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Diabetes affects 1 in 11 people globally and requires monitoring of blood glucose levels as a part of its treatment. Initial blood glucose monitoring devices involved finger prick testing at regular intervals daily, a self-monitoring strategy reliant on patient compliance. Advances in technology have facilitated continuous glucose monitors (CGMs), (semi-) implantable devices that can monitor glucose levels in vivo and transmit the data to mobile applications. Majority of commercial CGMs are electrochemical in nature and meet the requirements for a commercial sensing implant. There are three main factors that limit CGMs for in vivo use – namely oxygen dependence, low molecular weight (LMW) materials and foreign body response (FBR) – which negatively affect the lifetime and accuracy of CGMs. This thesis aims to detail strategies to combat these issues, building on previous work performed in the field of enzymatic electrochemical glucose sensors. Chapter 2 details the use of design of experiments (DoE) to optimise enzyme electrode components – Osmium complex-based redox polymer, commercial glucose oxidising enzyme (glucose oxidase, GOx) and crosslinker (polyethylene glycol diglycidyl ether, PEGDGE). Previous work established high current and stability of a similar system which also incorporated acid treated multiwalled carbon nanotubes (MWCNTs) as a nanosupport. The MWCNTs enable high currents and surface coverages, but the quantities required were quite high, which can be detrimental for in vivo applications. In this chapter, the grafting of enzyme to nanosupport was carried out to allow minimisation of MWCNT amounts while retaining high currents and operational stability. DoE facilitated the determination of electrode component amounts for optimal current density and stability. The optimised enzyme electrodes show a current density of 3.18 ± 0.30 mA cm−2 , representing a 146% increase in current density in 50 mM phosphate-buffered saline at 37 °C containing 5 mM glucose when compared to similar systems where enzyme and nanosupport are not grafted to each other. Using the predictive DoE model, component amounts were then modified to minimise the quantity of the enzyme-MWCNT nanoconjugate, resulting in a biosensor which showed similar electrochemical behaviour and current density to the optimised system while using 93% less of the nanoconjugate Commercial GOx shows excellent behaviour for glucose oxidation but uses oxygen in its half reaction to regenerate. This is problematic as in vivo oxygen levels can fluctuate resulting in errors in measurement. Additionally, enzyme regeneration by oxygen reduction gives hydrogen peroxide as a product. Peroxide can cause enzyme instability as it oxidises the methionine residues of the enzyme, decreasing its activity. To combat this use, GOx was replaced with engineered cellobiose dehydrogenase (CDH) in Chapter 3. CDH is a dehydrogenase and thus does not use oxygen in its half reactions and has been modified to selectively choose glucose as its substrate. The enzyme electrodes comprising osmium complex-based redox polymer, CDH and PEGDGE were optimised with DoE, while a direct electron transfer (DET) based system was also optimised through conventional methods. The resulting sensors had sensitivities in the same order of magnitude as those in literature. Most importantly, sensor signals showed no difference in the presence and absence of oxygen. The sensors derived from CDH were shown to be specific to glucose over other clinically relevant in vivo sugars and selective, i.e., capable of glucose sensing in the presence of interfering species present in complex media. While no individual species is classified as an interferent in complex media they seemed to exhibit a cooperative effect resulting in a minimisation of current (43%). This is usually overcome with the use of polymer coatings. However, polymer coatings themselves lead to reduced sensor signals on their application, due to the formation of a diffusion barrier. Chapter 4 focuses on the design of polymer coatings to enable protection against biofouling while retaining current density. This was done by designing polymer coatings with a compatible epoxy crosslinking moiety on the polymer backbone that could crosslink with the redox polymer used in the sensing layer. The polymers selected in this study were zwitterionic in nature because of their inherent ability to minimise biofouling. Protein adsorption and cell adhesion studies, using fibrinogen and fibroblasts respectively, allowed a screening to select the most effective of the synthesised polymers for biofouling resistance. This poly(2- methacryloyloxyethyl phosphorylcholine-co-glycidyl methacrylate (MPC)-type polymer showed similar biofouling resistance compared to commercial polymer Lipidure with ~50% reduction in fibrinogen adsorption and ~80% reduction in fibroblast adhesion. When used as coatings for glucose biosensors fabricated in Chapter 3, MPC showed ability to resist protein adsorption while retaining current density similar to a non-coated system with 1.5-fold increase in sensitivity. MPC polymers showed ability to impart biofouling resistance while maintaining current signals. Nevertheless, their ability to resist LMW materials was not proved. In Chapter 5, a series of different protective strategies were explored to determine which approach would be the best to protect from biological and LMW interferences. Enzymatic scavenging using enzymes that target LMW species was investigated but showed inefficient scavenging, likely due to low enzymatic activity. Polymer multilayer approach with successive anionic and MPC polymer layers was utilised and showed the best potential. MPC as the outerlayer showed biofouling resistance whereas an anionic interlayer ([Poly(1-vinylimidazole-co-4-styrene sulfonic acid sodium salt hydrate], P(VI1 -SSNa1 )) inhibited anionic LMW species such as uric acid and ascorbic acid which cause interference. Moreover, due to the compatible crosslinking sites, the layers intermix at the boundary between them, minimising diffusional barrier and allowing current signals similar to a non-coated system. This multilayer protection system extends linear range and enables higher current and stability than a non-coated system in 50 mM phosphate-buffered saline and artificial plasma. Chapter 6 summarises the results from Chapter 2-5 and highlights the significant conclusions that can be drawn from these results. Future directions that can improve on the strategies in this thesis are also discussed.

Herein, we reported a self-assembled fabrication of a network nanozyme (TMPyP-pSC4@GNPs) and a glucose-recognition molecule (APBA) for highly stable and selective glucose sensing. By involving the ...

Herein, a two-dimensional (2D) Co(OH)2 nanosheet (NS) was prepared by reacting Co(II) acetate with 2-ethylimidazole and trimethylamine at room temperature. The as-prepared Co(OH)2 NS-modified screen-printed electrode enabled glucose sensing in human blood plasma samples (HBP) diluted with phosphate buffer saline (PBS, pH 7.4) and NaOH (0.1 M, pH 13.0) solutions. The electrocatalytic activity of Co(OH)2 NS for glucose oxidation in a wide pH range can be ascribed to the enriched oxygen vacancies with a high surface area of the porous NS, which enabled the facile formation of CoII/CoIII redox pair. The oxidation current response as a function of glucose concentration displayed two straight lines in the ranges 55.12–117.50 μM and 180–12055 μM in PBS diluted HBP, and 62.80–180 μM and 305–12055 μM in NaOH diluted HBP with the sensitivity of 430 and 98.18 μA/cm2/mM and the limit of detection of 0.082 and 2.2 μM, in PBS and NaOH diluted HBP solutions, respectively. The sensor also exhibited good long-term stability, repeatability, and interference-free signals. The good analytical performance of the proposed sensor demonstrates the suitability of Co(OH)2 NS as a material to fabricate disposable systems for the direct detection of glucose in human body fluids at physiological pH.

Purpose The purpose of this study is to develop a non-enzymatic based glucose-sensing platform composed of Bodipy-BBV dual system which can be monitored by a photodetector under the blue LED excitation. Design/methodology/approach The sensor has been developed from a dual system including a fluorescent dye, an aldehyde derivative of boron dipyrromethene (Bodipy) and a quencher, orto-boronic acid linked viologen (o-BBV) where their combination resulted in a ratiometric fluorescence quenching in ethanol: PBS (1:1, pH:7.4) solution under UV light excitation. By glucose addition, o-BBV has been released from the Bodipy and binded to cis-diol groups of glucose, thereby fluorescence emission of Bodipy has been regained. Furthermore, a setup consisting of a light emitting diode (LED) and a photodiode (PD) was used to prove electrical detection of glucose without the need for expensive and bulky optical equipment, enabling the development of a miniaturized and low-cost glucose-sensing platform. Findings The fluorescence intensity of the Bodipy derivative in the solution (2 × 10−6 M) was diminished by 93% in the presence of o-BBV solution (5 × 10−3 M). Upon the glucose addition, 81% of the Bodipy fluorescence intensity has been recovered after introduction of 30 mM of glucose, where the ratio of o-BBV/Bodipy was 35:1. A linear response between 10 and 30 mM glucose concentration was obtained, which covers the biologically significant range. A high correlation between the photodiode current and Bodipy fluorescence intensity was achieved. Originality/value Even though Bodipy molecules are known with their superior optical properties and applied to the fluorescence-based detection of glucose, to the best of the authors’ knowledge, no work has been reported on Bodipy-BBV dual system to detect glucose molecules as a non-enzymatic based method. This design enables the dye and the quencher to independently coexist in the solution, allowing for tuning of their individual concentrations to optimize the glucose sensitivity. Furthermore, an electrical light detection scheme consisting of a LED and a photodiode has been implemented to eliminate the bulky optical equipment from the measurement setup and further this work for the development of a compact and inexpensive sensor. The results presented here demonstrate the feasibility of this system for the development of a novel glucose sensor.

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.

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., A novel sugar fluorescent chemosensor which combines a vibrational‐induced‐emission (VIE)‐active DPAC core and two N‐methylaminomethylphenylboronic acid moieties can detect glucose within seconds and discriminate between closely related monosaccharides including those commonly found in blood.

Hierarchical spinel NiCo2O4 microflowers have been successfully designed and synthesized by a successive mild spray-thermal treatment method via bimetallic NiCo-metal-organic framework formation. R...

MnO2 based electrochemical enzyme-free glucose sensors remain significantly limited by their low electronic conductivity and associated complex preparation. In this paper, an MnO2 nanosheet array supported on nickel foam (MnO2 NS/NF) was prepared using a simple hydrothermal synthesis and employed as a 3D integrated electrode for enzyme-free glucose detection. It was found that MnO2 NS/NF shows high performance with a wide linear range from 1 μM to 1.13 mM, a high sensitivity of 6.45 mA mM-1 cm-2, and a low detection limit of 0.5 μM (S/N = 3). Besides, MnO2 NS/NF shows high selectivity against common interferences and good reliability for glucose detection in human serum. This work demonstrates the promising role of MnO2 NS/NF as an efficient integrated electrode in enzyme-free glucose detection with high performance.

Glucose performs many essential functions associated with metabolic processes in the living system, and is closely related to many diseases such as diabetes and hypoglycemia. Most of the existing glucose concentration detection methods require complex instruments, which undoubtedly limit its widespread use. Here, we have designed a glucose colorimetric detection system composed of glucose, glucose oxidase (GOD), manganese dioxide nanosheets (MnO2 NSs) and 3,3',5,5'-tetramethylbenzidine (TMB) to achieve colorimetric detection with the naked eye. Compared with the single-color change of the colorimetric method in previous studies, multiple-color changes have been realized. MnO2 NSs, as a kind of nanomaterial imitating oxidase, can directly oxidize TMB to oxTMB. Because oxTMB showed a dark yellow color when strongly oxidized and light blue when weakly oxidized, this feature can achieve multiple-color changes rather than a single-color change, which is helpful for colorimetric observation with the naked eye. Finally, we successfully used MnO2 NSs for colorimetric detection of glucose and realized multiple-color changes, making it easier to achieve colorimetric observation with the naked eye. The linear detection range is 0-4000 μM and limit of detection is 5.0 μM. This is not only useful for glucose, but also has an important significance for other experiments considering colorimetric experiments with the naked eye.

Numerous studies have demonstrated that the construction of heterojunctions in electrode materials resulted in a significant improvement of electrochemical glucose sensing. However, there have so far been rare studies on the underlying relationship between heterojunctions and glucose sensing, and the mechanism for enhancing the glucose sensing ability is still elusive. Herein, with the aid of experimental and theoretical studies, the Cu2O–CuS heterostructure was constructed as a proof of concept to illustrate the role that heterojunctions play in the glucose sensing process. Density functional theory (DFT) calculations revealed that Cu2O–CuS heterojunctions possessed a decreased formation energy of electroactive Cu(III) species along with a lower adsorption energy of glucose molecules, enabling more favorable reaction kinetics for glucose electrooxidation. As expected, the Cu2O–CuS electrode shows superior electrochemical glucose sensing performance with respect to the Cu2O electrode. This work provides significant implications for designing advanced electrochemical sensors in the future.

The saturation of nonenzymatic blood glucose sensors at lower than normal blood glucose levels has blocked their practical applications. The mechanistic understanding of the saturation, however, has long been under debate. Employing cyclic voltammetry, amperometry, and FTIR with various electrolytes of varying concentrations, we were able to uproot the saturation cause. It was found to be related to the hydroxide ion concentration, which must be 11 times greater than that of the glucose concentration, contrary to the prior understanding. Together with the satisfactory sensitivity at high pH, nonenzymatic blood glucose sensing has finally been achieved, eliminating the usual problem of electrochemical current saturation as well as the need for enzyme found in the present technology.

A recent paper by Oh et al. identified a single pair of neurons in the fruit fly brain that directly senses ‘blood’ glucose levels and reciprocally regulates the secretion of insulin and glucagon. This study provides insight into how the brain regulates the circulation and storage of glucose.

Strenuous efforts have been made to develop nanozymes for achieving the performance of natural enzymes to broaden their application in practice, but the fabrication of high-performance and biocompatible nanozymes via facile and versatile approaches has always been a great challenge. Here, sponge-like casein-CuS hybrid has been facilely synthesized in the presence of amphiphilic protein-casein through a simple one-step approach. Casein-CuS hybrid exhibits substrates-dependent peroxidase-like activity. Casein-CuS hybrid exhibits well peroxidase-like activity with 3,3′,5,5′-tetramethylbenzidine (TMB) and 1,2-diaminobenzene (OPD) as substrates, and the affinity of OPD towards the hybrid nanozyme is much higher than that of TMB. More importantly, due to the high affinity of OPD and the well biocompatibility of the hybrid nanozyme, a superior enzyme cascade for glucose based on the well cooperative effect of casein-CuS hybrid and glucose oxidase is developed. The proposed glucose sensor exhibits a wide linear range of 0.083 to 75 μM and a detection limit of 5 nM. This suggests the promising utilization of protein–metal hybrid nanozymes as robust and potent peroxidase mimics in the medical, food and environmental detection fields.

On-site and instant glucose sensing is essential for objectively monitoring the change of glucose content that has decisive effects on the normal regulation of carbon metabolism. Colorimetric synergy based on indicators for real-time sensing seemed to be the potential route, but so far it has remained quite challenge to shift down the detection limit in a stable manner. Also, the lack of a direct identification of the underlying detection mechanism especially on the exhibited color change limited their practical use. In this study, the strategy is to employ the carbon nanodots with silver shells functioning as the highly sensitive indicators that enabled realization of the colorimetric sensing of glucose which is caused by oxidation of the surface silver shell observed by the naked eye. These were based on the robust core/shell architectures that allowed an ultralow limit of detection of 87.3 nM for glucose detection through the formation of Ag2O that led to the obvious particle aggregations, and the resu...

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.

Progress in the development of commercially available non-enzymatic glucose sensors continues to be problematic due to issues regarding selectivity, reproducibility and stability. Overcoming these issues is a research challenge of significant importance. This study reports a novel fabrication process using a double-layer self-assembly of (3 mercaptopropyl)trimethoxysilane (MPTS) on a gold substrate and co-deposition of a platinum–copper alloy. The subsequent electrochemical dealloying of the less noble copper resulted in a nanoporous platinum structure on the uppermost exposed thiol groups. Amperometric responses at 0.4 V vs. Ag/AgCl found the modification to be highly selective towards glucose in the presence of known interferants. The sensor propagated a rapid response time &lt, 5 s and exhibited a wide linear range from 1 mM to 18 mM. Additionally, extremely robust stability was attributed to enhanced attachment due to the strong chemisorption between the gold substrate and the exposed thiol of MPTS. Incorporation of metallic nanomaterials using the self-assembly approach was demonstrated to provide a more reproducible and controlled molecular architecture for sensor fabrication. The successful application of the sensor in real blood serum samples displayed a strong correlation with clinically obtained glucose levels.

Transitional hypoglycemia in normal newborns occurs in the first 3 days of life and has clinical features consistent with hyperinsulinism. We found a lower threshold for glucose-stimulated insulin secretion from freshly isolated embryonic day (E) 22 rat islets, which persisted into the first postnatal days. The threshold reached the adult level by postnatal day (P) 14. Culturing P14 islets also decreased the glucose threshold. Freshly isolated P1 rat islets had a lower threshold for insulin secretion in response to 2-aminobicyclo-(2, 2, 1)-heptane-2-carboxylic acid, a nonmetabolizable leucine analog, and diminished insulin release in response to tolbutamide, an inhibitor of β-cell KATP channels. These findings suggested that decreased KATP channel function could be responsible for the lower glucose threshold for insulin secretion. Single-cell transcriptomic analysis did not reveal a lower expression of KATP subunit genes in E22 compared with P14 β cells. The investigation of electrophysiological characteristics of dispersed β cells showed that early neonatal and cultured cells had fewer functional KATP channels per unit membrane area. Our findings suggest that decreased surface density of KATP channels may contribute to the observed differences in glucose threshold for insulin release.

A comprehensive review of the electroactive materials for non-enzymatic glucose sensing and sensing devices has been performed in this work. A general introduction for glucose sensing, a facile electrochemical technique for glucose detection, and explanations of fundamental mechanisms for the electro-oxidation of glucose via the electrochemical technique are conducted. The glucose sensing materials are classified into five major systems: (1) mono-metallic materials, (2) bi-metallic materials, (3) metallic-oxide compounds, (4) metallic-hydroxide materials, and (5) metal-metal derivatives. The performances of various systems within this decade have been compared and explained in terms of sensitivity, linear regime, the limit of detection (LOD), and detection potentials. Some promising materials and practicable methodologies for the further developments of glucose sensors have been proposed. Firstly, the atomic deposition of alloys is expected to enhance the selectivity, which is considered to be lacking in non-enzymatic glucose sensing. Secondly, by using the modification of the hydrophilicity of the metallic-oxides, a promoted current response from the electro-oxidation of glucose is expected. Lastly, by taking the advantage of the redistribution phenomenon of the oxide particles, the usage of the noble metals is foreseen to be reduced.

We created a glucose oxidase (GOx) working electrode on a silicon-on-insulator (SOI) wafer for glucose sensing. The SOI wafer was electrically connected to a copper wire, and the GOx was immobilized onto the hydrophilized SOI surface via silanization with aminopropyltriethoxysilane and glutaraldehyde. Electrochemical analysis (i.e., cyclic voltammetry) was employed to identify the sensing mechanism and to evaluate the performance of these SOI–GOx glucose sensors. The response of the SOI–GOx working electrode was significantly higher in the presence of oxygen than that without oxygen, indicating that a hydrogen peroxide pathway dominated in our SOI–GOx electrode. The height of cathodic peaks increased linearly with the increase of glucose concentrations up to 15 mM. The SOI–GOx working electrode displayed good stability after more than 30 cycles. On the 133rd day after the electrode was made, although the response of the SOI–GOx electrode dropped to about one-half of its original response, it was still capable of distinguishing different glucose concentrations. This work suggests that the SOI–GOx working electrode that we developed might be a promising candidate for implantable glucose sensors.

In addition to superior enzyme-mimicking abilities, nanozymes also have intrinsic physicochemical properties. Integrating the enzyme-like activities and tunable physicochemical properties into a single nanoparticle is a promising strategy for versatile nanozyme design and application. Herein, a composite nanozyme in which Au nanoparticles are encapsulated by Au nanoclusters (AuNP@AuNCs) is presented. By integrating the peroxidase-mimicking ability of fluorescent Au NCs with the glucose oxidase-like activity of Au NPs, the composite nanozyme realized cascade assay of glucose without the aid of external indicators. Compared to traditional multistep colorimetric methods, the analytical process was highly simplified by using the self-responsive nanozyme. This synthetic strategy provided valuable insights into exploring talented nanozymes for sensing diverse targets.

CuO nanoparticles (CuO NPs) were demonstrated as a novel nanoenzyme, i.e., haloperoxidase mimic, which catalyzes the oxidation of halide ions to form reactive halogen species (RHS). Two functions of CuO NPs have been demonstrated in the work. First, RHS halogenate bacterial signaling molecules, thus preventing biofilm formation. Second, CuO is used in sensitive colorimetric assays for H2O2 and glucose.

To circumvent the complicated natural peroxidases, palladium nanoparticles embedded in melamine cyanurate (MCA-Pd NPs) were synthesized. MCA-Pd NPs catalyzed the oxidation of ABTS2– by H2O2, and the solution turned green, which could be quantified via a typical absorption peak at 420 nm. MCA-Pd NPs had high peroxidase-like activity in a wider pH range than that of natural peroxidases. MCA-Pd NPs were used to develop a colorimetric sensor for H2O2 over the pH range of 7.0 to 11.0, which had same linear range, and their linear regression equations had similar slopes. Moreover, MCA-Pd NPs were applied to establish the biosensor for glucose by using glucose oxidase (GOx); it had a linear range of 5.0–120 μmol/L, with a linear regression equation of A = 0.04926 + 0.00536C (C: μmol/L, R = 0.9960) and a detection limit of 0.3 μmol/L (3σ/slope). When we applied it to detect glucose level in human blood, satisfactory results were obtained.

In our recent work [Electrochim. Acta 240 (2017) 388–398], we examined the adsorption energy of glucose on graphene via Ni nanoparticles. In the present study, we have responded to comments to clarify the intricacies of dispersion effect and adsorption energies in our previous work. We have explored the performance and accuracy of some established and promising theoretical schemes, namely, the two-, three- (DFT-D2/3), and many-body (MBD@rSC) dispersion approaches, to account properly for the dispersive force contributions, which were not previously included in the system. Incorporating dispersive forces drastically increased the adsorption energy of glucose (Eads), where different active sites were obtained. The calculated energies were in the order Eads(DFT−D2)

Diabetes mellitus is a chronic disease and leading cause of death worldwide, affecting more than 420 million people. High blood glucose levels are a common effect of uncontrolled diabetes, which can cause serious health damage. Diabetic individuals must measure their blood glucose levels regularly in order to control glycemic levels and minimize the effects of the disease. Glucose sensors have been used in the management of diabetes for more than 50 years, when Clark and Ann Lyons developed the first glucose enzyme electrode in 1962. Electrochemical sensors have become the leading technology for glucose concentration measuring with most of the commercially available devices being based on amperometric detection. However, the detection of glucose in the blood is still an object of intense research. The development of new fluorescent nanomaterials begins to constitute an alternative for glucose blood quantification. These sensors include carbon dots, quantum dots, graphene quantum dots, gold, silver and upconversion nanoparticles. This paper reviews the last 10 year fluorescent nanoparticles based technologies proposed for glucose monitoring and provide an insight into emerging optical fluorescence glucose biosensors.

1 We report a new strategy to synthesize hybrid fluorescent nanosensors consisting of phenylboronic acid-functionalized POSS (POSS–PBA) and diol-modified 8-anilino-1-naphthalenesulfonic acid (ANSA (a fluorescent dye)) for the detection of the biologically important d -glucose. The probe was characterized by FT-IR and 1H NMR analyses, and the photoluminescence intensity was measured under various conditions to confirm its glucose sensing ability. Our POSS-APBA-dye probe could detect glucose at concentrations of 0–20 mg/mL, with a good linear relationship even at low glucose concentrations of 0–1 mg/mL. The properties of the POSS-APBA-dye probe were evaluated and compared with those of an APBA-dye probe. The glucose sensing ability of our POSS-APBA-dye probe was largely unaffected by the presence of interfering substances. The probe showed high sensing ability in a pH 5 environment and long-term (approximately 40 days) fluorescence stability.

A self-powered nonenzymatic glucose sensor electrode boasts the advantages of both a glucose sensor and fuel cell. Herein, an electrode composed of ZnO–graphene hybrid materials on nickel foam (NF) is prepared by electrodeposition of Pd NPs. The electrode is characterized systematically and the dependence of electrocatalytic oxidation of glucose on the concentrations of KOH and glucose, temperature, and potential limit in the anodic direction is investigated. The Pd/NF-ZnO–G electrode shows high catalytic activity, sensitivity, stability, and selectivity in glucose detection, as exemplified by an electrocatalytic glucose oxidation current of 222.2 mA cm−2 under alkaline conditions, high linearity in the glucose concentration range from 5 μM to 6 mM (R2 = 0.98), and high sensitivity of 129.44 μA mM−1−1 cm−2. The Pd/NF-ZnO–G electrode which exhibits superior electrocatalytic activity under alkaline conditions has large potential in nonenzymatic glucose sensing and direct glucose fuel cells and is suitable for miniaturized self-powered nonenzymatic glucose sensing.

Point-of-care (POC) diagnostics have shown excellent potential in rapid biological analysis and health/disease monitoring. Here, we introduce a versatile, cost-effective, flexible, and wearable POC biomarker patch for effective sweat collection and health monitoring. We design and fabricate channels/patterns on filter paper using wax printing technology, which can direct sweat to collection and biomarker detection zones on the proposed platform. The detection zones are designed to measure the amount of collected sweat, in addition to measuring the sweat pH, and glucose (a potential diabetic biomarker), and lactate concentrations. It is significantly challenging to measure glucose in human sweat by colorimetric methods due to the extremely low glucose levels found in this medium. However, we overcame this issue by effectively engineering our wearable biosensor for optimal intake, storage, and evaporation of sweat. Our design concentrates the colorant (indicator) into a small detection zone and significantly increases the sensitivity for the sweat glucose sensing reactions. The device can thus detect glucose in physiological glucose concentration range of 50-300 μM. This cost-effective and wearable biosensor can provide instant in situ quantitative results for targets of interest, such as glucose, pH, and lactate, when coupled with the imaging and computing functionalities of smartphones. Meanwhile, it is also feasible to extract the air-dried sweat from the storage zone for further ex situ measurements of a broader portfolio of biomarkers, leading to applications of our wearable biosensor in personalized nutrition and medicine.

The current research performs the novelty fabricated of non-enzymatic biosensor based on copper nanoparticles decorated carbon black nanocomposite modified glassy carbon electrode (Cu/DCB/GCE) by u ...

In this work, we report a novel naked-eye and fluorescent dual-readout glucose sensing platform based on the bifunctional peroxidase mimicking and ON-OFF fluorescence of Pd nanoparticle-decorated graphitic C3N4 nanosheets (PdNPs/g-C3N4). The PdNPs/g-C3N4 hybrid not only exhibited a strong peroxidase-like activity to catalyze colorless o-phenylenediamine (OPD) into its yellow product OPDox in the presence of H2O2, but it also acted as a turn-off fluorescent sensor for the assembly of the generated OPDox on g-C3N4. When coupled with glucose oxidase (GOx), the platform could provide both visual and fluorescent responses for glucose specifically. Under optimal conditions, the platform was able to detect the target at concentrations as low as 50 μM and 0.4 μM in the linear ranges of 50-2000 μM and 1-1000 μM with the naked eye and a fluorometer, respectively. The developed platform integrates the equipment-free merit of naked-eye observation with the excellent performance of fluorometric analysis well, providing a new and powerful tool for both rough assessment and accurate detection of glucose in diabetes management and other applications.

In this communication, for the first time, an easy preparation method of nickel–iron (Ni–Fe) hybrid nanocubes for glucose oxidation, which is highly efficient in alkaline media, is described. As an impressive redox probe for glucose, the Ni–Fe hybrid nanocubes exhibit many remarkable sensing performances, for example, low-response time (7 s), broad detection range (from 10 μM to 20.5 mM), and low detection limit (0.64 μM, S/N = 3). The selectivity, reliability and stability of the Ni–Fe hybrid nanocubes for glucose oxidation are also investigated. The glucose sensor based on Ni–Fe hybrid nanocubes shows a superior sensing performance to that of Ni-based or Fe-based electrochemical sensors. Furthermore, the Ni–Fe hybrid nanocubes were used to detect glucose in real samples of human blood serum. All the findings demonstrate that the glucose sensor based on Ni–Fe hybrid nanocubes is successful for glucose detection and shows promise for future applications in medical diagnostics, the food industry and biological processes.

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.

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.

Biopolymers have been used for general biomedical applications for millennia and recently have gained attention for their suitability in diagnostic medicine. These naturally derived polymers offer unique appropriateness for use in diagnostics due to their general characteristics, including reduced toxicity, tailorable chemical structure, biodegradability, and tissue likeness. Numerous applications of biopolymers have been recently seen in the diagnosis of a large variety of diseases, such as infection, cancer, diabetes, and autoimmune hemolytic anemia. Multiple biopolymer-based systems have been employed for diagnostics, such as enzymatically activated dye systems, tear glucose sensing, theranostic chitosan nanoparticles, and silk-based immune sensors. This chapter discusses several biologically derived polymeric materials that have been recently employed in the diagnosis of various disease states.

The present chapter explains the progressive synthesis, structural modification and physicochemical response of chitosan built hydrogel for controlled drug delivery applications. The name chitosan built referred to the hydrogel where chitosan can be used as the main component in addition to other monomers. An overview of hydrogel classification, processing, drug loading and release mechanism is highly stressed to discover the production of in-situ gelling system and their functionalization with induced sensitivity (hydrophilicity, hydrophobicity, glucose sensing and self-assembling) for the controlled release of versatile hydrophilic and hydrophobic drugs. The detailed chemistry of various stimuli-responsive hydrogel in biomedical and pharmaceutical applications has been clarified to state of the art of physicochemical responses at physiological conditions. Particular attention is paid to stimuli, including glucose, pH, temperature, ionic strength and urea-responsive hydrogel at physiological conditions. The use of chitosan built hydrogel as a controlled drug delivery system is not only limited to structure–property–relationship but needs a fundamental understanding in terms of chemical, thermal, morphological, optical and interfacial properties. These areas are addressed in terms of synthesis of chitosan built hydrogel, the respective functionalization with induced moieties along with detailed characterization and physicochemical responses for controlled drug delivery applications.

A simple method for the reduction of 4-Nitrophenol (4-NP) to 4-Aminophenol (4-AP) has been described using ionic liquid incorporated graphene nanosheets (IMD-Si/FeCl4ˉ@GNS). The material was also tested for nonenzymatic glucose sensing and found to be a promising material as glucose sensor with very high sensitivity (0.57 ​mA ​mM-1.cm-2) and low detection limit (1.2 ​μm).

Glucose detection is of vital importance to diabetes diagnosis and treatment. Optical approaches in glucose sensing have received much attention in recent years due to the relatively low cost, portable, and mini-invasive or non-invasive potentials. Surface enhanced Raman spectroscopy (SERS) endows the benefits of extremely high sensitivity because of enhanced signals and specificity due to the fingerprint of molecules of interest. However, the direct detection of glucose through SERS was challenging because of poor adsorption of glucose on bare metals and low cross section of glucose. In order to address these challenges, several approaches were proposed and utilized for glucose detection through SERS. This review article mainly focuses on the development of surface enhanced Raman scattering based glucose sensors in recent 10 years. The sensing mechanisms, rational design and sensing properties to glucose are reviewed. Two strategies are summarized as intrinsic sensing and extrinsic sensing. Four general categories for glucose sensing through SERS are discussed including SERS active platform, partition layer functionalized surface, boronic acid based sensors, and enzymatic reaction based biosensors. Finally, the challenges and outlook for SERS based glucose sensors are also presented.