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PubMed1992

A study of tin dioxide and antimony tetroxide supported vanadium oxide catalysts by solid-state 51V and 1H NMR techniques.

A series of vanadia catalysts with various V2O5 loadings supported on SnO2 and alpha-Sb2O4 are investigated by the application of X-ray diffraction and solid-state 51V and 1H NMR techniques. XRD results show no evidence for the formation of a crystalline vanadia phase on both supports. However, the 51V NMR spectra of the catalysts reveal the existence of two types of vanadia species on the surface of the support: one due to a dispersed vanadia phase at lower vanadia loadings and the other due to a crystalline vanadia phase at higher vanadium content. The quantity of the dispersed vanadia phase, however, depends on the nature of the support material. The 1H NMR results provide evidence for the existence or non-existence of a metal oxide support interaction through the support surface hydroxyl groups.

Antimony↗
PubMed1993

The labeling of proteins and LDL with 99mTc: a new direct method employing KBH4 and stannous chloride.

A new direct labeling technique for proteins with technetium-99m (99mTc) has been developed and makes use of borohydride and stannous chloride. The method is simple and reproducible and gives a high labeling efficiency and high retention of biological activity for proteins, including polyclonal immunoglobulin (Ig), antifibrin monoclonal antibody, tissue type plasminogen activator, fibrinogen and low density lipoprotein (LDL). This method can be used in kit-format and takes about 20 min preparation time at room temperature. Both in vitro and in vivo studies indicate good stability of the label. In vivo, mice and rabbit images show significant accumulation of 99mTc-Ig at an inflammation area, 99mTc-antifibrin at a thrombus site and 99mTc-LDL in atherosclerotic lesions. The method is attractive for routine research and clinical purposes.

Animals↗
PubMed2006

Determination of daunomycin at a novel COOH/indium tin oxide ion implantation-modified electrode.

A novel COOH+ ion implantation-modified indium tin oxide (COOH/ITO) electrode was prepared for the first time and applied for determination of daunomycin (or daunorubicin [DNR]). The electrode showed higher catalytic activity than bare ITO electrode with good reproducibility and stability. The determination condition of linear voltammetry was optimized. A calibration curve was obtained over the range 2.0 x 10(-7) to 5.0 x 10(-6)mol/L, with a correlation coefficient of 0.9909 and a limit of detection of 1.0 x 10(-7)mol/L. The selectivity of the electrode was illustrated by determination of DNR in samples prepared of urine. X-ray photoelectron spectroscopy (XPS) analysis results showed that the implanted COOH+ maintained characteristics of organic group -COOH. A field emission-scanning electron microscope (FSEM) result showed that the implanted surface caused defects and partial dislocations and formed many active centers.

Daunorubicin↗
PubMed2006

Disposable biosensor based on enzyme immobilized on Au-chitosan-modified indium tin oxide electrode with flow injection amperometric analysis.

Indium tin oxide (ITO) electrode is used to fabricate a novel disposable biosensor combined with flow injection analysis for the rapid determination of H2O2. The biosensor is prepared by entrapping horseradish peroxidase (HRP) enzyme in colloidal gold nanoparticle-modified chitosan membrane (Au-chitosan) to modify the ITO electrode. The biosensor is characterized by scanning electron microscope, atomic force microscope, and electrochemical methods. Parameters affecting the performance of the biosensor, including concentrations of o-phenylenediamine (OPD) and pH of substrate solution, were optimized. Under the optimal experimental conditions, H2O2 could be determined in the linear calibration range from 0.01 to 0.5 mM with a correlation coefficient of 0.997 (n=8). The amperometric response of the biosensor did not show an obvious decrease after the substrates were injected continuously 34 times into the flow cell. The prepared biosensor not only is economic and disposable, due to the low-cost ITO film electrode obtained from industrial mass production, but also is capable with good detection precision, acceptable accuracy, and storage stability for the fabrication in batch.

Biosensing Techniques↗
PubMed2006

Carbon monoxide protects PC12 cells from peroxynitrite-induced apoptotic death by preventing the depolarization of mitochondrial transmembrane potential.

Heme oxygenase-1 (HO-1), the rate-limiting enzyme in catalyzing heme degradation into biliverdin, free iron, and carbon monoxide (CO), serves as a protective enzyme against oxidative and nitrosative stresses. In the present study, we investigated the cytoprotective effects of HO-1 upregulation and its product CO against the peroxynitrite-induced PC12 cell death. PC12 cells treated with 3-morphoinosydonimine (SIN-1), a generator of peroxynitrite (ONOO-), underwent apoptotic cell death as evidenced by dissipation of mitochondrial transmembrane potential (DeltaPsim), release of mitochondrial cytochrome c into cytoplasm, cleavage of poly(ADP-ribose)polymerase and fragmentation of internucleosomal DNA. Pretreatment of PC12 cells with a low non-toxic concentration of SIN-1 (0.5 mM) induced HO-1 expression and abrogated the cell death caused by subsequent challenge with high dose SIN-1 (2.5 mM). Furthermore, pretreatment of PC12 cells with SnCl2, a potent inducer of HO-1 expression, increased endogenous production of CO (HO activity) and rescued the PC12 cells from peroxynitrite-induced apoptosis. The cytoprotective effect of SnCl2 was abolished when the HO activity was inhibited by zinc protoporphyrin IX (ZnPP IX). PC12 cells treated directly with the CO-releasing molecule, tricarbonyldichlororuthenium (II) dimer ([Ru(CO)3Cl2]2) became tolerant to the depolarization of DeltaPsim and apoptosis induced by high dose peroxynitrite. Taken together, these data demonstrate that the adaptive protection against peroxynitrite-induced apoptotic death in PC12 cells is mediated by CO formed as a consequence of HO-1 induction.

Animals↗
PubMed2004

Cyclic voltammetry and voltabsorptometry studies of redox proteins immobilised on nanocrystalline tin dioxide electrodes.

Protein film cyclic voltammetry is a well-established technique for the study of redox proteins immobilised on electrode surfaces. In this paper, we use nanostructured SnO(2) electrodes to demonstrate that cyclic voltabsorptometry is an effective, complimentary approach to such studies of protein redox function. We exemplify this approach using two different redox systems: microperoxidase-11 (MP-11) and flavodoxin Desulfovibrio vulgaris Hildenborough (Fld). Both systems were immobilised on nanocrystalline SnO(2) electrodes and the resulting films investigated by simultaneous cyclic voltammetry and voltabsorptometry. We demonstrate that cyclic voltabsorptometry allows the unambiguous and background free observation of redox reactions for both systems studied.

Absorption↗
PubMed2005

Surface immobilized optical probes: pyrene molecules covalently attached to silica and indium-doped tin oxide.

We report on the covalent attachment of pyrene to quartz and indium-doped tin oxide (ITO) surfaces, and its characterization by steady-state and time-resolved emission spectroscopy. We estimate the chromophore surface coverage on the basis of their electrochemical oxidation mechanism in acidic solution. Electrochemical oxidation of immobilized pyrene results in the formation of radical cations, which are converted into hydroxypyrene and, after a second oxidation step, are transformed into isomeric forms of dihydroxypyrene/pyrenedione redox couples. Our findings demonstrate that surface-bound pyrene can be used as a spectral probe in environments that are isolated from oxidizing conditions and agents.

Indium↗
PubMed2004

Amperometric detection of morphine at a Prussian blue-modified indium tin oxide electrode.

In this work, the electrocatalytic oxidation of morphine (MO) at an optically transparent indium tin oxide (ITO) electrode modified by an electrodeposited Prussian blue (PB) thin film is first demonstrated, and the amperometric detection of MO was then investigated. Experimental results showed that the thin film on the ITO surface, confined to the PB/Berlin green (BG) redox pair, can serve as an excellent mediator which facilitates electron transfer and considerably lowers the overpotential required, as compared to a bare ITO electrode. Thus, PB can be regarded as a promising artificial peroxidase for MO. The rate of such an electrocatalytic reaction is pH dependent with the highest value at pH 5. By potential-step excitation from 0.55 to 0.70 V, a linear calibration curve, displaying the relationship between steady-state currents and MO concentrations (ranging from 0.09 to 1.0 mM), was obtained. The detection sensitivity is about 16.8 microA/cm2 mM. Most importantly, the method described herein can readily discriminate MO analogs lacking the phenolic -OH group, such as codeine, and can thus benefit the specific recognition of MO.

Biosensing Techniques↗
PubMed2005

Potentiometric sensor for dipicolinic acid.

A potentiometric chemosensor for selective determination of dipicolinic acid (2,6-pyridinedicarboxylic acid, DPA) was developed based on the surface imprinting technique coupled with a nanoscale transducer: an indium tin oxide (ITO)-coated glass plate. The sensor fabrication conditions, optimal recognition condition, as well as selectivity, sensitivity, and stability of the DPA sensor have been investigated. The DPA sensor could recognize DPA from 3,5-pyridinedicarboxylic acid. Potentiometric measurements demonstrated selective detection of DPA in a concentration range of 1.5 x 10(-6) to 0.0194 M. The response time of DPA sensor for 4 x 10(-4) M DPA was 25 s. The potentiometric response of the DPA sensor to DPA is at 90% of its initial magnitude after 550 times measurement. The viability of such a modified ITO electrode in the presence of other inorganic, organic, and biological materials was probed.

Bacillus anthracis↗
PubMed2005

AFM and impedance spectroscopy characterization of the immobilization of antibodies on indium-tin oxide electrode through self-assembled monolayer of epoxysilane and their capture of Escherichia coli O157:H7.

The microscopic surface molecular structures and macroscopic electrochemical impedance properties of the epoxysilane monolayer and anti-Escherichia coli antibody layer on an indium-tin oxide (ITO) electrode surface were studied in this paper. Characterization of stepwise changes in microscopic features of the surfaces and electrochemical properties upon the formation of each layer were carried out using both atomic force microscopy (AFM) and electrochemical impedance spectroscopy in the presence of [Fe(CN)6](3-/4-) as a redox couple. AFM images of the self-assembled monolayer (SAM) evidenced the dense, complete, and homogeneous morphology of the epoxysilane monolayer on the ITO surface. The uniformity of the epoxysilane SAM allowed antibodies to attach to the epoxy surface groups of the silanes in a similarly uniform fashion. The effects of epoxysilane monolayer and the antibody layer on the electrochemical properties of the electrode were quantitatively analyzed in terms of double layer capacitance, electron transfer resistance, Warburg impedance and solution resistance using Randles model as the equivalent circuit. It was demonstrated that the epoxysilane monolayer and the antibody layer act as barriers for the electron transfer between the electrode surface and the redox species in the solution, resulting in most significant increases in the electron transfer resistance compared to all the electric elements. Immunoreaction with E. coli O157:H7 cells demonstrated specific recognition of the immobilized anti-E. coli antibodies as evidenced by AFM imaging and impedance spectroscopy. It was found that the binding of E. coli cells mainly affected the electron transfer resistance and Warburg impedance.

Antibodies↗
PubMed2005

A molecularly imprinted polymer on indium tin oxide and silicon.

Molecular imprinting is a technique for creating artificial receptor sites in a polymer. Molecularly imprinted polymers (MIPs) are produced by forming a polymer around a molecule that is used as the template. Upon removal of the template, molecular holes remain which are specific in shape and size to the target molecule. In this research, a MIP was formed for theophylline using a copolymer of methacrylic acid and ethylene glycol dimethacrylate. The theophylline MIP was formed on two platforms: indium tin oxide (ITO) and silicon, which were used as the working electrode for cyclic voltammetry measurements. The presence of theophylline was measured using cyclic voltammetry and corresponded to the peak current on the cyclic voltammograms. The results of this research agreed with previous results of MIPs immobilized on an ITO platform. The peak currents of the MIP in the presence and absence of theophylline were compared to the blank polymer for each platform. The ratio of peak currents on ITO increased by a factor of 9.5 for the MIP compared to the non-imprinted polymer. Similarly, the ratio of peak currents on silicon increased by a factor of 6 compared to the non-imprinted polymer. This research demonstrated a procedure for evaluating a MIP layer on two different platforms.

Biosensing Techniques↗
PubMed2006

Application of europium(III) chelate-dyed nanoparticle labels in a competitive atrazine fluoroimmunoassay on an ITO waveguide.

We have demonstrated the use of an optical indium tin oxide (ITO) (quartz) waveguide as a new platform for immunosensors with fluorescent europium(III) chelate nanoparticle labels (Seradyn) in a competitive atrazine immunoassay. ITO as a solid surface facilitated the successful use of particulate labels in a competitive assay format. The limit of detection in the new nanoparticle assay was similar to a conventional ELISA. The effect of particle size on bioconjugate binding kinetics was studied using three sizes of bioconjugated particle labels (107, 304, and 396nm) and a rabbit IgG/anti-IgG system in a 96-well plate. A decrease in particle size resulted in faster binding but did not increase the assay sensitivity. Flux calculations based on the particle diffusivity prove that faster binding of the small particles in this study was primarily due to diffusion kinetics and not necessarily to a higher density of antibodies on the particle surface. The results suggest that ITO could make a good platform for an optical immunosensor using fluorescent nanoparticle labels in a competitive assay format for small molecule detection. However, when used in combination with fluorescent particulate labels, a highly sensitive excitation/detection system needs to be developed to fully utilize the kinetic advantage from small particle size. Different regeneration methods tested in this study showed that repeated washings with 0.1 M glycine-HCl facilitated the reuse of the ITO waveguide.

Atrazine↗
PubMed2006

Electrogenerated indium tin oxide-coated glass surface with photosensitive interfaces: surface analysis.

We present herein a photo-immobilization technique for the localized and specific conjugation of biochip platforms with different proteinaceous bioreceptors, such as antigen or antibodies. This methodology based on a photoactivable electrogenerated polymer film, pyrrole-benzophenone, allows the covalent immobilization of biomolecules through light mediation. The surface-conductive glass platform electropolymerized with poly(pyrrole-benzophenone) thin film may then be used to affinity-coat the chip with molecular recognition probes. This glass chip electroconductive surface modification is done by the deposition of a thin layer of indium tin oxide (ITO). Thereafter, pyrrole-benzophenone monomers are electropolymerized onto the conductive metal oxide surface and then exposed to an antigen Staphylococcal Enterotoxin B (SEB)) solution and illuminated with UV light (wavelength approximately 345 nm) through a mask. As a result of the photochemical reaction, a pattern thin layer of the antigen was covalently bound to the benzophenone-modified surface. Then the sample to be analyzed, along with its specific target antibody (anti-SEB antibodies), is introduced onto the glass surface and left to react with the previously photo-immobilized antigen. When the immuno-reaction is completed, the specifically attached immunoglobulin analytes are detected by using secondary antibodies conjugated with Fluorescein isothiocyanate (FITC). The fluorescence signal emanating from the biochip surface is then quantified by two methods, using a filtered intensified charge-coupled device (CCD) camera and a grating spectrometer.

Antibodies↗
PubMed2004

Evaluation of different electrochemical methods on the oxidation and degradation of Reactive Blue 4 in aqueous solution.

The oxidation of a reactive dye, Reactive Blue 4, RB4, (C.I. 61205), widely used in the textile industries to color natural fibers, was studied by electrochemical techniques. The oxidation on glassy carbon electrode and reticulated vitreous carbon electrode occurs in only one step at 2.0 < pH < 12 involving a two-electron transfer to the amine group leading to the imide derivative. Dye solution was not decolorized effectively in this electrolysis process. Nevertheless, the oxidation of this dye on Ti/SnO2/SbO(x) (3% mol)/RuO2 (1% mol) electrode showed 100% of decolorization and 60% of total organic carbon removal in Na2SO4 0.2 M at pH 2.2 and potential of +2.4V. Experiments on degradation photoelectrocatalytic were also carried out for RB4 degradation in Na2SO4 0.1 M, pH 12, using a Ti/TiO2 photoanode biased at +1.0 V and UV light. After 1h of electrolysis the results indicated total color removal and 37% of mineralization.

Antimony↗
PubMed2005

Comparison of catalytic activity of two platinised TiO2 films towards the oxidation of organic pollutants.

Two types of platinised TiO2 films, i.e., Pt-TiO2/ITO and Pt(TiO2)/ITO, were prepared by a procedure of dip-coating and subsequent photo-deposition, and photo-deposition and subsequent dip-coating, respectively. They were well characterized by DRS, XRD spectra, SEM microscopy and photoelectrochemical measurement. Their photocatalytic, dark catalytic and photoelectrocatalytic activities were investigated using formic acid as a model organic pollutants. Compared with pure TiO2/ITO film, the photocatalytic activity of the platinised TiO2 films were apparently improved. However, the improvement was considerably dependent on the preparation method of these films. Pt-TiO2/ITO not only possessed higher photocatalytic activity but also showed a dark catalytic activity towards HCOOH degradation. As a sequence, it was first emphasized that the dark catalytic effect of Pt-TiO2/ITO was partly responsible for degradation of formic acid in the photocatalytic oxidation process. Although the Pt(TiO2)/ITO film does not exhibit the dark catalytic activity, its photocatalytic degradation efficiencies towards HCOOH are higher than that of Pt-TiO2/ITO film. Therefore, in view of enhanced photocatalytic activity, the Pt(TiO2)/ITO was more favored than Pt-TiO2/ITO film.

Catalysis↗
PubMed2006

Electrochemical degradation of 4-chlorophenol at nickel-antimony doped tin oxide electrode.

The effectiveness of a novel nickel-antimony doped tin oxide electrode for electrochemical degradation of organic pollutants was investigated using 4-chlorophenol (4-CP) as a model toxic organic. The experimental results demonstrate that the optimal Ni content was at Ni:Sn=1:500 in atomic ratio in the precursor coating solution, whereas the Sb:Sn ratio was set at 8:500. Using the electrode prepared with the optimal Ni doping ratio for 4-CP degradation, the charge-based efficiencies were up to 89 microg C(-1) for 4-CP destruction and 15 microg C(-1) for TOC removal, which were considerably higher than the efficiencies observed for other electrodes. It is suggested that the enhancement of the electrode for electrochemical oxidation of organics could be attributed to the production of hydroxyl radicals in anodic water electrolysis.

Antimony↗
PubMed2005

The impact of ultraviolet light on bacterial adhesion to glass and metal oxide-coated surface.

Biofouling of glass and quartz surfaces can be reduced when the surface is coated with photocatalytically active metal oxides, such as TiO2 (anatase form) or SnO2. We measured the attachment of eight strains of bacteria to these two metal oxides (TiO2 and SnO2), and to an uncoated glass (control; designated Si-m) before and after exposure to UV light at wavelengths of 254 nm (UVC) or 340 nm UV (UVA). TiO2-coated surfaces were photocatalytically active at both 254 and 340 nm as evidenced by a decrease in the water contact angle of the surface from 59 degrees +/-2 to <5 degrees. The water contact angle of the SnO2 surface was reduced only at 254 nm, while contact angle of the Si-m glass surface was not altered by light of either wavelength. Bacterial adhesion decreased by 10-50% to photocatalyzed glass surfaces. In all cases, bacteria exposed to the UV light were completely killed due to a combination of exposure to UV light and the photocatalytic activity of the glass surfaces. These results show that UV light irradiation of TiO2-coated surfaces can be an effective method of reducing bacterial adhesion.

Bacillus subtilis↗
PubMed2005

Electroformation of giant liposomes from spin-coated films of lipids.

This paper describes spin-coating of solutions of lipids and using the resulting thin films for electroformation of giant liposomes. Spin-coating made it possible to generate uniform films of lipids with controllable thickness over large surfaces (>25 cm(2)) of indium tin oxide. Establishing a range of thicknesses optimal for electroformation (25-50 nm), we demonstrate formation of giant liposomes from lipids (such as asolectin, phosphatidylserine, and phosphatidylglycerol) that do not readily form giant liposomes from traditional, droplet-derived films. We compared liposomes from a spin-coated film of lipids to liposomes formed from traditional droplet-derived films and found that spin-coated films produced larger (by factor of 2-5) and more abundant liposomes than droplet-derived films of lipids. Electroformation from spin-coated, homogenous lipid films of optimal thickness provided a reproducible way to obtain liposomes with diameters that are predominantly larger than 30 microm over the entire surface of formation.

Biotechnology↗