Direct electrochemistry and electrocatalysis based on film of horseradish peroxidase intercalated into layered titanate nano-sheets

Intercalation of horseradish peroxidase (HRP) into layered titanate by assembling it with titanate nano-sheets (TNS) was firstly used for fabrication of enzyme electrode (HRP-TNS electrode). XRD result revealed that HRP-TNS film featured layered structure with HRP monolayer intercalated between the titanate layers. UV-vis spectra result indicated the intercalated HRP in TNS film well retained its native structure. The HRP-TNS film was uniform with porous structures which were confirmed by SEM. The immobilized HRP in the TNS film exhibited fast direct electron transfer and showed a good electrocatalytic performance to H2O2 with high sensitivity, wide linear range and low detection. The excellent electrochemical performance of the HRP-TNS electrode was attributed to biocompatibility of the titanate sheets, porous architectures of the HRP-TNS film which retained activity of HRP to large extent, avoided aggregation of HRP, provided better mass transport and allowed more HRP loading per unit area. Thus, the simple method described here provides a novel and effective platform for immobilization of enzyme in realizing direct electrochemistry and has a promising application in fabrication of the third-generation electrochemical biosensors.     

Direct electrochemistry of horseradish peroxidase based on biocompatible carboxymethyl chitosan-gold nanoparticle nanocomposite

The nanocomposite composed of carboxymethyl chitosan (CMCS) and gold nanoparticles was successfully prepared by a novel and in situ process. It was characterized by transmission electron microscopy (TEM) and Fourier transform infrared spectrophotometer (FTIR). The nanocomposite was hydrophilic even in neutral solutions, stable and inherited the properties of the AuNPs and CMCS, which make it biocompatible for enzymes immobilization. HRP, as a model enzyme, was immobilized on the silica sol-gel matrix containing the nanocomposite to construct a novel H(2)O(2) biosensor. The direct electron transfer of HRP was achieved and investigated. The biosensor exhibited a fast amperometric response (5s), a good linear response over a wide range of concentrations from 5.0 x 10(-6) to 1.4 x 10(-3)M, and a low detection limit of 4.01 x 10(-7)M. The apparent Michaelis-Menten constant (K(M)(app)) for the biosensor was 5.7 x 10(-4)M. Good stability and sensitivity were assessed for the biosensor.     

Mediatorless biosensor for H(2)O(2) based on recombinant forms of horseradish peroxidase directly adsorbed on polycrystalline gold

Four forms of horseradish peroxidase (HRP) have been used to prepare peroxidase-modified gold electrodes for mediatorless detection of peroxide: native HRP, wild type recombinant HRP, and two recombinant forms containing six-His tag at the C-terminus and at the N-terminus, respectively. The adsorption of the enzyme molecules on gold was studied by direct mass measurements with electrochemical quartz crystal microbalance. All the forms of HRP formed a monolayer coverage of the enzyme on the gold surface. However, only gold electrodes with adsorbed recombinant HRP forms exhibited high and stable current response to H(2)O(2) due to its bioelectrocatalytic reduction based on direct electron transfer between gold and HRP. The sensitivity of the gold electrodes modified with recombinant HRPs was in the range of 1.4-1.5 A M(-1) cm(-2) at -50 mV versus Agmid R:AgCl. The response to H(2)O(2) in the concentration range 0.1-40 microM was not dependent on the presence of a mediator (i.e. catechol) giving strong evidence that the electrode currents are diffusion limited. Lower detection limit for H(2)O(2) detection was 10 nM at the electrodes modified with recombinant HRPs.     

A novel hydrogen peroxide biosensor based on the immobilization of horseradish peroxidase onto Au-modified titanium dioxide nanotube arrays

In this study, we report on a promising H(2)O(2) biosensor based on the co-immobilization of horseradish peroxidase (HRP) and chitosan onto Au-modified TiO(2) nanotube arrays. The titania nanotube arrays were directly grown on a Ti substrate using anodic oxidation first; a gold thin film was then uniformly coated onto the TiO(2) nanotube arrays by an argon plasma technique. The morphology and composition of the fabricated Au-modified TiO(2) nanotube arrays were characterized by scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS). Cyclic voltammetry and chronoamperometry were used to study and to optimize the performance of the resulting electrochemical biosensor. The effect of pH, applied electrode potential, the presence of the electron-mediator methylene blue, and the anodic oxidation time of the Ti substrate on the electrochemical biosensor has been systemically studied. Our electrochemical measurements show that the Au-modified TiO(2) nanotube arrays provide excellent matrices for the immobilization of HRP and that the optimized electrochemical biosensor exhibits long linearity, a low detection limit, high stability and very good reproducibility for the detection of H(2)O(2). Under the optimized conditions the linearity of the developed biosensor for the detection of H(2)O(2) is observed from 5 x 10(-6) to 4 x 10(-4) moll(-1) with a detection limit of 2 x 10(-6) moll(-1) (based on the S/N=3).     

HRP/[Zn-Cr-ABTS] redox clay-based biosensor: design and optimization for cyanide detection

A novel inexpensive and simple amperometric biosensor, based on the immobilization of HRP into redox active [Zn-Cr-ABTS] layered double hydroxide, is applied to the determination of cyanide. The electrochemical transduction step corresponds to the reduction at 0.0 V of ABTS+* enzymatically formed in the presence of H2O2. The biosensor has a fast response to H2O2 (8s) with a linear range of 1.7 x 10(-9) to 2.1 x 10(-6) M and a sensitivity of 875 mA M(-1) cm(-2). The apparent Michaelis-Menten constant (KMapp) is 12 microM. The detection of cyanide is performed via its non competitive inhibiting action on the HRP/[Zn-Cr-ABTS] electrode. The concentration range of the linear response and the apparent inhibition constant (ki) are 5 x 10(-9) to 4 x 10(-8) and 1.4 x 10 (-7) M, respectively.     

Nano-composition of riboflavin-nafion functional film and its application in biosensing

A novel nafion-riboflavin membrane was constructed and characterized by the scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV-visible spectroscopy and cyclic voltammetric techniques. The estimated average diameter of the designed nanoparticles was about 60 nm. The functional membrane showed a quasi-reversible electrochemical behaviour with a formal potential of -562 +/- 5 mV (vs Ag/AgCl) on the gold electrode. Some electrochemical parameters were estimated, indicating that the system has good and stable electron transfer properties. Moreover, horseradish peroxidase (HRP) was immobilized on the riboflavin-nafion functional membrane. The electrochemical behaviour of HRP was quasi-reversible with a formal potential of 80 +/- 5 mV (vs Ag/AgCl). The HRP in the film exhibited good catalytic activity towards the reduction of H2O2. It shows a linear dependence of its cathodic peak current on the concentration of H2O2, ranging from 10 to 300 (micro)M.     

Direct electrochemistry of horseradish peroxidase bonded on a conducting polymer modified glassy carbon electrode

Direct electron transfer process of immobilized horseradish peroxidase (HRP) on a conducting polymer film, and its application as a biosensor for H2O2, were investigated by using electrochemical methods. The HRP was immobilized by covalent bonding between amino group of the HRP and carboxylic acid group of 5,2':5',2"-terthiophene-3'-carboxylic acid polymer (TCAP) which is present on a glassy carbon (GC). A pair of redox peaks attributed to the direct redox process of HRP immobilized on the biosensor electrode were observed at the HRPmid R:TCAPmid R:GC electrode in a 10 mM phosphate buffer solution (pH 7.4). The surface coverage of the HRP immobilized on TCAPmid R:GC was about 1.2 x 10(-12) mol cm(-2) and the electron transfer rate (ks) was determined to be 1.03 s(-1). The HRPmid R:TCAPmid R:GC electrode acted as a sensor and displayed an excellent specific electrocatalytic response to the reduction of H2O2 without the aid of an electron transfer mediator. The calibration range of H2O2 was determined from 0.3-1.5 mM with a good linear relation.     

Direct electrochemistry of horseradish peroxidase on TiO(2) nanotube arrays via seeded-growth synthesis

Horseradish peroxidase (HRP) was successfully immobilized on vertically oriented TiO(2) nanotube arrays (NTAs), which was prepared by a seeded-growth mechanism. The nanotubular structure of TiO(2) was characterized by scanning electron microscope (SEM). After encapsulated HRP on TiO(2) nanotube arrays, the direct electron transfer of HRP was observed. Owing to the redox reaction of electroactive center of HRP, the HRP/TiO(2) NTAs modified electrode exhibited a pair of quasi-reversible peaks with the peak-to-peak separation of 70mV and the formal potential of -0.122V (vs. SCE) in 0.2molL(-1) phosphate buffer solution (PBS, pH 7.0). The number of transference electron was 0.84 and the direct electron transfer (ET) constant (k(s)) was 3.82s(-1). The HRP/TiO(2) NTAs modified electrode displayed an excellent electrocatalytic performance for H(2)O(2) and the formal Michaelis-Menten constant (K(m)(app)) was 1.9mmolL(-1). The response currents had a good linear relation with the concentration of H(2)O(2) from 5.0x10(-7)molL(-1) to 1.0x10(-5)molL(-1) and 5.0x10(-5)molL(-1) to 1.0x10(-3)molL(-1), respectively.     

Amperometric third-generation hydrogen peroxide biosensor based on the immobilization of hemoglobin on multiwall carbon nanotubes and gold colloidal nanoparticles

A convenient and effective strategy for preparation nanohybrid film of multi-wall carbon nanotubes (MWNT) and gold colloidal nanoparticles (GNPs) by using proteins as linker is proposed. In such a strategy, hemoglobin (Hb) was selected as model protein to fabricate third-generation H2O2 biosensor based on MWNT and GNPs. Acid-pretreated, negatively charged MWNT was first modified on the surface of glassy carbon (GC) electrode, then, positively charged Hb was adsorbed onto MWNT films by electrostatic interaction. The {Hb/GNPs}n multilayer films were finally assembled onto Hb/MWNT film through layer-by-layer assembly technique. The assembly of Hb and GNPs was characterized with cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and transmission electron microscopy (TEM). The direct electron transfer of Hb is observed on Hb/GNPs/Hb/MWNT/GC electrode, which exhibits excellent electrocatalytic activity for the reduction of H2O2 to construct a third-generation mediator-free H2O2 biosensor. As compared to those H2O2 biosensors only based on carbon nanotubes, the proposed biosensor modified with MWNT and GNPs displays a broader linear range and a lower detection limit for H2O2 determination. The linear range is from 2.1x10(-7) to 3.0x10(-3) M with a detection limit of 8.0x10(-8) M at 3sigma. The Michaelies-Menten constant KMapp value is estimated to be 0.26 mM. Moreover, this biosensor displays rapid response to H2O2 and possesses good stability and reproducibility.     

Direct electron transfer and enzymatic activity of hemoglobin in a hexagonal mesoporous silica matrix

The direct electrochemistry of hemoglobin (Hb) immobilized on a hexagonal mesoporous silica (HMS)-modified glassy carbon electrode was described. The interaction between Hb and the HMS was investigated using UV-Vis spectroscopy, FT-IR, and electrochemical methods. The direct electron transfer of the immobilized Hb exhibited two couples of redox peaks with the formal potentials of -0.037 and -0.232 V in 0.1 M (pH 7.0) PBS, respectively, which corresponded to its two immobilized states. The electrode reactions showed a surface-controlled process with a single proton transfer at the scan rate range from 20 to 200 mV/s. The immobilized Hb retained its biological activity well and displayed an excellent response to the reduction of both hydrogen peroxide (H2O2) and nitrate (NO2-). Its apparent Michaelis-Menten constants for H2O2 and NO2- were 12.3 and 49.3 microM, respectively, showing a good affinity. Based on the immobilization of Hb on the HMS and its direct electrochemistry, two novel biosensors for H2O2 and NO2- were presented. Under optimal conditions, the sensors could be used for the determination of H2O2 ranging from 0.4 to 6.0 microM and NO2- ranging from 0.2 to 3.8 microM. The detection limits were 1.86 x 10(-9) M and 6.11 x 10(-7) M at 3sigma, respectively. HMS provided a good matrix for protein immobilization and biosensor preparation.     

A new film for the fabrication of an unmediated H2O2 biosensor

A novel and stable film made from polyethylene glycol (PEG) on pyrolytic graphite (PG) electrode was presented in this paper for incorporating horseradish peroxidase (HRP) to study the direct electrochemistry of the enzyme. In PEG film, HRP showed a thin-layer electrochemistry behavior. The apparent standard potential (E degrees ') was -0.379 V versus SCE at pH 7.2. Moreover, the PEG-HRP modified electrode exhibited excellent electrocatalytical response to the reduction of H2O2 with a calibration range between 2.0 x 10(-6) and 6.0 x 10(-4) M and a good linear relation from 2.0 x 10(-6) to 1.0 x 10(-4) M, on which an unmediated H2O2 biosensor was based. The detection limit of 6.7 x 10(-7) M was estimated when the signal-to-noise ratio was 3. The relative standard deviation (R.S.D.) was 4.7% for six successive determinations at a concentration of 4.0 x 10(-5) M. The apparent Michaelis-Menten constant (Km app) of the sensor was found to be 1.38 mM. Epinephrine, dopamine, and ascorbic acid did not interfere with the sensitive determination of H2O2.     

Effect of cysteine mutations on direct electron transfer of horseradish peroxidase on gold

Surface exposed cysteines were genetically engineered in the structure of recombinant horseradish peroxidase (rHRP). Recombinant forms of HRP with either a His-tag or a Strep-tag at the C-terminus were produced, which additionally had cysteines at positions 57, 189 or 309 (C-terminus) of the polypeptide chain. An E. coli expression system was exploited. The effect of these mutations on the direct electron transfer (ET) between Au and the enzyme was studied in the reaction of the bioelectrocatalytic reduction of H(2)O(2), at -50 mV versus Ag/AgCl, on rHRP-modified Au electrodes placed in a wall-jet flow-through electrochemical cell. Adsorptive immobilisation of rHRPs on pre-oxidised Au from the protein solution at pH 6.0 provided a high and stable current response to H(2)O(2) due to its bioelectrocatalytic reduction based on direct (mediatorless) ET between Au and the active site of the rHRPs. Comparative analysis of the direct ET rate constants, estimated from the amperometric data on direct and mediated ET in the presence of catechol at pH 7.4 and 6.0, gave evidence that the introduction of the His-tag or cysteine in the C-terminal area of the enzyme resulted in an increased efficiency of direct ET due to a favourable coupled electron and proton transfer pathway. Due to the high efficiency of direct ET, the sensitivity was independent on the addition of the mediator or change of pH indicating that the response to H(2)O(2) is determined solely by the mass transfer of the analyte to the active site of HRP. The sensitivities obtained for the Au electrodes modified with rHRPs (2.0+/-0.1 A M(-1) cm(-2)) and the low detection limit for H(2)O(2) (10 nM) paves the way to develop the P-chip (peroxidase chip)--a biosensors system of a microscopic size for a mediatorless detection of H(2)O(2) based on direct ET between Au and the recombinant forms of HRP.     

A third-generation hydrogen peroxide biosensor based on horseradish peroxidase immobilized in a tetrathiafulvalene-tetracyanoquinodimethane/multiwalled carbon nanotubes film

A new third-generation biosensor for H(2)O(2) assay was developed on the basis of the immobilization of horseradish peroxidase (HRP) in a nanocomposite film of tetrathiafulvalene-tetracyanoquinodimethane (TTF-TCNQ)/multiwalled carbon nanotubes (MWCNTs) modified gold electrode. The prepared HRP/TTF-TCNQ/MWCNTs/Au electrode was used for the bioelectrocatalytic reduction of H(2)O(2), with a linear range from 0.005 to 1.05mM and a detection limit of 0.5muM for amperometric sensing of H(2)O(2). In addition, a novel method on the basis of electrochemical quartz crystal microbalance (EQCM) measurements was proposed to determine the effective enzymatic specific activity (ESA) of the immobilized HRP for the first time, and the ESA was found to be greater at the TTF-TCNQ/MWCNTs/Au electrode than that at the MWCNTs/Au or TTF-TCNQ/Au electrode, indicating that the TTF-TCNQ/MWCNTs film is a good HRP-immobilization matrix to achieve the direct electron transfer between the enzyme and the electrode.     

A novel approach to construct a horseradish peroxidase|hydrophilic ionic liquids|Au nanoparticles dotted titanate nanotubes biosensor for amperometric sensing of hydrogen peroxide

The direct electrochemistry of horseradish peroxidase (HRP) on a novel sensing platform modified glassy carbon electrode (GCE) has been achieved. This sensing platform consists of Nafion, hydrophilic room-temperature ionic liquid (RTIL) and Au nanoparticles dotted titanate nanotubes (GNPs-TNTs). The composite of RTIL and GNPs-TNTs was immobilized on the electrode surface through the gelation of a small amount of HRP aqueous solution. The composite was characterized by transmission electron microscopy (TEM), powder X-ray diffraction (XRD) and infrared spectroscopy (IR). UV-Vis and IR spectroscopy demonstrated that HRP in the composite could retain its native secondary structure and biochemical activity. The HRP-immobilized electrode was investigated by cyclic voltammetry and chronoamperometry. The results from both techniques showed that the direct electron transfer between the nanocomposite modified electrodes and heme in HRP could be realized. The biosensor responded to H(2)O(2) in the linear range from 5×10(-6) to 1×10(-3) mol L(-1) with a detection limit of 2.1×10(-6) mol L(-1) (based on the S/N=3).     

Fabrication of hydrogen peroxide biosensor based on Ni doped SnO2 nanoparticles

Ni doped SnO(2) nanoparticles (0-5 wt%) have been prepared by a simple microwave irradiation (2.45 GHz) method. Powder X-ray diffraction (XRD) and transmission electron microscopy (TEM) studies confirmed the formation of rutile structure with space group (P(42)/mnm) and nanocrystalline nature of the products with spherical morphology. Direct electrochemistry of horseradish peroxidase (HRP)/nano-SnO(2) composite has been studied. The immobilized enzyme retained its bioactivity, exhibited a surface confined, reversible one-proton and one-electron transfer reaction, and had good stability, activity and a fast heterogeneous electron transfer rate. A significant enzyme loading (3.374×10(-10) mol cm(-2)) has been obtained on nano-Ni doped SnO(2) as compared to the bare glassy carbon (GC) and nano-SnO(2) modified surfaces. This HRP/nano-Ni-SnO(2) film has been used for sensitive detection of H(2)O(2) by differential pulse voltammetry (DPV), which exhibited a wider linearity range from 1.0×10(-7) to 3.0×10(-4)M (R=0.9897) with a detection limit of 43 nM. The apparent Michaelis-Menten constant (K(M)(app)) of HRP on the nano-Ni-SnO(2) was estimated as 0.221 mM. This excellent performance of the fabricated biosensor is attributed to large surface-to-volume ratio and Ni doping into SnO(2) which facilitate the direct electron transfer between the redox enzyme and the surface of electrode.     

Direct electrochemistry of myoglobin based on ionic liquid-clay composite films

The direct electron transfer of myoglobin (Mb) was realized by immobilizing Mb onto ionic liquid (1-butyl-3-methyl imidazolium tetrafluoraborate, [bmim][BF(4)])-clay composite film modified glassy carbon electrode. A pair of well-defined redox peaks of Mb with a formal potential (E(o)') of -0.297 V (vs. Ag/AgCl) was observed in 0.1M phosphate buffer solution (pH 6.0). The ionic liquid-clay composite film showed good biocompatibility and an obvious promotion capability for the direct electron transfer between Mb and electrode. The electron transfer rate constant (k(s)) of Mb was calculated to be (3.58+/-0.12)s(-1). UV-vis spectrum suggested that Mb retained its native conformation in the ionic liquid-clay system. Basal plane spacing of clay obtained by X-ray diffraction (XRD) indicated that there was an intercalation-exfoliation-restacking process, in ionic liquid and clay during the drying process of the modification, and the ionic liquid played the key role for promotion of the direct electron transfer between Mb and the ionic liquid-clay composite film modified electrode. The biocatalytic activity of Mb in the composite film was exemplified by the reduction of hydrogen peroxide. Under the optimal conditions, the reduction peak currents of Mb increased linearly with the concentration of H(2)O(2) in the range of 3.90 x 10(-6) to 2.59 x 10(-4)M, with a detection limit of 7.33 x 10(-7)M. The kinetic parameter I(max) and the apparent Michaelis constant (K(m)) for the electrocatalytic reactions were 3.87 x 10(-8)A and 17.6 microM, respectively. The proposed method would be valuable for the construction of a new third-generation H(2)O(2) sensor.     

Direct electrochemistry and electrocatalysis of hemoglobin immobilized on carbon paste electrode by silica sol-gel film

Direct electrochemical and electrocatalytic behaviors of hemoglobin (Hb) immobilized on carbon paste electrode (CPE) by a silica sol-gel film derived from tetraethylorthosilicate (TEOS) were investigated for the first time. Hb/sol-gel film modified electrodes showed a pair of well-defined and nearly reversible cyclic voltammetric peaks for Hb Fe(III)/Fe(II) redox couple at about -0.312 V (versus Ag/AgCl) in a pH 7.0 phosphate buffer. The formal potential of Hb heme Fe(III)/Fe(II) couple varied linearly with the increase of pH in the range of 5.0-10.0 with a slope of 49.44 mV pH(-1), which suggests that a proton transfer is accompanied with each electron transfer (ET) in the electrochemical reaction. The immobilized Hb displayed the features of peroxidase and gave excellent electrocatalytic performance to the reduction of O2, NO2(-) and H2O2. The calculated apparent Michaelis-Menten constant was 8.98 x 10(-4)M, which indicated that there was a large catalytic activity of Hb immobilized on CPE by sol-gel film toward H2O2. In comparison with other electrodes, the chemically modified electrodes, used in this direct electrochemical study of Hb, are easy to be fabricated and rather inexpensive. Consequently, the Hb/sol-gel film modified electrode provides a convenient approach to perform electrochemical research on this kind of proteins. It also has potential use in the fabrication of the third generation biosensors and bioreactors.     

Direct electrochemistry and electrocatalysis of myoglobin on redox-active self-assembling monolayers derived from nitroaniline modified electrode

The adsorption processes and electrochemical behavior of 4-nitroaniline (4-NA) and 2-nitroaniline (2-NA) adsorbed onto glassy carbon electrodes (GCE) have been investigated in aqueous 0.1M nitric acid (HNO(3)) electrolyte solutions using cyclic voltammetry (CV). Nitroaniline adsorbs onto GCE surfaces and upon potential cycling past -0.55 V is transformed into the arylhydroxylamine (ArHA), which exhibits a well-behaved pH dependent redox couple centered at 0.32 V (pH 1.5). This modified electrode can be readily used as an immobilization matrix to entrap proteins and enzymes. In our studies, myoglobin (Mb) was chosen as a model protein for investigation. A pair of well-defined reversible redox peaks for Mb(Fe(III)-Fe(II)) was obtained at the Mb/arylhydroxylamine modified glassy carbon electrode (Mb/HAGCE) by direct electron transfer between the protein and the GCE. The formal potential (E(0')), the surface coverage (Gamma) and the electron transfer rate constant (k(s)) were calculated as -0.317 V, 4.15+/-0.5 x 10(-11)mol/cm(2) and 51+/-5s(-1), respectively. Dramatically enhanced biocatalytic activity was exemplified at the Mb/HAGCE for the reduction of hydrogen peroxide (H(2)O(2)), trichloroacetic acid (TCA) and oxygen (O(2)). The Mb/ArHA film was also characterized by UV-vis spectra, scanning electron microscope (SEM) indicating excellent stability and good biocompatibility for protein in the film. The applicability of the method to the determination of H(2)O(2) ( approximately 3%) in a commercial antiseptic solution and soft-contact lenses cleaning solutions were demonstrated. This new Mb/HAGCE exhibited rapid electrochemical response (with in 2s) with good stability in physiological condition.     

One-step construction of biosensor based on chitosan-ionic liquid-horseradish peroxidase biocomposite formed by electrodeposition

A simple and controllable electrodeposition approach was established for one-step construction of hydrogen peroxide (H(2)O(2)) biosensors by in situ formation of chitosan-ionic liquid-horseradish peroxidase (CS-IL-HRP) biocomposite film on electrode surface. A highly porous surface with orderly three-dimensional network was revealed by scanning electron microscopy (SEM) investigation. The biocomposite provided improved conductivity and biocompatible microenvironment. The developed biosensor exhibited a fast amperometric response for the determination of H(2)O(2) and 95% of the steady-state current was obtained within 2s. The linear response of the developed biosensor for the determination of H(2)O(2) ranged from 6.0x10(-7) to 1.6x10(-4)M with a detection limit of 1.5x10(-7)M. Performance of the biosensor was evaluated with respect to possible interferences and a good selectivity was revealed. The fabricated biosensor exhibited high reproducibility and long-time storage stability. The ease of the one-step non-manual technique and the promising feature of biocomposite could serve as a versatile platform for the fabrication of electrochemical biosensors.     

Electrochemical study of a new methylene blue/silicon oxide nanocomposition mediator and its application for stable biosensor of hydrogen peroxide

A novel organic-inorganic nanocomposite of methylene blue (MB) and silicon oxide was synthesized and characterized by TEM, FTIR, and UV-vis. The as-prepared material was able to transfer the electron of the MB to electrode and was different from other SiO2 spheres structurally. It can be used as mediator to construct a biosensor with horseradish peroxidase (HRP) coimmobilized in the gelatine matrix and cross-linked with formaldehyde. The resulting biosensor exhibited fast amperometric response and good stability to hydrogen peroxide (H2O2). The linear range for H2O2 determination was from 1 x 10(-5) to 1.2 x 10(-3) M, with a detection limit of 4 x 10(-6) M based on S/N = 3. Moreover, the lifetime is more than 3 months under dry conditions at 4 degrees C.