Application of surfactants in the electrochemical sensing and biosensing of biomolecules and drug molecules.

Realizing sensitive and efficient detection of biomolecules and drug molecules is of great significance. Among the detection methods that have been proposed, electrochemical sensing is favored for its outstanding advantages such as simple operation, low cost, fast response and high sensitivity. The unique structure and properties of surfactants have led to a wide range of applications in the field of electrochemical sensors and biosensors for biomolecules and drug molecules.

Fully Converting Graphite into Graphene Oxide Hydrogels by Preoxidation with Impure Manganese Dioxide.

Potassium permanganate (KMnO4) has been proved to be an efficient oxidant for converting graphite into graphite oxide, but its slow diffusion in the interlayer of graphite seriously restricts the production of graphene oxide (GO). Here, we demonstrate that the preoxidation of graphite by impure manganese dioxide (MnO2) in a mixture of concentrated sulfuric acid (H2SO4) and phosphorus pentoxide (P2O5) can efficiently improve the synthesis of GO when KMnO4 is employed as the oxidant. The prepared honey-like GO hydrogels possess a high yield of single-layer sheets, large sizes (average lateral size up to 20 μm), wide ranges of stable dispersion concentrations (from dilute solutions, viscous hydrogels, to dry films), and good conductivity after reduction (~2.

Ultrasensitive photoelectrochemical biosensing of multiple biomarkers on a single electrode by a light addressing strategy.

Ultrasensitive multiplexed detection of biomarkers on a single electrode is usually a great challenge for electrochemical sensors. Here, a light addressable photoelectrochemical sensor (LAPECS) for the sensitive detection of multiple DNA biomarkers on a single electrode was reported. The sensor was constructed through four steps: (1) immobilization of capture DNA (C-DNA) of different targets on different areas of a single large-sized gold film electrode, (2) recognition of each target DNA (T-DNA) and the corresponding biotin-labeled probe DNA (P-DNA) through hybridization, (3) reaction of the biotin-labeled probe DNA with a streptavidin-labeled all-carbon PEC bioprobe, and (4) PEC detection of multiple DNA targets one by one via a light addressing strategy.

Rapid in situ detection of ultratrace 2,4-dinitrotoluene solids by a sandwiched paper-like electrochemical sensor.

This work reported the rapid in situ detection of ultratrace 2,4-dinitrotoluene (DNT) solids on various substrates by a sandwiched paper-like electrochemical sensor. The sensor, prepared by a simple electroless deposition method without using special instruments, possessed a unique thin-film structure of an insulated polyvinylidene fluoride (PVDF) membrane in between two gold (Au) conducting layers. The resulting gold-PVDF sandwich (GPVDFS) array exhibited excellent flexibility, porosity and electrochemical performance as a highly integrated dual-electrode sensor platform.

Preparation and application of a novel electrochemical sensing material based on surface chemistry of polyhydroquinone.

A new analogue of polydopamine (PDA), i.e., polyhydroquinone (PH2Q), was polymerized and its surface chemistry was studied by different ways of characterization.

Ultrasensitive all-carbon photoelectrochemical bioprobes for zeptomole immunosensing of tumor markers by an inexpensive visible laser light.

A novel enzyme-free and all-carbon photoelectrochemical (PEC) bioprobe, based on carboxylated multiwalled carbon nanotube-Congo red-fullerene nanohybrids (MWNTCOOH-CR-C60), for the ultrasensitive immunosensing of carcinoembryonic antigen (CEA) was reported. The MWNTCOOH-CR-C60 nanohybrids, prepared by mechanically grinding a mixture of MWNTCOOH, C60, and CR at a certain mass ratio, had good water dispersibility and high PEC conversion efficiency in visible light ranges. Covalent binding of the detection antibody of CEA on the MWNTCOOH-CR-C60 nanohybrids produced a sensitive PEC bioprobe for detection of CEA by sandwich immunosensing.

Inkjet printing of nanoporous gold electrode arrays on cellulose membranes for high-sensitive paper-like electrochemical oxygen sensors using ionic liquid electrolytes.

A simple approach to the mass production of nanoporous gold electrode arrays on cellulose membranes for electrochemical sensing of oxygen using ionic liquid (IL) electrolytes was established. The approach, combining the inkjet printing of gold nanoparticle (GNP) patterns with the self-catalytic growth of these patterns into conducting layers, can fabricate hundreds of self-designed gold arrays on cellulose membranes within several hours using an inexpensive inkjet printer. The resulting paper-based gold electrode arrays (PGEAs) had several unique properties as thin-film sensor platforms, including good conductivity, excellent flexibility, high integration, and low cost.

A disposable electrochemical sensor for the determination of indole-3-acetic acid based on poly(safranine T)-reduced graphene oxide nanocomposite.

A disposable electrochemical sensor for the determination of indole-3-acetic acid (IAA) based on nanocomposites of reduced graphene oxide (rGO) and poly(safranine T) (PST) was reported. The sensor was prepared by coating a rGO film on a pre-anodized graphite electrode (AGE) through dipping-drying and electrodepositing a uniform PST layer on the rGO film. Scanning electron microscopic (SEM) and infrared spectroscopic (IR) characterizations indicated that PST-rGO formed a rough and crumpled composite film on AGE, which exhibited high sensitive response for the oxidation of IAA with 147-fold enhancement of the current signal compared with bare AGE.

Fabrication and application of poly(alizarin red S)-carbon nanotubes composite film based nitrite sensor.

In this work, a novel electrochemical nitrite sensor for sensitive determination of nitrite based on poly(alizarin red S)-multi-wall carbon nanotubes (PARS-MWNTs) composite film on the glassy carbon electrode was described. The surface morphologies of different electrodes were characterized by scanning electron microscopy. Cyclic voltammetry, chronocoulometry and linear sweep voltammetry were used to investigate the electrochemical response and oxidation mechanism of nitrite at the PARS-MWNTs composite film based sensor.

Direct electrochemical determination of methyl jasmonate in wheat spikelet at a nano-montmorillonite film modified electrode by derivative square wave voltammetry.

The direct electrochemical determination of methyl jasmonate (MeJA) at a nano-montmorillonite modified glassy carbon electrode (nano-MMT/GCE) is reported. The modified electrode, prepared by a simple casting-drying method and characterized by scanning electron microscope (SEM) and electrochemical impedance spectra (EIS), was proved to process a uniform nanostructured surface with a large surface area and a fast electron transfer rate. This electrode exhibited a sensitive electrochemical response for the direct oxidation of MeJA in 0.

Electrochemical behavior of biocatalytical composite based on heme-proteins, didodecyldimethylammonium bromide and room-temperature ionic liquid.

A novel biocompatible composite film based on a water-insoluble surfactant, didodecyldimethylammonium bromide (DDAB), and a hydrophobic room-temperature ionic liquid (RTIL), 1-hexyl-3-methyl-imidazolium hexafluorophosphate (HIMIMPF(6)), for the immobilization of biocatalytical proteins was reported. Differential scanning calorimetry (DSC) showed that the DDAB-HIMIMPF(6) composite film has higher thermal stability than the DDAB film alone. SEM images indicated that different microstructures existed between the DDAB film and the composite film, indicating the interaction between DDAB and RTILs.

Nitric oxide sensor based on poly (p-phenylenevinylene) derivative modified electrode and its application in rat heart.

A novel nitric oxide (NO) electrochemical sensor was fabricated by electropolymerization with two-pulse potential method in aqueous solution containing poly (p-phenylenevinylene) derivative. The experimental results showed this sensor exhibits apparent current response to NO by cyclic voltammetry. Two anodic peaks potential are significantly shifted negatively compared with bare glass carbon electrode (GCE).

Direct electrochemistry and electrocatalysis of heme-protein based on N,N-dimethylformamide film electrode.

The heme-protein including myoglobin (Mb), hemoglobin (Hb) and horseradish peroxidase (HRP) were immobilized on normal graphite electrode by using N,N-dimethylformamide (DMF). The proteins undergo direct electron-transfer reactions. The current is linearly dependent on the scan rate, indicating that the direct electrochemistry of heme-protein in that case is a surface-controlled electrode process.

Electro-oxidation of glucose at self-assembled monolayers incorporated by copper particles.

A novel copper incorporated self-assembled monolayers (SAMs) modified gold electrode (Cu/SAMs) for determination of glucose was developed by electrodepositing Cu particles on the SAMs of hexanethiol. The scanning electron microscopic (SEM) images showed that copper formed orbicular particles of nanosizes on the SAMs, which was much different from the fractal-like particles of copper formed at gold electrode. The Cu/SAMs film electrode exhibited high sensitivity to glucose oxidation and depressed responses towards some interferents of glucose in blood like uric acid and ascorbic acid.

Glucose nanosensors based on redox polymer/glucose oxidase modified carbon fiber nanoelectrodes.

This paper describes glucose nanosensors based on the co-electrodeposition of a poly(vinylimidazole) complex of [Os(bpy)(2)Cl](+/2+) and glucose oxidase (GOD) on a low-noise carbon fiber nanoelectrodes (CFNE). The SEM image shows that the osmium redox polymer/enzyme composite film is uniform. The film modified CFNE exhibits the classical features of a kinetically fast redox couple bound to the electrode surface.

Simultaneous determination of cadmium (II) and lead (II) with clay nanoparticles and anthraquinone complexly modified glassy carbon electrode.

An anthraquinone (AQ) improved Na-montmorillonite nanoparticles (nano-SWy-2) chemically modified electrode (CME) has been developed for the simultaneous determination of trace levels of cadmium (II) and lead (II) by differential pulse anodic stripping voltammetry (DPASV). This method is based on a non-electrolytic preconcentration via ion exchange model, followed by an accumulation period via the complex formation in the reduction stage at -1.2V, and then by an anodic stripping process.

Electrochemical reduction and voltammetric determination of metronidazole at a nanomaterial thin film coated glassy carbon electrode.

Simple and sensitive electrochemical method for the determination of metronidazole, based on a nanostructured film coated glassy carbon electrode (GCE), is described. Multi-walled carbon nanotubes (MWNT) was dispersed into water in the presence of a hydrophobic surfactant to give very stable and homogeneous MWNT suspension, and a MWNT-film coated GCE was achieved via evaporating solvent. Metronidazole yields a well-defined reduction peak whose potential is -0.

Simultaneous determination of lead(II) and cadmium(II) at a diacetyldioxime modified carbon paste electrode by differential pulse stripping voltammetry.

A simple and effective chemically modified carbon paste electrode (CMCPE) for the simultaneous determination of lead(II) and cadmium(II) was developed in this work. The electrode was prepared by the addition of diacetyldioxime into a carbon paste mixture. Pb(2+) and Cd(2+) were preconcentrated on the surface of the modified electrode by complexing with diacetyldioxime and reduced at a negative potential (-1.

Voltammetric determination of diethylstilbestrol at carbon paste electrode using cetylpyridine bromide as medium.

In this paper, the voltammetric properties of diethylstilbestrol (DES) at the carbon paste electrode were described. The oxidation peak currents of DES increase significantly in the presence of surfactant cetylpyridine bromide (CPB), compared with that in the absence of CPB. Based on this fact, a voltammetric technique for determining DES is proposed.

Single-chain surfactant monolayer on carbon paste electrode and its application for the studies on the direct electron transfer of hemoglobin.

A variety of single-chain surfactants with different charge properties and tail lengths can spontaneously adsorb on the hydrophobic surface of carbon paste electrode and form stable monolayers on the electrode surface. Hemoglobin (Hb) was successfully immobilized on these surfactant monolayers to form stable protein-surfactant composite films regardless of the charge and the tail length of surfactants. The resulting surface-confined Hb exhibited well-defined direct electron-transfer behaviors in all positively, neutrally and negatively charged surfactant films, suggesting the important role of hydrophobic interactions in the adsorption of Hb on surfactant films.

Surface design of carbon nanotubes for optimizing the adsorption and electrochemical response of analytes.

Carbon nanotubes (CNTs) from different sources were dissolved in water with high solubility by Congo red (CR) via strong noncovalent pi-stacking interactions. The resulting CNTs were capable of forming uniform, compact, stable films on various substrates. This provided a chance to explore the relationship between the surface property of CNTs and the adsorptive behavior of analytes on CNTs without considering the influence of film structures or free additives.

Direct electron-transfer of native hemoglobin in blood: kinetics and catalysis.

A novel approach that uses nature biological tissues, fish blood, for the study of the direct electron-transfer of hemoglobin and its catalytic activity for H(2)O(2) and NO(2)(-) is observed. The direct electron-transfer of hemoglobin in red blood cells in fish blood on glassy carbon electrode was observed for the first time. By simply casting fish blood on GC electrode surface and being air-dried, a pair of well-defined redox peaks for HbFe (III)/HbFe (II) appeared at about -0.

Direct electron-transfer of myoglobin within a new zwitterionic gemini surfactant film and its analytical application for H2O2 detection.

The direct electron-transfer of myoglobin in a new zwitterionic gemini surfactant film with glassy carbon electrode surface has been investigated. A pair of well-defined and quasi-reversible voltammetric peaks was observed at -0.34 and -0.

Direct electron transfer of xanthine oxidase and its catalytic reduction to nitrate.

This work reports on the direct electrochemistry of the xanthine oxidase (XO) from buttermilk, a mononuclear molybdenum enzyme that comprises four redox active cofactors: a five-coordinate mononuclear Mo ion, two [2Fe-2S] clusters, and a flavin adenine dinucleotide (FAD) group. The Mo, [2Fe-2S] and FAD redox responses are obtained from the enzyme immobilized on an activated single-wall carbon nanotubes (SWNTs) modified glassy carbon electrode using protein film voltammetry. The formal potentials of which are -0.