One-step synthesis of poly(thionine)-Au nano-network and nanowires and its application for non-enzyme biosensing of hydrogen peroxide

We describe the preparation of novel poly(thionine)-Au materials, where the poly(thionine)-Au nano-network and nanowires have been synthesized in aqueous solution via the polymerization of thionine using HAuCl₄ as the oxidant in a single reaction setup. The synthesis process does not require templates, nor does it require large amounts of organic solvents or electrochemical methods. The morphology of the nanocomposites can be controlled by varying the thionine/HAuCl₄ ratio. The resulting poly(thionine)-Au network was used to fabricate a novel non-enzyme hydrogen peroxide (H₂O₂) biosensor. In pH 7.0 phosphate buffer, almost interference-free determination of H₂O₂ was realized at − 0.1 V versus Ag/AgCl with a linear of 1 × 10^− 4 to 5 × 10^− 2 M, a correlation coefficient of 0.998 and a response time of < 2 s. The developed biosensor showed a detection limit of 0.2 μM (S/N = 3) with very good stability, reproducibility and high selectivity.     

Electrocatalytic reaction of hydrogen peroxide and NADH based on poly(neutral red) and FAD hybrid film

A simple method to immobilize poly(neutral red) (PNR) and flavin adenine dinucleotide (FAD) hybrid film (PNR/FAD) by cyclic voltammetry is proposed. The PNR/FAD hybrid film can be easily prepared on an electrode surface involving electropolymerization of neutral red (NR) monomers and the electrostatic interaction between the positively charged PNR and the negatively charged FAD. It exhibits electroactive, stable, surface-confined, pH-dependent, nano-sized, and compatible properties. It provides good electrocatalytic properties to various species. It shows a sensitivity of 5.4 μA mM(-1) cm(-2) and 21.5 μA mM(-1) cm(-2) for hydrogen peroxide (H(2)O(2)) and nicotinamide adenine dinucleotide (NADH) with the linear range of 0.1 μM-39 mM and 5 × 10(-5) to 2.5 × 10(-4) M, respectively. It shows another linear range of 48.8-355.5 mM with the sensitivity of 12.3 μA mM(-1) cm(-2) for H(2)O(2). In particular, the PNR/FAD hybrid film has potential to replace some hemoproteins to be a cathode of biofuel cells and provide the biosensing system for glucose and ethanol.     

Platinum nanoparticles functionalized nitrogen doped graphene platform for sensitive electrochemical glucose biosensing

In this work, we reported an efficient platinum nanoparticles functionalized nitrogen doped graphene (PtNPs@NG) nanocomposite for devising novel electrochemical glucose biosensor for the first time. The fabricated PtNPs@NG and biosensor were characterized using transmission electron microscopy, high-resolution transmission electron microscopy, X-ray photoelectron spectroscopy, static water contact angle, UV–vis spectroscopy, electrochemical impedance spectra and cyclic voltammetry, respectively. PtNPs@NG showed large surface area and excellent biocompatibility, and enhanced the direct electron transfer between enzyme molecules and electrode surface. The glucose oxidase (GOx) immobilized on PtNPs@NG nanocomposite retained its bioactivity, and exhibited a surface controlled, quasi-reversible and fast electron transfer process. The constructed glucose biosensor showed wide linear range from 0.005 to 1.1 mM with high sensitivity of 20.31 mA M⁻¹ cm⁻². The detection limit was calculated to be 0.002 mM at signal-to-noise of 3, which showed 20-fold decrease in comparison with single NG-based electrochemical biosensor for glucose. The proposed glucose biosensor also demonstrated excellent selectivity, good reproducibility, acceptable stability, and could be successfully applied in the detection of glucose in serum samples at the applied potential of −0.33 V. This research provided a promising biosensing platform for the development of excellent electrochemical biosensors.     

聚中性红修饰电极测定卡马西平

研究了聚中性红薄膜修饰电极对卡马西平的电催化作用,建立一种定量检测卡马西平的电化学分析方法。探讨了修饰电极性能对卡马西平的最佳响应条件,并初步推断了反应机理。在p H=5.03的PBS缓冲底液中,线性范围2.2×10-6mol/L~5.0×10-3mol/L(r=0.9986),检出限为5×10-7mol/L。该方法操作简单、灵敏,可用于实际药品测定。     

A microfluidic electrochemical device for high sensitivity biosensing: Detection of nanomolar hydrogen peroxide

We report herein a simple device for rapid biosensing consisting of a single microfluidic channel made from poly(dimethylsiloxane) (PDMS) coupled to an injector, and incorporating a biocatalytic sensing electrode, reference and counter electrodes. The sensing electrode was a gold wire coated with 5 nm glutathione-decorated gold nanoparticles (AuNPs). Sensitive detection of H₂O₂ based on direct bioelectrocatalysis by horseradish peroxidase (HRP) was used for evaluation. HRP was covalently linked the glutathione–AuNPs. This electrode presented quasi-reversible cyclic voltammetry peaks at ?0.01 V vs. Ag/AgCl at pH 6.5 for the HRP heme Fe^III/Fe^II couple. Direct electrochemical activity of HRP was used to detect H₂O₂ at high sensitivity with a detection limit of 5 nM in an unmediated system.     

A novel biosensing mechanism based on a poly(N-butyl benzimidazole)-modified gold electrode for the detection of hydrogen peroxide

In pH 1.7-3.5 acid medium, palladium chloride could react with adenine (A) to form a ternary complex of [PdCl(2)·A], which would self-aggregate to form uniformly dispersed nanoparticles-[PdCl(2)·A](n) with an average size of 42 nm through the squeezing effect of aqueous phase and van der Waals force. This resulted in an enhancement of resonance Rayleigh scattering (RRS), second-order scattering (SOS) and frequency doubling scattering (FDS). The maximum wavelengths were located at 311 nm, 611 nm and 395 nm, respectively. The scattering intensities of the three methods were proportional to the concentration of adenine in certain ranges, and the detection limit of the most sensitive RRS method was 5.4×10(-9) mol L(-1) (0.73 ng mL(-1)). The experimental conditions were optimized and effects of coexisting substances were evaluated. The method showed excellent selectivity because a certain amount of other nucleobase, nucleoside or nucleotide would not influence the measurement. Accordingly, a novel rapid, convenient, sensitive and selective RRS method for determination of adenine was proposed and applied to detect adenine in tablet and hydrolyzates of ctDNA samples with satisfactory results. The shape of nanoparticles was characterized by atomic force microscopy. The reaction mechanism and the reasons for enhancement of scattering were discussed by infrared spectra, quantum chemical calculations and absorption spectroscopy.     

A glassy carbon electrode modified with poly(anthranilic acid), poly(diphenylamine sulfonate) and CuO nano-particles for the sensitive determination of hydrogen peroxide

We report on a modified glassy carbon electrode (GCE) for sensing hydrogen peroxide (H₂O₂). It was constructed by consecutive electrochemical deposition of poly(anthranilic acid) and poly(diphenylamine sulfonate) on the GCE, followed by the deposition of copper oxide (CuO). The morphology and electrochemistry of the modified electrode was characterized by atomic force microscopy, X-ray diffraction, cyclic voltammetry, and electrochemical impedance spectroscopy. The catalytic performance of the sensor was studied with the use of differential pulse voltammetry under optimized conditions. This sensor displayed significantly better electrocatalytic activity for the reduction of H₂O₂ in comparison to a GCE without or with modification with CuO or polymer films alone. The response to H₂O₂ is linear in the range between 0.005 to ~11 mM, and the detection limit is 0.18 μM (at an S/N of 3).

Grape tissue-based electrochemical sensor for the determination of hydrogen peroxide

The use of grape tissue as a source of catalase for the determination of hydrogen peroxide is reported. A slice of grape tissue attached to the membrane of a Clark-type oxgen sensor was used to monitor the oxidation of hydrogen peroxide by catalase. At the steady state, the sensor responds linearly to hydrogen peroxide in the concentration range 1 × 10^?5–5 × 10^?4 M. The response time (T₉₀) was of the order of 1 min for this sensor. No interference was observed from ethanol, amino acids, glucose and lactic acid. The long-term stability of the grape tissue sensor was much better than previously reported immobilized enzyme and liver tissue-based hydrogen peroxide sensors.     

Glucose oxidase inhibition in poly(neutral red) mediated enzyme biosensors for heavy metal determination

A biosensor for the determination of heavy metal cations based on glucose oxidase enzymatic inhibition has been developed. The biosensor was assembled on carbon film electrode supports with glucose oxidase immobilised by cross-linking with glutaraldehyde on top of a film of poly(neutral red) as redox mediator, prepared by electropolymerisation. The biosensor was used to determine the metallic cations, cadmium, copper, lead and zinc in the presence of chosen amounts of glucose. The detection limits were found to be 1 μg L^?1 for cadmium, 6 μg L^?1 for copper, 3 μg L^?1 for lead and 9 μg L^?1 for zinc. Inhibition constants were determined by using the Dixon plot, and the type of inhibition induced by the metallic cations was evaluated from Cornish-Bowden plots plus Dixon plots, it being found that the inhibition is reversible and competitive for cadmium, mixed for copper and lead and uncompetitive for zinc. Copper-inhibited glucose oxidase to a greater extent followed by cadmium, lead and zinc. Regeneration of the glucose oxidase response was studied by using Ethylene diamine tetracetic acid metal-chelating agent and the nonionic surfactant Triton X-100. The suitability of the biosensor for determination in foodstuffs or beverages which contain trace concentrations of metals was investigated by performing recovery tests in commercial milk samples.     

Amperometric sensor for hydrogen peroxide based on poly(aniline-co-p-aminophenol)

It was found that the poly(aniline-co-p-aminophenol) film can effectively catalyze the oxidation of hydrogen peroxide in a sodium citrate buffer solution with pH 5.0. Here, we applied the copolymer to the construction of an efficient electrochemical sensor to determine the concentration of hydrogen peroxide. The sensor exhibited an excellent electrocatalytic activity toward the oxidation of H₂O₂, and the interferences of ascorbic acid and phenol were completely avoided. Unlike the inherent instability of enzyme, the poly(aniline-co-p-aminophenol) film-based sensor showed an outstanding stability.     

An improved biosensor for acetaldehyde determination using a bienzymatic strategy at poly(neutral red) modified carbon film electrodes

Improved biosensors for acetaldehyde determination have been developed using a bienzymatic strategy, based on a mediator-modified carbon film electrode and co-immobilisation of NADH oxidase and aldehyde dehydrogenase. Modification of the carbon film electrode with poly(neutral red) mediator resulted in a sensitive, low-cost and reliable NADH detector. Immobilisation of the enzymes was performed using encapsulation in a sol-gel matrix or cross-linking with glutaraldehyde. The bienzymatic biosensors were characterized by studying the influence of pH, applied potential and co-factors. The sol-gel and glutaraldehyde biosensors showed a linear response up to 60 μM and 100 μM, respectively, with detection limits of 2.6 μM and 3.3 μM and sensitivities were 1.7 μA mM⁻¹ and 5.6 μA mM⁻¹. The optimised biosensors showed good stability and good selectivity and have been tested for application for the determination of acetaldehyde in natural samples such as wine.     

Novel electrochemical platform based on copolymer poly(aniline-4-aminophenol) for application in immunosensor for thyroid hormones

Journal of Solid State Electrochemistry - This paper reports the development of a novel electrochemical platform based on graphite electrodes modified with copolymer poly(aniline-4-aminophenol) and...     

Citrate selectivity of poly(neutral red) electropolymerized films

The synthesis and the spectroscopic and potentiometric characterization of electropolymerized films obtained from neutral red (NR) on Pt surface are described. FT Raman and NMR spectroscopy were used for evaluation of the resulting poly(NR) layers. Then potentiometry was applied to study the characteristics of the complexation of carboxylates with the poly(NR) films. A potentiometric poly(NR) sensor showing high selectivity for citrate anion was employed for its determination in soft drinks.     

A direct electrochemical biosensing platform constructed by incorporating carbon nanotubes and gold nanoparticles onto redox poly(thionine) film.

A direct electrochemical biosensing platform has been fabricated by covalent incorporation of carbon nanotubes (CNT) and gold nanoparticles (GNP) onto the poly(thionine) (PTH) film deposited by electropolymerization. With the synergic effects of the composite nanomaterials together with the excellent mediating redox polymer, the proposed platform could allow for faster electron transfer and higher enzyme immobilization efficiency than the platforms designed by using CNT or GNP alone. Comparison studies indicated that the as-developed H(2)O(2) sensor could show greatly improved performances of amperometric responses.     

Enhanced stability of a Prussian blue/sol-gel composite for electrochemical determination of hydrogen peroxide

We have prepared a sol–gel that incorporates Prussian Blue (PB) as a redox mediator. It is shown that the PB in the pores of the sol–gel retains its electrochemical activity and is protected from degradation at acidic and neutral pH values. TEM and EDX studies revealed the PB nanoparticles to possess a cubic crystal structure and to be well entrapped and uniformly dispersed in the pores of the matrix. The electrocatalytic activity of the materials toward hydrogen peroxide (H₂O₂) was studied by cyclic voltammetry and amperometry. The modified electrode displays good sensitivity for the electrocatalytic reduction of H₂O₂ both in acidic (pH 1.4) and neutral media. The sensor has a dynamic range from 3 to 210 μM of H₂O₂, and the detection limit is 0.6 μM (at an SNR of 3).

Characterisation of poly(neutral red) modified carbon film electrodes; application as a redox mediator for biosensors

The polymer redox mediator, poly(neutral red) (PNR), has been synthesised and characterised electrochemically to investigate the best electropolymerisation and mediation conditions for application in enzyme biosensors and to clarify the mechanism of action. Neutral red was electropolymerised by potential cycling on carbon film electrode substrates by allowing the monomer to be oxidised during the full 20 cycles of polymerisation or reducing the positive limit of the potential window after the first 2 cycles to impede monomer oxidation with a view to obtaining longer polymer chains and a lesser degree of branching. Comparison was made with glassy carbon substrates. The PNR films on carbon film electrodes were characterised using cyclic voltammetry and electrochemical impedance spectroscopy, as well as in glucose biosensors prepared with PNR. Glucose oxidase enzyme was immobilised by encapsulation in silica sol-gel and compared with that obtained by cross-linking with glutaraldehyde. The biosensors were evaluated by chronoamperometry in 0.1 M phosphate buffer saline solution, pH 7.0, and showed evidence of electron transfer between the enzyme cofactor flavin adenine dinucleotide and PNR dissolved in the enzyme layer competing with PNR-mediated electrochemical degradation of H₂O₂ formed during the enzymatic process. This paper is dedicated to Professor Dr. Algirdas Vaskelis on the occasion of his 70th birthday.     

Nickel-Zeolite modified carbon paste electrode as electrochemical sensor for hydrogen peroxide

In the present work, nickel-zeolite modified carbon paste electrode (Ni-ZMCPE) was prepared. The electrochemical behaviour of hydrogen peroxide at the surface of modified electrode was investigated by cyclic voltammetry and chronoamperometry in 0.1 M NaOH supporting electrolyte. The electrochemical characterization of Ni-ZMCPE exhibits redox behavior of Ni(III)/Ni(II) couple in alkaline medium. It has been shown that Ni-ZMCPE improves efficiency of the modified electrode toward hydrogen peroxide electrooxidation (It wasn’t remarkable different on ZMCPE and CPE in the presence and absence of hydrogen peroxide). Moreover, the effects of various parameters such as effect of different percents of Ni-Z to graphite, effect of pH and hydrogen peroxide concentration on the electrooxidation of hydrogen peroxide as well as stability of the Ni-ZMCPE have also been investigated. Under the selected conditions, the anodic peak current was linearly dependent on the concentration of hydrogen peroxide in the range 0.03–0.1 and 0.3–6 mM with amperometric method. The detection limit (S/N = 3) was also estimated to be 1 μM.     

Graphene prepared by one-pot solvent exfoliation as a highly sensitive platform for electrochemical sensing

Graphene was easily obtained via one-step ultrasonic exfoliation of graphite powder in N-methyl-2-pyrrolidone. Scanning electron microscopy, transmission electron microscopy, Raman and particle size measurements indicated that the exfoliation efficiency and the amount of produced graphene increased with ultrasonic time. The electrochemical properties and analytical applications of the resulting graphene were systematically studied. Compared with the predominantly-used reduced graphene oxides, the obtained graphene by one-step solvent exfoliation greatly enhanced the oxidation signals of various analytes, such as ascorbic acid (AA), dopamine (DA), uric acid (UA), xanthine (XA), hypoxanthine (HXA), bisphenol A (BPA), ponceau 4R, and sunset yellow. The detection limits of AA, DA, UA, XA, HXA, BPA, ponceau 4R, and sunset yellow were evaluated to be 0.8 μM, 7.5 nM, 2.5 nM, 4 nM, 10 nM, 20 nM, 2 nM, and 1 nM, which are much lower than the reported values. Thus, the prepared graphene via solvent exfoliation strategy displays strong signal amplification ability and holds great promise in constructing a universal and sensitive electrochemical sensing platform.