Neuronal glucose sensing mechanisms and circuits in the control of insulin and glucagon secretion

Glucose homeostasis is mainly under the control of the pancreatic islet hormones insulin and glucagon, which, respectively, stimulate glucose uptake and utilization by liver, fat, and muscle or glucose production by the liver. The balance between the secretion of these hormones is under the control of blood glucose concentrations. Indeed, pancreatic islet b-cells and a-cells can sense variations in glycemia and respond by an appropriate secretory response to restore euglycemia. However, the secretory activity of these cells is also under multiple additional metabolic, hormonal, and neuronal signals that combine to ensure the perfect control of glycemia over a lifetime. The central nervous system (CNS), which has an almost absolute requirement for glucose as a source of metabolic energy and, thus, a vital interest in ensuring that glycemic levels never fall below ~5mM, is equipped with populations of neurons responsive to changes in glucose concentrations. These neurons control pancreatic islet cells secretion activity in multiple ways: through both branches of the autonomic nervous system, through the hypothalamic-pituitary-adrenal axis, and by secreting vasopressin (AVP) in the blood at the level of the posterior pituitary. Here, we will present the autonomic innervation of the pancreatic islets; the mechanisms of neurons activation by a rise or a fall in glucose concentration; how current viral tracing, chemogenetic, and optogenetic techniques allow to integrate specific glucose sensing neurons in defined neuronal circuits that control endocrine pancreas function. Finally, how genetic screens in mice can untangle the diversity of the hypothalamic mechanisms controlling the response to hypoglycemia.

MOF-derived NiCo hydroxide for highly efficient non-enzymatic glucose biosensing

An efficient and robust electrocatalyst is significant for glucose biosensing. The emergence of metal-organic framework (MOF) derived materials opens up new avenues for the development of high-performance glucose sensing catalysts. Herein, MOF derived nickel-cobalt hydroxide supported on conductive copper sheet (NiCo-OH/Cu sheet) is prepared at room temperature. The as-obtained NiCo-OH is endowed with three-dimensional network structure which enables the effective exposure of active materials, sufficient contact between glucose molecule and catalyst. The NiCo-OH/Cu sheet is revealed as good glucose electrochemical sensing material with a wide linear range of 0.05∼6.0 mM and a high sensitivity of 1340μA mM-1cm-2. Additionally, the as-fabricated NiCo-OH/Cu sheet displays good anti-interference ability and long-term stability.

Dual-Probe SERS Nanosensor: A Promising Approach for Sensitive and Ratiometric Detection of Glucose in Clinical Settings

Diabetes is a major global health concern, with millions of annual deaths. Monitoring glucose levels is vital for clinical management, and urine samples offer a noninvasive alternative to blood samples. Optical techniques for urine glucose sensing have gained notable traction due to their cost-effectiveness and portability. Among these methods, surface-enhanced Raman spectroscopy (SERS) has attracted considerable attention thanks to its remarkable sensitivity and multiplexing capabilities. However, challenges remain in achieving reliable quantification through SERS. In this study, an alternative approach is proposed to enhance quantification involving the use of dual probes. Each probe is encoded with unique SERS signatures strategically positioned in the biologically silent region. One probe indicates the glucose presence, while the other acts as an internal reference for calibration. This setup enables ratiometric analysis of the SERS signal, directly correlating it with the glucose concentration. The fabrication of the sensor relies on the prefunctionalization of Fe sheets using an aryl diazonium salt bearing a -C≡CH group (internal reference), followed by the immobilization of Ag nanoparticles modified with an aryl diazonium salt bearing a -B(OH)2 group (for glucose capture). A secondary probe bearing a -B(OH)2 group on one side and a -C≡N group on the other side enables the ratiometric analysis by forming a sandwich-like structure in the presence of glucose (glucose indicator). Validation studies in aqueous solutions and artificial urine demonstrated the high spectral stability and the potential of this dual-probe nanosensor for sensitive glucose monitoring in clinical settings.

Glucose Oxidase Energized Osmium with Dual-Active Centers and Triple Enzyme Activities for Infected Diabetic Wound Management

Diabetic wounds are susceptible to bacterial infections, largely linked to high blood glucose levels (hyperglycemia). To treat such wounds, enzymes like glucose oxidase (GOx) can be combined with nanozymes (nanomaterials mimic enzymes) to use glucose effectively for purposes. However, there is still room for improvement in these systems, particularly in terms of process simplification, enzyme activity regulation, and treatment effects. Herein, the approach utilizes GOx to directly facilitate the biomineralized growth of osmium (Os) nanozyme (GOx-OsNCs), leading to dual-active centers and remarkable triple enzyme activities. Initially, GOx-OsNCs use vicinal dual-active centers, enabling a self-cascaded mechanism that significantly enhances glucose sensing performance compared to step-by-step reactions, surpassing the capabilities of other metal sources such as gold and platinum. In addition, GOx-OsNCs are integrated into a glucose-sensing gel, enabling instantaneous visual feedback. In the treatment of infected diabetic wounds, GOx-OsNCs exhibit multifaceted benefits by lowering blood glucose levels and exhibiting antibacterial properties through the generation of hydroxyl free radicals, thereby expediting healing by fostering a favorable microenvironment. Furthermore, the catalase-like activity of GOx-OsNCs aids in reducing oxidative stress, inflammation, and hypoxia, culminating in improved healing outcomes. Overall, this synergistic enzyme-nanozyme blend is user-friendly and holds considerable promise for diverse applications.

A Novel Biosensor for the Detection of Glucose Concentration Using the Dual-Peak Long Period Grating in the Near- to Mid-Infrared

In this article, we demonstrate an improved efficient fibre sensor with a high sensitivity to measure glucose concentrations in the physiological range of human beings, operating in a broad spectral bandwidth from the near- to mid-infrared. The sensor consists of a dual-peak long period grating (DPLPG) with a period of 150 μm inscribed in an optical fibre with a diameter of 80 μm. The investigation of sensing for refractive index results in a sensitivity of ~-885.7 nm/refractive index unit (RIU) and ~2008.6 nm/RIU in the range of 1.30-1.44. The glucose measurement is achieved by the immobilisation of a layer of enzyme of glucose oxidase (GOD) onto the fibre surface for the selective enhancement of sensitivity for glucose. The sensor can measure glucose concentrations with a maximum sensitivity of -36.25 nm/(mg/mL) in the range of 0.1-3.0 mg/mL. To the best of our knowledge, this is the highest sensitivity ever achieved for a measurement of glucose with a long period grating-based sensor, indicating its potential for many applications including pharmaceutical, biomedical and food industries.

Integrated electronic/fluidic microneedle system for glucose sensing and insulin delivery

Background: Precise and dynamic blood glucose regulation is paramount for both diagnosing and managing diabetes. Continuous glucose monitoring (CGM) coupled with insulin pumps forms an artificial pancreas, enabling closed-loop control of blood glucose levels. Indeed, this integration necessitates advanced micro-nano fabrication techniques to miniaturize and combine sensing and delivery modules on a single electrode. While microneedle technology can mitigate discomfort, concerns remain regarding infection risk and potential sensitivity limitations due to their short needle length. Methods: This study presents the development of an integrated electronic/fluidic microneedle patch (IEFMN) designed for both glucose sensing and insulin delivery. The use of minimally invasive microneedles mitigates nerve contact and reduces infection risks. The incorporation of wired enzymes addresses the issue of "oxygen deprivation" during glucose detection by decreasing the reliance on oxygen. The glucose-sensing electrodes employ wired enzyme functionalization to achieve lower operating voltages and enhanced resilience to sensor interference. The hollow microneedles' inner channel facilitates precise drug delivery for blood glucose regulation. Results: Our IEFMN-based system demonstrated high sensitivity, selectivity, and a wide response range in glucose detection at relatively low voltages. This effectively reduced interference from both external and internal active substances. The microneedle array ensured painless and minimally invasive skin penetration, while wired enzyme functionalization not only lowered sensing potential but also improved glucose detection accuracy. In vivo, experiments conducted in rats showed that the device could track subcutaneous glucose fluctuations in real-time and deliver insulin to regulate blood glucose levels. Conclusions: Our work suggests that the IEFMN-based system, developed for glucose sensing and insulin delivery, exhibits good performance during in vivo glucose detection and drug delivery. It holds the potential to contribute to real-time, intelligent, and controllable diabetes management.

Advancing Glucose Sensing Through Auto-Fluorescent Polymer Brushes: From Surface Design to Nano-Arrays

Designing smart (bio)interfaces with the capability to sense and react to changes in local environments offers intriguing possibilities for new surface-based sensing devices and technologies. Polymer brushes make ideal materials to design such adaptive and responsive interfaces given their large variety of functional and structural possibilities as well as their outstanding abilities to respond to physical, chemical, and biological stimuli. Herein, a practical sensory interface for glucose detection based on auto-fluorescent polymer brushes decorated with phenylboronic acid (PBA) receptors is presented. The glucose-responsive luminescent surfaces, which are capable of translating conformational transitions triggered by pH variations and binding events into fluorescent readouts without the need for fluorescent dyes, are grown from both nanopatterned and non-patterned substrates. Two-photon laser scanning confocal microscopy and atomic force microscopy (AFM) analyses reveal the relationship between the brush conformation and glucose concentration and confirm that the phenylboronic acid functionalized brushes can bind glucose over a range of physiologically relevant concentrations in a reversible manner. The combination of auto-fluorescent polymer brushes with synthetic receptors presents a promising avenue for designing innovative and robust sensing systems, which are essential for various biomedical applications, among other uses.

Unprecedented Multifunctionality in Novel Monophase Micro/Nanostructured Ti-Zn Alloy

It is always challenging to integrate multiple functions into one material system. However, those materials/devices will address society's critical global challenges and technological demands if achieved with innovative design strategies and engineering. Here, one such material with a broader spectrum of desired properties appropriate for seven applications is identified and explored, and a glucose-sensing-triggered energy-storage mechanism is demonstrated. To date, the Titanium (Ti)-Zinc (Zn) binary alloys are investigated only as mixed phases and for a maximum of three applications. In contrast, the novel single phase of structurally stable 50 Ti-50 Zn (Ti0.5 Zn0.5 ) is synthesized and proven suitable for seven emerging applications. Interestingly, it is thermally stable up to 750 °C and possesses excellent mechanical, tribological properties and corrosion resistance. While exceptional biocompatibility is evident even up to a concentration of 500 µg mL-1 , the antibacterial activity against E. coli is also seen. Further, rapid detection and superior selectivity for glucose, along with supercabattery behavior, unambiguously demonstrate that this novel monophase is a remarkable multifunctional material than the existing mixed-phase Ti-Zn compounds. The coin-cell supercapacitor shows outstanding stability up to 30 000 cycles with >100% retention capacity. This allows us to prototype a glucose-sensing-triggered energy-storage-device system for wearable point-of-care diagnostic applications.

The triggering pathway, the metabolic amplifying pathway, and cellular transduction in regulation of glucose-dependent biphasic insulin secretion

Introduction: Insulin secretion is a highly regulated process critical for maintaining glucose homeostasis. This abstract explores the intricate interplay between three essential pathways: The Triggering Pathway, The Metabolic Amplifying Pathway, and Cellular Transduction, in orchestrating glucose-dependent biphasic insulin secretion.Mechanism: During the triggering pathway, glucose metabolism in pancreatic beta-cells leads to ATP production, closing ATP-sensitive potassium channels and initiating insulin exocytosis. The metabolic amplifying pathway enhances insulin secretion via key metabolites like NADH and glutamate, enhancing calcium influx and insulin granule exocytosis. Additionally, the cellular transduction pathway involves G-protein coupled receptors and cyclic AMP, modulating insulin secretion.Result and Conclusion: These interconnected pathways ensure a dynamic insulin response to fluctuating glucose levels, with the initial rapid phase and the subsequent sustained phase. Understanding these pathways' complexities provides crucial insights into insulin dysregulation in diabetes and highlights potential therapeutic targets to restore glucose-dependent insulin secretion.

An extracellular glucose sensor for substrate-dependent secretion and display of cellulose-degrading enzymes

The efficient hydrolysis of lignocellulosic biomass into fermentable sugars is key for viable economic production of biofuels and biorenewable chemicals from second-generation feedstocks. Consolidated bioprocessing (CBP) combines lignocellulose saccharification and chemical production in a single step. To avoid wasting valuable resources during CBP, the selective secretion of enzymes (independent or attached to the surface) based on the carbon source available is advantageous. To enable enzyme expression and secretion based on extracellular glucose levels, we implemented a G-protein-coupled receptor (GPCR)-based extracellular glucose sensor; this allows the secretion and display of cellulases in the presence of the cellulosic fraction of lignocellulose by leveraging cellobiose-dependent signal amplification. We focused on the glucose-responsiveness of the HXT1 promoter and engineered PHXT1 by changing its core to that of the strong promoter PTHD3 , increasing extracellular enzyme activity by 81%. We then demonstrated glucose-mediated expression and cell-surface display of the β-glucosidase BglI on the surface of Saccharomyces cerevisiae. The display system was further optimized by re-directing fatty acid pools from lipid droplet synthesis toward formation of membrane precursors via knock-out of PAH1. This resulted in an up to 4.2-fold improvement with respect to the baseline strain. Finally, we observed cellobiose-dependent signal amplification of the system with an increase in enzymatic activity of up to 3.1-fold when cellobiose was added.

Ex Vivo Glucose Detection in Human Blood Serums with Carbon Quantum Dot-Doped Oleic Acid-Treated Chitosan Nanocomposites

Herein, carbon quantum dot (CQD)-doped oleic acid (OL)-treated chitosan (Ch) nanocomposites (Ch-OL/CQD) are prepared by a simple solution technique for nonenzymatic ex vivo detection of glucose in human blood samples. From the architecture of the structure, it is observed that the agglomeration of CQD is restricted by OL-treated Ch polymeric chain, and simultaneously the inhibition in the entanglement of Ch-OL polymeric chains in the matrix is attained by the incorporation of CQD, thereby proving the high stability of the nanocomposite. In vitro detection of glucose is studied by the "Turn ON-OFF" fluorescence technique which is again evidenced by the shining core image of nanocomposites in HRTEM. A highly selective glucose sensing against interfering sugars due to the specific spatial arrangement of the hydroxyl groups of glucose, leading to prominent hydrogen-bonding interaction is established, with a very low limit of detection (LOD) of 1.51 μM, covering a wide linear domain from 0 to 104 μM, R2 = 0.98. Moreover, the calculated glucose levels in real human blood serums by Ch-OL/CQD nanocomposites are compared with a commercial glucometer, with recovery percentages from 95.8 to 107.3%. The clinical potential is supported by studying the stimuli responsiveness of the nanocomposites as a function of pH and ionic strength, encouraging the operation of the sensor in a complex biological scenario. The present work may offer an opportunity for the monitoring of glucose in the blood for successful diabetes management.

Non-Invasive Glucose Sensing Technologies and Products: A Comprehensive Review for Researchers and Clinicians

Diabetes Mellitus incidence and its negative outcomes have dramatically increased worldwide and are expected to further increase in the future due to a combination of environmental and social factors. Several methods of measuring glucose concentration in various body compartments have been described in the literature over the years. Continuous advances in technology open the road to novel measuring methods and innovative measurement sites. The aim of this comprehensive review is to report all the methods and products for non-invasive glucose measurement described in the literature over the past five years that have been tested on both human subjects/samples and tissue models. A literature review was performed in the MDPI database, with 243 articles reviewed and 124 included in a narrative summary. Different comparisons of techniques focused on the mechanism of action, measurement site, and machine learning application, outlining the main advantages and disadvantages described/expected so far. This review represents a comprehensive guide for clinicians and industrial designers to sum the most recent results in non-invasive glucose sensing techniques' research and production to aid the progress in this promising field.

Review of Noninvasive Continuous Glucose Monitoring in Diabetics

For diabetics, taking regular blood glucose measurements is crucial. However, traditional blood glucose monitoring methods are invasive and unfriendly to diabetics. Recent studies have proposed a biofluid-based glucose sensing technique that creatively combines wearable devices with noninvasive glucose monitoring technology to enhance diabetes management. This is a revolutionary advance in the diagnosis and management of diabetes, reflects the thoughtful modernization of medicine, and promotes the development of digital medicine. This paper reviews the research progress of noninvasive continuous blood glucose monitoring (CGM), with a focus on the biological liquids that replace blood in monitoring systems, the technical principles of continuous noninvasive glucose detection, and the output and calibration of sensor signals. In addition, the existing limits of noninvasive CGM systems and prospects for the future are discussed. This work serves as a resource for further promoting the development of noninvasive CGM systems.

Diabetes Management by Fourth-Generation Glucose Sensors Based on Lemon-Extract-Supported CuO Nanoporous Materials

Diabetes is a major worldwide health issue, impacting millions of people around the globe and putting pressure on healthcare systems. Accurate detection of glucose is critical for efficient diabetes care, because it allows for prompt action to control blood sugar levels and avoid problems. Reliable glucose-sensing devices provide individuals with real-time information, allowing them to make more educated food, medicine, and lifestyle decisions. The progress of glucose sensing holds the key to increasing the quality of life for diabetics and lowering the burden of this prevalent condition. The present investigation addresses the synthesis of a CuO@lemon-extract nanoporous material using the sol-gel process. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to analyze the morphological properties of the composite, which revealed a homogeneous integration of CuO nanoparticles (NPs) on the surface of the matrix. The existence of primarily oxidized copper species, especially CuO, was confirmed by X-ray diffraction spectroscopy (XRD) investigation in combination with energy-dispersive X-ray (EDX) spectroscopy. The CuO@lemon-extract-modified glassy carbon electrode (CuO@lemon-extract GCE) performed well in non-enzymatic electrochemical sensing applications such as differential pulse voltammetry (DPV) and amperometric glucose detection. The electrode achieved a notable sensitivity of 3293 µA mM-1 cm-2 after careful adjustment, with a noticeable detection limit of 0.01 µM (signal-to-noise ratio of 3). The operational range of the electrode was 0.01 µM to 0.2 µM, with potential applied of 0.53 V vs. Ag/AgCl. These findings underscore the CuO@lemon-extract GCE's promise as a robust and reliable platform for electrochemical glucose sensing, promising advances in non-enzymatic glucose sensing (NEGS) techniques.

Obesity-associated microglial inflammatory activation paradoxically improves glucose tolerance

Hypothalamic gliosis associated with high-fat diet (HFD) feeding increases susceptibility to hyperphagia and weight gain. However, the body-weight-independent contribution of microglia to glucose regulation has not been determined. Here, we show that reducing microglial nuclear factor κB (NF-κB) signaling via cell-specific IKKβ deletion exacerbates HFD-induced glucose intolerance despite reducing body weight and adiposity. Conversely, two genetic approaches to increase microglial pro-inflammatory signaling (deletion of an NF-κB pathway inhibitor and chemogenetic activation through a modified Gq-coupled muscarinic receptor) improved glucose tolerance independently of diet in both lean and obese rodents. Microglial regulation of glucose homeostasis involves a tumor necrosis factor alpha (TNF-α)-dependent mechanism that increases activation of pro-opiomelanocortin (POMC) and other hypothalamic glucose-sensing neurons, ultimately leading to a marked amplification of first-phase insulin secretion via a parasympathetic pathway. Overall, these data indicate that microglia regulate glucose homeostasis in a body-weight-independent manner, an unexpected mechanism that limits the deterioration of glucose tolerance associated with obesity.

O-GlcNAcylation of Raptor transduces glucose signals to mTORC1

The mechanistic target of rapamycin complex 1 (mTORC1) regulates metabolism and cell growth in response to nutrient levels. Dysregulation of mTORC1 results in a broad spectrum of diseases. Glucose is the primary energy supply of cells, and therefore, glucose levels must be accurately conveyed to mTORC1 through highly responsive signaling mechanisms to control mTORC1 activity. Here, we report that glucose-induced mTORC1 activation is regulated by O-GlcNAcylation of Raptor, a core component of mTORC1, in HEK293T cells. Mechanistically, O-GlcNAcylation of Raptor at threonine 700 facilitates the interactions between Raptor and Rag GTPases and promotes the translocation of mTOR to the lysosomal surface, consequently activating mTORC1. In addition, we show that AMPK-mediated phosphorylation of Raptor suppresses Raptor O-GlcNAcylation and inhibits Raptor-Rags interactions. Our findings reveal an exquisitely controlled mechanism, which suggests how glucose coordinately regulates cellular anabolism and catabolism.

Tunable Non-Enzymatic Glucose Electrochemical Sensing Based on the Ni/Co Bimetallic MOFs

Constructing high-performance glucose sensors is of great significance for the prevention and diagnosis of diabetes, and the key is to develop new sensitive materials. In this paper, a series of Ni2Co1-L MOFs (L = H2BPDC: 4,4'-biphenyldicarboxylic acid; H2NDC: 2,6-naphthalenedicarboxylic acid; H2BDC: 1,4-benzenedicarboxylic acid) were synthesized by a room temperature stirring method. The effects of metal centers and ligands on the structure, compositions, electrochemical properties of the obtained Ni2Co1-L MOFs were characterized, indicating the successful preparation of layered MOFs with different sizes, stacking degrees, electrochemical active areas, numbers of exposed active sites, and glucose catalytic activity. Among them, Ni2Co1-BDC exhibits a relatively thin and homogeneous plate-like morphology, and the Ni2Co1-BDC modified glassy carbon electrode (Ni2Co1-BDC/GCE) has the highest electrochemical performance. Furthermore, the mechanism of the enhanced glucose oxidation signal was investigated. It was shown that glucose has a higher electron transfer capacity and a larger apparent catalytic rate constant on the Ni2Co1-BDC/GCE surface. Therefore, tunable non-enzymatic glucose electrochemical sensing was carried out by regulating the metal centers and ligands. As a result, a high-sensitivity enzyme-free glucose sensing platform was successfully constructed based on the Ni2Co1-BDC/GCE, which has a wide linear range of 0.5-2899.5 μM, a low detection limit of 0.29 μM (S/N = 3), and a high sensitivity of 3925.3 μA mM-1 cm-2. Much more importantly, it was also successfully applied to the determination of glucose in human serum with satisfactory results, demonstrating its potential for glucose detection in real samples.

Glucose-induced CRL4COP1-p53 axis amplifies glycometabolism to drive tumorigenesis

The diabetes-cancer association remains underexplained. Here, we describe a glucose-signaling axis that reinforces glucose uptake and glycolysis to consolidate the Warburg effect and overcome tumor suppression. Specifically, glucose-dependent CK2 O-GlcNAcylation impedes its phosphorylation of CSN2, a modification required for the deneddylase CSN to sequester Cullin RING ligase 4 (CRL4). Glucose, therefore, elicits CSN-CRL4 dissociation to assemble the CRL4^COP1 E3 ligase, which targets p53 to derepress glycolytic enzymes. A genetic or pharmacologic disruption of the O-GlcNAc-CK2-CSN2-CRL4^COP1 axis abrogates glucose-induced p53 degradation and cancer cell proliferation. Diet-induced overnutrition upregulates the CRL4^COP1-p53 axis to promote PyMT-induced mammary tumorigenesis in wild type but not in mammary-gland-specific p53 knockout mice. These effects of overnutrition are reversed by P28, an investigational peptide inhibitor of COP1-p53 interaction. Thus, glycometabolism self-amplifies via a glucose-induced post-translational modification cascade culminating in CRL4^COP1-mediated p53 degradation. Such mutation-independent p53 checkpoint bypass may represent the carcinogenic origin and targetable vulnerability of hyperglycemia-driven cancer.

Coacervate-Based Plexcitonic Assembly toward Peroxidase-like Activity and Ultrasensitive Glucose Sensing

Inbuilt catalytic centers anchored inside the confined architecture of artificial nanoreactors have gained tremendous attention owing to their vast applicability in various catalytic transformations. However, designing homogeneously distributed catalytic units with exposed surfaces in confined environment is a challenging task. Here, we have utilized quantum dot (QD)-embedded coacervate droplets (QD-Ds) as a confined compartment for the in situ synthesis of gold nanoparticles (Au NPs) without any additional reducing agent. High-resolution transmission electron microscopy images reveal homogeneous distribution of 5.6 ± 0.2 nm-sized Au NPs inside the QD-Ds (Au@QD-Ds). The in situ synthesized Au NPs are found to be stable over a period of 28 days without any agglomeration. Control experiments reveal that the free surface carboxylic acid groups of embedded QDs simultaneously act as reducing and stabilizing agents for Au NPs. Notably, these Au@QD-Ds exhibit superior peroxidase-like activity compared to bulk aqueous Au NPs and Au@QDs under similar experimental conditions. The observed peroxidase-like activity follows the classical Michaelis-Menten model inside the Au@QD-Ds via the fast electron-transfer pathway. The enhanced peroxidase-like activity has been explained by considering confinement, mass action, and the ligand-free surface of embedded Au NPs. The present plexcitonic nanocomposites exhibit excellent recyclability over several consecutive cycles without any compromise in their catalytic activity. Finally, a cascade reaction with glucose oxidase (GOx)-loaded Au@QD-Ds have been utilized for colorimetric detection of glucose with a limit of detection of 272 nM in solution as well as on filter paper. The present work highlights a facile and robust methodology for the fabrication of optically active functional hybrid plexcitonic assemblies and may find importance in various fields including bioanalytical chemistry and optoelectronics.

Two-Dimensional Transition Metal Dichalcogenide Tunnel Field-Effect Transistors for Biosensing Applications

Field-effect transistor (FET) biosensors based on two-dimensional (2D) materials have drawn significant attention due to their outstanding sensitivity. However, the Boltzmann distribution of electrons imposes a physical limit on the subthreshold swing (SS), and a 2D-material biosensor with sub-60 mV/dec SS has not been realized, which hinders further increase of the sensitivity of 2D-material FET biosensors. Here, we report tunnel FETs (TFETs) based on a SnSe₂/WSe₂ heterostructure and observe the tunneling effect of a 2D material in aqueous solution for the first time with an ultralow SS of 29 mV/dec. A bilayer dielectric (Al₂O₃/HfO₂) and graphene contacts, which significantly reduce the leakage current in solution and contact resistance, respectively, are crucial to the realization of the tunneling effect in solution. Then, we propose a novel biosensing method by using tunneling current as the sensing signal. The TFETs show an extremely high pH sensitivity of 895/pH due to ultralow SS, surpassing the sensitivity of FET biosensors based on a single 2D material (WSe₂) by 8-fold. Specific detection of glucose is realized, and the biosensors show a superb sensitivity (3158 A/A for 5 mM), wide sensing range (from 10^-9 to 10^-3 M), low detection limit (10^-9 M), and rapid response rate (11 s). The sensors also exhibit the ability of monitoring glucose in complex biofluid (sweat). This work provides a platform for ultrasensitive biosensing. The discovery of the tunneling effect of 2D materials in aqueous solution may stimulate further fundamental research and potential applications.

Engineer a double team of short-lived and glucose-sensing bacteria for cancer eradication

Rationally designed and engineered bacteria represent an emerging unique approach for cancer treatment. Here, we engineer a short-lived bacterium, mp105, that is effective against diverse cancer types and safe for intravenous administration. We reveal that mp105 combats cancer by direct oncolysis, depletion of tumor-associated macrophages, and elicitation of CD4⁺ T cell immunity. We further engineer a glucose-sensing bacterium named m6001 that selectively colonizes solid tumors. When intratumorally injected, m6001 clears tumors more efficiently than mp105 due to its post-delivery replication in tumors and potent oncolytic capacity. Finally, we combine intravenous injection of mp105 and intratumoral injection of m6001, forming a double team against cancer. The double team enhances cancer therapy compared with single treatment for subjects carrying both intratumorally injectable and uninjectable tumors. The two anticancer bacteria and their combination are applicable to different scenarios, turning bacterial therapy for cancer into a feasible solution.

Research Progress on Biomimetic Nanomaterials for Electrochemical Glucose Sensors

Diabetes has become a chronic disease that necessitates timely and accurate detection. Among various detection methods, electrochemical glucose sensors have attracted much attention because of low cost, real-time detection, and simple and easy operation. Nonenzymatic biomimetic nanomaterials are the vital part in electrochemical glucose sensors. This review article summarizes the methods to enhance the glucose sensing performance of noble metal, transition metal oxides, and carbon-based materials and introduces biomimetic nanomaterials used in noninvasive glucose detection in sweat, tear, urine, and saliva. Based on these, this review provides the foundation for noninvasive determination of trace glucose for diabetic patients in the future.

The phosphorylation status of Hsp82 regulates mitochondrial homeostasis during glucose sensing in Saccharomyces cerevisiae

Sensing extracellular glucose, budding yeast switches from aerobic glycolysis to oxidative phosphorylation to adapt to environmental changes. During the conversion of metabolic mode, mitochondrial function and morphology change significantly. Mitochondria are the main supply factories of energy for various life activities in cells. However, the research on the signal pathways from glucose sensing to changes in mitochondrial function and morphology is still scarce and worthy of further exploration. In this study, we found that in addition to the known involvement of molecular chaperone Hsp82 in stress response during the conversion of metabolic mode, the phosphorylation status of Hsp82 at S485 residue regulates mitochondrial function and morphology to maintain mitochondrial homeostasis. The Hsp82^S485A mutant that mimics dephosphorylation at S485 residue showed abnormal growth phenotypes related to mitochondrial defects, such as the petite phenotype, slow growth rates, and inability to use non-fermentable carbon sources. Further exploring the causes of growth defects, we found that the Hsp82^S485A mutant caused mitochondrial dysfunction, including a decrease in cellular oxygen consumption rate, defects in mitochondrial electron transport chain, decreased mitochondrial membrane potential and complete loss of mtDNA. Furthermore, the Hsp82^S485A mutant displayed fragmented or globular mitochondria, which may be responsible for its mitochondrial dysfunction. Our findings suggested that the phosphorylation status of Hsp82 at S485 residue might regulate mitochondrial function and morphology by affecting the stability of mitochondrial fission and fusion-related proteins. Thus, Hsp82 might be a key molecule in the signal pathway from glucose sensing to changes in mitochondrial function and morphology.

Model of Chronoamperometric Response towards Glucose Sensing by Arrays of Gold Nanostructures Obtained by Laser, Thermal and Wet Processes

Non-enzymatic electrochemical glucose sensors are of great importance in biomedical applications, for the realization of portable diabetic testing kits and continuous glucose monitoring systems. Nanostructured materials show a number of advantages in the applications of analytical electrochemistry, compared to macroscopic electrodes, such as great sensitivity and little dependence on analyte diffusion close to the electrode-solution interface. Obtaining electrodes based on nanomaterials without using expensive lithographic techniques represents a great added value. In this paper, we modeled the chronoamperometric response towards glucose determination by four electrodes consisting of nanostructured gold onto graphene paper (GP). The nanostructures were obtained by electrochemical etch, thermal and laser processes of thin gold layer. We addressed experiments obtaining different size and shape of gold nanostructures. Electrodes have been characterized by field emission scanning electron microscopy (FE-SEM), X-ray photoelectron spectroscopy (XPS), cyclic voltammetry, and chronoamperometry. We modeled the current-time response at the potential corresponding to two-electrons oxidation process of glucose by the different nanostructured gold systems. The finest nanostructures of 10-200 nm were obtained by laser dewetting of 17 nm thin and 300 °C thermal dewetting of 8 nm thin gold layers, and they show that semi-infinite linear diffusion mechanism predominates over radial diffusion. Electrochemical etching and 17 nm thin gold layer dewetted at 400 °C consist of larger gold islands up to 1 μm. In the latter case, the current-time curves can be fitted by a two-phase exponential decay function that relies on the mixed second-order formation of adsorbed glucose intermediate followed by its first-order decay to gluconolactone.

Highly Miniaturized, Low-Power CMOS ASIC Chip for Long-Term Continuous Glucose Monitoring

BACKGROUND

The objective of this work is to develop a highly miniaturized, low-power, biosensing platform for continuous glucose monitoring (CGM). This platform is based on an application-specific integrated circuit (ASIC) chip that interfaces with an amperometric glucose-sensing element. To reduce both size and power requirements, this custom ASIC chip was implemented using 65-nm complementary metal oxide semiconductor (CMOS) technology node. Interfacing this chip to a frequency-counting microprocessor with storage capabilities, a miniaturized transcutaneous CGM system can be constructed for small laboratory animals, with long battery life.

METHOD

A 0.45 mm × 1.12 mm custom ASIC chip was first designed and implemented using the Taiwan Semiconductor Manufacturing Company (TSMC) 65-nm CMOS technology node. This ASIC chip was then interfaced with a multi-layer amperometric glucose-sensing element and a frequency-counting microprocessor with storage capabilities. Variation in glucose levels generates a linear increase in frequency response of this ASIC chip. In vivo experiments were conducted in healthy Sprague Dawley rats.

RESULTS

This highly miniaturized, 65-nm custom ASIC chip has an overall power consumption of circa 36 µW. In vitro testing shows that this ASIC chip produces a linear (R2 = 99.5) frequency response to varying glucose levels (from 2 to 25 mM), with a sensitivity of 1278 Hz/mM. In vivo testing in unrestrained healthy rats demonstrated long-term CGM (six days/per charge) with rapid glucose response to glycemic variations induced by isoflurane anesthesia and tail vein injection.

CONCLUSIONS

The miniature footprint of the biosensor platform, together with its low-power consumption, renders this CMOS ASIC chip a versatile platform for a variety of highly miniaturized devices, intended to improve the quality of life of patients with type 1 and type 2 diabetes.

The β2-adrenergic receptor in the apical membrane of intestinal enterocytes senses sugars to stimulate glucose uptake from the gut

The presence of sugar in the gut causes induction of SGLT1, the sodium/glucose cotransporter in intestinal epithelial cells (enterocytes), and this is accompanied by stimulation of sugar absorption. Sugar sensing was suggested to involve a G-protein coupled receptor and cAMP - protein kinase A signalling, but the sugar receptor has remained unknown. We show strong expression and co-localization with SGLT1 of the β2-adrenergic receptor (β ₂-AR) at the enterocyte apical membrane and reveal its role in stimulating glucose uptake from the gut by the sodium/glucose-linked transporter, SGLT1. Upon heterologous expression in different reporter systems, the β ₂-AR responds to multiple sugars in the mM range, consistent with estimated gut sugar levels after a meal. Most adrenergic receptor antagonists inhibit sugar signaling, while some differentially inhibit epinephrine and sugar responses. However, sugars did not inhibit binding of I¹²⁵-cyanopindolol, a β ₂-AR antagonist, to the ligand-binding site in cell-free membrane preparations. This suggests different but interdependent binding sites. Glucose uptake into everted sacs from rat intestine was stimulated by epinephrine and sugars in a β ₂-AR-dependent manner. STD-NMR confirmed direct physical binding of glucose to the β ₂-AR. Oral administration of glucose with a non-bioavailable β ₂-AR antagonist lowered the subsequent increase in blood glucose levels, confirming a role for enterocyte apical β ₂-ARs in stimulating gut glucose uptake, and suggesting enterocyte β ₂-AR as novel drug target in diabetic and obese patients. Future work will have to reveal how glucose sensing by enterocytes and neuroendocrine cells is connected, and whether β ₂-ARs mediate glucose sensing also in other tissues.

Synthetic Protocell as Efficient Bioreactor: Enzymatic Superactivity and Ultrasensitive Glucose Sensing in Urine

It is believed that membraneless cellular condensates play a critical role in accelerating various slow and thermodynamically unfavorable biochemical processes. However, the exact mechanisms behind the enhanced activity within biocondensates remain poorly understood. Here, we report the fabrication of a high-performance integrated cascade bioplatform based on synthetic droplets for ultrasensitive glucose sensing. Using a horseradish peroxidase (HRP) and glucose oxidase (GOx) cascade pair, we report an unprecedented enhancement in the catalytic activity of HRP inside the synthetic membraneless droplet. Liquidlike membraneless droplets have been prepared via multivalent electrostatic interactions between adenosine triphosphate (ATP) and poly(diallyldimethylammonium chloride) (PDADMAC) in an aqueous medium. Compartmentalized enzymes (GOx/HRP@Droplet) exhibit high encapsulation efficiency, low leakage, prolong retention of activity, and exceptional stability toward protease digestion. Using an HRP@Droplet composite, we have shown that the enzymatic reaction within the droplet follows the classical Michaelis-Menten model. Our findings reveal remarkable enhancement in the catalytic activity of up to 100- and 51-fold for HRP@Droplet and GOx/HRP@Droplet, respectively. These enhanced activities have been explained on the basis of increased local concentrations of enzymes and substrates, along with altered conformations of sequestered enzymes. Furthermore, we have utilized highly efficient and recyclable GOx/HRP@Droplet composite to demonstrate ultrasensitive glucose sensing with a limit of detection of 228 nM. Finally, the composite platform has been exploited to detect glucose in spiked urine samples in solution and filter paper. Our present study illustrates the unprecedented activity of the compartmentalized enzymes and paves the way for next-generation composite bioreactors for a wide range of applications.

Remembrance of things past: The consequences of recurrent hypoglycaemia in diabetes

AIMS

People with type 1 and type 2 diabetes still frequently experience hypoglycaemia, which can be severe, leading to loss of consciousness. This review will examine the cellular consequences of recurrent hypoglycaemia.

METHODS

This review, based on the Dorothy Hodgkin Lecture given at the Diabetes UK 2022 annual symposium by the author, will discuss our current understanding of the mechanisms by which hypoglycaemia is detected and the consequences of recurrent exposure to hypoglycaemia.

RESULTS

Glucose-responsive cells found in the periphery as well as multiple areas of the brain are organised in a classical sensori-motor integrative network encompassing peripheral, hindbrain and hypothalamic components. The mechanism used by glucose-responsive neurons to detect hypoglycaemia parallel those of the classical glucose sensor the pancreatic ß-cell, namely in their use of glucokinase, K_ATP channels and AMP-activated protein kinase. Recurrent exposure to hypoglycaemia results in a series of cellular adaptations that may be designed to increase the resilience of cells to future hypoglycaemia. This review also highlights how hypoglycaemia, as an oxidative stressor, may also exacerbate chronic hyperglycaemia-induced increases in oxidative stress and inflammation, leading to damage to vulnerable brain regions.

CONCLUSIONS

Impaired awareness of hypoglycaemia follows the adaptation of central glucose-responsive neurons to repeated hypoglycaemia and may represent a form of memory called habituation. In diabetes, recurrent hypoglycaemia may have tissue consequences as a result of a profound disruption in the cellular response to a hypoglycaemic challenge that increases vulnerability to oxidative damage.

Synthesis of Copper Nanostructures for Non-Enzymatic Glucose Sensors via Direct-Current Magnetron Sputtering

In this paper, Cu nanocolumnar structure electrodes are synthetized using a clean and easy-to-scale-up direct-current magnetron sputtering (DC-MS) technique for non-enzymatic glucose sensing. The nanocolumnar structure increases the active surface area of the deposit, with the nanocolumns showing a mean size diameter of 121.0 nm ± 27.2 and a length of 2.52 µm ± 0.23. A scanning transmission electron (STEM) analysis shows the presence of Cu and a small amount of Cu₂O. The behavior of the electrodes in alkaline environments and the electrochemical affinity of the Cu nanocolumns (CuNCs) towards the electro-oxidation of glucose are investigated using cyclic voltammetry (CV). After performing CV in NaOH solution, the columnar structures present corrosion products containing Cu₂O, as revealed by STEM and X-ray diffraction (XRD) analyses. The amperometric responses of the CuNCs to the successive addition of glucose show a linear range up to 2 mM and a limit of detection of 5.2 µM. Furthermore, the electrodes are free from chloride poisoning, and they are insensitive to dopamine, uric acid, ascorbic acid, and acetaminophen at their physiological concentrations.

Responsive Ag@NiCo(2)O(4) Nanowires Anchored on N-Doped Carbon Cloth as Array Electrodes for Nonenzymatic Glucose Sensing

The development of responsive materials in a predictable manner is high on the list of the material industry's trends. In this work, responsive Ag@NiCo₂O₄ nanowires were, firstly, anchored on N-doped carbon cloth (NC) and, then, employed as array electrodes for a nonenzymatic glucose-sensing application. The results showed that the highly conductive NiCo₂O₄ nanowires supported Ag nanoparticles and exhibited high conductivity and electrocatalytic properties. The fully exposed crystalline planes of Ag nanoparticles provided more active surface sites. As a result, the assembled Ag@NiCo₂O₄-NC electrodes for the glucose-sensing evaluation delivered a selectivity of 2803 μA mM^-1 cm^-2 and a detection limit of 1.065 μM, which outperformed the literature-reported Ag- and NiCo₂O₄-based glucose-sensing catalysts.

Evaluation of Mesoporous TiO2 Layers as Glucose Optical Sensors

Porous materials are currently the basis of many optical sensors because of their ability to provide a higher interaction between the light and the analyte, directly within the optical structure. In this study, mesoporous TiO₂ layers were fabricated using a bottom-up synthesis approach in order to develop optical sensing structures. In comparison with more typical top-down fabrication strategies where the bulk constitutive material is etched in order to obtain the required porous medium, the use of a bottom-up fabrication approach potentially allows increasing the interconnectivity of the pore network, hence improving the surface and depth homogeneity of the fabricated layer and reducing production costs by synthesizing the layers on a larger scale. The sensing performance of the fabricated mesoporous TiO₂ layers was assessed by means of the measurement of several glucose dilutions in water, estimating a limit of detection even below 0.15 mg/mL (15 mg/dL). All of these advantages make this platform a very promising candidate for the development of low-cost and high-performance optical sensors.

Colorimetric and Electrochemical Screening for Early Detection of Diabetes Mellitus and Diabetic Retinopathy-Application of Sensor Arrays and Machine Learning

In this review, a selection of works on the sensing of biomarkers related to diabetes mellitus (DM) and diabetic retinopathy (DR) are presented, with the scope of helping and encouraging researchers to design sensor-array machine-learning (ML)-supported devices for robust, fast, and cost-effective early detection of these devastating diseases. First, we highlight the social relevance of developing systematic screening programs for such diseases and how sensor-arrays and ML approaches could ease their early diagnosis. Then, we present diverse works related to the colorimetric and electrochemical sensing of biomarkers related to DM and DR with non-invasive sampling (e.g., urine, saliva, breath, tears, and sweat samples), with a special mention to some already-existing sensor arrays and ML approaches. We finally highlight the great potential of the latter approaches for the fast and reliable early diagnosis of DM and DR.

Thermal Detection of Glucose in Urine Using a Molecularly Imprinted Polymer as a Recognition Element

Glucose bio-sensing technologies have received increasing attention in the last few decades, primarily due to the fundamental role that glucose metabolism plays in diseases (e.g., diabetes). Molecularly imprinted polymers (MIPs) could offer an alternative means of analysis to a field that is traditionally dominated by enzyme-based devices, posing superior chemical stability, cost-effectiveness, and ease of fabrication. Their integration into sensing devices as recognition elements has been extensively studied with different readout methods such as quartz-crystal microbalance or impedance spectroscopy. In this work, a dummy imprinting approach is introduced, describing the synthesis and optimization of a MIP toward the sensing of glucose. Integration of this polymer into a thermally conductive receptor layer was achieved by micro-contact deposition. In essence, the MIP particles are pressed into a polyvinyl chloride adhesive layer using a polydimethylsiloxane stamp. The prepared layer is then evaluated with the so-called heat-transfer method, allowing the determination of the specificity and the sensitivity of the receptor layer. Furthermore, the selectivity was assessed by analyzing the thermal response after infusion with increasing concentrations of different saccharide analogues in phosphate-buffered saline (PBS). The obtained results show a linear range of the sensor of 0.0194–0.3300 mM for the detection of glucose in PBS. Finally, a potential application of the sensor was demonstrated by exposing the receptor layer to increasing concentrations of glucose in human urine samples, demonstrating a linear range of 0.0444–0.3300 mM. The results obtained in this paper highlight the applicability of the sensor both in terms of non-invasive glucose monitoring and for the analysis of food samples.

Machine Learning Methods of Regression for Plasmonic Nanoantenna Glucose Sensing

The measurement and quantification of glucose concentrations is a field of major interest, whether motivated by potential clinical applications or as a prime example of biosensing in basic research. In recent years, optical sensing methods have emerged as promising glucose measurement techniques in the literature, with surface-enhanced infrared absorption (SEIRA) spectroscopy combining the sensitivity of plasmonic systems and the specificity of standard infrared spectroscopy. The challenge addressed in this paper is to determine the best method to estimate the glucose concentration in aqueous solutions in the presence of fructose from the measured reflectance spectra. This is referred to as the inverse problem of sensing and usually solved via linear regression. Here, instead, several advanced machine learning regression algorithms are proposed and compared, while the sensor data are subject to a pre-processing routine aiming to isolate key patterns from which to extract the relevant information. The most accurate and reliable predictions were finally made by a Gaussian process regression model which improves by more than 60% on previous approaches. Our findings give insight into the applicability of machine learning methods of regression for sensor calibration and explore the limitations of SEIRA glucose sensing.

3D-printed microneedles with open groove channels for liquid extraction

Microneedles (MNs) offer a simple and minimally invasive way to sample skin interstitial fluid for bioanalysis. Through the integration with portable or wearable sensing devices, it allows us to get qualitative information about some biomarkers in situ. This work is to show a MN platform with open groove channels that are manufactured using photopolymerization 3D printing. The grooves on the needle surface permit that liquid flows from the tips to the base under the influence of capillary force. The ultimate MN device can penetrate skin and tissues and sample liquid in the skin model. By taking the glucose as the model biomarker, we demonstrate that the biomarkers in the extracted liquid can be analyzed in situ by the commercial test strips attached to the back.

Extended Graphite Supported Flower-like MnO2 as Bifunctional Materials for Supercapacitors and Glucose Sensing

A simple, efficient, and cost-effective extended graphite as a supporting platform further supported the MnO₂ growth for the construction of hierarchical flower-like MnO₂/extended graphite. MnO₂/extended graphite exhibited an increase in sp² carbon bonds in comparison with that of extended graphite. It can be expected to display better electrical conductivity and further promote electron/ion transport kinetics for boosting the electrochemical performance in supercapacitors and glucose sensing. In supercapacitors, MnO₂/extended graphite delivered an areal capacitance value of 20.4 mF cm⁻² at 0.25 mA cm⁻² current densities and great cycling stability (capacitance retention of 83% after 1000 cycles). In glucose sensing, MnO₂/extended graphite exhibited a good linear relationship in glucose concentration up to about 5 mM, sensitivity of 43 μA mM⁻¹cm⁻², and the limit of detection of 0.081 mM. It is further concluded that MnO₂/extended graphite could be a good candidate for the future design of synergistic multifunctional materials in electrochemical techniques.

Simple synthesis route for fabrication of protective photo-crosslinked poly(zwitterionic) membranes for application in non-enzymatic glucose sensing

This work focuses on the fabrication of non-enzymatic glucose sensing materials based on laser-formed Au nanoparticles embedded in Ti-textured substrates. Those materials possess good catalytic activity toward glucose oxidation in 0.1 × phosphate buffered saline as well as resistance to some interferants, such as ascorbic acid, urea, and glycine. The electrodes are further coated with three different polymers, that is, Nafion, photo-crosslinked poly(zwitterions) based on sulfobetaine methacrylate, and a hybrid membrane consisting of both polymers. Both the optimal integrity of the material and its catalytic activity toward glucose oxidation were maintained by the hybrid membranes with a large excess of poly(zwitterions) (mass ratio 20:1). The chemical structures of the as-formed membranes are confirmed by Fourier transform infrared spectroscopy. Due to the zwitterionic nature of the coating, the electrodes are resistant to biofouling and maintain electrochemical activity toward glucose for 4 days. Moreover, due to the synergistic effect of both Nafion and poly(zwitterions), the interference from the two compounds, namely, from acetylsalicylic acid and acetaminophen, was diminished. Besides the presence of polymer membranes, the electrode possesses a sensitivity of 36.8 μA cm^-2  mM^-1 in the linear range of 0.4-12 mM, while the limit of detection was estimated to be 23 μM. Finally, the electrodes are stable, and their response is not altered even by 1,000 bending cycles.

Facile synthesis of Cu/Co-ZIF nanoarrays for non-enzymatic glucose detection

Cu/Co-ZIF nanoflake arrays on carbon cloth are fabricated by controlling the introducing of Cu²⁺ions during the growth of Co-ZIF. The Cu/Co-ZIF-20 electrode prepared with 20 mM Cu²⁺possesses large electrochemically active surface area and bimetallic active sites, which can be revealed by cyclic voltammetry tests. The amperometrici-tmeasurements demonstrate that the Cu/Co-ZIF-20 electrode displays a wide linear range from 0.05 mM to 6.0 mM, and a high sensitivity of 1.03 mA mM^-1cm^-2. Good selectivity, repeatability and practical applicability indicate its promising application in enzyme-free glucose sensing.

A Vibration-Induced-Emission-Based Fluorescent Chemosensor for the Selective and Visual Recognition of Glucose

The development of chemosensors to detect analytes in biologically relevant solutions is a challenging task. We report the synthesis of a fluorescent receptor that combines vibration-induced emission (VIE) and dynamic covalent chemistry for the detection of glucose in aqueous media. We show that the bis-2-(N-methylaminomethyl)phenylboronic acid-decorated N,N'-diphenyl-dihydrodibenzo[a,c]phenazine (DPAC) receptor 1 can detect glucose and discriminate between closely related monosaccharides including those commonly found in blood. Preliminary studies suggest monosaccharides bind to the DPAC-receptor with a 1:1 stoichiometry to produce pseudomacrocyclic complexes, which in turn leads to distinct optical changes in the fluorescent emission of the receptor for each host. Moreover, the complexation-induced change in emission can be detected visually and quantified in a ratiometric way. Our results highlight the potential of VIE-type receptors for the quantitative determination of saccharides in biological samples.

Increased glycolysis in skeletal muscle coordinates with adipose tissue in systemic metabolic homeostasis

Insulin‐independent glucose metabolism, including anaerobic glycolysis that is promoted in resistance training, plays critical roles in glucose disposal and systemic metabolic regulation. However, the underlying mechanisms are not completely understood. In this study, through genetically manipulating the glycolytic process by overexpressing human glucose transporter 1 (GLUT1), hexokinase 2 (HK2) and 6‐phosphofructo‐2‐kinase‐fructose‐2,6‐biphosphatase 3 (PFKFB3) in mouse skeletal muscle, we examined the impact of enhanced glycolysis in metabolic homeostasis. Enhanced glycolysis in skeletal muscle promoted accelerated glucose disposal, a lean phenotype and a high metabolic rate in mice despite attenuated lipid metabolism in muscle, even under High‐Fat diet (HFD). Further study revealed that the glucose metabolite sensor carbohydrate‐response element‐binding protein (ChREBP) was activated in the highly glycolytic muscle and stimulated the elevation of plasma fibroblast growth factor 21 (FGF21), possibly mediating enhanced lipid oxidation in adipose tissue and contributing to a systemic effect. PFKFB3 was critically involved in promoting the glucose‐sensing mechanism in myocytes. Thus, a high level of glycolysis in skeletal muscle may be intrinsically coupled to distal lipid metabolism through intracellular glucose sensing. This study provides novel insights for the benefit of resistance training and for manipulating insulin‐independent glucose metabolism.

Study of Microwave-Induced Ag Nanowire Welding for Soft Electrode Conductivity Enhancement

Silver nanowire (AgNW)-coated thin films are widely proposed for soft electronics application due to their good conductivity, transparency and flexibility. Here, we studied the microwave welding of AgNW-based soft electrodes for conductivity enhancement. The thermal effect of the microwave to AgNWs was analyzed by dispersing the nanowires in a nonpolar solution, the temperature of which was found to be proportional with the nanowire diameters. AgNWs were then coated on a thin film and welded under microwave heating, which achieved a film conductivity enhancement of as much as 79%. A microwave overheating of AgNWs, however, fused and broke the nanowires, which increased the film resistance significantly. A soft electrode was finally demonstrated using the microwave-welded AgNW thin film, and a 1.13 µA/mM sensitivity was obtained for glucose sensing. Above all, we analyzed the microwave thermal effect on AgNWs to provide a guidance to control the nanowire welding effect, which can be used for film conductivity enhancement and applied for soft and bio-compatible electrodes.

Organotrialkoxysilane-Functionalized Noble Metal Monometallic, Bimetallic, and Trimetallic Nanoparticle Mediated Non-Enzymatic Sensing of Glucose by Resonance Rayleigh Scattering

Organotrialkoxysilanes like 3-aminopropyltrimethoxysilane (3-APTMS)-treated noble metal cations were rapidly converted into their respective nanoparticles in the presence of 3-glycidoxypropylytrimethoxysilane (3-GPTMS). The micellar activity of 3-APTMS also allowed us to replace 3-GPTMS with other suitable organic reagents (e.g., formaldehyde); this approach has significant advantages for preparing bimetallic and trimetallic analogs of noble metal nanoparticles that display efficient activity in many practical applications. The formation of monometallic gold, silver, and palladium nanoparticles, bimetallic Ag-Pd, and Au-Pd nanoparticles at various ratios of noble metal cations, and trimetallic Ag-Au-Pd nanoparticles were studied; their biocatalytic activity in non-enzymatic sensing of glucose based on monitoring synchronous fluorescence spectroscopy (SFS) was assessed. Of these nanoparticles, Au-Pd made with an 80:20 Au:Pd ratio displayed excellent catalytic activity for glucose sensing. These nanoparticles could also be homogenized with Nafion to enhance the resonance Rayleigh scattering (RRS) signal. In this study, the structural characterization of noble metal nanoparticles as well as bi- and tri-metallic nanoparticles in addition to their use in non-enzymatic sensing of glucose are reported.

Integrated contact lens sensor system based on multifunctional ultrathin MoS2 transistors

Smart contact lenses attract extensive interests due to their capability of directly monitoring physiological and ambient information. However, previous demonstrations usually lacked efficient sensor modalities, facile fabrication process, mechanical stability, or biocompatibility. Here, we demonstrate a flexible approach for fabrication of multifunctional smart contact lenses with an ultrathin MoS₂ transistors-based serpentine mesh sensor system. The integrated sensor systems contain a photodetector for receiving optical information, a glucose sensor for monitoring glucose level directly from tear fluid, and a temperature sensor for diagnosing potential corneal disease. Unlike traditional sensors and circuit chips sandwiched in the lens substrate, this serpentine mesh sensor system can be directly mounted onto the lenses and maintain direct contact with tears, delivering high detection sensitivity, while being mechanically robust and not interfering with either blinking or vision. Furthermore, the in vitro cytotoxicity tests reveal good biocompatibility, thus holding promise as next-generation soft electronics for healthcare and medical applications.

CRISPRi-Mediated NIMPLY Logic Gate for Fine-Tuning the Whole-Cell Sensing toward Simple Urine Glucose Detection

Whole-cell biosensors have been regarded as a prominent alternative to chemical and physical biosensors due to their renewability, environmental friendliness, and biocompatibility. However, there is still a lack of noninvasive measurements of urine glucose, which plays a vital role in monitoring the risk of diabetes in the healthcare system, via whole-cell biosensors. In this study, we characterized a glucose-inducible promoter and further enhanced the sensing performance using three genetic effectors, which encompassed ribozyme regulator (RiboJ), clustered regularly interspaced short palindromic repeat interference (CRISPRi), and plasmid-based T7RNA polymerase (PDT7), to develop the noninvasive glucose biosensor by fluorescent signal. As a result, RiboJ increased dynamic range to 2989 au, but declined signal-to-noise (S/N) to 1.59, while CRISPRi-mediated NIMPLY gate intensified both dynamic range to 5720 au and S/N to 4.58. The use of single PDT7 orthogonal with T7 promoter in cells (i.e., P strain) achieved a 44 180 au of dynamic range with S/N at 3.08. By coupling the PDT7 and NIMPLY-mediated CRISPRi, we constructed an optimum PIGAS strain with the highest S/N value of 4.95. Finally, we adopted the synthetic bacteria into a microdevice to afford an integrative and portable system for daily urine glucose inspection, which would be an alternative approach for medical diagnosis in the future.

Simple Yeast-Direct Catalytic Fuel Cell Bio-Device: Analytical Results and Energetic Properties

This paper reports the analytical detection and energetic properties of a glucose-fed Direct Catalytic Fuel Cell (DCFC) operated in association with yeast cells (Saccharomyces Cerevisiae). The cell was tested in a potentiostatic mode, and the operating conditions were optimized to maximize the current produced by a given concentration of glucose. Results indicate that the DCFC is characterized by a glucose detection limit of the order to 21 mmol L⁻¹. The cell was used to estimate the “pool” of carbohydrate content in commercial soft drinks. Furthermore, the use of different carbohydrates, such as fructose and sucrose, has been shown to result in a good current yield.

The glucose-sensing transcription factor ChREBP is targeted by proline hydroxylation

Cellular energy demands are met by uptake and metabolism of nutrients like glucose. The principal transcriptional regulator for adapting glycolytic flux and downstream pathways like de novo lipogenesis to glucose availability in many cell types is carbohydrate response element-binding protein (ChREBP). ChREBP is activated by glucose metabolites and post-translational modifications, inducing nuclear accumulation and regulation of target genes. Here we report that ChREBP is modified by proline hydroxylation at several residues. Proline hydroxylation targets both ectopically expressed ChREBP in cells and endogenous ChREBP in mouse liver. Functionally, we found that specific hydroxylated prolines were dispensable for protein stability but required for the adequate activation of ChREBP upon exposure to high glucose. Accordingly, ChREBP target gene expression was rescued by re-expressing WT but not ChREBP that lacks hydroxylated prolines in ChREBP-deleted hepatocytes. Thus, proline hydroxylation of ChREBP is a novel post-translational modification that may allow for therapeutic interference in metabolic diseases.

FGF21 Signals to Glutamatergic Neurons in the Ventromedial Hypothalamus to Suppress Carbohydrate Intake

Fibroblast growth factor 21 (FGF21) is an endocrine hormone produced by the liver that regulates nutrient and metabolic homeostasis. FGF21 production is increased in response to macronutrient imbalance and signals to the brain to suppress sugar intake and sweet-taste preference. However, the central targets mediating these effects have been unclear. Here, we identify FGF21 target cells in the hypothalamus and reveal that FGF21 signaling to glutamatergic neurons is both necessary and sufficient to mediate FGF21-induced sugar suppression and sweet-taste preference. Moreover, we show that FGF21 acts directly in the ventromedial hypothalamus (VMH) to specifically regulate sucrose intake, but not non-nutritive sweet-taste preference, body weight, or energy expenditure. Finally, our data demonstrate that FGF21 affects neuronal activity by increasing activation and excitability of neurons in the VMH. Thus, FGF21 signaling to glutamatergic neurons in the VMH is an important component of the neurocircuitry that functions to regulate sucrose intake.

Continuous Flow Reactors from Microfluidic Compartmentalization of Enzymes within Inorganic Microparticles

Compartmentalization and selective transport of molecular species are key aspects of chemical transformations inside the cell. In an artificial setting, the immobilization of a wide range of enzymes onto surfaces is commonly used for controlling their functionality but such approaches can restrict their efficacy and expose them to degrading environmental conditions, thus reducing their activity. Here, we employ an approach based on droplet microfluidics to generate enzyme-containing microparticles that feature an inorganic silica shell that forms a semipermeable barrier. We show that this porous shell permits selective diffusion of the substrate and product while protecting the enzymes from degradation by proteinases and maintaining their functionality over multiple reaction cycles. We illustrate the power of this approach by synthesizing microparticles that can be employed to detect glucose levels through simultaneous encapsulation of two distinct enzymes that form a controlled reaction cascade. These results demonstrate a robust, accessible, and modular approach for the formation of microparticles containing active but protected enzymes for molecular sensing applications and potential novel diagnostic platforms.