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This paper reports a flexible glucose biosensor which is modified by a reduced-swelling and conductive zwitterionic hydrogel enzyme membrane that contains two forms of chemical cross-links. One chemical cross-linking is induced by thermal initiators and forms the basal network of the hydrogel. Another cross-linking is achieved by the coordination interactions between the multivalent metal ion Al3+ and anionic group -COO− of zwitterionic poly-carboxy betaine (pCBMA), which significantly increase the cross-linking density of the zwitterionic hydrogel, improving the reduced-swelling property and reducing the pore size. The better reduced-swelling property and reduced diameters of pores within the zwitterionic hydrogel make less glucose oxidase (GOx) leakage, thus significantly improving the enzyme membrane's service life. By introducing the Al3+ and Cl−, the conductivity of the zwitterionic hydrogel is enhanced approximately 10.4-fold. According to the enhanced conductivity, the reduced-swelling property, and the high GOx loading capacity of the zwitterionic hydrogel, the sensitivity of the biosensor with GOx/pCBMA-Al3+ is significantly improved by 5 times and has a long service life. Finally, the proposed GOx/pCBMA-Al3+ biosensor was applied in non-invasive blood glucose detection on the human body, verifying the capability in practice. [ABSTRACT FROM AUTHOR]

A highly efficient ratiometric electrochemiluminescence (ECL) immunoassay was explored by bidirectionally regulating the ECL intensity of two luminophors. The immunoassay was conducted in a split-type mode consisting of an ECL detection procedure and a sandwich immunoreaction. The ECL detection was executed using a dual-disk glassy carbon electrode modified with two potential-resolved luminophors (g-C3N4-Ag and Ru-MOF-Ag nanocomposites), and the sandwich immunoreaction using glucose oxidase (GOx)-modified SiO2 nanospheres as labels was carried out in a 96-well plate. The Ag nanoparticles (NPs) acted as bifunctional units both for triggering the resonance energy transfer (RET) with g-C3N4 and for accelerating the electron transfer rate of the Ru-MOF-Ag ECL reaction. When the H2O2 catalyzed by GOx in the 96-well plate was transferred to the dual-disk glass carbon electrode, the doped Ag NPs in the two luminophors could be etched, thus destroying the RET between C3N4 and the accelerated reaction to Ru-MOF, resulting in an opposite trend in the ECL signal outputted from the dual disks. Using the ratio of the two signals for quantification, the constructed immunosensor for a model target, i.e. myoglobin, exhibited a low detection limit of 4.7 × 10–14 g/mL. The ingenious combination of ECL ratiometry, bifunctional Ag NPs, and a split-type strategy effectively reduces environmental and human errors, offering a more precise and sensitive analysis for complex samples. [ABSTRACT FROM AUTHOR]

This study reports a micromachined parylene-C-coated integrated electrode (IDE) sensor fabricated on a polyimide film. Glucose and uric acid within the human sweat concentration range were tested using hydrothermally grown ZnO nanoparticles (NPs) immobilized on the IDE regions of sensors and modified with urate oxidase and glucose oxidase enzymes. Four important sensing parameters, including capacitance, impedance, resistance, and phase, were simultaneously investigated during the dynamic test. The sensor fabrication and characterization of ZnO NPs and ZnO NP formed sensing film were described in detail. The experimental results show that the amount of capacitance change and phase change vs. the concentration variation of glucose and uric acid exhibits an excellent linear regression relationship. On the other hand, the amount of impedance change vs. concentration variation of glucose and uric acid exhibits a power regression relationship. Sensitivities of uric acid and glucose detection based on capacitance changes were 0.1131 pF/µM and 0.7875 pF/µM, respectively. Limits of detection of uric acid and glucose were 1.23 µM and 0.311 µM, respectively. Thus, the developed sensor can be applied to wearable devices for the quantitative analysis of sweat composition in the future. [ABSTRACT FROM AUTHOR]

This study synthesized Fe-doped dopamine carbon dots (Fe-DACDs) as a reducing agent and template hybrid Au and Pt nanoparticles (Au@Pt/Fe-DACDs). Au@Pt/Fe-DACDs with core–shell structures show strong peroxidase (POD)-like activity at physiological pH. A colorimetric and surface-enhanced Raman scattering (SERS) dual-mode detection system for glucose in human serum was constructed by combining Au@Pt/Fe-DACDs with natural glucose oxidase (GOx). The cascade catalysis reactions convert glucose into hydrogen peroxide (H2O2), and then, the Au@Pt/Fe-DACDs as both POD-like nanozyme and Raman-enhancers oxidize colorless and weak Raman-active 3,3′,5,5′-tetramethylbenzidine (TMB) into blue and strong Raman-active ox-TMB. The linear response ranges of glucose are from 0.02 to 1 mM, with a detection limit of 2.3 μM for colorimetric detection and 0.01 mM to 0.7 mM with a detection limit of 1.4 μM for SERS sensors. Glucose content in human serum samples was successfully assayed with a good recovery from 97.6 to 105.3%. Overall, these results demonstrate a new way of designing biological detection systems based on SERS and colorimetric dual-mode sensing. [ABSTRACT FROM AUTHOR]

Directed toward the limitations of natural enzymes in diabetes management, it is possible to design nano-enzymatic structures and modulate the activity as needed to obtain superior materials that are more suitable for the specific application environment. In this work, noble metal–semiconductor composite nanozymes [Te–Au nanowires (NWs)] were designed and their enzyme-like activities were systematically investigated for diabetes management. The results indicated that Te–Au NWs exhibited pH-switching multi-enzyme-like activities and adapted to a wider range of reaction conditions than natural enzymes. The kinetics of their enzyme-catalyzed reactions followed the Michaelis–Menten model, showing their substrate affinity similar to that of natural enzymes. Actually, the nanozymes showed reliable application stability, maintaining more than 80% of various enzyme activities under prolonged or extreme storage conditions. Furthermore, the nanozymes can be flexibly applied to various paths of glucose detection. For example, we constructed three different colorimetric detection methods to achieve the detection of glucose in saliva and blood. All three detection methods showed a wider linear range and lower limit of detection (LOD), among which the most optimal method was the combination of Te–Au NWs and glucose oxidase (GOx), with a linear range of 0.05–4 mM and a LOD of 2.11 μM. In summary, nanozymes with multiple enzyme-like activities have significant advantages and effectively address the limitations of natural enzymes in the application of diabetes management. [ABSTRACT FROM AUTHOR]

Oxidative stress from excess H2O2 activates transcription factors that restore redox balance and repair oxidative damage. Although many transcription factors are activated by H2O2, it is unclear whether they are activated at the same H2O2 concentration, or time. Dose-dependent activation is likely as oxidative stress is not a singular state and exhibits dose-dependent outcomes including cell-cycle arrest and cell death. Here, we show that transcription factor activation is both dose-dependent and coordinated over time. Low levels of H2O2 activate p53, NRF2 and JUN. Yet under high H2O2, these transcription factors are repressed, and FOXO1, NF-κB, and NFAT1 are activated. Time-lapse imaging revealed that the order in which these two groups of transcription factors are activated depends on whether H2O2 is administered acutely by bolus addition, or continuously through the glucose oxidase enzyme. Finally, we provide evidence that 2-Cys peroxiredoxins control which group of transcription factors are activated. H2O2 stress is known to activate a slew of transcription factors that restore redox balance. Here, the authors use live-cell imaging and single-cell analysis to reveal that the transcription factors that are activated and their timing of activation is dose dependent. [ABSTRACT FROM AUTHOR]

Considering the application prospects of a cascade catalytic system in biomedical analysis, it remains significant to develop a cascade catalytic system for one-step rapid colorimetric detection. Herein, PVP/NH2-MIL-101(Fe) possessing enhanced peroxidase (POD)-like activity was successfully synthesized by microwave-assisted and polyvinylpyrrolidone (PVP) modification strategies. Then, PVP/NH2-MIL-101(Fe) and glucose oxidase (GOx) were covalently coupled via the bifunctional cross-linker glutaraldehyde, the GOx@PVP/NH2-MIL-101(Fe) with dual enzymatic functional activities (POD-like and GOx activities) was subsequently synthesized. GOx@PVP/NH2-MIL-101(Fe) had strong affinities for the substrates glucose, 3,3',5,5'-tetramethylbenzidine, and hydrogen peroxide. Based on this specific nanozyme GOx@PVP/NH2-MIL-101(Fe), a one-step colorimetric assay for rapid glucose determination was built. This detection method not only took 20 min to analyze but also possessed a linear range of 10–250 µM with a detection limit of 1.05 µM. Furthermore, the cascade catalytic system was applied to determine glucose concentrations in human serum samples. Compared with commercial blood glucose meters, the proposed method was also accurate and effective, making it a candidate method for determining blood glucose. [ABSTRACT FROM AUTHOR]

Wearable glucose biosensors enable noninvasive glucose monitoring, thereby enhancing blood glucose management. In this work, we present a wearable biosensor based on carbon black nanoparticles (CBNPs) for glucose detection in human sweat. The biosensor consists of CBNPs, Prussian blue (PB), glucose oxidase, chitosan, and Nafion. The fabricated biosensor has a linear range of 5 µM to 1250 µM, sensitivity of 14.64 µA mM−1 cm−2, and a low detection potential (−0.05 V, vs. Ag/AgCl). The detection limit for glucose was calculated as 4.83 µM. This reusable biosensor has good selectivity and stability and exhibits a good response to glucose in real sweat. These results demonstrate the potential of our CBNP-based biosensor for monitoring blood glucose in human sweat. [ABSTRACT FROM AUTHOR]

In this work, the β-cyclodextrins (βCD) grafted on magnetite@polynorepinephrine (Fe3O4@PNE) nanomaterial with glucose oxidase (GOx) from Aspergillus niger was presented. The electroactive nanoplatform was used to construct rapid response and long-live time biosensor for qualitative and quantitative glucose determination. The nanomaterial was deposited on the screen-printed electrode (SPE) and integrated with the potentiostat in tandem with a portable devices. The methodology may affect its relatively low unit cost, miniaturization aspect, and electrode system integrity. The potential usage is intended for advanced diabetes care with a focus on the point-of-care testing idea. The cyclic voltammetry and amperometry were used for electrochemical characterization. The presented SPE/Fe3O4@PNE@βCD-GOx biosensor enabled measurements in a wide range of concentrations (0.1–30.0 mM), an enhanced sensitivity (204.82 µA mM− 1 cm− 2), a low limit of detection (3.2 µM), and a rapid response (2.6 s). Moreover, the proposed sensor achieved long-term stability, up to 11 months. Testing on real samples (human blood, human serum, infusion fluids) showed recovery in range from 95.5 to 98.6%. The outcomes demonstrated that this biosensor has great potential for use in determining the amount of glucose in a biological fluids and commercial products. The novelty of this work would largely consist of the possibility of qualitative and quantitative measurements of glucose in real human samples with a long time stability. This portable system enables mobile diagnostics tests including point-of-care testing idea. Due to the applied β-cyclodextrins on the surface of the novel polynorepinephrine biopolymer coating, selectivity, stability, and sensitivity were improved. [ABSTRACT FROM AUTHOR]

Artificial actuators have been extensively studied due to their wide range of applications from soft robotics to biomedicine. Herein we introduce an autonomous bi-enzymatic system where reversible motion is triggered by the spontaneous oxidation and reduction of glucose and oxygen, respectively. This chemo-mechanical actuation is completely autonomous and does not require any external trigger to induce self-sustained motion. The device takes advantage of the asymmetric uptake and release of ions on the anisotropic surface of a conducting polymer strip, occurring during the operation of the enzymes glucose oxidase and bilirubin oxidase immobilized on its surface. Both enzymes are connected via a redox polymer at each extremity of the strip, but at the opposite faces of the polymer film. The time-asymmetric consumption of both fuels by the enzymatic reactions produces a double break of symmetry of the film, leading to autonomous actuation. An additional break of symmetry, introduced by the irreversible overoxidation of one extremity of the polymer film, leads to a crawling-type motion of the free-standing polymer film. These reactions occur in a virtually unlimited continuous loop, causing long-term autonomous actuation of the device. Owing to their interesting applications from soft robotics to biomedicine, methodologies to produce artificial actuators are desirable. Herein the authors develop an autonomous soft bioelectrochemical actuator with self-sustained motion triggered by spontaneous enzymatic reactions. [ABSTRACT FROM AUTHOR]

In this work, a novel amperometric biosensor for the determination of adenosine triphosphate (ATP) was developed. The biosensor was based on two enzymes (glucose oxidase and hexokinase) that were entrapped in the electrospun nanofibers. The biosensor was prepared by direct electrospinning of the enzymes/polymer mixture on the surface of platinum disc electrodes with subsequent UV cross-linking of the obtained nanofibers. Photocrosslinkable polymer (polyvinyl alcohol containing styrylpyridinium groups, PVA-SbQ) was chosen as matrix, while gold nanoparticles (GNPs) were added to the enzymes/polymer mixture to improve analytical characteristics of the biosensor. For the first time, incorporation of several enzymes in the nanofibers during electrospinning was demonstrated. Composition of the mixture for electrospinning was optimized. The obtained biosensors enabled successful detection of ATP by chronoamperometry, linear range was 25–200 μM. The analytical characteristics of the biosensors were compared with the biosensors prepared by manual drop-casting of the enzymes/polymer/GNP mixture. The biosensor can be also used to detect glucose in samples with known or very low (< 10 μM) ATP concentration; linear range of the glucose determination was 0.01–3 mM. The described approach for one-step electrospinning of several enzymes is fast and simple and can be easily modified for immobilization of other multi-enzyme systems, which opens possibilities to enlarge the range of the targets that can be determined by the biosensors produced using electrospinning. [ABSTRACT FROM AUTHOR]

The nanoscale thermal effect of ferrimagnetic vortex-domain iron oxide nanorings (FVIOs) was measured when exposed to an alternating magnetic field. A molecular temperature probe (fluorescein isomer I, FI) was attached to a thermo-sensitive molecule (4,4′-Azobis (4-cyanovaleric acid, AZO), then the molecule was bound to the nanoparticle surface through poly (ethylene glycol) (PEG, Mw = 1000, 2000, 5000 Da) spacers of different molecular weights. The magnetothermal effect induced the thermal decomposition of AZO driving the release of FI which was monitored by the photoluminescence method. It was found that the effective local temperature (Teff) decreased with the increase of Mw (PEG) and increased with the rise in field amplitudes B, and the temperature was found in a linear relationship with the applied magnetic field at all distances. The significant local heating temperature (T) rose to 60.3 °C when d = 0 of FVIOs, where d is the distance of the AZO-FI end group to the surface, while it fell exponentially with the increasing distance. The nanoscale thermal effect of the 20 nm superparamagnetic iron oxide nanoparticles (SPIOs) was also studied. The results revealed that FVIOs have much higher nanometer local heat than SPIOs for all the applied magnetic field amplitudes. These findings were then applied in the enzyme activity regulation experiment of FVIOs and SPIOs. The results indicated that glucose oxidase (GOD) had higher enzyme activity after nano-magnetothermal stimulation of FVIOs. [ABSTRACT FROM AUTHOR]

A procedure for the synthesis of a highly selective adsorbent based on an imprinted protein (IP), glucose oxidase (GO), and commercially available SiO2 microparticles for the sorption of mycotoxin zearalenone produced by fungi of the Fusarium species is developed. The use of 3D fluorescence spectroscopy for the control of the process of IP purification is proposed for the first time. A possibility of replacing the zearalenone molecule as a template molecule with structural analogues with lower toxicity is assessed. The analytical characteristics of the determination of zearalenone using imprinted GO as a receptor element in enzyme immunoassay are determined: the limit of detection is 5 ng/mL, the linear analytical range is 11–112 ng/mL. High sorption characteristics of the synthesized adsorbent based on IP (sorption capacity—7.6 μg/mg sorbent; imprinting factor—2.5) are shown. [ABSTRACT FROM AUTHOR]

In this work, Au nanoparticles were synthesized using eco-friendly protocol and then supported on reduced graphene oxide (rGO) nanosheets through in-situ polymerization of indole (In), focusing on their electrochemical efficiency against glucose oxidation in glucose-based biofuel cells (glucose/O2). The bioanode was fabricated by applying ferritin (Frt) and glucose oxidase (GOx) on the glassy carbon electrode (GCE) followed by deposition of Au@rGO/PIn nanocomposite. The physical characterizations such as Fourier transform infrared spectroscopy (FTIR), X-ray diffraction analysis (XRD), and scanning electron microscopy (SEM), have revealed the successful synthesis of Au@rGO/PIn nanocomposite. In addition, the electrochemical behavior of different modified bioanodes were analyzed using linear sweep voltammetry (LSV), electrochemical impedance spectroscopy (EIS), and cyclic voltammetry (CV). The modified bioanode Au@rGO/PIn/Frt/GOx attained a maximum current output of 7.2 mA cm−2 at the optimum glucose concentration of 50 mM in phosphate buffer solution (PBS) as an electrolyte. However, the obtained result is not the highest current density as reported in the literature but the materials are cost effective and method is easier and ecofriendly. This suggests that 3D fabricated bioanode could be used in enzymatic biofuel cell (EBFC) applications and allied fields, such as biosensors and bioreactors. [ABSTRACT FROM AUTHOR]

Bioinspired multi-compartment architectures are desired in synthetic biology and metabolic engineering, as credited by their cell-like structures and intrinsic ability of assembling catalytic species for spatiotemporal control over cascade reactions like in living systems. Herein, we describe a general Pickering double emulsion-directed interfacial synthesis method for the fabrication of multicompartmental MOF microreactors. This approach employs multiple liquid–liquid interfaces as a controllable platform for the self-completing growth of dense MOF layers, enabling the microreactor with tailor-made inner architectures and selective permeability. Importantly, simultaneous encapsulation of incompatible functionalities, including hydrophilic enzyme and hydrophobic molecular catalyst, can be realized in a single MOF microreactor for operating chemo-enzymatic cascade reactions. As exemplified by the Grubb' catalyst/CALB lipase driven olefin metathesis/ transesterification cascade reaction and glucose oxidase (GOx)/Fe-porphyrin catalyzed oxidation reaction, the multicompartmental microreactor exhibits 2.24–5.81 folds enhancement in cascade reaction efficiency in comparison to the homogeneous counterparts or physical mixture of individual analogues, due to the restrained mutual inactivation and substrate channelling effects. Our study prompts further design of multicompartment systems and the development of artificial cells capable of complex cellular transformations. The cell-like structures and the ability of assembling catalytic species are interesting features of bioinspired multicompartment architectures but it remains a challenge to build them. Here, the authors describe a Pickering double emulsion-directed interfacial synthesis to fabricate multi-compartmented metal-organic framework microreactors. The cell-like structures and the ability of assembling catalytic species are interesting features of bioinspired multicompartment architectures but it remains a challenge to build them. Here, the authors describe a Pickering double emulsion-directed interfacial synthesis to fabricate multi-compartmented metal-organic framework microreactors. [ABSTRACT FROM AUTHOR]

Self-adaptability is highly envisioned for artificial devices such as robots with chemical noses. For this goal, seeking catalysts with multiple and modulable reaction pathways is promising but generally hampered by inconsistent reaction conditions and negative internal interferences. Herein, we report an adaptable graphitic C6N6-based copper single-atom catalyst. It drives the basic oxidation of peroxidase substrates by a bound copper-oxo pathway, and undertakes a second gain reaction triggered by light via a free hydroxyl radical pathway. Such multiformity of reactive oxygen-related intermediates for the same oxidation reaction makes the reaction conditions capable to be the same. Moreover, the unique topological structure of CuSAC6N6 along with the specialized donor-π-acceptor linker promotes intramolecular charge separation and migration, thus inhibiting negative interferences of the above two reaction pathways. As a result, a sound basic activity and a superb gain of up to 3.6 times under household lights are observed, superior to that of the controls, including peroxidase-like catalysts, photocatalysts, or their mixtures. CuSAC6N6 is further applied to a glucose biosensor, which can intelligently switch sensitivity and linear detection range in vitro. Catalysts with multiple and modulable reaction pathways are promising but generally hampered by inconsistent reaction conditions and negative internal interferences. Herein, the authors report an adaptable graphitic C6N6-based copper singleatom catalyst [ABSTRACT FROM AUTHOR]

The hydrogen peroxide (H2O2) measurement is considered highly important in industrial wastewater quality assessment, environmental protection, and disease detection. Here, a simple high-performance paper-based sensor is proposed for rapid and in situ detection of H2O2. To this end, 3,3′,5,5′-tetramethylbenzidine is embedded in the sensor to act as a color indicator, whose reaction with hydrogen peroxide is catalyzed by a silver nanozyme modified by sericin. The result of the reaction clarified by the appearance of blue color in the sensor detection zone is received by a portable scanner, while also calculating its intensity by image analysis software. This method is sensitive to hydrogen peroxide in the concentration range of 0.5‒240 mg/dL, providing a detection limit of 0.15 mg/dL. The ability of the sensor to determine glucose is also evaluated by adding a layer containing glucose oxidase enzyme to the sensor structure. A desirable response is obtained in the range of 1.0‒160 mg/dL, together with a detection limit of 0.37 mg/dL. Accordingly, the proposed sensor shows satisfactory results compared to clinical methods for monitoring the amount of glucose in biological samples such as serum and saliva. [ABSTRACT FROM AUTHOR]

An accurate and sensitive competitive enzyme-linked immunosorbent assay (ELISA) based on persistent luminescence nanoparticles Zn2GeO4:Mn2+, Eu3+ (ZGME) was developed for detecting ochratoxin A (OTA), a powerfully toxic mycotoxin usually found in grains. As a signal output element of autofluorescence-free biosensors, ZGME can be integrated into ELISA with glucose oxidase (GOx)-binding OTA molecules due to its excellent pH-responsive persistent luminescence. In the absence of OTA, the OTA-GOx conjugate was captured by the anti-OTA monoclonal antibody (anti-OTA mAb) pre-coated on the 96-well plate. The results indicate a decrease in the pH value of the solution, which triggered the quenching of ZGME luminescence due to GOx-dependent gluconic acid production. The presence of OTA inhibited the binding of OTA-GOx on the plate, thus decreasing the production of gluconic acid and increasing the persistent luminous intensity of ZGME. Under the optimized concentrations of anti-OTA mAb and OTA-GOx, quantitative determination of OTA was achieved by plotting the increase or decrease in persistent luminescence intensity of ZGME at 535 nm. In this study, the linear range was from 0.1 μg L−1 to 63 μg L−1, and the limit of detection (LOD) was as low as 0.045 μg L−1. In five food samples (corn grit, brown rice, soybean, rice, and wheat), the results exhibited good stability and repeatability, with a recovery range from 81.3% to 94.4% and a relative standard deviation (RSD) of less than 4.2%. Hence, the established method provides a sensitive, accurate, and autofluorescence-free approach for the determination of OTA in different grain samples. [ABSTRACT FROM AUTHOR]

Highlights: Screen-printable functional nanocomposite inks are engineered for flexible, single-enzyme-based energy-harvesting, and self-powered biosensing devices. A BFC powered by the same biosubstrate (glucose) is developed to harvest energy in a biofluid model and act as a self-powered electrochemical glucose. Customized inks are advantageous in terms of integrating with flexible materials, which can be integrated with a wide range of wearables and soft bioelectronics. Developing flexible bioelectronics is essential to the realization of artificial intelligence devices and biomedical applications, such as wearables, but their potential is limited by sustainable energy supply. An enzymatic biofuel cell (BFC) is promising for power supply, but its use is limited by the challenges of incorporating multiple enzymes and rigid platforms. This paper shows the first example of screen-printable nanocomposite inks engineered for a single-enzyme-based energy-harvesting device and a self-powered biosensor driven by glucose on bioanode and biocathode. The anode ink is modified with naphthoquinone and multiwalled carbon nanotubes (MWCNTs), whereas the cathode ink is modified with Prussian blue/MWCNT hybrid before immobilizing with glucose oxidase. The flexible bioanode and the biocathode consume glucose. This BFC yields an open circuit voltage of 0.45 V and a maximum power density of 266 μW cm−2. The wearable device coupled with a wireless portable system can convert chemical energy into electric energy and detect glucose in artificial sweat. The self-powered sensor can detect glucose concentrations up to 10 mM. Common interfering substances, including lactate, uric acid, ascorbic acid, and creatinine, have no effect on this self-powered biosensor. Additionally, the device can endure multiple mechanical deformations. New advances in ink development and flexible platforms enable a wide range of applications, including on-body electronics, self-sustainable applications, and smart fabrics. [ABSTRACT FROM AUTHOR]

In this work, three specialized oxidases for glucose, lactate and cholesterol are absorbed on carbon microspheres (CSs), which can produce hydrogen peroxide during their substrate-specific enzymatic activity. Electrochemiluminescent (ECL) is generated by the electrochemical reaction between luminol and hydrogen peroxide on an ECL biosensor array, whose light signals are collected by a CCD camera. Under optimum conditions, calibration curves are constructed for glucose, lactate, cholesterol concentrations and ECL intensities. The detection limits of the different biosensors are found to be 12 μM for glucose, 3 μM for lactate and 19 μM for cholesterol. Furthermore, the resulting ECL biosensor array is expected to be an alternative analytical tool in clinical analysis because of its good stability, acceptable precision and reproducibility. [ABSTRACT FROM AUTHOR]

This paper describes a simple electrochemical sensing platform based on single-walled carbon nanotube (SWCNT) electrodes for glucose detection. The device fabrication using O2-plasma treatment allows precision and uniformity for the construction of three SWCNT electrodes on the flexible plastic substrate. Glucose assay can be simply accomplished by introducing a glucose sample into the fabricated biosensor. The marked electrocatalytic and biocompatible properties of biosensors based on SWCNT electrodes with the incorporation of ferrocenecarboxylic acid and polyethylene glycol enable effective amperometric measurement of glucose at a low oxidation potential (0.3 V) with low interferences from coexisting species. The device shows efficient electroanalytical performances with high sensitivity (5.5 μA·mM−1·cm−2), good reproducibility (CV less than 3%), and long-term stability (over a month). A linear range of response was found from 0 to 10 mM of glucose with a fast response time of 10 s. This attractive electroanalytical device based on GOx/FCA/PEG/SWCNT electrodes offers a promising system to facilitate a new approach for diverse biosensors and electrochemical devices. [ABSTRACT FROM AUTHOR]

Flexible, wearable biosensors have been extensively investigated in recent decades due to their potential applications in portable electronics and human health monitoring. However, low sensitivity and complex fabrication are still great challenges for flexible sensors. Herein, a flexible electrochemical biosensor for glucose was proposed, which was based on reduced graphene oxide and gold nanoparticle-modified screen-printed gold electrodes (rGO-Au/SPGE) as catalysts and gel instead of traditional liquid electrolyte. The biosensor combines the soft stretchability of the gel, the specific selectivity of glucose oxidase (GOx) and the high catalytic activity of the rGO-Au/SPGE nanocomposite. More importantly, the soft gel not only adheres well to the skin, but also promotes the penetration of water-soluble molecules, effectively improving the accumulation of bodily fluids on dry skin surfaces. The constructed GOx-gel-rGO-Au/SPGE biosensor maintains stable sensing performance even after 1000 bending cycles. In addition, the biosensor exhibited significantly current response to glucose at a detection range of 1.25–850 µM and 0.85–7.72 mM (covers the glucose level in human sweat), with a sensitivity of 53.7 and 27.4 μA/mM cm2 and low detection limit (1.25 µM). The flexible electrochemical biosensor based on GOx-gel-rGO-Au/SPGE could accurately determine glucose in human sweat, demonstrating a promising feature for personal healthcare diagnosis. [ABSTRACT FROM AUTHOR]

Objectives: Maximizing the utility value of enzymes was achieved by exploring the effects of small molecules on the efficiency of lignin degradation by lignin peroxidase. Methods: Using wheat straw as raw material and taking lignin degradation rate as index, it was found that laccase, glucose oxidase, malonic acid, citric acid, ZnSO4, CaCl2 could promote the lignin degradation by the lignin peroxidase from Irpex lacteus, respectively. Moreover, glucose oxidase, malonic acid and CaCl2 had obvious synergy effects on lignin degradation by the lignin peroxidase. Results: The optimal conditions of lignin degradation were obtained by response surface experiment: 4% glucose oxidase, 0.74% malonic acid and 3.29% CaCl2 were added for synergistic degradation at 37 ℃ with 50% of water content. After 72 h quickly enzymatic hydrolysis, the degradation rate of lignin was 45.84%. Conclusions: A new green and efficient method for lignin removal from straw was obtained, which provided a reference for the efficient utilization of straw and lignin peroxidase. [ABSTRACT FROM AUTHOR]

Bee pollen (BP) and bee bread (BB) have attracted great attention due to their biological activities including antibacterial activity. However, the mechanism of antibacterial activity is largely unknown. Therefore, we aimed to characterise the antibacterial effect of BP and BB aqueous extracts against bacterial pathogens (Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli, Proteus mirabilis and Enterococcus faecalis) and identify the key compound(s) responsible for this effect. Here, we demonstrate that BP and particularly BB extracts display antibacterial activity which is significantly increased in the presence of glucose. Immunoblot analysis of extracts revealed the presence of MRJP1 in all analysed BP and BB samples and the enzyme glucose oxidase (GOX) in the majority of BB samples. Treatment of extracts with catalase resulted in the restoration of bacterial growth but only in those samples where glucose supplementation caused the enhancement of antibacterial activity. Our findings provide a deeper understanding of antibacterial activity of BP/BB which is mediated by the enzymatic activity of bee-derived GOX. [ABSTRACT FROM AUTHOR]

The purpose of this work is to develop a bioanode using the enzymes of glucose oxidase (GOx) and alcohol dehydrogenase (ADH) as catalysts to oxidised glucose and alcohol present in different beverages. The study was carried out using the covalent bonding method for both enzymes via the functionalization of carbon nanofibers for the formation of carboxyl groups that can form bonds with the amine groups of the enzyme, as well as using tetrabutylammonium bromide (TBAB) with Nafion. The optimum operation parameters of both enzymes (pH and temperature) were determined for the later evaluation in a microfluidic fuel cell. In addition, using the scanning electrochemical microscopy technique, a local study of enzymatic processes is used to demonstrate that the enzymes immobilized on the same electrode remain active. The evaluation of the microfluidic fuel cell was carried out using different solutions, 0.01 M glucose, 0.01 M ethanol and a mixture of 0.01 M glucose and 0.01 M ethanol, all in phosphate buffer solutions at pH 7, where it was possible to obtain a maximum performance of 5.07 ± 0.1 mW cm−2, and there was a significant increase in current density compared to non-composite solutions (glucose or ethanol). In addition, different alcoholic beverages were used to evaluate the versatility and adaptability of the bi-enzymatic anode electrode with the perspective use in Lab-on-a-Chip systems. [ABSTRACT FROM AUTHOR]

Continuous glucose monitoring systems (CGMS) are becoming increasingly popular in diabetes management compared to conventional methods of self-blood glucose monitoring systems. They help understanding physiological responses towards nutrition intake, physical activities in everyday life and glucose control. CGMS available in market are of two types based on their working principle. Needle type systems with few weeks lifespan (e.g., enzyme-based Freestyle Libre) and implant type system (e.g., fluorescence-based Senseonics) with few months of lifespan are commercially available. An alternate to both working methods, herein, we propose electromagnetic-based sensor that can be subcutaneously implanted and capable of tracking minute changes in dielectric permittivity owing to changes in blood glucose level (BGL). Proof-of-concept of proposed electromagnetic-based implant sensor has been validated in intravenous glucose tolerance test (IVGTT) conducted on swine and beagle in a controlled environment. Sensor interface modules, mobile applications, and glucose mapping algorithms are also developed for continuous measurement in a freely moving beagle during oral glucose tolerance test (OGTT). The results of the short-term (1 h, IVGTT) and long-term (52 h, OGTT) test are summarized in this work. A close trend is observed between sensor frequency and BGL during GTT experiments on both animal species. [ABSTRACT FROM AUTHOR]

This paper presents a microwave microfluidic biosensor for monitoring blood glucose levels. The glucose sensor is a triple ring microstrip patch antenna integrated with a biomimetic microfluidic device capable of measuring a fixed volume of glucose solution. The sensor was utilized to detect 50–500 mg/dL glucose solutions. The interaction of the glucose solution with the electromagnetic field on the patch's surface influences both the resonance frequency and the magnitude of reflection coefficient. The results indicate that the microfluidic device can reduce experimental error and enhance the correlation between glucose concentration, resonant frequency, and reflection coefficient. Finally, the microfluidic sensor had a sensitivity of 0.25 MHz/(mg/dL), a detection limit as low as 7.7 mg/dL, and correlation coefficients of resonance frequency and reflection coefficient with a glucose concentration of 0.996 and 0.984, respectively. The experiment on the sensor's stability verifies the sensor's excellent stability and rapid response (~ 150 ms). Consequently, the device can be used to differentiate the concentration of glucose solutions, as well as to detect blood glucose levels at an early stage. [ABSTRACT FROM AUTHOR]

For the first time, a bio-photo-catalyst is synthesized in a microfluidic platform. The microchannel, which is wall-coated by in situ synthesized bio-photo-catalyst is used as an opto-fluidic reactor for amoxicillin degradation. Analyses including SEM, XRD, FTIR, Raman, UV–Vis spectra, and DLS have been used to characterize samples. The structure and morphology of TiO2 in microfluidic assisted synthesis are studied at 70–120 °C. The results show that both single-crystalline anatase sample and two-phase samples of anatase and rutile can be attained. According to SEM images, the smallest size and the narrowest particle size distribution (0.86 nm ± 0.14 ) is achieved by synthesis at 70 °C. Elemental mapping of Ti shows a uniform coating layer on inner walls. Raman signals besides the primary amines in FTIR results show the biological activity of the cross-linked Glucose oxidase (GOx), which is aimed for situ generation of H2O2. FTIR comparison of bulk and spiral microfluidic synthesized ZnO indicates identical bonds. SEM-coupled with performance experimentation reveal that by regulating the flowrate of spiral micromixer for ZnCl2 at 25 µl/min and NaOH at 50 µl/min, the narrowest size distribution and best the bio-photo-catalytic performance of ZnO nanoparticles is observed. [ABSTRACT FROM AUTHOR]

Tyramide signal amplification (TSA) is a highly sensitive method for histochemical analysis. Previously, we reported a TSA system, biotinyl tyramine-glucose oxidase (BT-GO), for bright-filed imaging. Here, we develop fluorochromized tyramide-glucose oxidase (FT-GO) as a multiplex fluorescent TSA system. FT-GO involves peroxidase-catalyzed deposition of fluorochromized tyramide (FT) with hydrogen peroxide produced by enzymatic reaction between glucose and glucose oxidase. We showed that FT-GO enhanced immunofluorescence signals while maintaining low background signals. Compared with indirect immunofluorescence detections, FT-GO demonstrated a more widespread distribution of monoaminergic projection systems in mouse and marmoset brains. For multiplex labeling with FT-GO, we quenched antibody-conjugated peroxidase using sodium azide. We applied FT-GO to multiplex fluorescent in situ hybridization, and succeeded in labeling neocortical interneuron subtypes by coupling with immunofluorescence. FT-GO immunofluorescence further increased the detectability of an adeno-associated virus tracer. Given its simplicity and a staining with a high signal-to-noise ratio, FT-GO would provide a versatile platform for histochemical analysis. [ABSTRACT FROM AUTHOR]

The design and construction of synthetic prototissues from integrated assemblies of artificial protocells is an important challenge for synthetic biology and bioengineering. Here we spatially segregate chemically communicating populations of enzyme-decorated phospholipid-enveloped polymer/DNA coacervate protocells in hydrogel modules to construct a tubular prototissue-like vessel capable of modulating the output of bioactive nitric oxide (NO). By decorating the protocells with glucose oxidase, horseradish peroxidase or catalase and arranging different modules concentrically, a glucose/hydroxyurea dual input leads to logic-gate signal processing under reaction-diffusion conditions, which results in a distinct NO output in the internal lumen of the model prototissue. The NO output is exploited to inhibit platelet activation and blood clot formation in samples of plasma and whole blood located in the internal channel of the device, thereby demonstrating proof-of-concept use of the prototissue-like vessel for anticoagulation applications. Our results highlight opportunities for the development of spatially organized synthetic prototissue modules from assemblages of artificial protocells and provide a step towards the organization of biochemical processes in integrated micro-compartmentalized media, micro-reactor technology and soft functional materials. A challenge for synthetic biology is the design and construction of prototissue. Here, the authors spatially segregate layers of enzyme-decorated coacervate protocells as a model prototissue capable of chemical signal processing and modulating outputs of nitric oxide to inhibit blood clot formation. [ABSTRACT FROM AUTHOR]

With the advantages of developed electronic devices, various biosensor applications have become attractive issues with excellent electrochemical performances against biomarkers and molecules in biomedical applications. In this study, novel polyacrylonitrile (PAN)-reduced graphene oxide (rGO) nanocomposite-based non-enzymatic electrochemical biosensors were prepared to investigate the detection performance of the glucose. The PAN-rGO nanocomposite-based biosensor detected glucose with a high sensitivity and stability due to enhanced redox mechanism arising from rGO additive. PAN-rGO nanocomposite-based biosensor detected glucose in (0.75–12) mM with a high sensitivity of 49 µAmM−1 cm−2 (2.5 times higher than PAN-based sensor). Concentration–response graphs correlating the non-enzymatic electrochemical signal to glucose concentration revealed a low limit of detection (LOD) of 0.6 mM within 1-min voltammetric cycle. The selectivity results confirmed a significant preferential response of the proposed PAN-rGO nanocomposite-based biosensor for glucose against possible interfering compounds. The proposed PAN-rGO nanocomposite-based biosensor has a great potential to be used as a nanostructured platform for detection of glucose in phosphate-buffered saline (pH 7.4) solution with high sensitivity, selectivity, stability, reproducibility, and fast response properties. [ABSTRACT FROM AUTHOR]

Covalent organic frameworks (COFs) with uniform porosity, good stability, and desired biocompatibility can function as carriers of immobilized enzymes. However, the obstructed pores or partially obstructed pores have hindered their applicability after loading enzymes. In this study, the hierarchical COFs were prepared as an ideal support to immobilize glucose oxidase (GOD) and obtain GOD@COF. The hierarchical porosity and porous structures of COFs provided sufficient sites to immobilize GOD and increased the rate of diffusion of substrate and product. Moreover, N,Fe-doped carbon dots (N,Fe-CDs) with peroxidase-like activity were introduced to combine with GOD@COF to construct an enzyme-mediated cascade reaction, which is the basis of the sensor GOD@COF/N,Fe-CDs. The sensor has been successfully built and applied to detect glucose. The limit of detection was 0.59 μM for determining glucose with the proposed fluorescence sensor. The practicability was illustrated by detecting glucose in human serum and saliva samples with satisfactory recoveries. The proposed sensor provided a novel strategy that introduced COF-immobilized enzymes for cascade reactions in biosensing and clinical diagnosis. [ABSTRACT FROM AUTHOR]

Carbon dots (CDs) have several superior characteristics including sufficient carbon sources, easy preparation, no toxicity, and high catalytic efficiency as a new kind of nanozyme. Herein, Ce-doped carbon dots (Ce-CDs), Cr-doped carbon dots (Cr-CDs), Cu-doped carbon dots (Cu-CDs), Fe-doped carbon dots (Fe-CDs), Mn-doped carbon dots (Mn-CDs), and non-metal-doped carbon dots (0-CDs) were synthesized to explore the detection of hydrogen peroxide (H2O2) and glucose as peroxidase mimic. The prepared CDs could efficiently oxidize the colorless 3,3′,5,5′-tetramethylbenzidine (TMB) into blue oxTMB in the presence of H2O2. After adding glucose oxidase (GOD) to the CDs/TMB system, a colorimetric method for glucose detection was developed. The results show that Fe-CDs possess the highest catalytic activity. When using Fe-CDs as peroxidase mimetics, the detection limit of this assay for glucose was 0.029 mmol L−1. This successfully provides a sensitive and selective colorimetric method for hydrogen peroxide and glucose determination. [ABSTRACT FROM AUTHOR]

A strategy to design imprinted proteins (IPs) able to detect a glycoprotein (ovalbumin, OVA) was proposed. Glucose oxidase (GOx) was used as a matrix for obtaining the binding cavities with high specificity towards the template protein. The effective method to purify the obtained IPs from the template molecules was developed based on a combination of dialysis and gel filtration. HRP was chosen as a model template to discover the optimal production conditions, and the optimal template concentration (100 µg⋅L−1) was chosen. The obtained imprinted proteins were characterized by the high adsorption selectivity towards the target protein (the imprinting factor towards OVA and HRP is 4.7). The developed method was transferred to the synthesis of the anti-OVA IPs. The binding properties of these IPs were estimated using the OVA conjugates with low- (FITC) and high- (HRP) molecular weight label molecules. The ability of the synthesized anti-OVA IPs as recognition elements in immunoassay was studied. Under the optimized experimental conditions, the proposed imprinted proteins exhibited a good linear response to OVA in the concentration range of 10–2000 ng⋅mL−1 with a detection limit of 6 ng⋅mL−1. The obtained recognition elements were tested for OVA determination in real samples of chicken egg white, and a sample of OVA-free cake spiked by OVA. [ABSTRACT FROM AUTHOR]

Entrapment of glucose oxidase (GOx) within metallic gold converts this widely used enzyme into a general saccharide oxidase. The following sugar molecules were oxidized by the entrapped enzyme (in addition to d-glucose): fructose, xylose, l-glucose, glucose-6-phosphate, sucrose, lactose, methylglucoside, and the tri-saccharide raffinose. With the exception of raffinose, none of these sugars have a natural specific oxidase. The origin of this generalization of activity is attributed to the strong protein-gold 3D interactions and to the strong interactions of the co-entrapped CTAB with both the gold, and the protein. It is proposed that these interactions induce conformational changes in the channel leading to the active site, which is located at the interface between the two units of the dimeric GOx protein. The observations are compatible with affecting the specific conformation change of pulling apart and opening this gate-keeper, rendering the active site accessible to a variety of substrates. The entrapment methodology was also found to increase the thermal stability of GOx up to 100 °C and to allow its convenient reuse, two features of practical importance. [ABSTRACT FROM AUTHOR]

Designing and developing electrochemical DNA biosensors based on nanotechnology to solve the low hybridization efficiency of DNA has gained wide attention in recent years because nanomaterials can enhance surface area of electrode and increase amount of probe DNA immobilization. Herein, a new label-free electrochemical DNA biosensor was constructed for sensitive detection of kirsten rat sarcoma viral oncogene (KRAS) DNA. During this process, based on the large specific surface of hollow mesoporous silica (HMS), amino-functionalized hollow mesoporous silica (NH2-HMS) nanocomposite was synthesized, and then highly dispersed gold nanoparticles (Au NPs) were uniformly and stably anchored onto its surface to form Au NPs combined with amino-functionalized hollow mesoporous silica (NH2-HMS@Au), which was utilized as supporting material for decorating the electrode surface. The amino-terminated probe DNA was subsequently immobilized onto the modified electrode surface via Au–N bond and employed as probes to determine the target DNA (t-DNA). The synergetic effects of NH2-HMS with Au NPs achieved enhance of the analytical performance of biosensor. Under the optimized conditions, the prepared DNA biosensor possessed a wide linear range from 1 × 10−12 to 1 × 10−7 M with a low detection limit of 0.366 pM. Moreover, the DNA biosensor displayed satisfying selectivity, remarkable stability, which provided a promising application for clinical diagnosis and analysis. [ABSTRACT FROM AUTHOR]

A novel and facile post-mortem interval (PMI) biosensor was fabricated using a double-label strategy to detect the glyceraldehyde 3-phosphate dehydrogenase (GAPDH) biomarker. A monoclonal anti-GAPDH antibody was immobilized on a surface label containing cadmium selenide quantum dots (CdSe QDs) on a cysteamine graphene oxide (Cys-GO) self-assembled monolayer. Glucose oxidase (GOx) was used as a signal label to conjugate with GAPDH. GAPDH recognition was achieved through the dissolution of the surface-attached CdSe QDs by hydrogen peroxide generated through GAPDH-conjugated GOx-catalyzed β-glucose oxidation. To enhance sensitivity, a competitive interaction was introduced between free and conjugated GAPDH to the active site of the anti-GAPDH antibody. The electrochemical response due to CdSe dissolution decreased proportionally with the concentration of free GAPDH. Differential pulsed voltammetry was conducted to determine the analytical characteristics of the immunosensor, including the limit of detection, linear dynamic range, target selectivity, system stability, and applicability toward the analysis of real samples. [ABSTRACT FROM AUTHOR]

Inhibited immune response and low levels of delivery restrict starvation cancer therapy efficacy. Here, we report on the co-delivery of glucose oxidase (GOx) and indoleamine 2,3-dioxygenase (IDO) inhibitor 1-methyltryptophan using a metal-organic framework (MOF)-based nanoreactor, showing an amplified release for tumor starvation/oxidation immunotherapy. The nanosystem significantly overcomes the biobarriers associated with tumor penetration and improves the cargo bioavailability owing to the weakly acidic tumor microenvironment-activated charge reversal and size reduction strategy. The nanosystem rapidly disassembles and releases cargoes in response to the intracellular reactive oxygen species (ROS). GOx competitively consumes glucose and generates ROS, further inducing the self-amplifiable MOF disassembly and drug release. The starvation/oxidation combined IDO-blockade immunotherapy not only strengthens the immune response and stimulates the immune memory through the GOx-activated tumor starvation and recruitment of effector T cells, but also effectively relieves the immune tolerance by IDO blocking, remarkably inhibiting the tumor growth and metastasis in vivo. Inhibited immune response and low levels of delivery inhibit starvation cancer therapies. Here, the authors report on the co-delivery of glucose oxidase and IDO inhibitor 1-methyltryptophan using metal organic frameworks and show amplified release in response to starvation therapy along with immune modulatory effects. [ABSTRACT FROM AUTHOR]

In this study, we used the concept of overnight hydrolysis of polyvinyl amine to grow cobalt oxide (Co3O4) nanostructures with enhanced catalytic properties. The controlled synthesis of Co3O4 nanostructures was carried out with the hydrothermal method using hydrolyzed products. Results showed that the hydrocarbon chain and amide groups produced during the growth process have a great impact on both the morphology and catalytic properties of Co3O4 nanostructures. In fact, the hydrolyzed products supported the growth of nanostructures with a well-defined almost one-dimensional (1-D) morphology of Co3O4 nanowires with a high surface/volume ratio. The as-prepared nanowires were loaded with a high amount of glucose oxidase in order to make them sensitive to glucose and observe a potentiometric response in its presence. The performance of the fabricated biosensor was evaluated in terms of different analytical parameters such as linear range, stability, reproducibility, repeatability, life time, selectivity, and response time. Thus, the obtained Co3O4-based glucose biosensor exhibited a linear response over the concentration range from 0.0005 to 6 mM, with a limit of detection of 0.0001 mM. The estimated Nernstian slope for the glucose biosensor was 42 mV/dec, with stability that exceeds four weeks. Using electrochemical impedance spectroscopy, the Co3O4 nanowires showed a low charge transfer resistance of 2.2 × 103 Ohms. Practically, the biosensor was used successfully to measure the glucose concentration in real blood samples. The results obtained confirm that the proposed glucose biosensor can be used as an alternative tool for monitoring glucose levels. The synthesis procedure described herein has a high potential to produce nanostructured materials on a large scale with well-defined morphology and improved catalytic properties for possible applications in batteries, supercapacitors, and water splitting. [ABSTRACT FROM AUTHOR]

Background: Inherent limitations of single cancer therapy are overcome by multi-therapy modality, which integrates characteristics of each therapeutic modality and material chemistry. The multi-modal method has the potential for becoming one of the next generation options for cancer treatments. Photothermal therapy (PTT) is an efficient, non-invasive treatment method that can be used on various cancer types. We propose an acid-triggered self-destructing nano-biocatalyst integrated starvation/chemical/photothermal triple therapy that is based on design principles and biomedical applications of GOx cancer treatment methods. Methods: Scanning electron microscopy (SEM), transmission electron microscopy (TEM), dynamic light scattering (DLS), and zeta potentials were used to analyze the physical as well as chemical properties of MoS2@DOX/GOx@MnO2 (M@D/G@M). Further, Fourier transform infra-red (FTIR), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD) were used to assess the compositions of the nanocatalysts. The biological effects of M@D/G@M on cells were studied in vitro by inverted fluorescence microscopy, confocal laser scanning microscopy (CLSM), flow cytometry, CCK-8 test, and hemolysis test. Treatment effects of the nanocatalysts were evaluated in MHCC-97H tumor BALB/c mice, whose body weights, tumor local temperature, tumor volumes, and tumor histological changes were evaluated. Results: There was a high DOX encapsulation efficiency of M@D/G@M (90.233%). The photothermal conversion efficiency (η) of M@D/G@M is 25.2%, and its oxygen production within 5 min reached 27.5 mg L−1. Cell internalization analysis showed that within 4 h, M@D/G@M was almost completely absorbed by HepG2 cells. Further, the highest red fluorescence and apoptosis effects of dead cells (59.07% apoptosis) as well as the lowest tumor volume index of mice (0.2862%) were observed in the M@D/G@M + pH6.0 + NIR treatment group. Conclusions: Our findings inform the development and applications of multi-modal methods in tumor therapy. [ABSTRACT FROM AUTHOR]

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

In order to directly detect the concentration of glucose in milk, carbon dots (CDs) rich in phenolic hydroxyl groups were synthesized in one step as a fluorescent probe. We presented a new glucose oxidase (GOx)-mediated strategy to detect glucose, which allowed the quantitative analysis of hydrogen peroxide (H2O2) and glucose. Furthermore, it was possible to detect H2O2 and glucose directly in complex systems such as milk. The result in milk showed that the fluorescence of the CDs was quenched by H2O2 with the concentration range from 1 to 100 μM linearly, and the correlation coefficient was 0.977 with a detection limit of 0.175 μM. Similarly, a linear correlation was built between the fluorescence of the CDs and the concentration of glucose in the range from 10 to 100 μM with a correlation coefficient of 0.968 and a detection limit of 0.686 μM. The recovery rate was 97.30–101.05%, which showed high sensitivity in the detection of glucose in milk. As far as we know, this was the first time that CDs were used as a fluorescent probe to detect glucose in milk directly, which removed the step of pretreating milk and provided a supplement and extension for the detection of glucose in fluorescent spectroscopy. [ABSTRACT FROM AUTHOR]

Developing a rapid and sensitive photo-electrochemical (PEC) sensing platform for glucose detection is highly desirable. Herein, a visible light-driven PEC enzyme biosensor for sensitive detection of glucose was proposed, employing reduced graphene oxide/titania (TiO2) nanotubes (RGO/TNTs) as photoactive materials and glucose oxidase (GOD) as the identification element. The RGO/TNTs composites were synthesized via a facile hydrothermal process. Notably, the unique nanostructure system significantly increases the absorption in the visible region and effectively separates the photo-generated electron–hole pairs, which is essential for promoting the PEC activity. In the presence of dissolved oxygen, the GOD immobilized on the modified electrode could specifically catalyze the electro-oxidation of glucose to produce H2O2, resulting in an increase of photocurrent intensity. Based on the variation of the photocurrent response, the constructed PEC enzyme biosensor exhibited high sensitivity with a wide linear range from 10–2 to 10 mM and a low detection limit of 5.0 μΜ. Meanwhile, the potential applicability of the PEC enzyme biosensor was evaluated by detecting glucose in human serum samples, and satisfactory results were obtained. The PEC enzyme biosensor based on RGO/TNTs composites successfully realized the sensitive detection of glucose and displayed good selectivity, high stability and satisfactory repeatability. [ABSTRACT FROM AUTHOR]

In the work, the possibility of using nanoparticles of gold (AuNPs) to upgrade bioselective elements of biosensors in order to improve their analytical characteristics is considered. The bioselective elements of biosensors based on acetylcholinesterase (AChE), butyryl cholinesterase (BuChE) and glucose oxidase (GOD) were used as an experimental model. Immobilization of enzymes on the surfaces of conductometric transducers was performed by the crosslinking of corresponding enzymes using glutaraldehyde. The conditions of immobilization of AChE with gold nanoparticles were optimized. Thus, we determined the optimal values of concentration of crosslinking agent (glutaraldehyde), duration of immobilization, the enzyme to AuNPs ratio, the AuNPs concentration and size. The performance characteristics of the biosensors based on enzymes and AuNPs were investigated and compared with the characteristics of biosensors based on enzymes only. It was also examined how the addition of AuNPs to the bioselective element of biosensors affects the biosensor stability. In particular, the reproducibility of preparation and continuous operation of biosensors was tested as well as their stability at storage. It was shown that the presence of AuNPs in the composition of bioselective elements can improve some characteristics of biosensors, which may be promising for further study and use. [ABSTRACT FROM AUTHOR]

Non-invasive visualization of dynamic molecular events in real-time via molecular imaging may enable the monitoring of cascade catalytic reactions in living systems, however effective imaging modalities and a robust catalytic reaction system are lacking. Here we utilize three-dimensional (3D) multispectral photoacoustic (PA) molecular imaging to monitor in vivo cascade catalytic therapy based on a dual enzyme-driven cyclic reaction platform. The system consists of a two-dimensional (2D) Pd-based nanozyme conjugated with glucose oxidase (GOx). The combination of nanozyme and GOx can induce the PA signal variation of endogenous molecules. Combined with the PA response of the nanozyme, we can simultaneously map the 3D PA signals of dynamic endogenous and exogenous molecules associated with the catalytic process, thus providing a real-time non-invasive visualization. We can also treat tumors under the navigation of the PA imaging. Therefore, our study demonstrates the imaging-guided potential of 3D multispectral PA imaging in feedback-looped cascade catalytic therapy. Photoacoustic imaging can be used to monitor chemical reaction in cells and tissues. Here, the authors develop a Pd based nanozyme conjugated with glucose oxidase that can induce the change of photoacoustic signals during the catalytic cascade process, the system can also be used to treat tumor-bearing mice. [ABSTRACT FROM AUTHOR]

Diabetes is a chronic endocrine disease that occurs due to an imbalance in glucose levels and altering carbohydrate metabolism. It is a leading cause of morbidity, resulting in a reduced quality of life even in developed societies, primarily affected by a sedentary lifestyle and often leading to mortality. Keeping track of blood glucose levels noninvasively has been made possible due to diverse breakthroughs in wearable sensor technology coupled with holistic digital healthcare. Efficient glucose management has been revolutionized by the development of continuous glucose monitoring sensors and wearable, non/minimally invasive devices that measure glucose concentration by exploiting different physical principles, e.g., glucose oxidase, fluorescence, or skin dielectric properties, and provide real-time measurements every 1–5 min. This paper presents a highly novel and completely non-invasive sweat sensor platform technology that can measure and report glucose concentrations from passively expressed human eccrine sweat using electrochemical impedance spectroscopy and affinity capture probe functionalized sensor surfaces. The sensor samples 1–5 µL of sweat from the wearer every 1–5 min and reports sweat glucose from a machine learning algorithm that samples the analytical reference values from the electrochemical sweat sensor. These values are then converted to continuous time-varying signals using the interpolation methodology. Supervised machine learning, the decision tree regression algorithm, shows the goodness of fit R2 of 0.94 was achieved with an RMSE value of 0.1 mg/dL. The output of the model was tested on three human subject datasets. The results were able to capture the glucose progression trend correctly. Sweet sensor platform technology demonstrates a dynamic response over the physiological sweat glucose range of 1–4 mg/dL measured from 3 human subjects. The technology described in the manuscript shows promise for real-time biomarkers such as glucose reporting from passively expressed human eccrine sweat. [ABSTRACT FROM AUTHOR]

The work considered the properties of a biosensor based on a novel nanomaterial—modified thermally expanded graphite (TEGM). The main focus was on whether the procedure of additional graphite thermal expansion would affect the electrochemical properties of biosensors based on membrane fractions of acetic acid bacteria Gluconobacter oxydans. Raman spectroscopy, scanning electron microscopy and electrochemical analysis were used for the study. Raman spectra showed that the formation of TEGM led to its stratification into smaller particles and a better orderly layered structure with high "graphenization" degree. Modification of TEG led to the formation of additional cavities into which bacterial cells or bacterial membrane fractions could be immobilized and affect the electrical conductivity of the biosensors positively. Calculation of the heterogeneous charge transfer constants showed that processes occurring on the electrodes are quasi-reversible. The limiting stage of these processes is the transfer of an electron from a biological component on the electrode surface, not the diffusion of the analyte from the solution to the active centers of the enzyme. We showed the possibility of developing third-generation mediator-free biosensors for glucose detection based on TEGM, as well as of second-generation mediator biosensors for glucose, ethanol and glycerol detection. [ABSTRACT FROM AUTHOR]

Improving the electron–hole separation efficiency and accelerating the reaction kinetics of semiconductors are effective methods for improving the photoelectric catalytic activity of TiO2. In this study, sulfur-doped TiO2 (S–TiO2) nanorod arrays grown on a fluorine-doped SnO2 transparent conductive glass were successfully prepared using a microwave-assisted method for the photoelectrochemical (PEC) biosensing of glucose. The charge separation efficiency on S–TiO2 was evaluated by subjecting the prepared material to X-ray photoelectron spectroscopy, PEC measurements, and theoretical calculations based on density functional theory. The results clearly showed that the sulfur impurity state could not only reduce the bandgap but also serve as "stairs" to facilitate the electron transfer. Sulfur atoms that were successfully doped into TiO2 significantly promote the separation of the photogenerated carriers and improve the photocatalytic activity of the photoelectrode. Consequently, excellent glucose-detection sensitivities of 54 and 19 μA mM−1 cm−2 were achieved for fragments with sizes of 0.1–1.5 and 2–12 mM, respectively. [ABSTRACT FROM AUTHOR]

Highlights: Gene-engineering tumor cell membrane with CD47 over-expression is achieved to improve the macrophage-mediated phagocytosis of tumor cells by blocking CD47 immune checkpoint. A cascade-enzyme nanoreactor combining tumor enzyme dynamic therapy, phototherapy, and deoxygenation-activated chemotherapy is proposed. Glucose oxidase and chloroperoxidase can generate sufficient HClO to kill normoxic tumor cells, and tirapazamine can be subsequently activated to kill hypoxic tumor cells. The enzyme-mediated elevation of reactive oxygen species (ROS) at the tumor sites has become an emerging strategy for regulating intracellular redox status for anticancer treatment. Herein, we proposed a camouflaged bionic cascaded-enzyme nanoreactor based on Ti3C2 nanosheets for combined tumor enzyme dynamic therapy (EDT), phototherapy and deoxygenation-activated chemotherapy. Briefly, glucose oxidase (GOX) and chloroperoxidase (CPO) were chemically conjugated onto Ti3C2 nanosheets, where the deoxygenation-activated drug tirapazamine (TPZ) was also loaded, and the Ti3C2-GOX-CPO/TPZ (TGCT) was embedded into nanosized cancer cell-derived membrane vesicles with high-expressed CD47 (meTGCT). Due to biomimetic membrane camouflage and CD47 overexpression, meTGCT exhibited superior immune escape and homologous targeting capacities, which could effectively enhance the tumor preferential targeting and internalization. Once internalized into tumor cells, the cascade reaction of GOX and CPO could generate HClO for efficient EDT. Simultaneously, additional laser irradiation could accelerate the enzymic-catalytic reaction rate and increase the generation of singlet oxygen (1O2). Furthermore, local hypoxia environment with the oxygen depletion by EDT would activate deoxygenation-sensitive prodrug for additional chemotherapy. Consequently, meTGCT exhibits amplified synergistic therapeutic effects of tumor phototherapy, EDT and chemotherapy for efficient tumor inhibition. This intelligent cascaded-enzyme nanoreactor provides a promising approach to achieve concurrent and significant antitumor therapy. [ABSTRACT FROM AUTHOR]

Use of enzyme for extraction of nanocellulose from sugarcane bagasse is greener alternative. Literature indicates that effectiveness of these enzymes can be improved by auxiliary enzymes or mediators. In the current study, extraction of nanocellulose using laccase with these moderators, auxiliary enzyme glucose oxidase and mediator molecule, ABTS [2,2′-azinobis(3-ethylbenzthiazoline-6-sulfonate)] individually was done. Cellulose and lignin content, FT-IR, TGA and DSC analysis, XRD, SEM and PSA were done. Enzyme moderators improved the performance of laccase in lignin degradation. Lignin and cellulose content, crystallinity were used as parameters to optimize the concentrations, which was found to be ABTS (at 1.4 mM) and glucose oxidase (at 0.15 mg ml−1). At the optimal concentration, nanocellulose was extracted. Properties of nanocellulose obtained from both routes were compared. Size analysis revealed 339 nm and 636 nm for nanocellulose obtained with glucose oxidase and ABTS, respectively. Defibrillation was better in the case of the former one as seen from SEM. [ABSTRACT FROM AUTHOR]