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• A smartphone-interfaced flow injection sensing system was developed. • An electrode was modified with Pd-PANI/Carbon microspheres@carbon nanotubes. • Sensitive determination of glucose was achieved in real human serum samples. Integrating a flow injection system with an electrochemical sensor controlled by a smartphone enables rapid, precise real-time monitoring and reduces analyte consumption, contamination and costs. An enzyme-free electrochemical sensor is presented for the monitoring of glucose, an important indicator of diabetes. The sensor integrates a smartphone and a flow injection amperometric system. The flow cell is fabricated from acrylic plastic and includes an electrochemical three-electrode cell that comprises a working electrode modified with a catalyst of palladium-polyaniline/carbon microspheres@carbon nanotubes (Pd-PANI/CM@CNTs/E) for the detection of glucose oxidation. In the optimal condition, the proposed system produced good analytical performances. The sensor determined glucose linearly in a range from 0.020 to 100 mM, with a sensitivity of 51.51 μA mM−1 cm−2, and a detection limit (LOD) of 0.0071 mM. The developed system also exhibited good repeatability, reproducibility, operational stability, and anti-interference properties, and accurately determined glucose levels in real human serum samples. This sensing platform provides an alternative tool for the development of a continuous glucose monitor system for clinical applications. [Display omitted] [ABSTRACT FROM AUTHOR]

Regular monitoring of blood sugar levels is essential for diabetics, both for adjusting medication or insulin doses and for preventing complications like blindness, nerve damage, heart disease, and kidney failure. This paper presents a novel smartphone-based electrochemical-colorimetric dual-mode detecting system for detecting glucose at low concentrations. This system utilizes a smartphone as a mobile terminal to control the electrochemical circuit board and enable data analysis. The circuit board integrates cyclic voltammetry and differential pulse voltammetry, providing a low-cost and palm-sized solution for glucose detection. Additionally, digital image colorimetry is employed to enable efficient and accurate colorimetric detection. The use of glucose oxidase and horseradish peroxidase (GOx/HRP) in combination with 2,2′-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) ABTS substrates facilitates glucose dual-mode quantitative analysis in a-coreaction system. The electrochemical and colorimetric methods exhibit limits of detection of 0.467 µM and 10 µM, respectively. This system shows a point-of-care testing (POCT) potential for reliable and convenient monitoring of blood glucose levels, particularly for individuals with diabetes. [ABSTRACT FROM AUTHOR]

In this study the development of a biofuel cell for potential application in microfluidics is described. The biocatalysts support is produced through vacuum-filtration of a Vulcan carbon black suspension resulting in flexible, paper-like electrodes. The glucose oxidase bioanode was assembled using an enzyme precipitate coating procedure whereas the biocathode was implemented by attaching bilirubin oxidase enzyme onto the carbon black surface via a pyrene intermediate. The bioelectrodes were first characterized by voltammetry and by chronoamperometry on their sensing ability towards the respective substrates, namely glucose and oxygen. Finally, bioanode and biocathode were integrated in a single-compartment of a heterogeneous poly (methyl methacrylate) - polydimethylsiloxane microfluidic platform and the power density produced was assessed. In 10 mM glucose solution at pH 7.0, the biofuel cell showed an open circuit potential (OCP) of 0.43 V and a maximum power density of about 28 μW cm−2 at 0.24 V. Also we demonstrate here the viability of human propelled fluidics by introducing in the microfluidic device a finger-pressure mechanism. [ABSTRACT FROM AUTHOR]

LiNbO 3 nanotubes are prepared by biotemplate-assisted synthetic route. The mesoporous LiNbO 3 nanotubes can be an ideal platform to immobilize glucose oxidase (GOx) for glucose biosensing. As the GOx-biocatalyzed oxidation of glucose yield H 2 O 2 , and LiNbO 3 can direct catalyze the generated H 2 O 2 . What's more, one dimensional channels will facilitate the diffusion of reactants and ensure adequate contact between glucose and enzymes. Thus the as-prepared biosensor exhibit high sensitivity (52.4 μA·mM −1 ·cm −2 ), fast response (<2 s) and excellent selectivity to glucose. The results suggest the potential implementation of LiNbO 3 as a sensing platform for electrochemical detection of biology reagents. [ABSTRACT FROM AUTHOR]

• Electrodeposition of nanoplatelets like structure of samarium oxides. • High charge transfer rate constant and roughness factor. • Hydrogen peroxide reduction from −0.10 V (vs. Ag/AgCl). • Physical adsorption of glucose oxidase. • Glucose determination in serum samples. A nanostructured samarium oxide electrode was constructed by electrodeposition onto the surface of a gold electrode on SiO 2 /Si wafer. The samarium oxides electrode's surface morphology was investigated by scanning electron microcopy showing a quasi-monodispersed nanoplatelets like structure. X-rays diffraction analysis demonstrated a mixture of monoclinic and hexagonal phases while the X-rays photoelectron spectroscopy indicated the co-existence of both Sm2+ and Sm3+ species in a 1:3 proportion. Cyclic voltammetry and electrochemical impedance spectroscopy were used to investigate the charge transfer processes at the surface of the samarium oxide electrode in the absence and in the presence of redox probes. A roughness factor of 2.5 was determined from the samarium oxide electrode while the charge transfer constant was almost double when compared to the planar gold electrode. Then, the samarium oxide electrode was used for the H 2 O 2 detection by fixed potential amperometry at -0.20 V (vs. Ag/AgCl) with a linear region between 0.01 and 1.00 mM, a sensitivity of 153 µA cm−2 mM−1 and a LoD = 2.70 µM. Glucose oxidase was used as a model enzyme in order to test the capacity of the samarium oxides electrode for biosensing. The enzyme was immobilized by physical adsorption and the optimum conditions for glucose analysis investigated. The biosensor showed a linear range for glucose detection between 0.10 and 1.20 mM with a sensitivity of 8.40 µA cm−2 mM−1 and a LoD = 8.00 µM. Selectivity was tested toward common interfering species, and the results revealed the lack of biosensor response. The glucose biosensor on samarium oxides was tested for glucose detection in serum samples with a recovery factor of 90%, and the result validated with a commercial glucometer. [Display omitted] [ABSTRACT FROM AUTHOR]

In this work, we report a high-performance graphene flexible paper electrode composed of core-shell Gold@Prussian blue nanoparticles (Au@PB NPs) for real-time monitoring of living cell and biosensor platform. Core-shell Au@PB NPs with high stability, low cost, excellent biocompatibility and electrochemical activity was prepared. At the same time, combined with the robust mechanical properties of reduced graphene oxide (rGO) paper, an independent flexible graphene paper electrode was prepared and broadly characterized. Because of the unique structural properties and the combinational advantages of different components in the Au@PB NPs-rGO composite, the resultant nanohybrid paper electrode exhibits good electrochemical sensing performance toward hydrogen peroxide (H 2 O 2) and it also displays a very short response time (1 s) in the tracking of H 2 O 2 secretion by living HepG2 cells. Meanwhile, the as-prepared Au@PB NPs-rGO paper electrode can be further used as an enzyme-based biosensor. In this regard, glucose oxidase (GODx) used as an example for glucose detection and analysis, which proves its excellent performance as an enzyme sensing platform. The excellent properties of the kind of nanocomposites are expected to be further used in the field of flexible devices and Point-of-Care (POC). [ABSTRACT FROM AUTHOR]

Enzymatic biofuel cells are a promising and environmentally friendly technology for energy generation from renewable fuel sources. Glucose biofuel cells employ enzymatic catalysts at both the anode and cathode to oxidize glucose and reduce oxygen while producing electricity. Consequently, there is a need for materials capable of immobilizing enzymes and facilitating efficient electron transfer between an electrode surface and an enzymatic active site. Here, we describe a chloroferrocene-modified linear poly(ethylenimine) capable of mediating electro-enzymatic oxygen reduction by laccase. Enzymatic biocathodes constructed using this mediator generated current densities up to 2.66 mA cm−2, and up to 636 μW cm−2 (E oc = 0.6 V) power when combined with a tetramethylferrocene-mediated glucose oxidase bioanode to construct a biofuel cell mediated entirely by ferrocenes. [Display omitted] [ABSTRACT FROM AUTHOR]

• Co 3 Mn-CO 3 LDH is an electrocatalyst for H 2 O 2 oxidation. • A GOx/LDH biosensor is built with a multilayer configuration. • An inner-layer based on Co 3 Mn-CO 3 can be used to replace a Pt electrode in GOx/LDH biosensors. • A top-layer of carrageenan improves the enzyme immobilization and hence the biosensor performance. A glucose amperometric biosensor has been prepared by a multilayer deposition on a glassy carbon electrode of Co 3 Mn-CO 3 layered double hydroxide, glucose oxidase (GOx) and a biopolymer (carrageenan), respectively. The original transduction step consists in the electrocatalytic oxidation of H 2 O 2 , enzymatically formed, in the Co 3 Mn-CO 3 inner-layer at 0.65 V/Ag-AgCl. The sensitivity and the detection limit, obtained with this optimized bioelectrode (Co 3 Mn-CO 3 /GOx/carrageenan, 30/20/10 µg), are 12.8 mA M−1 cm−2 and 0.02 mM, respectively. A 3D-porous bioelectrode was also prepared by impregnation of a carbon felt (CF) with a colloidal suspension of Co 3 Mn-CO 3 nanoparticles and then with GOx. The structure and the morphology of the Co 3 Mn-CO 3 /CF composite were characterized by X-ray diffraction and electron scanning microscopy and the bioelectrode GOx/Co 3 Mn-CO 3 /CF was finally tested in cyclic voltammetry in the presence of glucose. [Display omitted] [ABSTRACT FROM AUTHOR]

Continuous glucose monitoring devices (CGM) are the present and the future for the challenging task of diabetes management. With a yearly increase of patients worldwide, glucose biosensors with high accuracy and low interference effect become crucial and should be developed. Here we show the development of an oxygen insensitive glucose biosensor which comprises FAD-dependent glucose dehydrogenase, dichlorophenol indophenol (DCPIP) or 2,3-dichloro-naphthoquinone (DCNQ) as redox mediators and polydopamine as a constraining layer. The sensors were fully characterized and the effect of interferences on glucose-sensing was analyzed. We further show long term bioelectrocatalytic activity for at least 3 days without any additional coating or treatment. The system shows great reproducibility via an easy fabrication methodology that should allow low-cost manufacturing. Those encouraging results show great promise for future sensor development of enzyme-based bioelectronics devices. Image, graphical abstract [ABSTRACT FROM AUTHOR]

• Electrochemical glucose biosensor based on metal-free N-doped carbon material obtained from polyaniline. • High glucose sensitivity 23.57 ± 1.77 μA cm−2 mM−1 and linear working range 5 µM- 5 mM at −0.4 V vs. Ag/agcl (3 M KCl). • Glucose detection and quantification in commercial sugary drink and human urine sample have been performed. An enzymatic metal-free electrochemical biosensor based on immobilized glucose oxidase on a N-doped porous carbon material has been studied for the detection of glucose in different real samples. The N-doped carbon material, which contains quaternary nitrogen groups, has been obtained by heat treatment of polyaniline. These functionalities promote the electrocatalytic activity to oxygen reduction reaction. The electrochemical biosensor presents a remarkable electrochemical activity towards oxygen reduction reaction, being able to detect changes in oxygen concentration generated by the enzymatic oxidation of glucose, allowing the indirect detection of this compound in phosphate buffered solution (0.1 M PB solution, pH=7.2). The metal-free electrochemical biosensor shows an outstanding performance, with a linear detection range between 5 µM and 5 mM and a high sensitivity of 23.57±1.77 µA mM−1 cm−2 at -0.4 V vs. Ag/AgCl. At these conditions, the addition of ascorbic acid, dopamine, uric acid and l -gluconic acid does not interfere with glucose determination. The method has been successfully applied to human urine and commercial sugary drink samples, without significant matrix effects, providing an alternative for glucose detection. Image, graphical abstract [ABSTRACT FROM AUTHOR]

It is critical to monitor glucose level in the health management of diabetes patients. In this work, we developed a polylactic acid (PLA) based microneedle (MN) based glucose sensor. This PLA MN base was then coated with gold as the conductive layer, overoxidized polypyrrole (OPPy), gold nanoparticles (AuNPs), glucose oxidase (GOx), and Nafion. In vitro test, this glucose MN sensor showed a linear range from 0 to 2.6 mM with a sensitivity of 8.09 μA/mM, limit of detection (LOD) of 40 μM and not affected by ascorbic acid (AA), urea, glycine (Gly), acetaminophen (AP) in phosphate buffer solution,. The composite of OPPy and AuNPs improved the sensor sensitivity and GOx adhesive ability to the electrode. Nafion film protected the sensor from interfering substances. In the stability test, the sensor exhibited a stable monitoring sensitivity after 2 weeks. This work demonstrates this MN sensor has the potential to be applied in minimally invasive glucose monitoring. Image, graphical abstract [ABSTRACT FROM AUTHOR]

This work compares the performance of bioelectrocatalytic films composed of glucose oxidase, dimethylferrocene-modified linear poly(ethyleneimine) and either glutaraldehyde (GA) or ethylene glycol diglycidyl ether (EGDGE) as cross-linking agents. While GA has been widely employed as an enzyme cross-linker, its use with mediator-modified linear poly(ethyleneimine)s has not been reported. Here, we evaluate both types of polymers for use in a drop-based biosensor and a microfluidic fuel cell. In the sensing context, GA-based polymers presented higher stability at the expense of linear response range. In the energy production device, significant differences in current were not observed when comparing the performance of complete cells. We conclude that glutaraldehyde is a suitable alternative to the widespread epoxide cross-linkers for the fabrication of enzyme-containing ferrocene-modified linear poly(ethyleneimine) hydrogels. Image 1 [ABSTRACT FROM AUTHOR]

The design of sensitive and fast-response of catalysts are very important for non-enzymatic glucose biosensors. In this work, monodisperse copper selenide (Cu 2-x Se) nanoparticles (NPs) are prepared by thermal decomposition of copper acetylacetonate (Cu(acac) 2) in the solution of oleylamine, then selenide at different temperatures with reduce graphene oxide (RGO) as support. These Cu 2-x Se NPs are active catalysts as ultrahigh sensitive non-enzymatic glucose biosensor, which exhibits sensitivity of 536 μA mM−1 cm−2, a wide linear range up to 3.375 mM and a low detection limit of 0.05 mM (S/N = 3). Based on good selectivity, sensitivity and the ability of anti-interference, the Cu 2-x Se NPs will be the promising sensor for enzyme-free monitoring of glucose. A reliable strategy is developed to fabricate monodisperse copper selenide (Cu 2-x Se) nanoparticles (NPs) with RGO as support. The Cu 2-x Se NPs which could avoid the agglomeration of NPs and enhance the conductivity with RGO as support, even provide a large number of active sites compared with Cu NPs after selenization, which may open up a promising avenue for developing ultrahigh sensitive sensor for the non-enzymatic detection of glucose. Image 1 [ABSTRACT FROM AUTHOR]