used for the analysis of an electron transfer process from noble metal to metal oxide to electrolyte in demonstrating the improved sensitivity at neutral pH for glucose measurements due to the Schottky barrier adjustment mechanism at an applied flat band potential of 0.3 V. This work opens a new venue in illustrating the metal oxide/metal materials in the glucose neutral response mechanism. In the end, human serum samples were tested against current commercial glucose meter to certify the accuracy of the proposed sensor.

Machine Learning Enables Reliable Colorimetric Detection of pH and Glucose in Wearable Sweat Sensors

AbstractIn healthcare, blood pH and glucose levels are critical indicators, especially for chronic conditions like diabetes. Although taking blood samples is accurate, it is invasive and unaffordable for many. Wearable sensors offer non‐invasive and continuous detection methods, yet face major challenges, such as high cost, inaccuracies, and complex interpretation. Colorimetric wearable sensors integrated with machine learning (ML) are introduced for accurately detecting pH values and glucose concentrations in sweat. These battery‐free and cost‐effective biosensors, made of cotton textiles, are designed to work seamlessly with smartphones for data collection and automated analysis. A new pH indicator is synthesized with enhanced sensitivity and two types of glucose sensors are developed by depositing enzymatic solutions onto cotton substrates. The sensors' performance is assessed using standard solutions with known pH levels ranging from 4 to 10 and glucose concentrations between 0.03 to 1 mm. The photos captured from these sensors are then analyzed by image processing and three different ML algorithms, achieving an accuracy of 90% in pH and glucose detection. These findings provide effective synthesis methods for textile‐based sweat sensors and demonstrate the significance of employing different ML algorithms for their colorimetric analysis, thus eliminating the need for human intervention in the process.

Confinement synthesis of few-layer MXene-cobalt@N-doped carbon and its application for electrochemical sensing

Herein, the few-layer Ti3C2Tx nanosheets loaded zeolitic imidazolate framework-67 nanoplates (Ti3C2Tx-ZIF-67) with a unique structure has been synthesized by surfactant control method, and then is employed as the core of precursor. A thin layer of polydopamine as the shell of precursor covered Ti3C2Tx-ZIF-67 forms a micro-nano reactor, leading to the confinement carbonization process. Consequently, a novel sensing material that few-layer Ti3C2Tx nanosheets loaded Co nanoparticles coated N-doped carbon (Ti3C2Tx-Co@NC) is obtained for the non-enzymatic determination of glucose. Owing to the impressive structure, the established glucose sensor based on Ti3C2Tx-Co@NC/glassy carbon electrode exhibits 0.5–100.0 μM of linear detection range and 66.8 nM of detection limit, which tends to detect low concentration of glucose. The synergistic few-layer Ti3C2Tx nanosheets, Co nanoparticles and NC are considered through a series of control experiments. First, few-layer Ti3C2Tx nanosheets provide a good transport channel for electron transfer, resulting in the lower steric hindrance. Second, Co nanoparticles provide active centers for the electrochemical detection. Third, N-doped carbon with conductivity and hydrophilia plays the role of stabilizing material structure to prevent the fragmentation of Ti3C2Tx and the agglomeration of Co nanoparticles. Such work proposes a confined strategy to develop MXene-ZIF-67-derived nanocomposite with high-performance structure.

Promoted Non-enzymatic Glucose Sensor Based on Synergistic Effect of Hydrothermal Synthesized Ni(OH)2-Graphene Nanocomposite

Promoted Non-enzymatic Glucose Sensor Based on Synergistic Effect of Hydrothermal Synthesized Ni(OH)2-Graphene Nanocomposite

Electrochemical glucose sensor based on a phenothiazine derivative mediator with nicotinamide adenine dinucleotide-dependent glucose dehydrogenase

The phenothiazine derivative (M2) was utilized as a redox mediator for the redox processes of the nicotinamide adenine dinucleotide (NAD+) cofactor. The composite solutions were prepared by mixing NAD+-dependent glucose dehydrogenase with NAD+, M2, poly-l-lysine, and glutaraldehyde. Glucose sensors were fabricated by casting various composite solutions onto the reduced graphene oxide-modified gold electrode and additional Nafion coating processes. The composition of electrode materials (ratio and amount of each component) and measurement conditions (applied potential, pH, and temperature) were optimized to obtain the highest sensitivity. The sensor showed a low reference effect, high selectivity toward interfering species, and long-term stability. The glucose sensor performed well when human serum was injected as the actual sample and compared with a standard solution. These findings promote the development of electrochemical sensors based on other NAD+-dependent enzymes.

A high-performance enzyme-free glucose sensor based on CuS nanoplates with exposed (110) planes

The exposing of active crystal facets plays a crucial role in tailoring the electrochemical properties of nanocrystals. Herein, CuS hexagonal nanoplates with exposed (110) planes (CuS-P) were synthesized via a microwave-assisted homogeneous precipitation route. Structural characterization, including XRD and TEM, revealed that the CuS nanoplates were (110) facet exposed and that their morphologies could be mediated through polyvinylpyrrolidone coordination. These CuS-P nanoplates possessed excellent electrochemical properties and demonstrated good catalytic activity in the electro-oxidation of glucose. The (110) crystal facets on CuS improve the adsorption and activation of glucose, accelerating the electrochemical reaction. A novel nonenzymatic glucose sensor was fabricated by modifying a glassy carbon electrode (GCE) with CuS-P nanoplates. The sensor exhibited an ultrafast response rate (< 0.1 s), a low detection limit of 0.38 µM and a wide linear range of 10 µM ∼ 15.0 mM. In addition, the developed method showed good anti-interference capability and outstanding stability. When the nonenzymatic sensor was adopted to detect glucose in human serum, the recoveries ranged from 98.8 % to 101.4 %, and the relative standard deviation (RSD) was less than 2.0 %, indicating its practical use. This study offers an in-depth understanding of the crystal facet effect in the construction of high-performance electrochemical sensors.

A Passive Perspiration Inspired Wearable Platform for Continuous Glucose Monitoring.

The demand for glucose monitoring devices has witnessed continuous growth from the rising diabetic population. The traditional approach of blood glucose (BG) sensor strip testing generates only intermittent glucose readings. Interstitial fluid-based devices measure glucose dynamically, but their sensing approaches remain either minimally invasive or prone to skin irritation. Here, a sweat glucose monitoring system is presented, which completely operates under rest with no sweat stimulation and can generate real-time BG dynamics. Osmotically driven hydrogels, capillary action with paper microfluidics, and self-powered enzymatic biochemical sensor are used for simultaneous sweat extraction, transport, and glucose monitoring, respectively. The osmotic forces facilitate greater flux inflow and minimize sweat rate fluctuations compared to natural perspiration-based sampling. The epidermal platform is tested on fingertip and forearm under varying physiological conditions. Personalized calibration models are developed and validated to obtain real-time BG information from sweat. The estimated BG concentration showed a good correlation with measured BG concentration, with all values lying in the A+B region of consensus error grid (MARD = 10.56% (fingertip) and 13.17% (forearm)). Overall, the successful execution of such osmotically driven continuous BG monitoring system from passive sweat can be a useful addition to the next-generation continuous sweat glucose monitors.

A Tamm-Fano resonance glucose sensor based on Cu and distributed bragg reflector plasmonic coupling interface in the near-infrared regime

A Tamm-Fano resonance glucose sensor based on Cu and distributed bragg reflector plasmonic coupling interface in the near-infrared regime

AuNPs@MoS2 functionalized copper metal organic framework for boosting electrocatalytic glucose oxidation

A novel non-enzyme glucose sensor based on functionalized copper metal–organic framework composite material, AuNPs@MoS2/Cu-MOF, was developed for rapid glucose analysis. Cu-MOF nanomaterial was prepared via a hydrothermal method, followed by the surface loading of core–shell structured AuNPs@MoS2 to synthesize AuNPs@MoS2/Cu-MOF composite material. Consequently, a novel gold nanoparticle @ molybdenum disulfide/copper metal–organic framework (AuNPs@MoS2/Cu-MOF/GCE) non-enzyme glucose sensor was constructed. Scanning electron microscopy (SEM), energy dispersive spectrometer (EDS) and X-ray powder Diffraction (XRD) was used to verify that the non-enzyme glucose sensor had been constructed effectively. Traditional electrochemical characterization methods were employed to study the electrocatalytic performance of the AuNPs@MoS2/Cu-MOF/GCE sensor and its catalytic oxidation of glucose. The experimental results demonstrated a good linear correlation between the concentration of glucose and the peak current within the range of 0.05–14.85 mM, with a detection limit of 16.7 μM. The AuNPs@MoS2/Cu-MOF/GCE sensor exhibited rapid electrochemical response to glucose (within 0.5 s), along with long-term stability and excellent selectivity. This is because Cu(II) in Cu-MOF can serve as active sites for the electrocatalytic oxidation of glucose, while the core–shell structure of AuNPs@MoS2 with excellent conductivity can lower the energy barrier in the reaction, further accelerating this catalytic reaction. The AuNPs@MoS2/Cu-MOF/GCE sensor is cost-effective, easy to operate, and suitable for accurate rapid quantification of glucose.

Microfibrous Carbon Paper Decorated with High-Density Manganese Dioxide Nanorods: An Electrochemical Nonenzymatic Platform of Glucose Sensing.

Nanorod structures exhibit a high surface-to-volume ratio, enhancing the accessibility of electrolyte ions to the electrode surface and providing an abundance of active sites for improved electrochemical sensing performance. In this study, tetragonal α-MnO2 with a large K+-embedded tunnel structure, directly grown on microfibrous carbon paper to form densely packed nanorod arrays, is investigated as an electrocatalytic material for non-enzymatic glucose sensing. The MnO2 nanorods electrode demonstrates outstanding catalytic activity for glucose oxidation, showcasing a high sensitivity of 143.82 µA cm-2 mM-1 within the linear range from 0.01 to 15 mM, with a limit of detection (LOD) of 0.282 mM specifically for glucose molecules. Importantly, the MnO2 nanorods electrode exhibits excellent selectivity towards glucose over ascorbic acid and uric acid, which is crucial for accurate glucose detection in complex samples. For comparison, a gold electrode shows a lower sensitivity of 52.48 µA cm-2 mM-1 within a linear range from 1 to 10 mM. These findings underscore the superior performance of the MnO2 nanorods electrode in both sensitivity and selectivity, offering significant potential for advancing electrochemical sensors and bioanalytical techniques for glucose monitoring in physiological and clinical settings.

One‐Pot Carbothermal Reduction Preparation of Cu‐BTC@Cu/C Heterostructure for Enhanced Nonenzymatic Electrochemical Glucose Sensing

AbstractA heterostructure based on MOFs with a small lattice mismatch is ideal for improving glucose‘s electrochemical sensing performance. Herein, a novel one‐pot carbothermal reduction technique to prepare Cu‐BTC@Cu/C heterostructure with intimate interfacial contact and high yield was developed, by in situ integrating Cu‐BTC (Cu3(BTC)2 ⋅ 3H2O) and its derived Cu/C nanocomposites. Structure characterizations demonstrated that Cu‐BTC@Cu/C heterostructure shows a synergistic effect in the combination of these two components, with more electrochemical active sites and lower resistance. Compared with each individual component, Cu‐BTC@Cu/C heterostructure exhibits better glucose electrooxidation performance. Under optimal condition, an extremely sensitive nonenzymatic glucose sensor with a low detection limit of 6.78 μM, sensitivity of 911.03 μA mM−1 cm−2, linear range of 0.001–2.0 mM, and anti‐interference performance is presented. Meanwhile, the newly constructed sensor was effectively employed for detecting glucose in honey sample with perfect recoveries, showing its great potential toward glucose monitoring in real sample. In addition, it has been demonstrated Cu(II) can be induced into Cu(I) by glucose in solution, while Cu(I) could be electrochemically converted to Cu(II), therefore achieving a Cu(I)/Cu(II) redox cycle. It offers a promising strategy for synthesis of advanced electrocatalysts with high efficiency and promising applications in this paper.

Graphene/PEDOT/Ni-Based electrochemical Non-Enzymatic glucose sensor

Compared to enzymatic glucose sensors, non-enzymatic glucose sensors offer significant advantages in sensitivity, stability, and cost. In this study, a green and simple electrochemical method was employed to prepare an electrochemical non-enzymatic glucose sensor based on graphene/PEDOT/Ni materials. The modified electrode was characterized using scanning electron microscopy (SEM), Raman spectroscopy, Fourier-transform infrared spectroscopy (FTIR), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). The electrochemical behavior of glucose on the modified electrode was investigated, and the results indicated that the sensor exhibited a good electrochemical response to glucose. Experimental conditions were optimized, and under the optimal conditions, the sensor showed a good linear relationship with glucose concentration in the range of 0.0001 to 7 mM, with a detection limit of 0.012 μM. The sensitivity was 1561 μA·mM−1·cm−2, demonstrating excellent reliability, stability, and accuracy.

Analytical Performance of the FreeStyle Libre 2 Glucose Sensor in Healthy Male Adults.

Continuous Glucose Monitoring (CGM) not only can be used for glycemic control in chronic diseases (e.g., diabetes), but is increasingly being utilized by individuals and athletes to monitor fluctuations in training and everyday life. However, it is not clear how accurately CGM reflects plasma glucose concentration in a healthy population in the absence of chronic diseases. In an oral glucose tolerance test (OGTT) with forty-four healthy male subjects (25.5 ± 4.5 years), the interstitial fluid glucose (ISFG) concentration obtained by a CGM sensor was compared against finger-prick capillary plasma glucose (CPG) concentration at fasting baseline (T0) and 30 (T30), 60 (T60), 90 (T90), and 120 (T120) min post OGTT to investigate differences in measurement accuracy. The overall mean absolute relative difference (MARD) was 12.9% (95%-CI: 11.8-14.0%). Approximately 100% of the ISFG values were within zones A and B in the Consensus Error Grid, indicating clinical accuracy. A paired t-test revealed statistically significant differences between CPG and ISFG at all time points (T0: 97.3 mg/dL vs. 89.7 mg/dL, T30: 159.9 mg/dL vs. 144.3 mg/dL, T60: 134.8 mg/dL vs. 126.2 mg/dL, T90: 113.7 mg/dL vs. 99.3 mg/dL, and T120: 91.8 mg/dL vs. 82.6 mg/dL; p < 0.001) with medium to large effect sizes (d = 0.57-1.02) and with ISFG systematically under-reporting the reference system CPG. CGM sensors provide a convenient and reliable method for monitoring blood glucose in the everyday lives of healthy adults. Nonetheless, their use in clinical settings wherein implications are drawn from CGM readings should be handled carefully.

Flexible surface plasmon based coupled triple band UHF-microwave sensor for glucose sensing application

Although the correlation between a glucose concentration and its permittivity is somewhat weak to be measured, the glucose concentration is a strong function of the dispersion. In terahertz or microwave frequencies, dispersion can be observed or measured along the interface between an object under test and a metamaterial or surface plasmonic surface, which is basically a metal structure characterized by periodically arrayed holes, grooves, or metal grating. In this work, we have focused on the method for improving the accuracy of a glucose measurement by proposing a new triple-band microwave sensor design and by measuring the resonant frequency shift associated with a glucose concentration at three frequencies simultaneously. A new triple-band glucose sensor of dimension (30 mm x 10 mm) was designed with the main sensing region as compact as 14 mm with two conducting microstrip lines on both ends of the sensor. The sensor design has been realized on a thin flexible substrate of 0.15 mm thickness. The proposed sensor has been designed to measure glucose concentration through the measurement of a resonant frequency shift at 650 MHz, 4.45 GHz, and 10.35 GHz. Overall, the glucose concentration has been found to be correlated positively and linearly with the resonant frequency shift at these frequencies.

Use of glucose sensors for post-discharge care triaging of insulin-treated patients with type 2 diabetes: a feasibility study.

The use of glucose sensors to triage post-discharge follow-up was investigated among hospital inpatients with type 2 diabetes. Feasibility, utility and patient satisfaction with this model of care were studied. Feasibility was 36.5%, with 90/198 (45.5%) inpatients discharged with glucose sensors but 9.0% unable to use glucose sensors effectively. Follow-up plans were altered in 76.3% of the patients able to use the sensor technology. Patient satisfaction was high and was improved on follow-up after 6 months.

Hydrogen-Substituted Graphdiyne Encapsulated Cu2O Nanowires as Binder-Free Electrodes for Non-Enzymatic Glucose Sensing

Hydrogen-Substituted Graphdiyne Encapsulated Cu₂O Nanowires as Binder-Free Electrodes for Non-Enzymatic Glucose Sensing

Highly stable and selective determination of glucose by a modified glassy carbon electrode based on micro-rods [Ni(HL)NCS] complex as a novel modifier

Non-enzymatic glucose sensors have acquired a lot of attention, where the modifier materials perform as an electrocatalyst instead of an enzyme on the surface of electrodes. More active sites, increased synergistic reactions, and expanded contacts between the electrolyte and the catalyst are essential to enhance catalytic performances. Numerous efforts have been made to fabricate novel non-enzymatic glucose sensors with electrode modification strategies. Herein, a non-enzymatic electrochemical glucose sensor was constructed by a modified glassy carbon electrode (GCE) based on micro-rods [Ni(HL)NCS] complex (MR-NiC/GCE) as a novel modifier for the glucose detection. In alkali media, the non-enzymatic glucose sensor showed a linear dynamic range (LDR) of 100-1100 µM with an excellent limit of detection (LOD) of 15.8 μM (S/N= 3). The proposed sensor demonstrated remarkable stability (after recording 50 continuous cycles), good reproducibility, and significant anti-interference performance toward fructose (Fru), ascorbic acid (AA), dopamine (DA), citric acid (CA), uric acid (UA) and sucrose. According to this study, complexes can be an excellent suggestion to fabricate non-enzymatic glucose sensors.

Glucose-Operated Widget (GLOW) for Closed-Loop Optogenetic Glycemic Control.

Closed-loop control systems for precise control of therapeutic gene expression are promising candidates for personalized treatment of chronic ailments such as diabetes. Pancreatic iβ-cells are engineered with blue-light-inducible melanopsin to drive rapid insulin release by vesicular secretion from intracellular stores. In this work, a glucose-operated widget (GLOW) is designed as a component of a closed-loop control system for diabetes treatment by employing a probe that emits blue fluorescence in a glucose-concentration-dependent manner as a real-time glucose sensor to precisely control insulin release from these iβ-cells. As proof-of-concept of the complete control system, the probe is encapsulated together with iβ-cells in alginate-poly-(L-lysine) hydrogel-microbeads(400µm in diameter and containing about 500 cells) called GLOWiβ (GLOW with iβ-cells), are subcutaneously implanted into type-1-diabetic (T1D) mice. Illumination by UV-A light at 390nm results in glucose-concentration-dependent blue-light emission from the probe at 445nm that in turn induces glucose-concentration-dependent insulin release from the iβ-cells in a fully reversible manner. Activation of the injected GLOWiβ at 390nm for 15 min effectively restores normoglycemia within 60-120 min in a closed-loop manner in these diabetic mice. The system is robust, as normoglycemia is well maintained by daily activation for at least 7 days.

Growth of WO3 nanostructure deposited on TiO2 nanotube arrays for electrochemical enzyme-free glucose sensor

In this study, a novel WO3-TiO2 hybrid nanostructure-based electrochemical non-enzymatic glucose biosensor has been developed. The anodization method was utilized to successfully produce TiO2 nanotubes on Ti6Al4V alloy functioning as substrates and WO3 nanomaterial decorate on the surface of TiO2 nanotubes (TNTs) deposited through electrochemical technique. The incorporation of WO3 on TNTs has resulted in a high electroactive surface and more degradation resistance in comparison to pure TNTs, resulting in enhanced electron transfer rate and electrode stability. High-resolution transmission electron microscopy (HR-TEM), field emission scanning electron microscopy (FE-SEM), and X-ray diffraction were used to investigate the crystalline structure and morphology of the WO3-TiO2 nanostructure. The electrochemical properties of the hybrid electrodes were investigated employing amperometry, cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). The hybrid electrode had a promising sensitivity (1228.12 μA/mM/cm2), low detection limit (0.19 mM), wide linear range (1.0–6.5 mM), and short response time (2-s). The sensors also demonstrated superior levels of reproducibility, repeatability, and stability.