Synthesis of Ag nanoparticle-decorated 2,4,6-tris(2-pyridyl)-1,3,5-triazine nanobelts and their application for H2O2 and glucose detection

The present paper reports on the first preparation of 2,4,6-tris(2-pyridyl)-1,3,5-triazine nanobelts (TPTNBs) by adjusting the pH value of the solution and the subsequent synthesis of Ag nanoparticle (AgNP)-decorated TPTNBs (AgNP-TPTNBs) by mixing an aqueous AgNO(3) solution with preformed TPTNBs without use of any external reducing agent. It is found that the resultant AgNP-TPTNBs exhibit notable catalytic performance for H(2)O(2) reduction. A glucose biosensor was fabricated by immobilizing glucose oxidase (GOD) onto a AgNP-TPTNBs-modified glassy carbon electrode (GCE) for glucose detection. The constructed glucose sensor has a wide linear response range from 3 mM to 20 mM (r: 0.999) with a detection limit of 190 μM. It is further shown that this glucose biosensor can be used for glucose detection in human blood serum.     

Electrocatalytic Reduction of H2O2 and Oxygen on the Surface of Thionin Incorporated onto MWCNTs Modified Glassy Carbon Electrode: Application to Glucose Detection

A new H₂O₂ enzymeless sensor has been fabricated by incorporation of thionin onto multiwall carbon nanotubes (MWCNTs) modified glassy carbon electrode. First 50 μL of acetone solution containing dispersed MWCNTs was pipetted onto the surface of GC electrode, then, after solvent evaporations, the MWCNTs modified GC electrode was immersed into an aqueous solution of thionin (electroless deposition) for a short period of time <5–50 s. The adsorbed thin film of thionin was found to facilitate the reduction of hydrogen peroxide in the absence of peroxidase enzyme. Also the modified electrode shows excellent catalytic activity for oxygen reduction at reduced overpotential. The rotating modified electrode shows excellent analytical performance for amperometric determination of hydrogen peroxide, at reduced overpotentials. Typical calibration at ?0.3 V vs. reference electrode, Ag/AgCl/3 M KCl, shows a detection limit of 0.38 μM, a sensitivity of 11.5 nA/μM and a liner range from 20 μM to 3.0 mM of hydrogen peroxide. The glucose biosensor was fabricated by covering a thin film of sol–gel composite containing glucose oxides on the surface of thionin/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 1 μM, 18.3 μA/mM and 10 μM–6.0 mM, respectively. In addition biosensor can reach 90% of steady currents in about 3.0 s and interference effect of the electroactive existing species (ascorbic acid–uric acid and acetaminophen) is eliminated. The usefulness of biosensor for direct glucose quantification in human blood serum matrix is also discussed. This sensor can be used as an amperometric detector for monitoring oxidase based biosensors.     

A promising dehydrogenase-based bioanode for a glucose biosensor and glucose/O2 biofuel cell

A new type of dehydrogenase-based amperometric glucose biosensor was constructed using glucose dehydrogenase (GDH) which was immobilized on the edge-plane pyrolytic graphite (EPPG) electrode modified with poly(phenosafranin)-functionalized single-walled carbon nanotubes (PPS-SWCNTs). The PPS-SWCNT-modified EPPG electrode was prepared by electropolymerization of phenosafranin on the EPPG electrode which had been previously coated with SWCNTs. The performance of the GDH/PPS-SWCNT/EPPG bioanode was evaluated using cyclic voltammetry and amperometry in the presence of glucose. The GDH/PPS-SWCNT/EPPG electrode possesses promising characteristics as a glucose sensor: a wide linear dynamic range of 50 to 700 μM, low detection limit of 0.3 μM, fast response time (1-2 s), high sensitivity (96.5 μA cm(-2) mM(-1)), and anti-interference and anti-fouling abilities. Moreover, the performance of the GDH/PPS-SWCNT/EPPG bioanode was tested in a glucose/O(2) biofuel cell. The maximum power density delivered by the assembled glucose/O(2) biofuel cell could reach 64.0 μW cm(-2) at a cell voltage of 0.3 V with 40 mM glucose.     

Amperometric determination of H2O2 at nano-TiO2/DNA/thionin nanocomposite modified electrode

We report electrochemical preparation and characterization of a new biosensor made of nanostructured titanium dioxide (nano-TiO(2)) particles and deoxyribonucleic acid (DNA). Thionin (TN) redox mediator was electrochemically deposited onto DNA/nano-TiO(2) modified glassy carbon electrode (GCE). The X-ray diffraction analysis, atomic force microscope (AFM) and scanning electron microscope (SEM) were used for surface analysis of TN/DNA/nano-TiO(2) film. In neutral buffer solution, TN/DNA/nano-TiO(2)/GCE biosensor exhibited excellent electrocatalytic activity towards the reduction of hydrogen peroxide (H(2)O(2)) and oxygen (O(2)). The biosensor shows excellent analytical performance for amperometric determination of H(2)O(2), at reduced overpotential (-0.2V). The detection limit and liner calibration range were found to be 0.05mM (S/N=3) and 0.05-22.3mM, respectively. In addition, determination of H(2)O(2) in real samples was carried out using the new biosensor with satisfactory results. The TN/DNA/nano-TiO(2)/GCE showed stable and reproducible analytical performance towards the reduction of H(2)O(2). This biosensor can be used as an amperometric biosensor for the determination of H(2)O(2) in real samples.     

Prussian Blue bulk modified screen-printed electrodes for H(2)O(2) detection and for biosensors

A sensor for H(2)O(2) amperometric detection based on a Prussian Blue (PB) bulk modified carbon screen-printed electrode was developed. It has been optimised with respect to the lowest limit of detection achieved. PB was made chemically by the reaction of FeCl(3) with K(4)[Fe(CN)(6)]. The resulting powder, obtained by forced crystallisation induced by acetone, was dried and activated at 150 degrees C for 10 h. PB microparticles (<38 mum) were prepared and mixed with carbon ink. The limit of detection achieved was 0.4 muM with the linear range up to 100 muM of H(2)O(2) with the sensitivity of 137 muA mM(-1) cm(-2), that was comparable with sensors based on electrodeposited PB film. The transducer was applied for a glucose biosensor, that exhibited LOD of 0.22 mM, linear range up to 3 mM, K(M)(app) of 4.6 mM, and the sensitivity of 3.21+/-0.16 muA mM(-1) cm(-2). The peroxide sensor, as well as the glucose biosensor, were totally insensitive to oxygen, ascorbate, urate, and paracetamol.     

Self-gelatinizable copolymer immobilized glucose biosensor based on prussian blue modified graphite electrode

A novel poly(vinyl alcohol) grafting 4-vinylpyridine self-gelatinizable copolymer was adapted to immobilize glucose oxidase. The reduction of hydrogen peroxide (H2O2) was detected at a Prussian Blue (PB) modified graphite electrode. A stable and sensitive glucose amperometric biosensor is described. The copolymer is a good biocompatible polymer in which the glucose oxidase retains high activity. Moreover, the copolymer can adhere firmly to the inorganic PB membrane. The sensor showed an apparent Michaelis-Menten constant of 18 +/- 0.2 mM and a maximum current density of 1.14 microA cm-2 mM-1. The linear range is from 5 microM to 4.5 mM glucose and the detection limit is 0.5 microM glucose. The catalytic efficiency of PB for the reduction of H2O2 is higher than that for the oxidation of H2O2. Glucose concentrations in serum samples from healthy persons and diabetic patients were determined using the sensor. The results compared well with those provided by the hospital using a spectroscopy method.     

Amperometric biosensor for hydrogen peroxide based on direct electrocatalysis by hemoglobin immobilized on gold nanoparticles/1,6-diaminohexane modified glassy carbon electrode.

A facile strategy of an amperometric biosensor for hydrogen peroxide based on the direct electrocatalysis of hemoglobin (Hb) immobilized on gold nanoparticles (GNPs)/1,6-diaminohexane (DAH) modified glassy carbon electrode (GCE) has been described. A uniform monolayer film of DAH was initially covalently bound on a GCE surface by virtue of the electrooxidation of one amino group of DAH, and another amino group was modified with GNPs and Hb, successively. The fabrication process was characterized by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and scanning electron microscopy (SEM). The proposed biosensor exhibited an effective and fast catalytic response to the reduction of H2O2 with good reproducibility and stability. A linear relationship existed between the catalytic current and the H2O2 concentration in the range of 1.5x10(-6) to 2.1x10(-3) M with a correlation coefficient of 0.998 (n=24). The detection limit (S/N=3) was 8.8x10(-7) M.     

RNA Modified Electrodes for Simultaneous Determination of Dopamine and Uric Acid in the Presence of High Amounts of Ascorbic Acid

A promising electrochemical biosensor was fabricated by electrochemical grafting of ribonucleic acid (RNA) at 1.8 V (vs. SCE) on glassy carbon electrode (GCE) (denoted as RNA/GCE), for simultaneous detection of dopamine (DA) and uric acid (UA) with coexistence of excess amount of ascorbic acid (AA). The electrode was characterized by X‐ray photoelectron spectroscopy (XPS), cyclic voltammetry (CV) and differential pulse voltammetry (DPV) techniques. The RNA modified layer on GCE exhibited superior catalytic ability and anionic exclusive ability in comparison with the DNA modified electrode. Three separated anodic DPV peaks were obtained at 0.312, 0.168 and ?0.016 V for UA, DA and AA, respectively, at the RNA/GCE in pH 7.0 PBS. In the presence of 2.0 mM AA, a linear range of 0.37 to 36 μM with a detection limit of 0.2 μM for DA, and in the range of 0.74 to 73 μM with a detection limit of 0.36 μM for UA were obtained. The co‐existence of 5000 fold AA did not interfere with the detection of DA or UA. The modified electrode shows excellent selectivity, good sensitivity and good stability.     

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.     

Fabrication of Co3O4 nanoparticles-decorated graphene composite for determination of L-tryptophan

A novel Co(3)O(4) nanoparticles-decorated graphene (GR) composite was synthesized by electro-deposition and characterized by scanning electron micrographs, energy dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy and transmission electron microscopy. Then, amperometric biosensors based on a Co(3)O(4) nanoparticles-decorated GR composite modified glassy carbon electrode (GCE) were developed for the sensitive determination of L-tryptophan (Trp). The direct electrooxidation behaviors of Trp on the Co(3)O(4)/GR/Nafion/GCE were carefully investigated by cyclic voltammetry and square wave voltammetry. The results indicated that Trp showed an increase of the oxidation peak current with a negative shift of the oxidation peak potential compared with that on the bare GCE. Under optimum conditions, the proposed biosensor can be applied to the quantification analysis of Trp with a wide linear range covering 0.05-10 μM (R = 0.996) and a low detection limit of 0.01 μM. The experimental results also showed that the sensor exhibited good reproducibility, long-term stability as well as high selectivity. Moreover, the novel biosensor for the detection of Trp in a real amino acid sample with satisfactory results has been proved.     

Amperometric Ethanol Biosensor Based on Integration of Alcohol Dehydrogenase with Meldola's Blue/Ordered Mesoporous Carbon Electrode

An amperometric ethanol biosensor was fabricated by integration of alcohol dehydrogenase (ADH) with meldola's blue (MB)/ordered mesoporous carbon (OMC) composite modified glassy carbon electrode (MB/OMC/GCE). The MB/OMC/GCE was highly sensitive for nicotinamide adenine dinucleotide (NADH) measurement (9.1±0.25 μA/mM) and gave a low detection limit of 0.21±0.02 μM. The ethanol biosensor exhibited a wide linear range up to 6 mM with a lower detection limit of 19.1±0.58 μM as well as a high sensitivity of 34.58±2.43 nA/mM without suffering any interference from some common electroactive compounds.     

脉冲恒电位一步法制备聚3,4-乙烯二氧噻吩石墨烯复合材料构建无酶葡萄糖传感器

本研究利用石墨烯(rGO)与3,4-乙烯二氧噻吩(EDOT)单体芳香环之间的π-π*相互作用和氢键作用,采用脉冲恒电位一步法制备了聚3,4-乙烯二氧噻吩石墨烯(PEDOT-rGO)复合膜,将纳米镍(NiNPs)电沉积在此复合膜(PEDOT-rGO)表面,制备了NiNPs/PEDOT-rGO修饰玻碳电极(NiNPs/PEDOT-rGO/GCE),研究了此修饰电极对葡萄糖的电催化氧化性能.实验结果表明,此NiNPs/PEDOT-rGO/GCE可以作为无酶传感器实现对葡萄糖的检测.本方法稳定性高,选择性好,线性范围宽(2μmol/L~58 mmol/L),检出限低至0.7μmol/L,可以用于对葡萄糖的快速、灵敏检测.     

Three-dimensional network polyamidoamine dendrimer-Au nanocomposite for the construction of a mediator-free horseradish peroxidase biosensor

A three-dimensional network PAMAM-Au nanocomposite (3D-PAMAM-Au NC) was prepared by using the first generation polyamidoamine dendrimer (G1 PAMAM) as the dispersant agent. The resultant 3D-PAMAM-Au NC was successfully used as an immobilization matrix for the construction of a reagentless mediator-free horseradish peroxidase (HRP)-based H(2)O(2) biosensor on a multi-walled carbon nanotubes (MWCNTs) modified glassy carbon electrode. With the advantages of the three-dimensional network, the organic-inorganic hybrid materials dramatically facilitate the direct electron transfer of HRP, and good bioelectrocatalytic activity towards H(2)O(2) was demonstrated. Under optimum conditions, the current response of the enzyme modified electrode at -0.30 V was detected. The current response is linearly correlated to H(2)O(2) concentration within the range of 18.00 μM to 20.80 mM with a correlation coefficient of 0.9992 and a sensitivity of 377.78 μA mM(-1) cm(-2). The detection limit was down to 6.72 μM (S/N = 3). Furthermore, the biosensor exhibits some other excellent characteristics, such as high selectivity, short response time, and long-term stability. The 3D-PAMAM-Au NC has proved to be a promising biosensing platform for the construction of mediator-free biosensors, and may find wide potential applications in biosensors, biocatalysis, bioelectronics and biofuel cells.     

A Nitrite Biosensor Based on Coimmobilization of Nitrite Reductase and Viologen‐Modified Polysiloxane on Glassy Carbon Electrode

Copper containing nitrite reductase (Cu‐NiR) and viologen‐modified sulfonated polyaminopropylsiloxane (PAPS‐SO₃H‐V) were co‐immobilized on glassy carbon electrode (GCE) by hydrophilic polyurethane (HPU) drop‐coating, and the electrode was tested as a reagentless electrochemical biosensor for nitrite detection. The newly synthesized PAPS‐SO₃H‐V as an electron transfer (ET) mediator between electrode and NiR was effective, and could be effectively immobilized in HPU membrane. The NiR and PAPS‐SO₃H‐V co‐immobilized GCE used as a nitrite biosensor showed the following performance factors: sensitivity=12.0 nA μM^?1, limit of detection (LOD)=60 nM (S/N=3), linear response range=0–18 μM (r²=0.996) and response time (t_90%)=60 s, respectively. Lineweaver–Burk plot shows that apparent Michaelis–Menten constant (K is 101 μM. Storage stability of the sensor is 51 days (80% of initial activity) in condition of storing in ambient air at room temperature. The sensor showed a relative standard deviation (RSD) of 3.2% (n=5) even in condition of injection of 1 μM nitrite. Interference study showed that common anions in water sample such as chlorate, chloride, sulfate and sulfite do not interfere with the nitrite detection. However, nitrate interfered with a relative sensitivity of 80% due to inherent character of the enzyme used.     

A novel H2O2 sensor based on the enzymatically induced deposition of polyaniline at a horseradish peroxide/aligned single-wall carbon nanotubes modified Au electrode

A novel H(2)O(2) sensor based on enzymatically induced deposition of electroactive polyaniline (PANI) at a horseradish peroxide (HRP)/aligned single-wall carbon nanotubes (SWCNTs) modified Au electrode is fabricated, and its electrochemical behaviors are investigated. Electrochemical impedance spectroscopy of the sensor confirmed the formation of PANI on SWCNTs through the HRP catalytic reaction. Cyclic voltammograms of PANI/HRP/SWCNTs modified Au electrodes showed a pair of well-defined redox peaks of PANI with reduction peak potentials of 0.211 and oxidation peak potentials of 0.293 V in 0.1 M HOAc-NaOAc (pH 4.3) solution. The oxidation peak current response of PANI is linearly related to H(2)O(2) concentration from 2.5 μM to 50.0 μM with a correlation coefficient of 0.9923 and a sensitivity of 200 μA mM(-1). The detection limit is determined to be 0.9 μM with a signal-to-noise ratio of 3. Thus, the synergistic performance of the enzyme, the highly efficient polymerization of PANI, and the templated deposition of SWCNTs provided an extensive platform for the design of novel electrochemical biosensors.     

A Simple and Renewable Nanoporous Gold‐based Electrochemical Sensor for Bisphenol A Detection

A sensitive and simple electrochemical sensor based on nanoporous gold (NPG) was developed for the detection of bisphenol A (BPA). NPG was prepared by the dealloying method. The NPG modified glassy carbon electrode (GCE) displayed excellent catalytic activity towards the electrooxidation of BPA. The mechanism of the electrooxidation of BPA on NPG/GCE sensor was inferred. The sensor showed a linear range from 0.1 μM to 50 μM with a detection limit of 12.1 nM BPA. Specially, a simple but effective approach was attempted to renew the used sensor. The application of the sensor for real sample analysis was demonstrated.     

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.     

基于Hemin/多壁碳纳米管纳米复合物构建的过氧化氢生物传感器的研究

利用卟啉(Hemin)具有模拟酶的功能,与多壁碳纳米管(MWCNTs)构建了一种新型的过氧化氢(H2O2)生物传感器。首先,利用Hemin与MWCNTs之间的π-π键作用,在超声分散下制备Hemin/MWCNTs纳米复合物;采用滴涂技术并在nafion的作用下将其固载在电极表面,制得该H2O2生物传感器(nafion/Hemin/MWCNTs/GCE)。采用紫外-可见分光光度法(UV-Vis)对合成的纳米复合物进行了分析;采用扫描电镜(SEM)对电极的表面形貌进行了表征;采用循环伏安法和计时电流法考察了该修饰电极的电化学行为;并对传感器的行为进行了详细的研究。在最优条件下,此修饰电极对H2O2具有明显的催化作用,电流与H2O2的浓度在6.0×10-7~1.8×10-3 mol/L范围内呈现良好的线性关系,检出限达2.0×10-7 mol/L。此传感器制作简单,具有较高的灵敏度和良好的稳定性及重现性。     

基于纳米金自组装膜固定辣根过氧化物酶的生物传感研究

将辣根过氧化物酶(HRP)通过纳米技术和自组装技术固定于电极表面,制得了酶修饰电极.纳米金与HRP形成了静电复合物并高效地保持了HRP的生物活性,以对苯二酚作为电子媒介体,差示脉冲伏安法(DPV)研究生物酶电极测定H2O2的线性范围为5.0×10-6～1.0×10-3 mol/L,检测限为2.5×10-6 mol/L,线性方程为△I=0.34765+4.05553CH2O2(mM).酶电极的表观米氏常数(K(app))为0.0675 mmol/L.实验同时证明该生物酶电极具有良好的稳定性和使用寿命.     

基于石墨烯-壳聚糖-辣根过氧化物酶的H2O2生物传感器的研制

制备了石墨烯-壳聚糖(GR-CS)纳米复合材料,并将之与辣根过氧化物酶(HRP)混合,构建了基于石墨烯-壳聚糖-辣根过氧化物酶的生物传感器(GR-CS-HRP/GC)。探针及循环伏安研究表明,该界面具有优异的电子传导能力、较大的比表面积和良好的生物相容性,对H2O2的还原显示出较好的电催化活性,在工作电位为-0.2 V,0.05 mol/L的磷酸盐缓冲盐溶液(PBS,pH 6.8)中,该酶传感器对过氧化氢响应灵敏度高,检测范围宽,测定H2O2的线性范围为5.0×10-7～2×10-3mol/L(相关系数为0.998)。检出限为2.0×10-7mol/L(S/N=3)。并且表现出良好的稳定性和高选择性。该电极用于实际样品中H2O2的测定,结果令人满意。