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According to the latest statistics, more than 537 million people around the world struggle with diabetes and its adverse consequences. As well as acute risks of hypo- or hyper- glycemia, long-term vascular complications may occur, including coronary heart disease or stroke, as well as diabetic nephropathy leading to end-stage disease, neuropathy or retinopathy. Therefore, there is an urgent need to improve diabetes management to reduce the risk of complications but also to improve patient's quality life. The impact of continuous glucose monitoring (CGM) is well recognized, in this regard. The current review aims at introducing the basic principles of glucose sensing, including electrochemical and optical detection, summarizing CGM technology, its requirements, advantages, and disadvantages. The role of CGM systems in the clinical diagnostics/personal testing, difficulties in their utilization, and recommendations are also discussed. In the end, challenges and prospects in future CGM systems are discussed and non-invasive, wearable glucose biosensors are introduced. Though the scope of this review is CGMs and provides information about medical issues and analytical principles, consideration of broader use will be critical in future if the right systems are to be selected for effective diabetes management.
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Glicemia , Diabetes Mellitus , Humanos , Automonitorização da Glicemia , Diabetes Mellitus/diagnóstico , GlucoseRESUMO
This is the first report demonstrating proof of concept for the passive, non-invasive extraction and in situ potentiometric detection of human sweat chloride ions (Cl- ions) using a stable printed planar liquid-junction reference electrode-integrated hydrogel-based touch-sensor pad without activities such as exercise to induce perspiration, environmental temperature control, or requiring cholinergic drug administration. The sensor pad was composed entirely of a screen-printed bare Ag/AgCl-based chloride ion-selective electrode and a planar liquid-junction Ag/AgCl reference electrode, which were fully covered by an agarose hydrogel in phosphate-buffered saline (PBS). When human skin contacted the hydrogel pad, sweat Cl- ions were continuously extracted into the gel, followed by in situ potentiometric detection. The planar liquid-junction Ag/AgCl reference electrode had a polymer-based KCl-saturated inner electrolyte layer to stabilize the potential of the Ag/AgCl electrode even with a substantial change in the chloride ion concentration in the hydrogel pad. We expect this fully screen-printed sensor to achieve the low-cost passive and non-invasive daily monitoring of human Cl- ions in sweat in the future.
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Colinérgicos/farmacologia , Eletrólitos , Hidrogéis/química , Íons , Polímeros/química , Potenciometria/instrumentação , Técnicas Biossensoriais , Cloretos/química , Eletroquímica , Eletrodos , Desenho de Equipamento , Humanos , Eletrodos Seletivos de Íons , Potenciometria/métodos , Sefarose/química , Pele/efeitos dos fármacos , Suor , TemperaturaRESUMO
The electrochemical properties of screen-printed diamond electrodes with various insulating polyester (PES) resin binder/boron-doped diamond powder (BDDP) ratios were investigated for high sensitivity electrochemical detection. For PES/BDDP weight ratios in the range of 0.3-0.5, the BDDP-printed electrodes exhibited cyclic voltammetry (CV) characteristics for Fe(CN)6(3-/4-) that are typical of a planar electrode, whereas microelectrode-like characteristics with sigmoidal CV curves were observed for PES/BDDP ratios of 1.0-2.0. Cu elemental mapping images of copper-electrodeposited BDDP-printed electrodes indicated the formation of island structures with conductive BDDP domains surrounded by an insulating PES matrix for large PES/BDDP ratios. The electrochemical detection of ascorbic acid (AA) and 8-hydroxy-2'-deoxyguanosine (8-OHdG) was also investigated using polycrystalline BDD thin-film and BDDP-printed electrodes (PES/BDDP ratio = 0.3 and 1.0). As a result, the signal-to-background (S/B) ratios for the voltammetric detection of AA and 8-OHdG were in the order BDDP-printed electrode (PES/BDDP = 1.0) > BDDP-printed electrode (PES/BDDP = 0.3) > polycrystalline BDD thin film electrode, based on the large faradaic current with respect to the background current. Therefore, the BDDP-printed electrode with a large insulating binder/BDDP ratio has the potential for use as a disposable electrode for electrochemical detection. The electrode is cheaper, lighter and more sensitive than conventional BDD electrodes.
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An instantly usable screen-printed paper-based Ag/AgCl electrode was fabricated for use as a cost-effective disposable reference electrode. The reference electrode showed potential stability for approximately 75 h. The setup time, which is less than 1 min, is much shorter than those for similar previously reported electrodes.
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The ATP-induced behavior of the unicellular flagellate alga Chlamydomonas reinhardtii was recorded as changes in the redox currents for a coexisting redox marker. The ATP concentration was estimated using the presented compact electrochemical system, which is based on monitoring of the motility of the flagellates.
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Trifosfato de Adenosina/análise , Técnicas Biossensoriais/métodos , Ensaios de Migração Celular/métodos , Chlamydomonas reinhardtii/fisiologia , Técnicas Eletroquímicas/métodos , Movimento Celular , Chlamydomonas reinhardtii/química , Clorófitas/química , Flagelos , Monitorização Fisiológica , Oxirredução , Volvox/fisiologiaRESUMO
We report simultaneous photoelectrocatalytic (PEC) glucose sensing and biohydrogen generation for the first time from the direct PEC oxidation of glucose at multifunctional and robust Cu2O-TiO2 photocatalysts. Striking improvement of 30% in overall H2 gas evolution (â¼122 µmol h(-1) cm(-2)) by photoholes assisted glucose oxidation opens a new platform in solar-driven PEC biohydrogen generation.
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Técnicas Biossensoriais , Cobre/química , Glucose/química , Hidrogênio/química , Titânio/química , Catálise , Eletrodos , Oxirredução , Processos FotoquímicosRESUMO
Acetaldehyde, which is an intermediate product of alcohol metabolism, is known to induce symptoms, including alcohol flushing, vomiting, and headaches in humans. Therefore, real-time monitoring of acetaldehyde levels is crucial to mitigating these health issues. However, current methods for detecting low-concentration gases necessitate the use of complex measurement equipment. In this study, we developed a low-cost, low-detection-limit, enzyme-based electrochemical biosensor for acetaldehyde gas detection that does not require sophisticated equipment. The sensor was constructed by screen-printing electrodes onto a porous polyimide film, using grafted MgO-templated carbon (GMgOC) as working electrode material, carbon for the counter electrode, and silver/silver chloride for the reference electrode. Pyrroloquinoline-quinone-dependent aldehyde dehydrogenase was immobilized on the working electrode, and a chamber was attached to the electrode chip and filled with 1-methoxy-5-methylphenazinium methyl sulfate solution. The sensor can be used to measure acetaldehyde gas concentrations from 0.02 to 0.1 ppm, making it suitable for monitoring human skin gas. This low detection limit was achieved by delivering the analyte through the porous polyimide film on which the electrodes were printed and accumulating acetaldehyde in the mesoporous GMgOC of the working electrode. This mechanism suggests that this sensor design can be adapted to develop other low-detection limit gas sensors, such as those for screening skin gas biomarkers.
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Técnicas Biossensoriais , Carbono , Humanos , Técnicas Biossensoriais/métodos , Acetaldeído , Porosidade , EletrodosRESUMO
Wearable ion sensors for the real-time monitoring of sweat biomarkers have recently attracted increasing research attention. Here, we fabricated a novel chloride ion sensor for real-time sweat monitoring. The printed sensor was heat-transferred onto nonwoven cloth, allowing for easy attachment to various types of clothing, including simple garments. Additionally, the cloth prevents contact between the skin and the sensor and acts as a flow path. The change in the electromotive force of the chloride ion sensor was -59.5 mTV/logâ¯CCl-. In addition, the sensor showed a good linear relationship with the concentration range of chloride ions in human sweat. Moreover, the sensor displayed a Nernst response, confirming no changes in the film composition due to heat transfer. Finally, the fabricated ion sensors were applied to the skin of a human volunteer subjected to an exercise test. In addition, a wireless transmitter was combined with the sensor to wirelessly monitor ions in sweat. The sensors showed significant responses to both sweat perspiration and exercise intensity. Thus, our research demonstrates the potential of using wearable ion sensors for the real-time monitoring of sweat biomarkers, which could significantly impact the development of personalized healthcare.
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Suor , Dispositivos Eletrônicos Vestíveis , Humanos , Cloretos , Temperatura Alta , Biomarcadores , Impressão TridimensionalRESUMO
This study aimed to develop a lactate sensor with a microchannel that overcomes the issue of air bubbles interfering with the measurement of lactate levels in sweat and to evaluate its potential for continuous monitoring of lactate in sweat. To achieve continuous monitoring of lactate, a microchannel was used to supply and drain sweat from the electrodes of the lactate sensor. A lactate sensor was then developed with a microchannel that has an area specifically designed to trap air bubbles and prevent them from contacting the electrode. The sensor was evaluated by a person while exercising to test its effectiveness in monitoring lactate in sweat and its correlation with blood lactate levels. Furthermore, the lactate sensor with a microchannel in this study can be worn on the body for a long time and is expected to be used for the continuous monitoring of lactate in sweat. The developed lactate sensor with a microchannel effectively prevented air bubbles from interfering with the measurement of lactate levels in sweat. The sensor showed a concentration correlation ranging from 1 to 50 mM and demonstrated a correlation between lactate in sweat and blood. Additionally, the lactate sensor with a microchannel in this study can be worn on the body for an extended period and is expected to be useful for the continuous monitoring of lactate in sweat, particularly in the fields of medicine and sports.
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Técnicas Biossensoriais , Ácido Láctico , Humanos , Suor , Microfluídica , EletrodosRESUMO
In this study, the performance of a paper-based, screen-printed biofuel cell with mesoporous MgO-templated carbon (MgOC) electrodes was improved in two steps. First, a small amount of carboxymethyl cellulose (CMC) was added to the MgOC ink. Next, the cathode was modified with bilirubin prior to immobilizing the bilirubin oxidase (BOD). The CMC increased the accessibility of the mesopores of the MgOC, and subsequently, the performance of both the bioanode and biocathode. CMC also likely increased the stability of the electrodes. The pre-modification with bilirubin improved the orientation of the BOD, which facilitated direct electron transfer. With these two steps, an open circuit potential of 0.65 V, a maximal current density of 1.94 mA cm-2, and a maximal power density of 465 µW cm-2 was achieved with lactate oxidase as bioanode enzyme and lactate as fuel. This is one of the highest reported performances for a biofuel cell.
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Fontes de Energia Bioelétrica , Carbono , Bilirrubina , Eletrodos , Enzimas Imobilizadas , Glucose , Tinta , Oxirredutases atuantes sobre Doadores de Grupo CH-CHRESUMO
Porous carbon electrodes have considerably improved the performance of biofuel cells and biosensors in recent years. In this paper, we propose a novel in-situ analysis method for porous enzyme electrodes. By combining three-dimensional (3D) impedance measurement and a double-channel transmission line model, the stability of porous enzyme electrodes during operation can be evaluated. The proposed method can distinguish between the functional stability of the enzyme and mediator reaction and the general structural stability of the electrode. We demonstrated this method by evaluating bilirubin oxidase-modified carbon cloth (CC) electrodes with and without a magnesium oxide (MgO)-templated carbon coating. In case of the CC electrode, a remarkable increase in the charge transfer resistance within the first 500 s indicated the elution of the enzyme and mediator. When the CC was coated with MgO-templated carbon before enzyme modification, the charge transfer resistance remained constant, indicating an effective suppression of the elution of the enzyme and mediator. The electric double-layer capacitance values of both electrodes indicated that their general electrode structures were stable during the analysis. Thus, the proposed analytical method, based on 3D impedance, can be a powerful tool for simultaneously detecting possible changes in the general electrode structure of enzyme electrodes and in the amount of active enzymes and mediators on the electrode surface.
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Técnicas Biossensoriais , Carbono , Enzimas , Espectroscopia Dielétrica , Eletrodos , PorosidadeRESUMO
A self-driven sensor that can detect urine and urine sugar and can be mounted on diapers is desirable to reduce the burden of long-term care. In this study, we created a paper-based glucose biofuel cell that can be mounted on diapers to detect urine sugar. Electrodes for biofuel cells were produced by printing MgO-templated porous carbon on which poly(glycidyl methacrylate) was modified using graft polymerization. A new bioanode was prepared through covalently modifying flavin-adenine-dinucleotide-dependent glucose dehydrogenase and azure A with pendant glycidyl groups of poly(glycidyl methacrylate). We prepared a cathode with covalently bonded bilirubin oxidase. Covalent bonding of enzymes and mediators to both the bioanode and biocathode suppressed elution and improved stability. The biofuel cell could achieve a maximum output density of 0.12 mW cm-2, and by combining it with a wireless transmission device, the concentration of glucose sensed from the transmission frequency was in the range of 0-10 mM. The sensitivity of the sensor was estimated at 0.0030 ± 0.0002 Hz mmol-1 dm3. This device is expected to be a new urine-sugar detection device, composed only of organic materials with a low environmental load and it can be useful for detecting postprandial hyperglycemia.
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Fontes de Energia Bioelétrica , GlucoseRESUMO
In this study, magnesium oxide (MgO)-templated mesoporous carbon (MgOC) and chitosan cross-linked with genipin (chitosan-genipin) were considered bio-composite inks for screen-printed bioanodes. The fabrication processes were optimized using rheological and structural data, and a bioanode ink containing glucose oxidase (GOx) and 1,2-naphthoquinone (1,2-NQ) was successfully developed. The optimal bioanode-ink contained MgOC pre-treated by washing to achieve a hydrophilic and neutral surface, which helped maintain enzyme activity and resulted in a highly porous electrode structure, which is essential for the accessibility of glucose to GOx. A bioanode fabricated using this ink showed a linear response current dependency up to 8 mM glucose with a sensitivity of 25.83 µA cm-2 mM-1. Combined with a conventional biocathode, an electromotive force of 0.54 V and a maximal power density of 96 µW cm-2 were achieved. These results show that this bio-composite ink can be used to replace the multi-step process of printing with conventional ink followed by drop-casting enzyme and mediator with a one-step printing process.
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We developed a novel sticker device that can convert any metal or alloy into the working electrode of a three-electrode system, enabling simple and accurate measurement. The sticker, containing a counter electrode and a stable and accurate liquid junction-type reference electrode, is attached to the metal or alloy; meanwhile the surface exposed from a hole in the device functions as the working electrode. This sticker device was fabricated by screen-printing. The polarization curve of the copper and tin-plated copper measured using the sticker device exhibited approximately the same behavior as that obtained for the conventional three-electrode system. The characteristics of various materials can be easily evaluated using this system by only dropping a small amount of solution.
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An algal array was prepared on a single transparent electrode, and photosynthetic activity of each algal channel and its inhibition by a toxin were monitored with a single-channel potentiostat by successive light irradiation with a LED array.
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Técnicas Biossensoriais/instrumentação , Eucariotos/isolamento & purificação , Eletrodos , Monitoramento Ambiental/instrumentação , Monitoramento Ambiental/métodos , Eucariotos/fisiologia , Fotossíntese , Poluição da Água/análiseRESUMO
Faradaic electrochemical impedance spectroscopy (faradaic EIS) is an attractive measurement principle for biosensors. However, there have been no reports on sensors employing direct electron transfer (DET)-type redox enzymes based on faradaic EIS principle. In this study, we have attempted to construct the 3rd-generation faradaic enzyme EIS sensor, which used DET-type flavin adenine dinucleotide (FAD) dependent glucose dehydrogenase (GDH) complex, to elucidate its characteristic properties as well as to investigate its potential application as the future immunosensor platform. The gold disk electrodes (GDEs) with DET-type FADGDH prepared using self-assembled monolayer (SAM) showed the glucose concentration dependent impedance change, which was confirmed by the change in the charge transfer resistance (Rct). The Δ(1/Rct) values were also affected by DC bias potential and the length of SAM. Based on the Nyquist plot and Bode plot simulations, glucose sensing by imaginary impedance monitoring under fixed frequency (5 mHz) was carried out, revealing the higher sensitivity at low glucose concentration with wider linear range (0.02-0.2â¯mM). Considering this high sensitivity toward glucose, the 3rd-generation faradaic enzyme EIS sensor would provide alternative platform for future impedimetric immunosensing system, which does not use redox probe.
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Técnicas Biossensoriais/métodos , Glucose 1-Desidrogenase/química , Glucose/análise , Bactérias/enzimologia , Impedância Elétrica , Eletrodos , Transporte de Elétrons , Flavina-Adenina Dinucleotídeo/química , Ouro/químicaRESUMO
A novel paper-based biofuel cell with a series/parallel array structure has been fabricated, in which the cell voltage and output power can easily be adjusted as required by printing. The output of the fabricated 4-series/4-parallel biofuel cell reached 0.97±0.02â mW at 1.4â V, which is the highest output power reported to date for a paper-based biofuel cell. This work contributes to the development of flexible, wearable energy storage device.
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The channel flow double electrode (CFDE) was used for the evaluation of the oxygen reduction activities in alkaline solution of rare-earth oxide-supported silver catalysts. The CFDE cell was modified for the experiment using the powder catalyst as a working electrode. In the present experiment, the silver electrode was supported with CeO2 in order to improve the performance of the oxygen reduction. The detecting electrode current for HO2- emitted from the working electrode was recorded simultaneously with the measurement of the i-E curve of each working electrode. Moreover, the average number of charge transfers n was calculated from the working and detecting electrode currents. The value of n for the oxygen reduction was approximately 4 for silver electrode supported with rare-earth oxide, compared with the n value of pure silver that was smaller than 4. On the basis of these results, the mechanisms of oxygen reduction on these electrodes and role of the rare-earth oxide in alkaline solution were discussed.
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We demonstrate a flexible paper-based biofuel cell using porous carbon inks for high power output. The power density of the fabricated biofuel cell reached 0.12 mW cm(-2) (at 0.4 V), which is the highest output power reported to date, to the best of our knowledge.
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Fontes de Energia Bioelétrica , Carbono/química , Papel , Impressão , Soluções Tampão , Eletrodos , Glucose/química , PorosidadeRESUMO
A new nanomotor-based surface-patterning technique based on the movement of a magnetically powered enzyme-functionalized flexible nanowire swimmer offers the ability to create complex helical metal microstructures.