A Novel Glucose Biosensor Based on Glucose Oxidase Immobilized on AuPt Nanoparticle – Carbon Nanotube – Ionic Liquid Hybrid Coated Electrode

A novel amperometric glucose biosensor is presented in this article, which is based on the adsorption of glucose oxidase on gold‐platinum nanoparticle (AuPt NP)‐multiwalled carbon nanotube (MWNT) – ionic liquid (i.e., 1‐octyl‐3‐methylimidazolium hexafluorophosphate, [OMIM]PF₆) composite. The gold‐platinum nanoparticles is prepared through direct electrodeposition. Owing to the synergistic action of AuPt nanoparticle, MWNT and [OMIM]PF₆, the biosensor shows good response to glucose, with wide linear range (0.01 to 9.49 mM), short response time (3 s), and high sensitivity (3.47 μA mM⁻¹). With the biosensor the determination of glucose in human serum is performed.     

Prussian Blue Modified Carbon Ionic Liquid Electrode: Electrochemical Characterization and Its Application for Hydrogen Peroxide and Glucose Measurements

Prussian blue modified carbon ionic liquid electrodes (PB‐CILEs) were fabricated using chemical and electrochemical procedures. Chemically fabricated PB‐CILE exhibited an excellent sensitivity (0.0866 μA μM^?1), low detection limit (0.01 μM) and two linear ranges (0.01–1 and 1–600 μM) toward hydrogen peroxide. Then, glucose oxidase (GOx) was immobilized on the surface of PB‐CILE to fabricate glucose biosensor using three different procedures involving cross linking with glutaraldehyde (GLU) and bovine serum albumin (BSA), entrapment into the Nafion matrix and covering with a sol‐gel layer. Glucose biosensor fabricated using cross linking procedure showed the best sensitivity (0.0019 μA μM^?1) and operational stability for glucose.     

Remarkable Electrochemical Responses of Ferrocene/NaY Zeolite Composite modified Electrode Based on Hydrophobic Ionic Liquid

The ferrocene/NaY zeolite composites (Fc/NaY) are introduced on the surface of a glassy carbon electrode together with the hydrophobic ionic liquid 1‐butyl‐3‐methylimidazolium hexafluorophosphate (BMIMPF₆). The modified electrode thus constructed exhibits a pair of reversible redox peaks corresponding to ferrocene. Additionally the peak separation remains almost constant (58–75 mV) and the value of the ratio i_pa/i_pc is close to 1 for scan rates in the range from 10 to 1000 mV s^?1. The effects of the scan rate, aqueous supporting electrolytes, hydrophobic ionic liquid and the contents of ferrocene encapsulated by electrochemistry are investigated. The extrazeolite electron transfer process is discussed. Furthermore, the Fc/NaY/IL‐modified electrode shows good mediation towards oxidation of ascorbic acid, dopamine, hydroquinone, and catechol.     

Carbon Nanotubes‐Ionic Liquid and Chloropromazine Modified Electrode for Determination of NADH and Fabrication of Ethanol Biosensor

Potential cycling was used for oxidation of chloropromazine and producing an electroactive redox couples which strongly adsorbed on the electrode surface modified with carbon nanotubes and ionic liquid nanocomposite. The modified electrode shows excellent electrocatalytic activity toward NADH oxidation. The differential pulse voltammetry detection provided high sensitivity, 0.5835 A M^?1, low detection limit, 80 nM at concentration range up to 20 μM. An ethanol biosensor was also developed by immobilizing alcohol dehydrogenase enzyme onto nanocomposite. Differential pulse voltammetric detection of ethanol gives linear responses over the concentration range 40 μM–1.5 mM with detection limit 5 μM and sensitivity 1.97 μA mM^?1.     

Electrochemiluminescence Biosensor for Glucose Based on Graphene/Nafion/GOD Film Modified Glassy Carbon Electrode

Glucose oxidase(GOD) was encapsulated in the Graphene/Nafion film modified glassy carbon electrode(GCE) and used as an ECL sensor for glucose. The GOD retains its bioactivity after being immobilized into the composite film. The sensor gives a linear response for glucose in the range of 2.0×10^?6–1.0×10^?4 mol/L with a detection limit of 1.0×10^?6 mol/L. The sensor showed good stability, the RSD for continuous scanning for 5.0×10^?5 mol/L glucose was 4.21 % (n=5). After being stored in 0.05 mol/L pH 7.4 PBS in 4 °C for two weeks, the modified electrode maintains 80 % of its initial activity. The glucose sensor provides new opportunity for clinical diagnosis applications.     

High-Sensitive Glucose Biosensor Based on Ionic Liquid Doped Polyaniline/Prussian Blue Composite Film

The Prussian blue/ionic liquid-polyaniline/multiwall carbon nanotubes (PB/IL-PANI/MWNTs) composite film was fabricated by using cyclic voltammetry. The ion liquid acting as a lubricating agent, could enhance the electron delocalization degree and reduce the struc-tural defects of the polyaniline. The surface morphology of the composite film revealed that the PB nanoparticles have smaller size than that in pure PB film. Due to the introduction of ion liquid, the PB/IL-PANI/MWNTs composite film showed wonderful synergistic effect which can remarkably enhance sensitivity, expand linear range and broaden acidic adapt-ability for hydrogen peroxide detection. The composite film demonstrated good stability in neutral solution contrast to pure PB film, with a linear range from 2.5 μmol/L to 0.5 mmol/Land a high sensitivity of 736.8 μA·(mmol/L)^-1·cm^-2 for H₂O₂ detection. Based on the com-posite film, an amperometric glucose biosensor was then fabricated by immobilizing glucose oxidase. Under the optimal conditions, the biosensor also exhibits excellent response to glucose with the linear range from 12.5 μmol/L to 1.75 mmol/L and a high sensitivity of 94.79 μA (mmol/L)^-1·cm^-2 for H₂O₂. The detection limit was estimated 1.1 μmol/L. The resulting biosensor was applied to detect the blood sugar in human serum samples without any pretreatment, and the results were comparatively in agreement with the clinical assay.     

Sensitive Amperometric Determination of Thiocyanates at Ionic Liquid Nanohybrid Kaolinite Modified Glassy Carbon Electrode

Electrochemical sensors have been developed by modifying a glassy carbon electrode with organo‐kaolinite hybrid materials. These materials were obtained by the grafting of four ionic liquids (1‐(2‐hydroxyethyl)‐4‐benzylpyridinium chloride, 1‐(2‐hydroxyethyl)‐4‐(tert‐butyl)pyridinium chloride, 1‐(2‐hydroxyethyl)‐4‐ethylpyridinium chloride and 1‐(2‐hydroxyethyl)‐4‐methylpyridinium chloride) on the interlayer aluminol surfaces of kaolinite. With the presence of ionic liquids in the interlayer space of kaolinite, the hybrid materials acquired anion exchange properties and were successfully applied as electrode modifier for the electroanalysis of thiocyanate (SCN⁻), an anion of medical and environmental concern. A pre‐concentration/detection strategy was used to overcome the interfering effect of the electrolytic solution. After the optimisation of some key experimental parameters (sodium nitrate as electrolyte, 5 min of accumulation time) calibration curves were plotted. Excellent linearity was obtained in the low concentration region (1×10⁻⁶ M to 4×10⁻⁵ M). The lowest detection limit (15 nM) was obtained with the benzylpyridinium functionalized kaolinite and the highest (60 nM) with the methylpyridinium functionalized kaolinite. Interfering anions (NO₃⁻, Cl⁻, SO₄²⁻ and CH₃COO⁻) present in the pre‐concentration solution were found to interfere with SCN⁻ but the sensors remained stable and produced reproducible signals. The most sensitive sensor was successfully applied for the amperometric determination of SCN⁻ in human saliva samples.     

纳米铂颗粒修饰薄膜金电极的新型葡萄糖传感器研究

在没有引入电子媒介体条件下,为了提高传感器的响应灵敏度,降低工作电位,利用电化学沉积法在薄膜金电极表面修饰纳米铂颗粒,并通过戊二醛固定酶的方法制备了一种新型生物传感器。研究了在薄膜金电极上修饰纳米铂颗粒前后传感器对低浓度葡萄糖的响应影响。结果表明,纳米铂颗粒修饰后所制备的葡萄糖传感器工作电位下降为0.4 V,测定葡萄糖的检出限从100μmol/L下降到10μmol/L。传感器对10~1300μmol/L低浓度葡萄糖的响应灵敏度为50.8 nA/(cm2μmol/L);响应时间30 s;r为0.9974;传感器精密度为2.1%,并具有较好的稳定性。     

Electrochemical Characteristics of Glucose Oxidase Adsorbed at Carbon Nanotubes Modified Electrode with Ionic Liquid as Binder

Multiwall carbon nanotubes (CNTs)‐modified electrode has been prepared by using ionic liquid (IL) as the binder. The as‐prepared CNTs‐IL composite modified electrode has good biocompatibility and is a suitable matrix to immobilize biomolecules. Glucose oxidase (GOx), containing flavin adenine dinucleotide as active site, stably adsorbed on modified electrode surface has resulted in the direct electron transfer. The electron transfer rate of 9.08 s^?1 obtained is much higher than that of GOx adsorbed on the CNTs papers (1.7 s^?1), and the process is more reversible with small redox peak separation of 23 mV. This may be due to the synergetic promotion of CNTs and IL to electron transfer of the protein, especially the IL as the binder, showing better electrochemical properties than that of chitosan and Nafion. Furthermore, GOx adsorbed at the modified electrode exhibits good stability and keeps good electrocatalytic activity to glucose with broad linear range up to 20 mM. Besides, the simple preparation procedure and easy renewability make the system a basis to investigate the electron transfer kinetics and biocatalytic performance of GOx and provide a promising platform for the development of biosensors.     

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.     

化学修饰电极循环伏安法的数值模拟

用ＣＮ法对化学修饰电极（ＣＭＥ）的循环伏安法（ＣＶ）进行了数值模拟。建立了ＣＭＥ的有限扩散理论模型,引入了活度系数比、扩散系数校正因子及动力学参数等。模拟的普鲁士兰（ＰＢ）修饰电极与文献相符很好。     

Electrochemical Reduction of a Conjugated Cinnamic Acid Diazonium Salt as an Immobilization Matrix for Glucose Biosensor

Initial results on the synthesis of a new conjugated diazonium salt of trans‐4‐cinnamic acid diazonium fluoroborate, which is used for the chemical modification of the glassy carbon (GC) electrode with trans‐4‐cinnamic acid groups through electrochemical reduction, and direct covalent immobilization of glucose oxidase (GOD) on the cinnamic acid groups are presented. The chemically modified GC electrode exhibits a good selectivity relative to the bare GC electrode for the various possible interfering compounds in glucose analysis: namely ascorbic acid and 4‐acetamidophenol. Covalent immobilization of GOD on the chemically modified GC electrode produces a biosensor which responds to glucose concentration changes in the presence of a soluble redox mediator (ferrocenemethanol). The chemical modification of GC by cinnamic acid groups is potentially useful for the attachment of other enzymes and biochemical reagents.     

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.     

Electrocatalytic Activity of Riboflavin Chemically Modified Electrode Toward Dioxygen Reduction

Abstract

A chemically modified electrode (CME) exhibiting electrocatalytic response toward dioxygen was constructed by adsorbing the mediator riboflavin onto spectroscopic graphite. The electron transfer between the riboflavin functionality and the graphite was fast. The surface apparent coverage was at most 9.6 × 10^?10 mol cm^?2. The modified electrode permitted the dioxygen electroreduction to take place at the reduction potential of the mediator molecule. Dioxygen accepted two electrons from a reduced mediator to form hydrogen peroxide. Characterisation of the performance of the CME was carried out. After 30 min of continuous electrochemical cycling of pH 6.8, 30% of the original coverage remained for the CME. The effect of the solution pH and temperature on the electrocatalytic activity of the CME for oxygen reduction was also investigated.     

化学修饰电极富集石墨炉原子吸收法测定痕量金

本文提出用聚丙烯脒硫氰酸盐化学修饰石墨管内壁、电化学预富集石墨炉原予吸收测定Au的分析方法.分析灵敏度提高100倍.应用于矿石中痕量Au的测定,获得了满意的结果.     

天青Ⅰ为电子媒介体金纳米颗粒修饰葡萄糖生物传感器

用纳米金溶胶与聚乙烯醇缩丁醛(PVB)构成复合固酶基质,采用溶胶凝胶法固定葡萄糖氧化酶(GOx)于铂金电极表面,并在葡萄糖溶液中加入天青Ⅰ作为电子媒介体,制成了新型葡萄糖生物传感器。实验证明,葡萄糖氧化酶吸附在纳米金颗粒表面上稳定且保持其生物活性;而电子媒介体的存在,显著提高了传感器的响应灵敏度。该传感器对葡萄糖响应的线性范围为2.5×10-5～7.5×10-3mol/L;检出限为8.5×10-6mol/L(S/N=3)。该生物传感器用于人体血清中的葡萄糖测定,结果令人满意。     

Electrochemical Biosensor Based on Carbon Ionic Liquid Electrode Modified with Nafion/Hemoglobin/DNA Composite Film

A new electrochemical biosensor was constructed by immobilization of hemoglobin (Hb) on a DNA modified carbon ionic liquid electrode (CILE), which was prepared by using 1‐ethyl‐3‐methylimidazolium tetrafluoroborate (EMIMBF₄) as the modifier. UV‐vis absorption spectroscopic result indicated that Hb remained its native conformation in the composite film. The fabricated Nafion/Hb/DNA/CILE was characterized by scanning electron microscopy (SEM), electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). A pair of well‐defined redox peaks was obtained on the modified electrode, indicated that the Nafion and DNA composite film provided an excellent biocompatible microenvironment for keeping the native structure of Hb and promoting the direct electron transfer rate of Hb with the basal electrode. The electrochemical parameters of Hb in the composite film were further calculated with the results of the charge transfer coefficient (α) and the apparent heterogeneous electron transfer rate constant (k_s) as 0.41 and 0.31 s^?1. The proposed electrochemical biosensor showed good electrocatalytic response to the reduction of trichloroacetic acid (TCA), H₂O₂, NO and the apparent Michaelis–Menten constant (K_M^app) for the electrocatalytic reaction was calculated, respectively.     

Unadulterated Glucose Biosensor Based on Direct Electron Transfer of Glucose Oxidase Encapsulated Chitosan Modified Glassy Carbon Electrode

Glucose oxidase (GOD) was encapsulated in chitosan matrix and immobilized on a glassy carbon electrode, achieving direct electron transfer (DET) reaction between GOD and electrode without any nano‐material. On basis of such DET, a novel glucose biosensor was fabricated for direct bioelectrochemical sensing without any electron‐mediator. GOD incorporated in chitosan films gave a pair of stable, well‐defined, and quasireversible cyclic voltammetric peaks at about ?0.284 (E_pa) and ?0.338 V (E_pc) vs. Ag/AgCl electrode in phosphate buffers. And the peak is located at the potentials characteristic of FAD redox couples of the proteins. The electrochemical parameters, such as midpoint potential (E_1/2) and apparent heterogeneous electron‐transfer rate constants (k_s) were estimated to ?0.311 V and 1.79 s^?1 by voltammetry, respectively. Experimental results indicate that the encapsulated GOD retains its catalytic activity for the oxidation of glucose. Such a GOD encapsulated chitosan based biosensor revealed a relatively rapid response time of less than 2 min, and a sufficient linear detection range for glucose concentration, from 0.60 to 2.80 mmol L^?1 with a detection limit of 0.10 mmol L^?1 and electrode sensitivity of 0.233 μA mmol^?1. The relative standard deviation (RSD) is under 3.2% (n=7) for the determination of practical serum samples. The biologic compounds probably existed in the sample, such as ascorbic acid, uric acid, dopamine, and epinephrine, do not affect the determination of glucose. The proposed method is satisfactory to the determination of human serum samples compared with the routine hexokinase method. Both the unique electrical property and biocompatibility of chitosan enable the construction of a good bio‐sensing platform for achieved DET of GOD and developed the third‐generation glucose biosensors.     

Fabrication and Application of a Sensitive and Highly Stable Copper Hexacyanoferrate Modified Carbon Ionic Liquid Paste Electrode for Hydrogen Peroxide and Glucose Detection

A three‐factor mixture design and response surface methodology were employed to find the optimal weight ratio of graphite powder, n‐dodecylpyridinium hexafluorophosphate and paraffin for the fabrication of a copper hexacyanoferrate modified carbon ionic liquid paste electrode (CuHCFe‐CILPE). The fabricated sensor showed electrocatalytic activity towards oxidation and reduction of hydrogen peroxide. It also was observed that the electrocatalytic activity for hydrogen peroxide oxidation was much higher than the electrocatalytic activity for hydrogen peroxide reduction. Glucose oxidase was then successfully immobilized on the surface of the proposed sensor to examine the possibility of using CuHCFe‐CILPE for the biosensor fabrication.