Characterization of procaine metabolism as probe for the butyrylcholinesterase enzyme investigation by simultaneous determination of procaine and its metabolite using capillary electrophoresis with electrochemiluminescence detection

Capillary electrophoresis with electrochemiluminescene detection was used to characterize procaine hydrolysis as a probe for butyrylcholinesterase by in vitro procaine metabolism in plasma with butyrylcholinesterase acting as bioscavenger. Procaine and its metabolite N,N-diethylethanolamine were separated at 16 kV and then detected at 1.25 V in the presence of 5.0 mM Ru(bpy)(3)(2+), with the detection limits of 2.4 x 10(-7) and 2.0 x 10(-8) mol/L (S/N=3), respectively. The Michaelis constant K-m value was 1.73 x 10(-4) mol/L and the maximum velocity V-max was 1.62 x 10(-6) mol/L/min. Acetylcholine bromide and choline chloride presented inhibition effects on the enzymatic cleavage of procaine, with the 50% inhibition concentration (IC50) of 6.24 x 10(-3) and 2.94 x 10(-4) mol/L.

A novel sensitive solid-state electrochemiluminescence sensor material: Ru(bpy)(2+)(3) doped SiO2@MWNTs coaxial nanocable

A simple, large scale, and one-step process for the preparation of tris(2,2'-bipyridyl)ruthenium(I) (Ru(bpy)(3)(2+)) doped SiO2@carbon nanotubes (MVNTs) coaxial nanocable used for an ultrasensitive electrochemiluminescence (ECL) is presented for the first time. More importantly, a directly coated as-formed functional material on ITO electrode surface exhibits excellent ECL behavior, good stability, and high sensitivity in the presence of tripropylamine (TPA). This novel functional material will find potential applications in biosensor, electrophoresis and electroanalysis.

Electrochemical impedance detection of DNA hybridization based on dendrimer modified electrode

Bioactive ultrathin films with the incorporation of amino-terminated G4 PAMAM dendrimers have been prepared via layer-by-layer self-assembly methods on a gold electrode and used for the DNA hybridization analysis. Surface plasmon resonance (SPR), X-ray photoelectron spectroscopy (XPS), and electrochemical impedance spectroscopy (EIS) are used to characterize the successful construction of the multicomponent film on the gold substrate. The dendrimer-modified surfaces improve the immobilization capacity of the probe DNA greatly, compared to the AET (2aminoethanethiol) SAM sensor surfaces without dendrimer molecules. DNA hybridization analysis is monitored by EIS. The dendrimer-based electrochemical impedance DNA biosensor shows high sensitivity and selectivity for DNA hybridization assay. The multicomponent films also display a high stability during repeated regeneration and hybridization cycles.

Interaction between alpha-actinin and negatively charged lipids membrane investigated by surface plasmon resonance and electrochemical methods

alpha-Actinin has been shown to be capable of interacting with some special membrane phospholipids directly, which is important for its function. In this study, hybrid bilayer membranes composed of negatively charged lipids are constructed on the surface plasmon resonance gold substrate and on the gold electrode, respectively, and the interaction between alpha-actinin and negatively charged lipids membrane is investigated by surface plasmon resonance, cyclic voltammetry and electrochemical impedance spectroscopy methods. alpha-Actinin is proved to be able to interact with the negatively charged lipids membrane directly. It can also insert at least partly into the membrane or lead to some defect or lesion in the membrane, which increase the permeability of the membrane. This study would bring some insight on the interaction between the alpha-actinin and the cell membranes in vivo.

Electrochemiluminescence-based DNA detection using guanine oxidation at electrostatic self-assembly of Ru(bpy)(3)(2+)-doped silica nanoparticles on indium tin oxide electrode

A Ru(bpy)(3)(2+)-doped silica nanoparticle-[Ru@Silica] modified indium tin oxide electrode was prepared by simple electrostatic self-assembly technique, and one-electron catalytic oxidation of guanine bases in double-strand and denatured DNA was realized using the electrochemiluminescence detection means.

Reusable, label-free electrochemical aptasensor for sensitive detection of small molecules

We report a sensitive electrochemical aptasensor for adenosine based on electrochemical impedance spectroscopy measurement, which gives not only a label-free but also a reusable platform to make the detection of small molecules simple and convenient.

Direct electrochemistry and electrocatalysis of horseradish peroxidase immobilized in sol-gel-derived ceramic-carbon nanotube nanocomposite film

The sol-gel-derived ceramic-carbon nanotube (SGCCN) nanocomposite film fabricated by doping multiwall carbon nanotubes (MWNTs) into a silicate get matrix was used to immobilize protein. The SGCCN film can provide a favorable microenvironment for horseradish peroxidase (HRP) to perform direct electron transfer (DET) at glassy carbon electrode. The HRP immobilized in the SGCCN film shows a pair of well-defined redox waves and retains its bioelectrocatalytic activity to the reduction of O-2 and H2O2, which is superior to that immobilized in silica sol-gel film.

Electrochemical catalysis and thermal stability characterization of laccase-carbon nanotubes-ionic liquid nanocomposite modified graphite electrode

The hydrophobic carbon nanotubes-ionic liquid (CNTs-IL) get forms a stable modified film on hydrophobic graphite electrode surface. Laccase immobilized on the CNTs-IL gel film modified electrode shows good thermal stability and enhanced electrochemical catalytic ability. The optimal bioactivity occurs with increasing temperature and this optimum is 20 degrees C higher in comparison to free laccase. The improvement of laccase thermal stability may be due to the microenvironment of hydrophobic CNTs-IL gel on graphite electrode surface. On the other hand, the sensitive detection of oxygen has been achieved due to the feasibility of oxygen reduction by both of laccase and nanocomposite of CNTs-IL gel. Furthermore, the laccase hybrid nanocomposite also shows the fast electrochemical response and high sensitivity to the inhibitors of halide ions with the approximate IC50 of 0.01, 4.2 and 87.5 mM for the fluoride, chloride and bromide ions, respectively. It implies the feasibility of laccase modified electrode as an inhibition biosensor to detect the modulators of laccase.

pH-dependent protein conformational changes in albumin : gold nanoparticle bioconjugates: A spectroscopic study

The conformational changes of bovine serum albumin (BSA) in the albumin:gold nanoparticle bioconjugates were investigated in detail by various spectroscopic techniques including UV-vis absorption, fluorescence, circular dichroism, and Fourier transform infrared spectroscopies. Our studies suggested that albumin in the bioconjugates that was prepared by the common adsorption method underwent substantial conformational changes at both secondary and tertiary structure levels. BSA was found to adopt a more flexible conformational state on the boundary surface of gold nanoparticles as a result of the conformational changes in the bioconjugates. The conformational changes at pH 3.8, 7.0, and 9.0, which corresponded to different isomeric forms of albumin, were investigated, respectively, to probe the pH effect on the conformational changes of BSA in the bioconjugates. The results showed that the pH of the medium influenced the changes greatly and that fluorescence and circular dichroism studies further indicated that the changes were larger at higher pH.

A biofuel cell with enhanced power output by grape juice

Glucose oxidase and laccase immobilized at multiwalled carbon nanotubes-ionic liquid gel modified electrodes are used as the catalysts of anode and cathode of biofuel cells (BFCs), respectively. The BFC based on glucose and air is proposed. When ferrocene monocarboxylic acid is adopted as the mediator of anode, the power output of the BFC is ca. 4.1 mu W (power density ca. 10.0 mu W cm(-2)), which is higher than the value of 2.7 mu W (power density ca. 6.6 mu W cm(-2)) by taking ferrocene dicarboxylic acid as the mediator. This implies that the mediator with formal potential closing to that of the enzyme does improve the power output. Furthermore, the power output of the BFC is greatly improved by taking grape juice as the fuel of anode rather than glucose. This system also indicates that grape juice as a fuel of the BFC not only is feasible and can also enhances the power output of the BFCs. Besides, it greatly lowers the cost and simplifies the preparation procedure of the BFCs, making the BFC towards "green" bioenergy.

Sensitive biomimetic sensor based on molecular imprinting at functionalized indium tin oxide electrodes

We initially report an electrochemical sensing platform based on molecularly imprinted polymers (MIPs) at functionalized Indium Tin Oxide Electrodes (ITO). In this research, aminopropyl-derivatized organosilane aminopropyltriethoxysilane (APTES), which plays the role of functional monomers for template recognition, was firstly self-assembled on an ITO electrode and then dopamine-imprinted sol was spin-coated on the modified surface. APTES which can interact with template dopamine (DA) through hydrogen bonds brought more binding sites located closely to the surface of the ITO electrode, thus made the prepared sensor more sensitive for DA detection. Potential scanning is presented to extract DA from the modified film, thus DA can rapidly and completely leach out. The affinity and selectivity of the resulting biomimetic sensor were characterized using cyclic voltammetry (CV). It exhibited an increased affinity for DA over that of structurally related molecules, the anodic current for DA oxidation depended on the concentration of DA in the linear range from 2 x 10(-6) M to 0.8 x 10(-3) M with a correlation coefficient of 0.9927.In contrast, DA-templated film prepared under identical conditions on a bare ITO showed obviously lower response toward dopamine in solution.

Self-assembled silver nanoparticle monolayer on glassy carbon: an approach to SERS substrate

In this paper, the fabrication of an active surf ace-enhanced Raman scattering (SERS) substrate by self-assembled silver nanoparticles on a monolayer of 4-aminophenyl-group-modified glassy carbon (GC) is reported. Silver nanoparticles are attached to the substrate through the electrostatic force between the negatively charged silver nanoparticles and the positively charged 4-aminophenyl groups on GC. The active SERS substrate has been characterized by means of tapping-mode atomic force microscopy (AFM), indicating that large quantities of silver nanoparticles are uniformly coated on the substrate. Rhodamine 6G (R6G) and p-aminothiophenol (p-ATP) are used as the probe molecules for SERS, resulting in high sensitivity to the SERS response, with the detection limit reaching as low as 10(-9) m. This approach is easily controlled and reproducible, and more importantly, can extend the range of usable substrates to carbon-based materials for SERS with high sensitivity.

Gene transfection of hyperbranched PEI grafted by hydrophobic amino acid segment PBLG

The complex copolymer of hyperbranched polyethylenimine (PEI) with hydrophobic poly(gamma-benzyl L-glutamate) segment (PBLG) at their chain ends was synthesized. This water-soluble copolymer PEI-PBLG (PP) was characterized for DNA complexation (gel retardation assay, particle size, DNA release and DNase I protection), cell viability and in vitro transfection efficiency. The experiments showed that PP can effectively condense pDNA into particles. Size measurement of the complexes particles indicated that PP/DNA tended to form smaller nanoparticles than those of PEI/DNA, which was caused by the hydrophobic PBLG segments compressing the PP/DNA complex particles in aqueous solution. The representative average size of PP/DNA complex prepared using plasmid DNA (pEGFP-N1, pDNA) was about 96 nm. The condensed pDNA in the PP/pDNA complexes was significantly protected from enzymatic degradation by DNase1. Cytotoxicity studies by MTT colorimetric assays suggested that the PP had much lower toxicity than PEI. The in vitro transfection efficiency of PP/pDNA complexes improved a lot in HeLa cells, Vero cells and 293T cells as compared to that of PEI25K by the expression of Green Fluorescent Protein (GFP) as determined by flow cytometry. Thus, the water-soluble PP copolymer showed considerable potential as carriers for gene delivery.

Carbon nanotubes and glucose oxidase bionanocomposite bridged by ionic liquid-like unit: Preparation and electrochemical properties

For their biocompatibility and potential bionanoelectronic applications, integration of carbon nanotubes (CNTs) with biomolecules such as redox enzyme is highly anticipated. Therein, CNTs are expected to act not only as an electron transfer promoter, but also as immobilizing substrate for biomolecules. In this report, a novel method for immobilization of biomolecules on CNTs was proposed based on ionic interaction, which is of universality and widespread use in biological system. As illustrated, glucose oxidase (GOD) and single-walled carbon nanotubes (SWNTs) were integrated into a unitary bionanocomposite by means of ionic liquid-like unit on functionalized SWNTs. The resulted bionanocomposite illustrated better redox response of immobilized GOD in comparison of that prepared by weak physical absorption without ionic interaction. As a potential application of concept, the electrochemical detection of glucose was exemplified based on this novel bionanocomposite.