Glucose Biosensor Based on Oxygen Electrode. Part II: Long-Term Operational Stability of the Rechargeable Glucose Biosensor

Abstract

A potentially implantable glucose biosensor for measuring blood or tissue glucose levels in diabetic patients has been developed. The glucose biosensor is based on an amperometric oxygen electrode and immobilized glucose oxidase enzyme, in which the immobilized enzyme can be replaced (the sensor recharged) without surgical removal of the sensor from the patient. Recharging of the sensor is achieved by injecting fresh immobilized enzyme into the sensor using a septum. A special technique for immobilization of the enzyme on Ultra-Low Temperature Isotropic (ULTI) carbon powder held in a liquid suspension has been developed.

In vitro studies of the sensors show stable performance during several recharge cycles over a period of 3 months of continuous operation.

Diffusion membranes which ensure linear dependence of the sensor response on glucose concentration have been developed. These membranes comprise silastic latex-rubber coatings over a microporous polycarbonate membrane. Calibration curves of the amperometric signal show linearity over a wide range of glucose concentrations (up to 16 mM), covering hypoglycemic, normoglycemic and hyperglycemic conditions.

The experimental results confirm the suitability of the sensors for in vitro measurements in undiluted human sera.     

A Telemetry-Instrumentation System for Long-Term Implantable Glucose and Oxygen Sensors

Abstract

This paper describes the development of a compact, low power, implantable system for in vivo monitoring of oxygen and glucose concentrations. The telemetry-instrumentation system consists of two amperometric sensors: one oxygen and one glucose biosensor and two potentiostats for biasing the sensors, an instrumentation amplifier to subtract and amplify sensor output signals, and a signal transmitter subunit to convert and transmit glucose dependent signal from the sensors to a remote data acquisition system. The system produces a unipolar glucose dependent voltage in the range of 1 to 3.6 V which is converted to a frequency and then transmitted using a frequency-modulated (FM) oscillator. Initial tests were performed on an open model electronic circuit using resistors to simulate sensor outputs in the 10 to 1000 nA range. Further in vitro evaluation of the system was conducted with a compact printed circuit board embedded in silicone elastomer, entirely submerged in buffer solution using actual sensors. The test results indicated satisfactory operation of the system in simulated implantation conditions for seven days. Response curve of transmitted signal vs glucose concentration was obtained. The results of the in vitro evaluation of the telemetry system permits its subcutaneous implantation in an animal model.     

Amperometric Glucose Sensor Fabricated by Combining Glucose Oxidase Micelle Membrane and Aminated Glassy Carbon Electrode

Abstract

An amperometric glucose biosensor based on the detection of the reduction of oxygen has been developed by combining an aminated glassy carbon electrode with a polystyrene (PS) membrane containing glucose oxidase (GOD) micelles. The structure of GOD micelles contained in PS membrane was observed by scanning electron microscope. The micelle has a roughly spherical shape, and the enzyme colony is contained inside the micelle. This glucose sensor exhibited good sensitivity with short response time (within 2 min). A good linear relationship was observed in the concentration range of 0.2 mM to 2.6 mM when the applied potential was ? 0.45 V vs. Ag/AgCl.     

Glucose Biosensor Based on Oxygen Electrode Part III: Long-Term Performance of the Glucose Biosensor in Blood Plasma at Body Temperature

Abstract

A potentially implantable glucose biosensor for continuous monitoring of glucose levels in diabetic patients has been developed. The glucose biosensor is based on an amperometric oxygen electrode and Glucose Oxidase immobilized on carbon powder held in a form of a liquid suspension. The enzyme material can be replaced (the sensor recharged) without sensor disassembly. Glucose diffusion membranes from polycarbonate (PC) and from polytetrafluorethylene (PTFE) coated with silastic are used.

Sensors were evaluated continuously operating in phosphate buffer solution and in undiluted blood plasma at body temperature. Calibration curves of the sensors were periodically obtained. The sensors show stable performance during at least 1200 hours of operation without refilling of the enzyme. The PTFE membrane demonstrates high mechanical stability and is little effected by long-term operation in undiluted blood plasma.     

Amperometric Detection of Glucose with Glucose Oxidase Immobilized in Layered Double Hydroxides

A novel cheap and simple amperometric biosensor, based on the immobilization of glucose oxidase (GOD) into anionic clay; layered double hydroxides (LDHs) [Zn₃‐Al‐Cl] is presented. GOD can be entrapped in the LDHs gel via electrostatic interaction. Amperometric detection of glucose with an unmediated sensor at 0.6 V (vs. SCE) results in a rapid response (5 s), a wide linear range of 0.001–12 mM, as well as good operational stability. The low detection limit was 0.1 μM at 3σ. The apparent Michaelis‐Menten constant (K is 4.4 mM. The general interferences that coexisted in blood serum do not affect glucose determination, except for uric acid. In addition, optimization of the biosensor construction and the effects of the applied potential on the amperometric response of the sensor were investigated and discussed herein.     

Amperometric Glucose Biosensor Based on Pt‐Pd Nanoparticles Supported by Reduced Graphene Oxide and Integrated with Glucose Oxidase

A novel glucose biosensor was developed based on the immobilization of glucose oxidase (GOx) on reduced graphene oxide incorporated with electrochemically deposited platinum and palladium nanoparticles (PtPdNPs). Reduced graphene oxide (RGO) was more hybridized by chemical and heat treatment. Bimetallic nanoparticles were deposited electrochemically on the RGO surface for potential application of the Pd? Pt alloy in biosensor preparation. The as‐prepared hybrid electrode exhibited high electrocatalytic activities toward H₂O₂, with a wide linear response range from 0.5 to 8 mM (R²=0.997) and high sensitivity of 814×10^?6 A/mMcm². Furthermore, glucose oxidase with active material was integrated by a simple casting method on the RGO/PdPtNPs surface. The as‐prepared biosensor showed good amperometric response to glucose in the linear range from 2 mM to 12 mM, with a sensitivity of 24×10^?6 A/mMcm², a low detection limit of 0.001 mM, and a short response time (5 s). Moreover, the effect of interference materials, reproducibility and the stability of the sensor were also investigated.     

Amperometric Glucose Biosensor Based on Ultrafine Platinum Nanoparticles

Abstract

In the present paper the ultrafine and highly dispersed platinum nanoparticles (average size 3 nm) were used for the construction of a glucose biosensor in a simple method. An excellent response to glucose has been obtained with a high sensitivity (137.7 µA mM^?1 cm^?2) and fast response time (5 s). The biosensor showed a detection limit of 5 µM (at the ratio of signal to noise, S/N=3) and a linear range form 0.2 to 3.2 mM with a correlation coefficient r=0.999. The apparent Michaelis–Menten constant (k _m) and the maximum current were estimated to be 9.36 and 1.507 mA mM^?1 cm^?2, respectively. In addition, effects of pH value, applied potential and the interferents on the amperometric response of the sensor were investigated and discussed.     

Development of Silver Nanowires Based Highly Sensitive Amperometric Glucose Biosensor

The fabrication of a highly sensitive amperometric glucose biosensor based on silver nanowires (AgNWs) is presented. The electrochemical behavior of glassy carbon electrode modified by Ag NWs exhibits remarkable catalytic performance towards hydrogen peroxide (H₂O₂) and glucose detection. The biosensor could detect glucose in the linear range from 0.005 mM to 10 mM, with a detection limit of 50 µM (S/N=3). The glucose biosensor shows high and reproducible sensitivity of 175.49 µA cm^?2 mM and good stability. In addition, the biosensor exhibits a good anti‐interference ability and favorable stability over relatively long‐term storage (more than 21 days).     

A Fiber Optic Biosensor Based on Hydrogel-Immobilized Enzyme Complex for Continuous Determination of Cholesterol and Glucose

A multiparameter fiber optic biosensor for continuous determination of cholesterol and glucose was developed. This sensor was based on poly(N-isopropylacrylamide) (PNIPAAm)-immobilized glucose oxidase (GOx) complex (PIGC) and immobilized cholesterol oxidase (COD). The immobilized COD catalysis to the oxidation of cholesterol and PIGC catalysis to the oxidation of glucose could be performed at different temperatures. Therefore, the sensor could detect cholesterol and glucose continuously by changing temperature. The optimal detection conditions for glucose were achieved with pH 6.5, 30 °C, and 10 mg GOx (in 100-mg carrier), and those for cholesterol were achieved with pH 7.5, 33 °C, and 25 mg COD (in 250-mg carrier). The sensor has the cholesterol detection range of 20–250 mg/dL and the glucose detection range of 50–700 mg/dL. This biosensor has outstanding repeatability and selectivity, and the detection results of the practical samples are satisfactory.

     

Measurement of Glucose Concentration in Blood Plasma Based on a Wireless Magnetoelastic Biosensor

Abstract

A wireless magnetoelastic glucose biosensor in blood plasma is described, based on using a mass sensitive magnetoelastic sensor as transducer. The glucose biosensor was fabricated by coating the ribbon‐like, magnetoelastic sensor with a pH sensitive polymer and a biolayer of glucose oxidase (GOx) and catalase. The pH response polymer swells or shrinks, thereby changing sensor mass loading, respectively, in response to increase or decrease of pH values. The GOx–catalyzed oxidation of the glucose in blood plasma produces gluconic acid, resulting in the pH sensitive polymer shrinking, which in turn decreases the sensor mass loading. The results show that the proposed magnetoelastic glucose biosensor can be successfully applied to determine the concentration of glucose in blood plasma. At glucose concentration range of 2.5–20.0 mmol/l, the biosensor responses are reversible and linear, with a detection limit of 1.2 mmol/l. Since no physical connections between the sensor and the monitoring instruments are required, this proposed biosensor can potentially be applied to in vivo and in situ measurement of glucose concentration in physiological fluids.     

Fast and Effective Turn‐on Paper‐based Phosphorescence Biosensor for Detection of Glucose in Serum

In this study, a turn‐on paper‐based optical analytical system with a rapid, sensitive and quantitative response for glucose was developed. The luminescence sensing material, crystalline iridium(III)‐Zn(II) coordination polymers, or Ir‐Zn_e, was grown electrochemically on stainless steel mesh and then deposited on filter paper. This sensing substrate was subsequently built up under glucose oxidase encapsulated in hydrogel and then immobilized on egg membrane with the layer‐by‐layer method. Once the glucose solution was dropped onto the paper, the oxygen content was depleted simultaneously with a concomitant increase in the phosphorescence of Ir‐Zn_e. The detection limit for glucose was 0.05 mM. The linear dynamic range for the determination of glucose was 0.05–8.0 mM with a correlation coefficient (R²) of 0.9956 (y=68.11 [glucose]?14.72). The response time was about 0.12 s, and the sample volume was less than 5 μL. The effects of mesh size, buffer concentration, pH, enzyme concentration, temperature, and interference, and the stability of the biosensor, have also been studied in detail. Finally, the biosensor was successfully applied to the determination of glucose in human serum.     

Electrocatalytic Oxidation of Glucose by the Glucose Oxidase Immobilized in Graphene‐Au‐Nafion Biocomposite

Graphene was successfully prepared and well separated to individual sheets by introducing  SO₃⁻. XRD and TEM were employed to characterize the graphene. UV‐visible absorption spectra indicated that glucose oxidase (GOx) could keep bioactivity well in the graphene‐Au biocomposite. To construct a novel glucose biosensor, graphene, Au and GOx were co‐immobilized in Nafion to further modify a glassy carbon electrode (GCE). Electrochemical measurements were carried out to investigate the catalytic performance of the proposed biosensor. Cyclic voltammograms (CV) showed the biosensor had a typical catalytic oxidation response to glucose. At the applied potential +0.4 V, the biosensor responded rapidly upon the addition of glucose and reached the steady state current in 5 s, with the present of hydroquinone. The linear range is from 15 μM to 5.8 mM, with a detection limit 5 μM (based on the S/N=3). The Michaelis‐Menten constant was calculated to be 4.4 mM according to Lineweaver–Burk equation. In addition, the biosensor exhibits good reproducibility and long‐term stability. Such impressive properties could be ascribed to the synergistic effect of graphene‐Au integration and good biocompatibility of the hybrid material.     

Glucose concentration determination based on silica sol-gel encapsulated glucose oxidase optical biosensor arrays

Optical biosensor arrays for rapidly determining the glucose concentrations in a large number of beverage and blood samples were developed by immobilizing glucose oxidase (GOD) on oxygen sensor layer. Glucose oxidase was first encapsulated in silica based gels through sol-gel approach and then immobilized on 96-well microarrays integrated with oxygen sensing film at the bottom. The oxygen sensing film was made of an organically modified silica film (ORMOSIL) doped with tris(4,7-diphenyl-1,10-phenanthroline) ruthenium dichloride (Ru(dpp)₃Cl₂). The oxidation reaction of glucose by glucose oxidase could be monitored through fluorescence intensity enhancement due to the oxygen consumption in the reaction. The luminescence changing rate evaluated by the dynamic transient method (DTM) was correlated with the glucose concentration with the wide linear range from 0.1 to 5.0 mM (Y = 13.28X − 0.128, R = 0.9968) and low detection limit (0.06 mM). The effects of pH and coexisting ions were systemically studied. The results showed that the optical biosensor arrays worked under a wide range of pH value, and normal interfering species such as Na⁺, K⁺, Cl⁻, PO₄³⁻, and ascorbic acid did not cause apparent interference on the measurement. The activity of glucose oxidase was mostly retained even after 2-month storage, indicating their long-term stability.     

Amperometric Biosensor Coupled to Capillary Electrophoresis for Glucose Determination

A novel glucose biosensor has been fabricated and employed as the amperometric detector of a capillary electrophoresis (CE) system. (±)-1-Ferrocenylethylamine and chitosan were successively modified on a 500-µm diameter disc platinum electrode by dip-coating. The modified electrode was subsequently immersed in glucose oxidase (GOx) solution to entrap the enzyme in the chitosan membrane. The primary amino groups of 1-ferrocenylethylamine, GOx, and chitosan were cross-linked by glutaraldehyde to obtain a biosensing membrane so as to reduce leaching of 1-ferrocenylethylamine and GOx. The electrochemical behavior of the target biosensor was investigated. It was demonstrated that the investigated biosensor features fast response, high stability, long lifetime, and ideal compatibility with the CE system. When CE was employed to introduce a glucose plug into the surface of the biosensor, the current response was linear to the glucose concentration in the range of 0.0025 to 2.5 mM with a detection limit of 1.2 µM (S/N = 3) at a working potential of +0.6 V (vs. SCE). The CE-biosensor system was applied to the determination of the glucose level in human serum. The results were satisfactory and in good agreement with the hospital assay results.     

A Novel Chronoimpedimetric Glucose Sensor in Real Blood Samples Modified by Glucose‐imprinted Pyrrole‐Aminophenylboronic Acid Modified Screen Printed Electrode

In this study, a molecularly imprinted sensor technology is engineered to detect glucose in real blood samples by chronoimpedimetrically. The imprinting process of glucose (Glc) was carried out by electrochemical polymerization of aminophenylboronic acid (APBA) and pyrrole (Py) by performing cyclic voltammetry (CV). Afterwards, glucose molecule was removed from imprinted surface by 5 % acetic acid to reveal glucose imprinted cavities. Electrochemical Impedance Spectroscopy (EIS) was used to characterize sensor modification steps and glucose removal. Glucose monitoring process was carried out chronoimpedimetrically(CI) for the first time in real blood samples. Calibration curve was prepared between 20–800 mg/dL. The standard deviations of the 18 calibration curves R² were calculated as 0.9866±0.0066 to assess reproducibility. Recovery was calculated by using 105 mg/dL Glc Serum Sample, which was monitored by auto analyzer and into this sample 50 mg/dL Glc added and our sensor response was 147.92±2.43 mg/dL, 98.6±1.62 % (n=5). Non‐imprinted (NIP) sensor gave no signal for the glucose concentration.     

Amperometric Glucose Biosensors Based on Integration of Glucose Oxidase onto Prussian Blue/Carbon Nanotubes Nanocomposite Electrodes

Nanosized Prussian blue (PB) particles were synthesized with a chemical reduction method and then the PB nanoparticles were assembled on the surface of multiwall carbon nanotubes modified glassy carbon electrode (PB/MWNTs/GCE). The results showed that the PB/MWNTs nanocomposite exhibits a remarkably improved catalytic activity towards the reduction of hydrogen peroxide. Glucose oxidase (GOD) was immobilized on the PB/MWNTs platform by an electrochemically polymerized o‐phenylenediamine (OPD) film to construct an amperometric glucose biosensor. The biosensor exhibited a wide linear response up to 8 mM with a low detection limit of 12.7 μM (S/N=3). The Michaelis–Menten constant K_m and the maximum current i_max of the biosensor were 18.0 mM and 4.68 μA, respectively. The selectivity and stability of the biosensor were also investigated.     

Fabrication of Glucose Biosensor Based on Encapsulation of Glucose‐Oxidase on Sol‐Gel Composite at the Surface of Glassy Carbon Electrode Modified with Carbon Nanotubes and Celestine Blue

A simple procedure was developed to prepare a glassy carbon electrode modified with multi walled carbon nanotubes (MWCNTs) and Celestin blue. Cyclic voltammograms of the modified electrode show stable and a well defined redox couple with surface confined characteristic at wide pH range (2–12). The formal potential of redox couple (E′) shifts linearly toward the negative direction with increasing solution pH. The surface coverage of Celestine blue immobilized on CNTs glassy carbon electrode was approximately 1.95×10^?10 mol cm^?2. The charge transfer coefficient (α) and heterogeneous electron transfer rate constants (k_s) for GC/MWCNTs/Celestine blue were 0.43 and 1.26 s^?1, respectively. The modified electrode show strong catalytic effect for reduction of hydrogen peroxide and oxygen at reduced overpotential. The glucose biosensor was fabricated by covering a thin film of sol‐gel composite containing glucose oxides (GOx) on the surface of Celestine blue /MWCNTs modified GC electrode. The biosensor can be used successfully for selective detection of glucose based on the decreasing of cathodic peak current of oxygen. The detection limit, sensitivity and liner calibration rang were 0.3 μM, 18.3 μA/mM and 10 μM–6.0 mM, respectively. The accuracy of the biosensor for glucose detection was evaluated by detection of glucose in a serum sample, using standard addition protocol. In addition biosensor can reach 90% of steady currents in about 3.0 sec and interference effect of the electroactive existing species (ascorbic acid–uric acid and acetaminophen) was eliminated. Furthermore, the apparent Michaelis–Menten constant 2.4 mM, of GOx on the nano composite exhibits excellent bioelectrocatalytic activity of immobilized enzyme toward glucose oxidation. Excellent electrochemical reversibility of redox couple, high stability, technically simple and possibility of preparation at short period of time are of great advantages of this procedure for modification of glucose biosensor.     

Synthesis of PtxSn/MWCNTs and their Application in Non‐enzymatic Glucose and Hydrogen Peroxide Sensors

Pt_xSn/MWCNTs (x=1, 2, 3) nanocomposites were synthesized by chemical reduction. Comparing all of the materials, the results revealed that the best material was Pt₃Sn/MWCNTs. The sensor based on Pt₃Sn/MWCNTs exhibited excellent catalytic activities towards glucose and hydrogen peroxide. Sensing of glucose had a double‐linear range: one was between 50 μM and 550 μM, the other was between 1.35 mM and 16.35 mM. These were due to the fact that more and more intermediate species were adsorbed onto the electrode surface with increasing concentration of glucose, which limited the following glucose oxidation. Meanwhile, the sensor also had a linear response range between 0.05 mM and 18.95 mM for hydrogen peroxide. Furthermore, the glucose and hydrogen peroxide sensors exhibited excellent selectivity, stability, and reproducibility. Thus the sensors had potential utilities in the detection of glucose and hydrogen peroxide.     

Glucose Biosensor Based on Oxygen Electrode. Part I: Silastic Coated Polycarbonate Membranes for Biosensor Application

Abstract

An amperometric glucose biosensor based on the oxygen electrode principle has been developed. Polycarbonate membranes (pore size from 0.01 μm to 0.4 μm) were used as external glucose diffusion membranes in order to obtain direct proportionality of the amperometric signal to the substrate concentration in the entire physiological range. The commercially available membranes - standard (hydrophilic, treated with Polyvinylpyrrolidone/(PVP)) and PVP-free membranes were compared with membranes coated with a silicone elastomer (silastic). Spindrop coating technique was used to create stable, adhesive coatings over the polycarbonate membranes. These coated membranes achieved diffusion control of the glucose flux such that the amperometric signal of the biosensor was linearly proportional to the substrate concentration up to 16 mM glucose. The membrane parameters were optimized by varying the parameters of the coating process-spin rate of the membrane rotation and the silastic/water ratio in the coating emulsion.     

Glucose Sensor Based On an Amorphous Silicon Isfet

Abstract

An amorphous silicon ion sensitive field effect transistor (a-ISFET) was first applied to glucose sensors. When glucose oxidase was immobilized on the membrane, the sensor gave a linear relationship between the initial rate of the gate output voltage change and the logarithmic value of glucose concentration between 0.1 and 1 mg/ml at pH 7.0, 37°C. Determination of glucose was possible within 1 min. the system can be used for three weeks with only slight loss of enzymatic activity.