Non-enzymatic Glucose Detection Research Articles

High entropy alloy nanoparticle - graphene (HEA:G) composite for non-enzymatic glucose oxidation : optimization for enhanced catalytic performance

High entropy alloy (HEA) metal nanoparticles engineered graphene composites (HEA:G) were produced via green approach involving mechanical milling and sonication assisted exfoliation. Mixture of metal powders and graphite (metal-to-graphite weight ratio: 20%, 50%, 70%, 90%) were ball milled and exfoliated. As produced 20:80, 50:50, 70:30, 90:10 - HEA:G composites electrochemical activity was explored using the redox probe potassium ferricyanide [K3Fe(CN)6] and for the non-enzymatic detection of glucose. From cyclic voltammetry(CV) response, the significant electron transfer kinetics for K3Fe(CN)6 was found for 20:80, 50:50, 70:30 composites, whereas reduced activity was observed with 90:10. Also, 20:80, 50:50, 70:30 composites exhibited notable oxidation of glucose in 0.1 M PBS compared to 90:10. The anodic current indicating oxidation of glucose was found to be increasing linearly with HEA:G composite - 20:80<50:50<70:30. However, DPV measurements indicate better working potential from 0.45 V to 0.4 V followed by saturation in the oxidation currents for 50:50 and 70:30 composites. The sensitivity obtained for HEA:G composites 20:80, 50:50, 70:30 were 12.09 μAmM−1cm−2, 22.99 μAmM−1cm−2, 18.2 μAmM−1cm−2 respectively. Hence, 50:50 and 70:30 are the efficient composites exhibiting excellent catalytic activity indicating the prominence of HEA:Graphene composites and their synergism.

Free-standing hybrid material of Cu/Cu2O/CuO modified by graphene with commercial Cu foil using for non-enzymatic glucose detection

Free-standing Cu/Cu2O/CuO modified by graphene was formed through two steps: Firstly, the commercial Cu foil was thermal annealed to form Cu/Cu2O/CuO; Secondly, the Cu/Cu2O/CuO was modified by graphene through electrochemical exfoliated method. The SEM, XRD, TEM and XPS have been used to characterize the morphology, the crystalline phase, and the surface composition of the hybrid electrode as-prepared. The effects of Cu and its oxides on graphene has been uncovered by the Raman results. The sensitivity of the glucose sensor in 0.1 M NaOH by using the as-prepared hybrid material reaches 3102 μA·mM−1 cm−2 within a linear range of 0.002–2.88 mM, which is better than that of the Cu/graphene and the Cu/Cu2O/CuO prepared at the same conditions. The sensor also shows excellent anti-interference ability, good cycling stability and time stability. The advantage of the sensor is caused by the strengthened synergistic effects between the graphene and the Cu/Cu2O/CuO due to the alleviated detrimental effects of the metal on the property of the graphene through using oxides middle layer as well as the large active area that obtained. This work provides a new way to study the effects of graphene in improving the property of the metal oxide especially in using for glucose sensor.

Electrochemical fabrication of Co(OH)2 nanoparticles decorated carbon cloth for non-enzymatic glucose and uric acid detection.

Cobalt hydroxide nanoparticles (Co(OH)2 NPs) were uniformly deposited on flexible carbon cloth substrate (Co(OH)2@CC) rapidly by a facile one-step electrodeposition, which can act as an enzyme-free glucose and uric acid sensor in an alkaline electrolyte. Compositional and morphological characterization were examined by X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS), which confirmed the deposited nanospheres were Co(OH)2 nanoparticles (NPs). The electrochemical oxidation of glucose and uric acid at Co(OH)2@CC electrode was investigated by electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), differential pulse voltammetry (DPV), and chronoamperometry methods. The results revealed a remarkable electrocatalytic activity toward the single and simultaneous determination of glucose and uric acid at about 0.6 V and 0.3V (vs. Ag/AgCl), respectively, which isattributed to a noticeable synergy effect between Co(OH)2 NPs and CC with good repeatability, satisfactory reproducibility, considerable long-term stability, superior selectivity, outstanding sensitivity, and wide linear detection range from 1 uM to 2mM and 25nM to 1.5 uM for glucose and UA, respectively. The detection limits were 0.36nM for UA and 0.24μM for glucose (S/N = 3). Finally, theCo(OH)2@CC electrode was utilized for glucose and uric acid determination in human blood samples and satisfying results were obtained. The relative standard derivations (RSDs) for glucose and UA were in the range 6 to 14% and 0 to 3%, respectively. The recovery ranges for glucose an UA were 97 to 103% and 95 and 101%, respectively. These features make the novel Co(OH)2@CC sensor developed by a low-cost, efficient, and eco-friendly preparation method apotentially practical candidate for application to biosensors.

Imprinted-Zeolite-X-Based Sensor for Non-Enzymatic Detection of Blood Glucose by Potentiometry

The development of sensors based on imprinted zeolite X to detect blood glucose through potentiometry was performed. In this study, the sensor was made of a mixture of carbon paste and imprinted zeolite X. Zeolite X was synthesized using a sol–gel-hydrothermal method at a temperature of 100 °C with basic materials of NaAlO2, NaOH, TEOS, and distilled water. The characterization results of XRD showed the presence of specific peaks, which were confirmed with standard zeolite X. Imprinted zeolite X exhibited a 20 times greater adsorption capacity size, and an adsorption efficiency 3 times greater than that of zeolite X. This is thought to be due to the presence of a molecular template within it. The IZ–carbon paste electrode showed optimum performance due to a mass ratio of carbon, paraffin, and imprinted zeolite X of 12:7:1. The electrode performance was expressed by the Nernst factor value of 30 mV/decade, the measuring range of 10−4–10−2 M, the upper detection limit of 1.38 × 10−2 M, and the lower detection limit of 1.28 × 10−4 M, so this electrode can be used for glucose analysis with a normal concentration (70–110 mg/dL or equivalent to 3.8 × 10−3–6.1 × 10−3 M), as well as the glucose concentration of people with diabetes mellitus (&gt;200 mg/dL or about 10−2 M). This electrode showed precision values of 97.14–99.02%, accuracy values of 98.65–99.39%, and electrode response times of 10–13 s. The electrodes showed high stability for more than 5 weeks with 141 uses. The electrodes also showed high selectivity for glucose in the matrix of uric acid, urea, NaCl, and KCl. Therefore, its use as an alternative electrode for routine glucose analysis in the medical field is recommended.

Engineering Co3O4 with Co defects for highly sensitive nonenzymatic detection of glucose

Defect engineering was considered as an effective strategy to regulate electrocatalytic activities of transition metal oxides. However, there are seldom reports about metal defects in electrochemical sensing. In this work, Co-defected Co3O4 was synthesized via thermal treatment of glycerolatocobalt (CoGly) precursor for constructing a novel electrochemical nonenzymatic glucose sensor. The obtained nanomaterials were characterized by transmission electron microscopy (TEM), powder X-ray diffractometry (XRD), Raman spectra, X-ray photoelectron spectroscopy (XPS) and electrochemical techniques. The presence of Co defects regulated electronic structure of Co3O4, which not only speeds up electron transfer rate but also exposes more high-valent Co sites, thus improving electrocatalytic activities. Under optimized conditions, Co-defected Co3O4 electrode exhibited excellent performance for glucose analysis with a wide linear range of 0.2 µM to 0.5 mM, a low detection limit of 0.16 µM. Importantly, an ultrahigh sensitivity of 2595.7 µA·mM−1·cm−2 was also obtained, which was about 10 times higher than that of conventional Co3O4. Therefore, engineering Co3O4 with Co defects is an effective strategy to tailor electrocatalytic activity, which sheds light on the potential applications of metal defects in the field of electrochemical nonenzymatic sensing.

Surface modification of copper selenide for reliable non-enzymatic glucose sensing

Improvement in the catalytic activity of the electrode material can be achieved by altering surface morphology. Herein, the effect of complexing agent (ammonia, NH4OH) concentration on the surface morphology of copper selenide (Cu3Se2) film electrodes synthesized using the chemical bath deposition method was evaluated. Thin films of Cu3Se2 were characterized using structural, morphological, and elemental composition analyses. The electrochemical glucose sensing performance of films was evaluated using cyclic voltammetry and i-t amperometry techniques. The broad linear range of detection (2.8 μM–1.5 mM of glucose concentration) and high sensitivity (18,500 μA/mM cm2) as well as the low limit of detection limit (2.8 μM) project Cu3Se2 films with spherical nanoparticles morphology as a promising electrode material for non-enzymatic glucose detection application. The measurement of glucose levels from a human blood sample using Cu3Se2 films confirms practical applicability for further device fabrication.

Bi-functional 3D-NiCu-Double Hydroxide@Partially Etched 3D-NiCu Catalysts for Non-Enzymatic Glucose Detection and the Hydrogen Evolution Reaction.

Hydrogen production, which is in the spotlight as a promising eco-friendly fuel, and the need for inexpensive and accurate electronic devices in the biochemistry field are important emerging technologies. However, the use of electrocatalytic devices based on expensive noble metal catalysts limits commercial applications. In recent years, to improve performance and reduce cost, electrocatalysts based on cheaper copper or nickel materials have been investigated for the non-enzymatic glucose oxidation reaction (GOR) and hydrogen evolution reaction (HER). In this study, we demonstrate a facile and easy electrochemical method of forming a cheap nickel copper double hydroxide (NiCu-DH) electrocatalyst deposited onto a three-dimensional (3D) CuNi current collector, which can effectively handle two different reactions due to its high activity for both the GOR and the HER. The as-prepared electrode has a structure comprising abundant 3D-interconnected porous dendritic walls for easy access of the electrolyte ions and highly conductive networks for fast electron transfer; additionally, it provides numerous electroactive sites. The synergistic combination of the dendritic 3D-CuNi with its abundant active sites and the self-made NiCu-DH with its excellent electrocatalytic activity toward the oxidation of glucose and HER enables use of the catalyst for both reactions. The as-prepared electrode as a glucose sensor exhibits an outstanding glucose detection limit value (0.4 μM) and a wide detection range (from 0.4 μM to 1.4 mM) with an excellent sensitivity of 1452.5 μA/cm2/mM. The electrode is independent of the oxygen content and free from chloride poisoning. Furthermore, the as-prepared electrode also requires a low overpotential of -180 mV versus reversible hydrogen electrode to yield a current density of 10 mA/cm2 with a Tafel slope of 73 mV/dec for the HER. Based on this performance, this work introduces a new paradigm for exploring cost-effective bi-functional catalysts for the GOR and HER.

(Digital Presentation) Paper-Based Sensor for Monitoring Urea Oxidation Using Hierarchical Nickel Cobalt Oxide

Urea has attracted attention because of its various potential applications such as hydrogen production, fuel cells, fertilizers, and electrochemical sensors. [1] Their long-term usages can lead to soil acidification and eutrophication, disturbing the ecosystem.[2] As an end-product of human metabolism, urea is a crucial biomarker that can access various human disorders such as kidney and renal function. Thus, the rapid sensing of the urea level in urine can play an important role in diagnostic areas, especially point-of-care testing devices. Most electrochemical biosensors rely on the enzymatic method. However, the utilization of the enzyme for the sensors appears to be limited due to complex processes of enzyme immobilization, high cost, short shelf life from the denaturation of the enzyme. [3] To overcome the limitations from using enzyme, non-enzymatic catalyst, especially nickel oxide, has been attracted with the advantage of good stability re-usability, high sensitivity, simplicity, low cost, and an excellent catalytic activity on detection of urea by the formation of the redox couple of Ni(II) and Ni(III).[4]Despite many efforts to achieve a higher catalytic effect with bimetallic oxides with Co[5], Mo[6], and Mn[7], the improvement of electrochemical response of oxidation of urea is still challenging due to the low exposure of active sites. Therefore, the formation of hollow structured hierarchical catalysts can be considered to improve the sensitivity of urea detection besides exploration of highly performing compositions. Such a hierarchical structure will provide structural stability and facile transport channels for electrolytes by exploiting its inner and outer surface as active sites. For a flexible and disposable sensor platform, the paper has merit due to a porous cellulose matrix. The paper naturally allows a liquid sample to infiltrate the paper matrix by capillary force. Furthermore, the capillary force-driven transport can be utilized in the catalyst loading process to distribute the catalyst and conductive network uniformly within the paper, which made the fabrication process simpler and enhanced performance.In this study, the combination of the hierarchical structure of nickel oxide and the paper matrix has demonstrated an increase in the sensitivity toward electrochemical sensing of urea. A filter paper and CNTs were used for the porous matrix and the conductive network, respectively. The hierarchical nickel cobalt oxide was synthesized with a one-pot hydrothermal method with the variation of Ni:Co atomic ratio, and then applied to the paper substrate. The structure and morphology of paper-based electrodes were characterized by XRD, SEM, and EDS, and the electrochemical response was measured by a potentiostat. A detailed description of the fabrication of paper-based sensors and the effect of hierarchical structure and bimetallic composition will be presented.[1] B. K. Boggs, R. L. King, and G. G. Botte, “Urea electrolysis: direct hydrogen production from urine,” Chem. Commun., no. 32, pp. 4859–4861, Aug. 2009, doi: 10.1039/B905974A.[2] L. Liu, H. Mo, S. Wei, and D. Raftery, “Quantitative analysis of urea in human urine and serum by 1 H nuclear magnetic resonance,” Analyst, vol. 137, no. 3, pp. 595–600, 2012, doi: 10.1039/C2AN15780B.[3] K. Kim et al., “Fabrication of a Urea Biosensor for Real-Time Dynamic Fluid Measurement,” Sensors, vol. 18, no. 8, Art. no. 8, Aug. 2018, doi: 10.3390/s18082607.[4] Nie, Huagui, et al. "Non-enzymatic electrochemical detection of glucose using well-distributed nickel nanoparticles on straight multi-walled carbon nanotubes." Biosensors and Bioelectronics 30.1 (2011): 28-34.[5] Ding, Rui, et al. "Facile synthesis of mesoporous spinel NiCo2O4 nanostructures as highly efficient electrocatalysts for urea electro-oxidation." Nanoscale 6.3 (2014): 1369-1376.[6] Liang, Yanhui, et al. "Enhanced electrooxidation of urea using NiMoO4· xH2O nanosheet arrays on Ni foam as anode." Electrochimica Acta 153 (2015): 456-460.[7] Periyasamy, Sivakumar, et al. "Exceptionally active and stable spinel nickel manganese oxide electrocatalysts for urea oxidation reaction." ACS applied materials & interfaces 8.19 (2016): 12176-12185.

Quasi-aligned Cu2S/Cu(OH)2 nanorod arrays anchored on Cu foam as self-supported electrode for non-enzymatic glucose detection

Self-supported Cu2S/Cu(OH)2 composite nanorods for highly sensitive non-enzymatic glucose sensing were in situ grown on Cu foam by simple hydrothermal treatment of aligned Cu(OH)2 nanorods. The physicochemical and electrochemical properties of the as-fabricated Cu2S/Cu(OH)2 composite nanorods were characterized by scanning electron microscopy, transmission electron microscopy, x-ray diffraction, Raman spectroscope, x-ray photoelectron spectroscope, cyclic voltammetry, electrochemical impedance spectroscopy, amperometric i–t measurements. The mechanism of the composite nanorods produced on conductive substrates was also explored. The electrode exhibits a sensitivity of 9626.88 μA mM−1 cm−2 towards glucose with good anti-interference ability, indicating it a promising electrode material for the enhanced non-enzymatic glucose detection.

Noble Metal Construction for Electrochemical Nonenzymatic Glucose Detection

AbstractPrecise glucose monitoring is needed to meet the growing demand of blood glucose determination in diabetes diagnosis. In spite of good selectivity and high sensitivity of enzyme‐based glucose sensors, the activity of enzyme is sensitive to pH and temperature, which makes them unstable in detecting glucose level. Alternatively, nonenzymatic electrocatalysts have attracted intensive attention because of their chemical and thermal stability. Noble metal (NM) electrocatalysts based on Pt, Au, and Pd exhibit high activity and stability for the oxidation of glucose in both neutral and alkaline environments, further showing promising potential in the field of nonenzymatic glucose sensors. Since the electrocatalytic ability of NM nanomaterials directly depends on the surface and interface states, it is very important to effectively control the surface and interface state of nanomaterials for preparing NM nanocatalysts with optimized catalytic performance. In this review, the fundamentals and development of glucose sensors are briefly introduced. Then, the modification strategies of NM nanomaterials and their applications in enzyme‐free glucose detection are discussed from the surface construction and interface modification. Finally, the challenges and opportunities for NM materials in electrochemical nonenzymatic glucose detection are proposed.

Nickel phthalocyanine-borophene nanocomposite-based electrodes for non-enzymatic electrochemical detection of glucose

Nickel phthalocyanine-borophene nanocomposite-based electrodes for non-enzymatic electrochemical detection of glucose

Nickel foam electrode decorated with Fe-CdIn2O4 nanoparticles as an effective electrochemical sensor for non-enzymatic glucose detection

The non-enzymatic glucose electrochemical sensors have great significance in the prevention and diagnosis of diabetes. In this work, Fe-CdIn2O4 was grown in situ on the nickel foam with the one step non-aqueous sol-gel method. The nickel foam modified by Fe-CdIn2O4 was directly used to detect glucose. The high specific surface area of the nickel foam enhances the contact surface with glucose, and effectively promotes the transmission of electrons. The 30% Fe-CdIn2O4 had a good electrochemical performance for the detection of glucose when 30% Fe was combined with CdIn2O4. XRD showed that the 30% Fe-CdIn2O4 had better crystallinity. SEM, SEM-Mapping, and TEM showed that the 30% Fe-CdIn2O4 particles grew evenly and exposed abundant active sites. The detection results showed that the 30% Fe-CdIn2O4 had an excellent response to glucose. The linear detection range was wide (0.01–1 mM), the limit detection was low (1.68 μM), the response time was rapid (2.65 s), as well as satisfactory stability, excellent selectivity, and great sensitivity (8992 μA·mM−1·cm−2). Meanwhile, based 30% Fe-CdIn2O4 non-enzymatic electrochemical sensor was used to detect glucose in real human serum, and its detection performance was excellent. This study has practical application value in the detection of glucose in real human serum.

Fe doping induced formation of crystalline/amorphous NiCo2O4 core/shell heterostructure for highly sensitive nonenzymatic detection of glucose

A novel strategy was reported to improve electrocatalytic activity of NiCo 2 O 4 by doping Fe. It is interesting to find that the doping of Fe induces formation of nanorod composing with crystalline core and thin amorphous shell. The composition, structure and properties of NiCo 2 O 4 are well characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), cyclic voltammetry and amperometric method. The results display that the presence of thin amorphous shell is conducive to accelerating electron transfer rate and exposing more effective active sites, therefore making the sensor based on Fe-doped NiCo 2 O 4 detect glucose in a wide linear range from 0.2 μM to 3.1 mM with a high sensitivity of 3055.7 μA mM −1 cm −2 and a low detection limit of 0.19 μM. This unique crystalline core/amorphous shell-structured NiCo 2 O 4 demonstrates promising potential as an effective electrocatalyst for glucose sensing. • A unique NiCo 2 O 4 crystalline core/amorphous shell heterostructure is developed. • The doping of Fe induces the formation of crystalline core surrounding with thin amorphous shell. • The presence of thin amorphous shell is beneficial to improve electron transfer and increase active sites. • The sensor based on Fe-doped NiCo 2 O 4 exhibited remarkable catalytic performance for glucose detection.

Cu and Ni Co-sputtered heteroatomic thin film for enhanced nonenzymatic glucose detection

In this work, we report a wafer-scale and chemical-free fabrication of nickel (Ni) and copper (Cu) heteroatomic Cu–Ni thin films using RF magnetron sputtering technique for non-enzymatic glucose sensing application. The as-prepared wafer-scale Cu–Ni thin films exhibits excellent electrocatalytic activity toward glucose oxidation with a 1.86 μM detection limit in the range of 0.01 mM to 20 mM range. The Cu–Ni film shows 1.3- and 5.4-times higher glucose oxidation activity in comparison to the Cu and Ni electrodes, respectively. The improved electrocatalytic activity is attributed to the synergistic effect of the bimetallic catalyst and high density of grain boundaries. The Cu–Ni electrodes also possessed excellent anti-interference characteristics. These results indicate that Cu–Ni heteroatomic thin film can be a potential candidate for the development of non-enzymatic glucose biosensor because of its chemical free synthesis, excellent reproducibility, reusability, and long-term stability.

Copper Cobalt Sulfide Structures Derived from MOF Precursors with Enhanced Electrochemical Glucose Sensing Properties.

Nonenzymatic electrochemical detection of glucose is popular because of its low price, simple operation, high sensitivity, and good reproducibility. Co-Cu MOFs precursors were synthesized via the solvothermal way at first, and a series of porous spindle-like Cu-Co sulfide microparticles were obtained by secondary solvothermal sulfurization, which maintained the morphology of the MOFs precursors. Electrochemical studies exhibit that the as-synthesized Cu-Co sulfides own excellent nonenzymatic glucose detection performances. Compared with CuS, Co (II) ion-doped CuS can improve the conductivity and electrocatalytic activity of the materials. At a potential of 0.55 V, the as-prepared Co-CuS-2 modified electrode exhibits distinguished performance for glucose detection with wide linear ranges of 0.001–3.66 mM and high sensitivity of 1475.97 µA·mM−1·cm−2, which was much higher than that of CuS- and Co-CuS-1-modified electrodes. The constructed sulfide sensors derived from MOF precursors exhibit a low detection limit and excellent anti-interference ability for glucose detection.

Preparation of Non-Enzymatic Glucose Sensing Nanocomposite Based on NiCo&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;4&lt;/sub&gt; Nanosheets@ Reduced Graphene Oxide and Design of Glucose Detection System

A non-enzymatic glucose sensing nanomaterial which consists of the NiCo2O4 nanosheets grown on reduced graphene oxide (NiCo2O4@rGO) is synthesized by a simple co-precipitation procedure. Firstly, the morphology and composition of the NiCo2O4@rGO are analyzed. Subsequently, the glucose sensing characteristics of the NiCo2O4@rGO are researched by Cyclic Voltammetry and Amperometry. The test results show that the prepared NiCo2O4@rGO has excellent glucose sensing properties. In the two linear detection range of 0.01mM-5.50mM and 5.50mM-15.50mM, the sensitivity reaches 4372.9μA·mM-1cm-2 and 1686.1μA·mM-1cm-2, respectively. In addition, in order to reduce the cost of electrochemical testing and improve the convenience and practicability of detection, a portable potentiostatic glucose detection system based on three electrodes is designed. Through testing, it is found that the non-enzymatic glucose detection system based on NiCo2O4@rGO has good practical application potential in the field of glucose detection.

One-pot, rapid microwave-assisted synthesis of bimetallic metal–organic framework for efficient enzyme-free glucose detection

Hybrid transition metal-based compounds show excellent performance in the field of enzyme-free glucose sensing. Herein, a one-step, green, facile, highly efficient microwave-assisted strategy for fabricating bimetallic Co/Zn metal–organic frameworks (denoted as ZIF67/ZIF8) is proposed. The structural characterization and phase investigation of ZIF67/ZIF8 are assessed by microscopically studies, elemental mapping, X-ray diffraction and X-ray photoelectron spectroscopy. The proportion of Co and Zn elements of ZIF67/ZIF8 has been elaborately regulated, resulting in enhanced electro-oxidation performance toward glucose compared to mono-metal organic frameworks. The synergy effect between Co and Zn proves to be crucial for optimizing electroanalytical ability, which endows outstanding glucose sensing performance, including high sensitivity of 833.61 μA/mM/cm2, wide linear range up to 5 mM and low detection limit to be 6.5 μM. Furthermore, to demonstrate the practical application capability of ZIF67/ZIF8, real-time analysis in human serum sample is conducted, which confirms its good anti-interference ability and recovery rate. With the advantages of low cost, ease of production and high environment tolerance, this work provides a versatile method to obtain non-noble metal based biosensing materials for non-enzymatic glucose detection.

Sensitive Electrochemical Non-Enzymatic Detection of Glucose Based on Wireless Data Transmission.

Miniaturization and wireless continuous glucose monitoring are key factors for the successful management of diabetes. Electrochemical sensors are very versatile and can be easily miniaturized for wireless glucose monitoring. The authors report a microneedle-based enzyme-free electrochemical wireless sensor for painless and continuous glucose monitoring. The microneedles (MNs) fabricated consist of a 3 × 5 sharp and stainless-steel electrode array configuration. Each MN in the 3 × 5 array has 575 µm × 150 µm in height and width, respectively. A glucose-catalyzing layer, porous platinum black, was electrochemically deposited on the tips of the MNs by applying a fixed cathodic current of 2.5 mA cm−2 for a period of 200 s. For the non-interference glucose sensing, the platinum (Pt)-black-coated MN was carefully packaged into a biocompatible ionomer, nafion. The surface morphologies of the bare and modified MNs were studied using field-emission scanning electron microscopy (FESEM) and energy-dispersive X-ray analysis (EDX). The wireless glucose sensor displayed a broad linear range of glucose (1→30 mM), a good sensitivity and higher detection limit of 145.33 μA mM−1 cm−2 and 480 μM, respectively, with bare AuMN as a counter electrode. However, the wireless device showed an improved sensitivity and enhanced detection limit of 445.75, 165.83 μA mM−1 cm−2 and 268 μM, respectively, with the Pt-black-modified MN as a counter electrode. The sensor also exhibited a very good response time (2 s) and a limited interference effect on the detection of glucose in the presence of other electroactive oxidizing species, indicating a very fast and interference-free chronoamperometric response.

Synthesis of CoNi2S4 Nanoflake-modified Nickel Wire Electrode for Sensitive Non-enzymatic Detection of Glucose

In this study, CoNi2S4 nanoflake-modified nickel wire sensor for detecting glucose was successfully prepared by hydrothermal method and room temperature vulcanization. Due to the special morphology with large specific surface area and the synergistic effect between Ni and Co, the active material had good electrochemical performance as a biosensor. The results showed that the CoNi2S4 nanoflake-modified nickel wire electrode exhibited good performance in the measurement of glucose amperes. Two linear response ranges (0.001∼3 mM and 3∼8 mM) were exhibited when glucose was tested using the prepared electrode, and the corresponding sensitivity was 2473 μA mM−1 cm−2 and 1794 μA mM−1 cm−2, respectively. The detection limit was 0.3 μM with a signal-to-noise ratio of 3. These results indicate that the CoNi2S4 nanoflake-modified nickel wire electrode has broad application prospects in the development of non-enzymatic glucose sensors.

Thioflavin-modified molecularly imprinted hydrogel for fluorescent-based non-enzymatic glucose detection in wound exudate.

The concentration of glucose in the body's fluids is an important parameter that can indicate pathological conditions such as the progress of infected wounds. Several wearables and implantable detection approaches have been developed with high selectivity and sensitivity for glucose. However, all of them have drawbacks such as low stability, limited selectivity, and often require complex technology. In this work, we present a fluorescent-based cost-efficient imprinted hydrogel (MIH_GSH) capable of detecting glucose within 30 ​min. The imprinting approach allows us to improve the selectivity for glucose, overcoming the low specificity and limited binding efficiency at neutral pH of boronic acid-based detection mechanisms. The binding affinity determined for glucose-MIH_GSH was indeed 6-fold higher than the one determined for the non-imprinted hydrogel with a calculated imprinting factor of 1.7. The limit of detection of MIH_GSH for glucose in artificial wound exudate was calculated as 0.48 ​mM at pH 7.4 proving the suitability of the proposed approach to diagnose chronic wounds (ca. 1 ​mM). MIH_GSH was compared with a commercial colorimetric assay for the quantification of glucose in wound exudate specimens collected from hospitalized patients. The results obtained with the two methods were statistically similar confirming the robustness of our approach. Importantly, whereas with the colorimetric assay sample preparation was required to limit the interference of the sample background, the fluorescent signal of MIH_GSH was not affected even when used to measure glucose directly in bloody samples. The sensing mechanism here proposed can pave the way for the development of cost-efficient and wearable point-of-care tools capable of monitoring the glucose level in wound exudate enabling the quick assessment of chronic injuries.