High Glucose Sensitivity Research Articles

High-sensitive glucose sensor based on tilted fiber Bragg gratings

In this paper, we proposed a high-sensitive glucose sensor using the tilted fiber Bragg gratings (TFBGs). The TFBGs with different tilt angle has been fabricated by phase mask scanning method with an argon ion double-frequency 244 nm laser. As tilt angle increases, the bandwidth of the cladding mode excited by TFBGs gradually expands and cladding mode region shifts towards shorter wavelengths. The higher-order cladding modes appeared at the shorter wavelength side demonstrate a larger separation in the spectrum. TFBGs with different tilt angles for glucose concentration measurement have been investigated experimentally. When the concentration of glucose solution increases, the surrounding refractive index changing make the cut-off mode resonance shift to a longer wavelength. In addition, the tilt angle of TFBGs does affect the glucose sensitivity, that the larger tilt angle is, the higher sensitivity could achieve. In this work, a maximum glucose sensitivity of 80.91 pm/(mg/ml) could be obtained for TFBGs with tilt angle of 10°. The proposed TFBGs with superiorities of high glucose sensitivity and wider detection range, makes it potential for glucose detection in the field of chemical and biomedical sensing.

Transient paper-based electrochemical biosensor Fabricated by superadditive Cu-TCPP(Fe)/Mxene for Multipathway non-invasive, highly sensitive detection of Bodily metabolites

Current advances in non-invasive fluid diagnostics highlight unique benefits for monitoring metabolic diseases. However, the low concentrations and complex compositions of biomarkers in fluids such as sweat, urine, and saliva impose stringent demands on the sensitivity and stability of detection technologies. Here, we developed a high-sensitivity, low-cost instantaneous electrochemical sensor based on the superadditive effect mechanism of Cu-TCPP(Fe)/Mxene (MMs Paper-ECL Sensor), which has been successfully applied for the simultaneous real-time detection of glucose and uric acid. Strong interfacial interactions between Mxene and Cu-TCPP(Fe) were revealed through precise simulation calculations and multi-dimensional characterization analysis, significantly enhancing the sensor's electrocatalytic performance and reaction kinetics. Experimentally, this exceptional electrocatalytic activity was demonstrated in its unprecedented high sensitivity and wide linear detection range for glucose and uric acid, with a non-invasive linear range from 0.001 nM to 5 mM, 0.025 nM–5 mM, detection limits as low as 1.88 aM and 5.80 pM, and stability extending up to 100 days. This represents not only a breakthrough in sensitivity and stability but also provides an effective, low-cost solution that overcomes the limitations of existing electronic devices, enabling multi-channel simultaneous detection. The universality of this sensor holds vast potential for application in the field of non-invasive fluid diagnostics.

Long-term restraint stress as a predictor of insulin resistance development in experimental rats

The aim of the work was to define the pattern of changes and pathogenetic mechanisms of glycemic curve shape during a glucose tolerance test in rats at 6, 15, and 21 weeks of environmental space restriction. Materials and methods. A total of 55 male Wistar rats aged 6–10 months were used and divided into 4 groups (1 – intact control, 10 rats; 2, 3 and 4 of 15 rats each, which were in conditions of restricted environmental space for 6, 15 and 21 weeks, respectively). Fasting plasma levels of glucose (test strips Test Strip II on a Glucocard glucometer (ARKRAY Inc., Japan)), insulin and corticosterone (by an immunoenzymatic method using commercial kits for rats from Monobind, USA) were measured, glucose tolerance tests (GTT) were performed, the HOMA index and the insulin/corticosterone ratio were calculated. Results. The 6-week environmental space restriction, immobility and complex communication relations resulted in a hypoinsulinemic-hypoglycemic type of the glycemic curve with high tissue glucose sensitivity in animals which were in the conditions described (the HOMA index was significantly decreased to 0.21 versus 0.55 in the control), the characteristic delayed hyperglycemic peak at the 30th min of the test slowly returned to the euglycemic level by only the 90th min against the 30th min in the controls. The 15-week restriction caused a hypoinsulinemic curve with preserved tissue glucose sensitivity (the HOMA index 0.33 versus 0.55 in the controls). Alterations in postprandial glucose absorption were manifested by the highest glucose concentration at the 15th min of the test, a very slow decrease in the glucose level in the post-absorption period not being restored to baseline values by the 90th min. The 21-week restriction shaped a diabetic type of the glycemic curve, impaired tissue glucose sensitivity (a substantial and significant increase in the calculated HOMA index from 0.55 in the controls to 0.95) and resulted in the development of insulin resistance. Conclusions. The environmental space restriction, immobility and complex communication relations gradually induce a range of disorders in animals and change the glycemic response shape to glucose load, impair prandial insulin secretion, augment hyperglycemic effects of counterinsular hormones (corticosterone), and realize dysfunctional manifestations of prandial/postprandial glycemia. 6 weeks of restrictions and challenges shape the hypoinsulinemic-hypoglycemic type of the glycemic curve with high tissue glucose sensitivity, while 15 weeks result in the hypoinsulinemic curve with preserved tissue glucose sensitivity. 21 weeks show the diabetic type of the glycemic curve with impaired tissue glucose sensitivity and the development of insulin resistance.

Analysing the bifunctional ability of CuO/BiOBr/rGO as an electrode for non-enzymatic glucose sensor and supercapacitor

Diabetes is a serious medical disease that involves regular blood glucose monitoring. There is a huge demand for cost-effective glucose sensors that can rapidly and accurately measure blood glucose levels. To meet this demand, nonenzymatic electrochemical glucose sensors have been developed for clinical research and are of significant interest. A CuO/rGO/BiOBr (CRB) composite was synthesized via a facile hydrothermal method. Electrochemical studies were conducted on the as-prepared composite to evaluate its suitability for sensing and energy storage applications. In this study, the sensing ability of the composites was examined at various molar concentrations of glucose. Thus, the synthesized composite exhibited a high sensitivity and excellent selectivity for glucose sensing. In addition, the CV, GCD and EIS findings indicate that the electrode is a suitable candidate for supercapacitor application. The synergetic effect of the materials makes the composite well-suited for dual applications.

Flexible Nanoarchitectonics for Biosensing and Physiological Monitoring Applications (Small 9/2023)

Flexible Mesoporous Electronics In article number 2204946, Hoang-Phuong Phan, Yusuke Yamauchi, Tuan-Khoa Nguyen, Mostafa Kamal Masud, and co-workers develop flexible mesoporous architectures using selective electrochemical deposition. Soft metallic nanopores formed on thin polyimide films offer excellent mechanical bendability, high sensitivity for glucose sensing, and low impedance that facilitates detection of neural activities. These features suggest the promise of soft mesoporous material systems for biomedical applications.

Electroactive bacteria as whole-cell biosensor for sensitive detection of hydrogen peroxide

Hydrogen peroxide (H2O2) is a widely used strong oxidizer and has harmful effects on human health with excessive exposure. Herein, we proposed a simple and effective method for H2O2 detection by utilizing electroactive bacteria (EAB) as a whole-cell biosensor. The proposed method was achieved by utilizing the multiheme c-type cytochromes (central components of microbial extracellular electron transfer) of model EAB Shewanella oneidensis MR-1 to catalyze the oxidation of tetramethylbenzidine in the presence of H2O2. Owing to the excellent peroxidase-like activity of the multiheme c-cyts, this H2O2 detection method has a wide dynamic range between 0.1 and 1000 μM and a low detection limit of 0.17 μM. The proposed method, when coupled with glucose oxidase, displayed a high sensitivity (0.57 μM) and broad linear range (1 μM - 10 mM) for glucose. Moreover, this method has high specificity and good recovery for detecting H2O2-spiked real samples. Overall, this study has developed a novel biosensing platform that provides an alternative approach to H2O2 detection.

Acid-treated carbon nanotubes/polypyrrole/fluorine-doped tin oxide electrodes with high sensitivity for saliva glucose sensing

To alleviate the discomfort caused by the blood sampling process, a noninvasive saliva glucose sensor is investigated in this study. Owing to the low glucose concentration in the body fluid, the fabricated sensor is requested to possess high sensitivity. Herein, a chemical polymerization method is used to deposit polypyrrole (PPy) on a fluorine-doped tin oxide (FTO) conductive glass substrate followed by modification with acid treated carbon nanotubes (acid-CNTs) via the drop-casting method in order to fabricate acid-CNTs/PPy/FTO electrodes. In addition, the sensing device uses glucose oxidase as an enzyme to catalyze the redox reaction and improve the electrode selectivity. The electron transfer resistance decreases with layer-by-layer CNTs modification, and the acid-treatment time of CNTs significantly affects the sensing performance. The acid-CNTs/PPy/FTO electrodes exhibit excellent sensing performance with a high sensitivity of 95.26 μA/mMcm2 and a broad linear range of 10–700 μM with a R2 of 0.9958. Moreover, the acid-CNTs/PPy/FTO electrodes show high selectivity to glucose along with excellent stability. Furthermore, the sensing capability of the acid-CNTs/PPy/FTO electrode is tested using artificial saliva, that further confirms high potential of acid-CNTs/PPy/FTO electrodes in the noninvasive diagnosis of diabetes.

High Blood Glucose and Excess Body fat Enhance Pain Sensitivity and Weaken Pain Inhibition in Healthy Adults: A Single-blind Cross-over Randomized Controlled Trial

To investigate links between blood glucose, body fat mass and pain, the effects of acute hyperglycaemia on pain sensitivity and pain inhibition were examined in healthy adults with normal (n = 24) or excess body fat (n = 20) determined by dual-energy X-ray absorptiometry. Effects of hyperglycaemia on heart rate variability and reactive hyperaemia were also explored. For the overall sample, ingesting 75-g glucose enhanced pain sensitivity during 1-minute cold-water immersion of both feet (conditioning stimulus) and weakened the pain inhibitory effect of cold water on pressure pain thresholds (test stimulus). Exploratory subgroup analyses not adjusted for multiple comparisons suggested that this effect was limited to people with excess fat mass. In addition, acute hyperglycaemia suppressed resting heart rate variability only in people with excess fat mass. Furthermore, regardless of blood glucose levels, people with excess fat mass had weaker pain inhibition for pinprick after cold water and reported more pain during 5-minutes of static blood flow occlusion. Neither high blood glucose nor excess body fat affected pinprick-temporal summation of pain or reactive hyperaemia. Together, these findings suggest that hyperglycaemia and excess fat mass interfere with pain processing and autonomic function. PerspectiveIngesting 75-g glucose (equivalent to approximately 2 standard cans of soft drink) interfered with pain-processing and autonomic function, particularly in people with excess body fat mass. As both hyperglycaemia and overweight are risk factors for diabetes, whether these are sources of pain in people with diabetes should be further explored.

A High-Performance Non-Enzymatic Sensor Based on Nickel Foam Decorated with Co-CdIn2O4 Nanoparticles for Electrochemical Detection of Glucose and Its Application in Human Serum

Glucose concentration is an essential evaluation index for many diseases, so it is highly essential to develop a reliable sensor for quantitative glucose measurement. In this paper, based on the high conductivity of CdIn2O4, fast electron transfer rate and excellent electrocatalytic activity of transition metal Co, Co-CdIn2O4 is directly in situ grown on nickel foam conductive substrate, which has sizeable active surface area and three-dimensional interconnected properties by a simple non-aqueous sol-gel method. A series of electrochemical experiments proved that Co-CdIn2O4 material has better electrocatalytic activity than CdIn2O4. According to the detection results, it can be seen that Co-CdIn2O4/NF electrochemical sensor has high detection sensitivity for glucose, which is 13857 μA·mM−1·cm−2, a rapid response time of 1.56 s. The wide linear range of glucose is from 1–1 × 103 μM, and a low detection limit of 0.08 μM. At the same time, the prepared sensor also showed good selectivity and long-term stability. The recovery rates of glucose quantitative test in human serum samples are between 101.4% and 103.3%. All the above results demonstrate that the Co-CdIn2O4/NF sensor has promising usages in the direction of non-enzymatic glucose sensing.

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.

A self-healing carboxymethyl chitosan/oxidized carboxymethyl cellulose hydrogel with fluorescent bioprobes for glucose detection

Self-healing hydrogel as a soft material with high durability and life-time has been successfully applied in various fields, including electronic skins, wearable electronic devices, and soft sensors. However, it is still a challenge to design a hydrogel with rapid self-healing, biodegradable and biosensing properties. Here, a self-healing carboxymethyl chitosan (CMCS)/oxidized carboxymethyl cellulose (OCMC) hydrogel with fluorescent bioprobes was developed for glucose detection. In this biosensing system, gold nanoclusters (AuNCs) and glucose oxidase (GOx) were encapsulated into the CMCS/OCMC hydrogel matrix as the fluorescent bioprobes. The CMCS/OCMC hydrogel with fluorescent bioprobes exhibited high sensitivity for glucose sensing with a linearly detection range of 100 μM to 5 mM and a detection limit of 0.029 mM, which covered the level of glucose in clinical detection. Furthermore, this hydrogel exhibited good biocompatibility. Finally, In vitro blood fluorescence tests and in vivo fluorescence investigation of the AuNCs-CMCS/OCMC hydrogel in diabetic mice indicated that this biocompatible and self-healing hydrogel based on fluorescent sensing system had potential application in implantable biosensing area for glucose monitoring.

Cu2O nanowires with exposed {111} facet for nonenzymatic detection of glucose in complex biological fluids

Accurate glucose sensing in complex biological fluids could enable diagnostics for home healthcare. However, glucose oxidase (GOx) has been suffered from poor reproducibility and chemical instability due to intrinsic nature of enzymes. Here, we report a free-standing and robust reduced graphene oxide wrapped Cu foam (rGO/CuF)-supported Cu2O nanowires (Cu2O NWs) with exposed {111} facet via facile electrodeposition route. When being used as an electrode for nonenzymic glucose detection, Cu2O NWs@rGO/CuF exhibited the distinguished performances with powerful reliability for analyzing human plasma and even whole blood samples. These unprecedented performances could be ascribed to nanoscale hydrophilic structure of Cu2O NWs, which could control the fouling level especially for protein. Moreover, taking into account the Cu2O NWs with exposed {111} facet, Cu2O NWs {111} could reduce ion diffusion distance and couple with improved electronic conductivity, thus leading to high glucose sensitivity. Through the theoretical calculations, a reliable interpretation of the catalytic mechanism with Cu2O NWs {111} has been provided. This study deepens the understanding of hydrophilic nanostructure and facet-dependent activity of Cu2O NWs and points out a strategy to improve their sensitivity and stability.

Silk fibroin hydrogel encapsulated graphene filed-effect transistors as enzyme-based biosensors

Graphene field-effect transistor (GFET) is a useful device which could be designed as an ultrasensitive and high-throughput biosensor in biological sensing. However, bioprobes like enzymes are easy to lose activity after immobilizing on the graphene. In addition, measurement of biomarkers in aqueous solutions with high ionic concentration and multiple interfering components is still a challenge. Here, the enzymatic cross-linked silk fibroin (SF) hydrogel is selected as a carrier for glucose oxidase and horseradish peroxidase to encapsulate GFET biosensor functionally, in order to detect glucose in a physiological buffer solution. The SF hydrogel showed the effects of prolonging the lifetime of these enzymes and enabled the reduction of nonspecific adsorption of the GFET. The SF hydrogel encapsulated GFET exhibited high sensitivity for glucose sensing with a wide detection range of 1 µM to 10 mM and a limit of detection (LOD) down 200 nM, as well as a high specificity over other carbohydrates such as sucrose and trehalose. Moreover, the biosensor has exhibited renewability, which maintained a consistent sensing response after 10 times of regenerative cycles, with a variation less than 4.9%. These results demonstrate that the strategy for encapsulating GFET using the SF hydrogel is valid, suggesting the potential application of the SF hydrogel in biosensors.

Multifunctional Nanostructured Metal Selenides for Non-Enzymatic Electrochemical Sensors: Dopamine and Glucose Detection

Glucose and dopamine (DA) play essential physiological functions associated with disorders such as diabetes mellitus, Parkinson's disease and schizophrenia. For both analytical applications and diagnostic testing, accurate glucose and DA determination is essential. In this current work, efforts have been made to develop non-enzymatic direct electrochemical sensors for DA and glucose based on transition metal chalcogenides as electrocatalysts . The bifunctional sensors capable of detecting glucose and DA levels simultaneously is highly desirable because diabetes often changes dopaminergic function and alters dopamine-regulated activity. Among all the niche applications and properties of transition metal chalcogenides, recently these materials have gained attention due to their favorable electrochemical properties owing to tunable redox behavior of the transition metal center. Recently we have identified several binary metal selenides and tellurides compositions grown on different flexible substrates through electrodeposition, hydrothermal synthesis as well as by chemical vapor deposition which exhibits exceptional activity for DA detection and electrocatalytic glucose oxidation at low applied potential. Typically, copper selenide nanostructures were synthesized which could detect glucose and dopamine with high selectivity at different applied potentials. These sensors also showed enhanced sensing parameters including low limit of detection and high sensitivity (0.068 µM and 26 µA µM-1 cm-2 respectively, for copper selenide catalyst) for glucose and dopamine, respectively. The electrochemical studies shows long-term stability as well as sensitivity with a detection region from 5 nm to 2 μM of dopamine, rapid response time along with excellent reproducibility. Furthermore, for practical application, human blood serum was also tested for accurate detection of DA and glucose level. The results suggested that such nanostructured metal chalcogenides-based sensor may be a potential candidate for designing continuous monitoring devices for detection of DA and glucose in physiological environments with blood and other tissue fluids. In this talk we will present detailed study of transition metal chalcogenides as electrocatalysts for dopamine sensing and direct glucose oxidation along with an understanding of their structure-property relationship.

Copper selenide as multifunctional non-enzymatic glucose and dopamine sensor

Cu2Se, synthesized through one-pot hydrothermal synthesis, was identified as highly efficient bifunctional sensor for co-detection of glucose and dopamine with high selectivity. As-synthesized copper selenide could electro-oxidize glucose and dopamine at different applied potentials. Glucose oxidation was observed at 0.35 V while dopamine oxidized at 0.2 V. This copper selenide-based non-enzymatic sensor showed high sensitivity for both glucose (15.341 mA mM−1 cm−2) and dopamine (12.43 μA μM−1 cm−2) with low limit of detection (0.26 μM and 84 nM). Such high sensitivity and low LOD makes this sensor attractive for possible detection of glucose/dopamine in physiological body fluids which have low concentration of these biomolecules. Extremely low applied potential for detection also makes it ideal for integrating into wearable continuous monitoring devices with low operational power requirement. This sensor showed high reproducibility, reusability and long-term operational stability along with high degree of selectivity for dopamine and glucose sensing in presence of other interferents.

Yeasts Isolated from Traditional Brem Bali Show Stress Tolerance Phenotype against Fermentation-Related Stresses

The search for microbes, primarily yeasts with unique characters such as the tolerance against fermentation-related-stresses, is gaining significant interest nowadays. Traditionally made alcoholic beverages can be used as sources for such yeasts, given that during fermentation and storage, microbes may develop stress tolerance responses leading to naturally stress-tolerant yeast strains. In this study, we used an alcoholic beverage, that is, Brem Bali, as the source of potential yeast isolates. We isolated nine yeast isolates from two traditional Brem Bali products. All isolates showed tolerance against high glucose stress (40–50%) and sensitivity against high-temperature stress (37–50 °C). Notably, isolate BT5 showed tolerance phenotype against ethanol stress (up to 12.5%). Notably, the ethanol stress tolerance phenotype shown by isolate BT5 was unlikely correlated to the ability of the isolates in combating other stresses. Based on the internal transcribed spacer sequence, isolates BT2, BT5, and BT6 shared high similarity with Wickerhamomyces anomalus (98%). Further approaches may be needed to clarify the identity of these isolates. Based on our study, isolate BT5 bears potential as a fermentation agent based on its ability to combat high glucose and ethanol stresses.

A hierarchical hollow Ni/Co-functionalized MoS2 architecture with highly sensitive non-enzymatic glucose sensing activity.

A hierarchical hollow Ni/Co-codoped MoS2 architecture was successfully prepared using a Ni/Co Prussian Blue analogue as the precursor followed by the solvothermal-assisted insertion of MoS42- and extraction of [Co(CN)6]3- at 200 °C for 32 h. The obtained Ni/Co-codoped MoS2 composite exhibited a hollow microcubic structural characteristic, and the morphology, structure, and chemical compositions were carefully characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS), respectively. The Ni/Co-codoped MoS2 composite used as an electrode material featured excellent glucose sensing activity and a high sensitivity of 2546 μA mM-1 cm-2 with a relatively low detection limit of 0.69 μM (S/N = 3). In addition, the Ni/Co-codoped MoS2 composite showed good anti-interference sensing performance in the presence of ascorbic acid (AA), lysine (Lys), cysteine (Cys), urea, H2O2, KCl, and other interferents. These experimental results revealed that the composite is a promising electrode material for enzyme-free glucose sensing, and the feasible synthetic strategy may provide an effective and controlled route to prepare other multi-metal substituted sulfide-based hierarchical structures with high electrochemical sensing performance.

Nanosized CuO encapsulated Ni/Co bimetal Prussian blue with high anti-interference and stability for electrochemical non-enzymatic glucose detection.

Non-enzymatic glucose sensors based on metal oxides are receiving remarkable attention owing to their outstanding characteristics of being easy-to use, low cost, and reusability. However, the disadvantage of weak anti-interference associated with poor selectivity significantly restricts their applicability. Herein, we report a two-step in situ fabrication of nanosized CuO encapsulated Ni/Co bimetal Prussian blue (PB) with a typical core-shell structure, which can be efficiently used for non-enzymatic glucose detection, ascribing to the permeability and abundant active sites of out-shelled crystalline porous Ni/Co PB and the high catalytic activity and conductivity of embedded CuO nanoparticles, afforded by their mutual synergistic interactions. The glassy carbon electrode modified with the hybrid of the CuO-encapsulated Ni/Co PB (simplified as the Ni/Co-PB/CuO/GCE electrode) exhibited a high glucose sensitivity of 600 μA mM-1 cm-2 with a low detection limit of 0.69 μM (S/N = 3), a fast response time (less than 3 s), and excellent long-term stability. In addition, the CuO-encapsulated Ni/Co PB showed favorable anti-interference ability in the presence of ascorbic acid (AA), L-lysine (Lys), dopamine (DA), cysteine (Cys), dopamine (DA), and KCl interferences. The reusability and long-term stability, as well as the practicability of the Ni/Co-PB/CuO/GCE sensing electrode verified by testing real serum samples were also investigated, and the experimental results demonstrated the applicability of the core-shell NiCo-PB/CuO based flexible electrochemical sensor for non-enzymatic glucose sensing in practical applications.

Multi-functional NiO/g-C3N4 hybrid nanostructures for energy storage and sensor applications

A multi-functional NiO/g-C3N4 (NC) hybrid nanostructure was synthesized by a hydrothermal process using melamine and Ni(OH)2 as precursors followed by thermal treatment. The optimal conditions were determined by studying the process conditions, such as the Ni(OH)2 to melamine ratio and thermal treatment temperature. The NC prepared in this study exhibited both excellent glucose sensing properties and supercapacitor properties. A very high glucose sensitivity, as high as 5,387.1 µA mM−1cm−2, and excellent energy density of 49.6 Wh kg−1 at a power density of 1,064.2 W kg−1 were obtained when NC was used as the electrode material for glucose sensing and symmetric supercapacitor, respectively. A flexible glucose sensing device using a flexible substrate and self-powered glucose sensor system that used the same material (NC) for the both power supply and sensing devices were also demonstrated.

The development of an antifouling interpenetrating polymer network hydrogel film for salivary glucose monitoring.

Owing to its rapid response and broad detection range, a phenylboronic acid (PBA)-functionalized hydrogel film-coated quartz crystal microbalance (QCM) sensor is used to non-invasively monitor salivary glucose in diabetic patients. However, nonspecific protein adsorption on the PBA-functionalized hydrogel film can cause dramatic loss of sensitivity and accuracy of the sensor. A traditional zwitterionic polymer surface with ultra-low protein fouling can hinder the interaction of PBA in the hydrogel matrix with glucose molecules owing to its steric hindrance, resulting in poor glucose sensitivity of the sensor. Herein, we developed a novel hydrogel film that enhanced the antifouling properties and sensitivity of the QCM sensor by infiltrating a glucose-sensitive monomer (i.e., PBA) into a zwitterionic polymer brush matrix to form an interpenetrating polymer network (IPN). The IPN hydrogel film could minimize the glucose sensitivity loss since the antifouling polymer distributed in its matrix. Moreover, a stable hydration layer was formed in this film that could prevent water from transporting out of the matrix, thus further improving its antifouling properties and glucose sensitivity. The experimental results confirmed that the IPN hydrogel film possessed excellent resistance to protein fouling by mucin from whole saliva with reductions in adsorption of nearly 88% and could also enhance the glucose sensitivity by nearly 2 fold, compared to the PBA-functionalized hydrogel film. Therefore, the IPN hydrogel film provides improved antifouling properties and sensitivity of the QCM sensor, which paves the way for non-invasive monitoring of low concentrations of glucose in saliva.