Direct Electron Transfer Of Cytochrome Research Articles

Electrochemical biointerface based on electrodeposition AuNPs on 3D graphene aerogel: Direct electron transfer of Cytochrome c and hydrogen peroxide sensing

An electrochemical biointerface of 3D graphene aerogel (3DGA) decorated with Au nanoparticles (AuNPs) was fabricated to immobilize Cytochrome c (Cyt c) for H2O2 detection. Morphology and surface characterization of 3DGA-AuNPs reveal a successful formation of 3D-networked structure that can enhance conductivity and effectively immobilize enzyme. The immobilized Cyt c retained its bioactivity and realized the direct electron transfer on electrode owing to the biocompatibility of AuNPs and large surface area of 3DGA. The as-prepared 3DGA-AuNPs/Cyt c/GCE exhibited a pair of well-defined redox peaks of FeIII/II redox couple of Cyt c and revealed excellent catalytic activity toward H2O2 with high sensitivity of 351.57μA·mM−1·cm−2. This biosensor was further successfully used to real-time detection of trace amount of H2O2 released from living cells, indicating the promise for practical application.

Optically transparent carbon nanotube film electrode for thin layer spectroelectrochemistry.

Carbon nanotube (CNT) film was evaluated as an optically transparent electrode (OTE) for thin layer spectroelectrochemistry. Chemically inert CNT arrays were synthesized by chemical vapor deposition (CVD) using thin films of Fe and Co as catalysts. Vertically aligned CNT arrays were drawn onto a quartz slide to form CNT films that constituted the OTE. Adequate conductivity and transparency make this material a good OTE for spectroelectrochemistry. These properties could be varied by the number of layers of CNTs used to form the OTE. Detection in the UV/near UV region down to 200 nm can be achieved using these transparent CNT films on quartz. The OTE was characterized by transmission electron microscopy, scanning electron microscopy, Raman spectroscopy, UV-visible spectroscopy, cyclic voltammetry, electrochemical impedance spectroscopy, and thin layer spectroelectrochemistry. Ferricyanide, tris(2,2'-bipyridine) ruthenium(II) chloride, and cytochrome c were used as representative redox probes for thin layer spectroelectrochemistry using the CNT film OTE, and the results correlated well with their known properties. Direct electron transfer of cytochrome c was achieved on the CNT film electrode.

Real-Time Dynamic Adsorption Processes of Cytochrome c on an Electrode Observed through Electrochemical High-Speed Atomic Force Microscopy

An understanding of dynamic processes of proteins on the electrode surface could enhance the efficiency of bioelectronics development and therefore it is crucial to gain information regarding both physical adsorption of proteins onto the electrode and its electrochemical property in real-time. We combined high-speed atomic force microscopy (HS-AFM) with electrochemical device for simultaneous observation of the surface topography and electron transfer of redox proteins on an electrode. Direct electron transfer of cytochrome c (cyt c) adsorbed on a self-assembled monolayers (SAMs) formed electrode is very attractive subject in bioelectrochemistry. This paper reports a real-time visualization of cyt c adsorption processes on an 11-mercaptoundecanoic acid-modified Au electrode together with simultaneous electrochemical measurements. Adsorbing cyt c molecules were observed on a subsecond time resolution simultaneously with increasing redox currents from cyt c using EC-HS-AFM. The root mean square roughness (R RMS) from the AFM images and the number of the electrochemically active cyt c molecules adsorbed onto the electrode (Γ) simultaneously increased in positive cooperativity. Cyt c molecules were fully adsorbed on the electrode in the AFM images when the peak currents were steady. This use of electrochemical HS-AFM significantly facilitates understanding of dynamic behavior of biomolecules on the electrode interface and contributes to the further development of bioelectronics.

Screen-printed graphite macroelectrodes for the direct electron transfer of cytochrome c: a deeper study of the effect of pH on the conformational states, immobilization and peroxidase activity

The direct electron transfer of cytochrome c has been studied at screen-printed graphite macroelectrodes without recourse to mediators or the need for any electrode pre-treatment as is commonly employed within the literature. A wide range of pH values from 2.0 to 11.0 have been explored upon the electrochemical response of cytochrome c and different voltammetric signatures have been observed. The direct electron transfer of the alkaline transition of cytochrome c was found impeded within alkaline media leading to either an irreversible redox process or even no voltammetric responses. In acidic aqueous media the electrochemical process is observed to undergo a mixed diffusion and adsorption controlled process rather than a purely diffusional process of the native conformation as observed at pH 7.0. Interestingly, at pH 3.5 a new conformational state is revealed in cooperation with the native conformation. The immobilization of the protein was satisfactorily obtained using a simple method by cycling the protein at specific solution pH values allowing amperometric responses to be obtained and gives rise to useful pseudo-peroxidase activity for sensing H2O2. Apparent Michaelis-Menten constant values (Km) were calculated via the Lineweaver-Burk method with deduced values of 25 ± 4, 98 ± 12 and 230 ± 30 mM, respectively for pH values of 2.0, 3.0 and 7.0. Such work is important for those utilising cytochrome c in bio-electrochemical and related applications.

Modulation of direct electron transfer of cytochrome c by use of a molecularly imprinted thin film

We describe the preparation of a molecularly imprinted polymer film (MIP) on top of a self-assembled monolayer (SAM) of mercaptoundecanoic acid (MUA) on gold, where the template cytochrome c (cyt c) participates in direct electron transfer (DET) with the underlying electrode. To enable DET, a non-conductive polymer film is electrodeposited from an aqueous solution of scopoletin and cyt c on to the surface of a gold electrode previously modified with MUA. The electroactive surface concentration of cyt c was 0.5 pmol cm(-2). In the absence of the MUA layer, no cyt c DET was observed and the pseudo-peroxidatic activity of the scopoletin-entrapped protein, assessed via oxidation of Ampliflu red in the presence of hydrogen peroxide, was only 30% of that for the MIP on MUA. This result indicates that electrostatic adsorption of cyt c by the MUA-SAM substantially increases the surface concentration of cyt c during the electrodeposition step, and is a prerequisite for the productive orientation required for DET. After template removal by treatment with sulfuric acid, rebinding of cyt c to the MUA-MIP-modified electrode occurred with an affinity constant of 100,000 mol(-1) L, a value three times higher than that determined by use of fluorescence titration for the interaction between scopoletin and cyt c in solution. The DET of cyt c in the presence of myoglobin, lysozyme, and bovine serum albumin (BSA) reveals that the MIP layer suppresses the effect of competing proteins.

Direct electron transfer of cytochrome c at mono-dispersed and negatively charged perylene–graphene matrix

Mono-dispersed 3,4,9,10-perylene tetracarboxylic acid (PTCA) functionalized graphene sheets (PTCA-graphene) were fabricated by a chemical route and dispersed well in aqueous solution. PTCA-graphene with plenty of –COOH groups as electrostatic absorbing sites were beneficial to the loading of Cytochrome c (Cyt c). Cyt c, which was tightly immobilized on the PTCA-graphene modified glassy carbon electrode, maintained its natural conformation. Direct electron transfer of Cyt c and the electro-catalytic activity towards the reduction of H2O2 were also achieved. It has been substantiated that PTCA-graphene is a preferable biocompatible matrix for Cyt c.

Mechanisms for the Direct Electron Transfer of Cytochrome c Induced by Multi-Walled Carbon Nanotubes

Multi-walled carbon nanotube (MWCNT)-modified electrodes can promote the direct electron transfer (DET) of cytochrome c (Cyt c). There are several possible mechanisms that explain the DET of Cyt c. In this study, several experimental methods, including Fourier transform infrared spectroscopy, circular dichroism, ultraviolet-visible absorption spectroscopy, and electron paramagnetic resonance spectroscopy were utilized to investigate the conformational changes of Cyt c induced by MWCNTs. The DET mechanism was demonstrated at various nano-levels: secondary structure, spatial orientation, and spin state. In the presence of MWCNTs, the secondary structure of Cyt c changes, which exposes the active site, then, the orientation of the heme is optimized, revolving the exposed active center to the optimum spatial orientation for DET; and finally, a transition of spin states is induced, providing relatively high energy and a more open microenvironment for electron transfer. These changes at different nano-levels are closely connected and form a complex process that promotes the electron transfer of Cyt c.

Electrochemistry and biosensing activity of cytochrome c immobilized on a mesoporous interface assembled from carbon nanospheres

We report on an amperometric biosensor for hydrogen peroxide. It is obtained via layer-by-layer assembly of ordered mesoporous carbon nanospheres and poly(diallyldimethylammonium) on the surface of an indium tin oxide (ITO) glass electrode and subsequent adsorption of cytochrome c. UV–vis absorption spectroscopy was applied to characterize the process of forming the assembled layers. Cyclic voltammetry revealed a direct and quasi-reversible electron transfer between cytochrome c and the surface of the modified ITO electrode. The surface-controlled electron transfer has an apparent heterogeneous electron-transfer rate constant (ks) of 5.9 ± 0.2 s−1 in case of the 5-layer electrode. The biosensor displays good electrocatalytic response to the reduction of H2O2, and the amperometric signal increase steadily with the concentration of H2O2 in the range from 5 μM to 1.5 mM. The detection limit is 1 μM at pH 7.4. The apparent Michaelis-Menten constant (Km) of the sensor is 0.53 mM. We assume that the observation of a direct electron transfer of cytochrome c on mesoporous carbon nanospheres may form the basis for a feasible approach for durable and reliable detection of H2O2.

Heme plane orientation dependent direct electron transfer of cytochrome c at SAMs/Au electrodes with different wettability

It is proposed that direct electron transfer is dependent on the orientation of the heme plane in cytochrome c (cyt c) assembled on electrode surfaces. Orientation with the heme plane in cyt c parallel to the gold electrode surface favors the direct electron transfer, while vertical orientation of the heme plane makes the direct electron transfer difficult. A preferable electron transport pathway for cyt c is through the axial ligand (His-18) of the heme center rather than the porphyrin ring.

Electrochemistry and biosensing activity of cytochrome c immobilized in macroporous materials

An amperometric biosensor for hydrogen peroxide (H2O2) has been constructed by immobilizing cytochrome c on an indium/tin oxide (ITO) electrode modified with a macroporous material. Cyclic voltammetry showed that the direct and quasi-reversible electron transfer of cytochrome c proceeds without the need for an electron mediator. A surface-controlled electron transfer process can be observed with an apparent heterogeneous electron-transfer rate constant (ks) of 29.2 s−1. The biosensor displays excellent electrocatalytic responses to the reduction of H2O2 to give amperometric responses that increase steadily with the concentration of H2O2 in the range from 5 μM to 2 mM. The detection limit is 0.61 μM at pH 7.4. The apparent Michaelis-Menten constant (Km) of the biosensor is 1.06 mM. This investigation not only provided a method for the direct electron transfer of cytochrome c on macroporous materials, but also established a feasible approach for durable and reliable detection of H2O2.

Screen printed graphite macroelectrodes for the direct electron transfer of cytochrome c

We report the direct electrochemistry of cytochrome c at screen printed graphite electrodes which exhibits quasi-reversible voltammetric responses without the need for any chemical or electrochemical pre-treatment, use of mediators or nanomaterials. Through voltammetric studies and X-ray photoelectron spectroscopy (XPS) it is shown that carbonyl and carboxylic surface oxygenated species likely residing at edge plane like- sites/defects of the graphite comprising the screen printed electrodes are responsible for the favourable interaction of the cytochrome c with that of the screen printed electrochemical sensing platform.

Direct electron transfer of cytochrome c and its biosensor based on poly(ferrocenylsilane)–DNA composite film

Cytochrome c (Cyt c) was successfully immobilized on poly(ferrocenylsilane)–DNA (PFS–DNA) composite film modified gold electrode by electrostatic adsorption. The direct electron transfer of Cyt c in the composite film modified electrode and its application as hydrogen peroxide (H 2O 2) biosensor were investigated. The results suggested that Cyt c could be effectively immobilized in the PFS–DNA composite modified electrode. The adsorbed Cyt c showed a good electrochemical activity with a pair of quasi-reversible redox peaks in 0.20 M, pH 7.0 phosphate buffer solution. PFS–DNA composite films showed an obvious promotion for the direct electron transfer between Cyt c and the underlying electrode. The immobilized Cyt c also exhibited a good electro-catalytic activity towards the reduction of H 2O 2. The catalytic current increased linearly to the H 2O 2 concentration in a range of 3.0 μM–1.83 mM ( r = 0.999; n = 19) and the detection limit was calculated to be 0.72 μM based on the criterion of a signal-to-noise ratio of 3. Based on the novel construction, a third-generation biosensor could be obtained for the determination of H 2O 2.

Electron transfer mechanism of cytochrome c at graphene electrode

We report the direct electron transfer of cytochrome c (Cyt c) observed at graphene electrodes. Graphene nanosheets were chemically synthesized and immobilized on to a glassy carbon electrode. Cyclic voltammetry of Cyt c in phosphate buffered saline was performed at these electrodes. Results indicated a pair of reversible redox waves with a peak-to-peak separation value of 0.07 V in a diffusion controlled electrochemical process. Furthermore, the voltammetric response of these electrodes in Cyt c were found to be stable over time with negligible electrode fouling toward Cyt c.

Direct electrochemistry of cytochrome c on nanotextured diamond surface

Nanotextured diamond surfaces with geometrical properties close to protein dimensions were used for the realization of direct electron transfer of cytochrome c (cyt c) without any covalent bonding. The peroxidase activity of native and denatured cyt c was also investigated. Cyclic voltammograms of native cyt c show quasi-reversible electron transfer reactions, while no heme redox activity is detected for denatured cyt c. Unfolding (denaturation) of cyt c can be achieved in the presence of hydrogen peroxide. Partially or fully denatured cyt c showed higher peroxidase activity than native cyt c. This is because denatured cyt c loses its tertiary structure and hydrogen peroxide is easier to access the heme redox center. The apparent Michaelis–Menten constant K m for native and denatured cyt c has been determined to be 0.23 mM and 0.08 mM.

Electrochemical biosensor for the detection of H 2O 2 from living cancer cells based on ZnO nanosheets

In this work, direct electron transfer of cytochrome c (cyt. c)—a model for studying the electron transfer of enzymes is achieved at hexagonal ZnO nanosheets by one-step electrodeposition. UV–vis spectra and electrochemical data demonstrate that such ZnO nanosheets can supply a bio-compatible surface to keep the bioactivity of cyt. c. The redox formal potential ( E 0′) of cyt. c is estimated to be 338.2 ± 4.3 mV (vs. AgǀAgCl) at the nanostructured ZnO surface. This value is much more positive than those of enzymes previously obtained at other metal oxides and zeolite surfaces. Experiment data show, under the optimized potential of 0.0 V (vs. AgǀAgCl), the electrochemical determination of H 2O 2 is free from not only anodic interferences like ascorbic acid (AA) and dopamine (DA), but also a cathodic interference—O 2. Such an excellent selectivity enable the present H 2O 2 biosensor determine the extracellular H 2O 2 released from living human hepatoma cells.

Direct electron transfer of cytochrome C and its electrocatalytic properties on multiwalled carbon nanotubes/ciprofloxacin films

In this study, stable and homogenous thin films of multiwalled carbon nanotubes (MWCNTs) were obtained on conducting surface using ciprofloxacin (CF, fluoroquinolone antibiotic) as an effective-dispersing agent. Further, MWCNTs/CF film modified electrodes (glassy carbon and indium tin oxide-coated glass electrode) are used successfully to study the direct electrochemistry of proteins. Here, cytochrome C (Cyt-C) was used as a model protein for investigation. A MWCNTs/CF film modified electrode was used as a biocompatible material for immobilization of Cyt-C from a neutral buffer solution (pH 7.2) using cyclic voltammetry (CV). Interestingly, Cyt-C retained its native state on the MWCNTs/CF film. The Cyt-C adsorbed MWCNTs/CF film was characterized by scanning electron microscopy (SEM), UV–visible spectrophotometry (UV-vis) and CV. SEM images showed the evidence for the adsorption of Cyt-C on the MWCNTs/CF film, and UV–vis spectrum confirmed that Cyt-C was in its native state on MWCNTs/CF film. Using CV, it was found that the electrochemical signal of Cyt-C was highly stable in the neutral buffer solution and its redox peak potential was pH dependent. The formal potential (−0.27 V) and electron transfer rate constant (13 ± 1 s−1) were calculated for Cyt-C on MWCNTs/CF film modified electrode. A potential application of the Cyt-C/MWCNTs/CF electrode as a biosensor to monitor H2O2 has been investigated. The steady-state current response increases linearly with H2O2 concentration from 2 × 10−6 to 7.8 × 10−5 M. The detection limit for determination of H2O2 has been found to be 1.0 × 10−6 M (S/N = 3). Thus, Cyt-C/MWCNTs/CF film modified electrode can be used as a biosensing material for sensor applications.

Graphene-based modified electrode for the direct electron transfer of Cytochrome c and biosensing

Chitosan-dispersed graphene nano-flakes were prepared by a chemical route to reduce graphene oxide and dispersed fully in water to form a stable black aqueous solution. The as-prepared graphene nano-flakes were successfully immobilized on glassy carbon electrode to construct a graphene modified electrode. Cytochrome c was adsorbed tightly on the surface of the modified electrode and the direct electron transfer of Cytochrome c was achieved. Cytochrome c on the surface of electrode maintains its bioactivity and shows an enzyme-like activity for the reduction of nitric oxide, displaying a potential application for the fabrication of novel biosensors to sense nitric oxide. This research will enlarge the applications of graphene-based materials in biosensor field.

Plasmon-Induced Enhancement in Analytical Performance Based on Gold Nanoparticles Deposited on TiO2 Film

This paper demonstrates a novel approach for developing the analytical performance of electrochemical biosensors in which hydrogen peroxide (H(2)O(2)) is selected as a model target, based on surface plasmon resonance of gold nanoparticles (Au NPs) deposited onto a TiO(2) nanoneedle film. Direct electron transfer of cytochrome c (cyt. c) is realized at Au NPs deposited onto a TiO(2) nanoneedle film (Au/TiO(2) film), and both anodic and cathodic currents of the redox reaction at the Au/TiO(2) film upon visible-light irradiation are amplified. Meanwhile, in the presence of oxidized or reduced states of cyt. c, cathodic or anodic photocurrents are generated respectively by the Au/TiO(2) film, suggesting that the amplified anodic and cathodic currents are ascribed to the visible-light excitation. The photocurrent action spectrum obtained at the Au/TiO(2) film in the presence of cyt. c is in a good agreement with the surface plasmon absorption spectrum of Au NPs deposited onto the TiO(2) film, and maximum photocurrent is also consistent with the plasmon absorption peak of Au NPs themselves. It indicates that the enhanced photocurrents generated by visible-light irradiation are attributed to the surface plasmon resonance of Au NPs. On the other hand, experimental results reveal that cyt. c is stably immobilized onto the Au/TiO(2) film and maintains inherent enzymatic activity toward H(2)O(2) even under continuous visible-light illumination. The amplified redox currents of cyt. c produced by surface plasmon resonance of Au NPs, combined with the stability and enzymatic activity of cyt. c confined on the Au/TiO(2) film even after continuous visible-light illumination, subsequently provide the enhanced analytical performance in determination of H(2)O(2). The sensitivity of the present biosensor for H(2)O(2) is 4-fold larger than that obtained without visible-light irradiation, the detection limit is achieved to be 4.5 x 10(-8) M and the dynamic detection linear range extends from 1 x 10(-7) M to 1.2 x 10(-2) M.

Study on the Electrochemistry of a Na3[Ti2P2O10F]·xH2O-Modified Glassy Carbon Electrode

A new oxyfluorinated titanium phosphate Na3[Ti2P2O10F]·xH2O (TiP)-modified electrode was prepared by casting the dispersion of TiP on a glassy carbon electrode. The electrochemical behavior of the modified electrode was investigated by cyclic voltammetry, and a couple of reduction/reoxidation peaks corresponding to the reduction of Ti (IV) were found at −1.29 V versus SCE in the 0.1 M NaCl solution, which was supported by UV−vis and FTIR characterization. The modified electrode showed electrocatalysis toward the reduction of H2O2. Furthermore, the addition of phosphate in the supporting electrolyte resulted in an easier reduction of Ti(IV) and direct electron transfer of cytochrome c at the modified electrode due to changes in the surface structure of the TiP films. The results indicate that TiP can act as not only a good electron-transfer mediator but also an electron-transfer promoter.

A bifunctional structure for the direct electron transfer of Cytochrome c

It was found that silicon dioxide (SiO2) nanoparticles modified onto glassy carbon (GC) electrode exhibited a dramatic promotion on the direct electron transfer of Cytochrome c (Cyt c). The corresponding mechanism was discussed based on the electrochemical characteristics and a spatial geometrical model of the bifunctional structure. The model could offer insight to the study of biosensors and bioreactors without chemical mediator and serve as a basis for their fabrication. (c) 2008 Elsevier Ltd. All rights reserved.