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A cobalt hexacyanoferrate (CoHCF) nanoparticle (size ca. 60 nm) chemically modified electrode (CME) was fabricated and the electrochemical behavior of thiols at this nanosized CoHCF CME was studied. In comparison with a bare glassy carbon (GC) electrode and with a general CoHCF CME which was electrode-posited in the traditional manner, the present nanosized CoHCF CME efficiently performed electrocatalytic oxidation for glutathione (GSH) and L-Cysteine (L-Cys) with relatively high sensitivity, outstanding stability, and long-life. Combined with high-performance liquid chromatography (HPLC), the nanosized CoHCF CME was used for electrochemical determination (ECD) of GSH and L-Cys. The peak currents were a linear function of concentrations in the range 2.0 x 10(-7) to 2.0 x 10(-4) mol L(-1) for both GSH and L-Cys, with detection limits of 1.2 x 10(-7) and 1.0 x 10(-7) mol L(-1), respectively. Coupled with microdialysis sampling, the HPLC-ECD system has been successfully used to assess the GSH and L-Cys content of rat striatum.

A new chemically modified electrode based on the immobilization of Pt particles is fabricated and exhibits electrocatalytic oxidation for l-cysteine (l-Cys), glutathione (GSH) and penicillamine (PEN) with relatively high sensitivity. It is also adaptable to HPLC for pulsed amperometric detection (PAD) of these thiols. PAD largely improves the detection sensitivity because the alternated polarizations can effectively clean and reactivate the electrode surface. It is shown that the peak currents of l-Cys, GSH and PEN are linear to their concentrations, with the calculated detection limit of 1.1 × 10−7, 1.8 × 10−7 and 3.8 × 10−7 mol L−1, respectively (S/N = 3). The method has been successfully applied to assess the contents of l-Cys and GSH in rat striatal microdialysates. The average contents of the two analytes in rat striatum are 2.6 × 10−6 and 2.8 × 10−6 mol L−1, respectively. Copyright © 2004 John Wiley & Sons, Ltd.

An electrochemical method suitable for the simultaneous measurement of cerebral glucose, lactate, L-glutamate and hypoxanthine concentrations from in vivo microdialysis sampling has been successfully performed for the first time using a neutral red-doped silica (NRDS) nanoparticle-derived enzyme sensor system. These uniform NRDS nanoparticles (about 50 +/- 3 nm) were prepared by a water-in-oil (W/O) microemulsion method, and characterized by a TEM technique. The neutral red-doped interior maintained its high electron-activity, while the exterior nano-silica surface prevented the mediator from leaching out into the aqueous solution, and showed high biocompability. These nanoparticles were then mixing with the glucose oxidase (GOD), lactate oxidase (LOD), L-glutamate oxidase (L-GLOD) or xanthine oxidase (XOD), and immobilized on four glassy carbon electrodes, respectively. A thin Nafion film was coated on the enzyme layer to prevent interference from molecules such as ascorbic acid and uric acid in the dialysate. The high sensitivity of the NRDS modified enzyme electrode system enables the simultaneous monitoring of trace levels of glucose, L-glutamate, lactate and hypoxanthine in diluted dialysate samples from a rat striatum.

In this paper, multi-wall carbon nanotubes (MWNTs)/Pt microparticles nanocomposite was prepared by electrodepositing Pt microparticles onto the MWNTs matrix. The surface of glassy carbon electrode was modified with this kind of nanocomposite for measurement of thiols, such as l -cysteine ( l -Cys) and glutathione (GSH). Compared with the MWNTs or Pt microparticles modified electrode, the nanocomposite modified electrode exhibited high sensitivity and good stability for detection of thiols. According to the results of experiments, the peak currents of l -Cys and GSH are linear with their concentrations and the detection limits (S/N = 3) are 2.9 × 10−8 mol/L and 4.5 × 10−8 mol/L, respectively. Coupled with microdialysis, the method has been successfully applied to the determination of these two thiols in rat striatal microdialysates.

A novel method for fabricating a nano array electrode (NAE) by using micropores of aluminium anodic film as templates was investigated. To evaluate the NAE, cyclic scanning of NAE in Fe(CN)63− solution was performed and a sigmoidal shaped voltammogram was obtained. The NAE was designed to measure nitric oxide (NO) in vitro and in vivo. Studies showed that it was a sensitive and selective NO electrochemical sensor. NO release from myocardial cells was directly measured with this NAE and the results were satisfactory.

A Pt microelectrode modified with nickel(II) polytetramethyldibenzo[b,i]tetraaza[14]annulene was prepared by electropolymerization of nickel(II) tetramethyldibenzo[b,i]tetraaza[14]annulene monomers and applied to determine sulfur dioxide in vitriol plant wastewater. For determination of SO2 with this electrochemically modified Pt microelectrode, the linear range was from 9.6 × 10−6 to 2.4 × 10−4 mol L−1, the sensitivity was 1.8 × 10−4 A L mol−1, the detection limit was calculated to be 4.8 × 10−6 mol L−1 (S/N = 3), the response time was less than 20 s and the relative standard deviation was found to be 2.1% on analyzing 4.8 × 10−5 mol L−1 SO2 solution repeatedly (n = 7). These results demonstrated good accuracy compared with those obtained by the conventional iodimetric method.

The research studied the concentration variation of peroxynitrite anion (O=N-O-O-) released from cultured neonatal myocardial cells induced by ischemia/reperfusion and studied the protective effect of melatonin on the injury. For this purpose, amperometry peroxynitrite ultramicrosensors (UMS) were fabricated and constructed by electropolymerizing inorganic macromolecular film of tetraaminophthalocyanine manganese(II) and coating chemically with poly(4-vinylpyridine). Under optimum conditions, the UMS showed high selectivity and sensitivity to peroxynitrite determination with a calculated detection limit of 1.8 x 10(-8) mol/L (S/N of 3). The detection of peroxynitrite was based on electrocatalytic reduction of peroxynitrite. The mechanism of catalysis was also discussed. The UMS should be promising for in vivo measurement of peroxynitrite without interference or fouling. Peroxynitrite released from myocardial cells both in the ischemic period and in the reperfusion period was measured directly. This approach may lead to important information for myocardial cells on the mechanism of injury and prospective treatments of medicine such as melatonin.

Nitric oxide (NO) plays an important role in various physiological processes, acting either as an intra- and intercellular messenger or as a toxic agent. The detection and quantification of NO have been accomplished by a variety of methodologies. In the present study, real-time production of NO in the rat heart was continuously measured by using a novel copper–platinum microparticle-modified NO electrochemical microsensor. The linearity range of the microsensor is between 8.0×10−8 and 4.8×10−6 mol L−1 and the detection limit is 3.0 × 10−8 mol L−1. NO release from the rat heart stimulated by the agonists L-arginine and acetylcholine was observed, and the responses were decreased by the NO synthase inhibitor L-Nω-nitroarginine. In addition, the effect of sodium nitroprusside (SNP), a NO donor, was also studied. SNP increases the concentration of NO in the rat heart. The experiments showed that electrochemical detection is suitable for detecting and quantifying NO in biological systems.

The paper reports on covalent clicking of rhodamine-B (RhB) bearing a terminal azide group to alkyne-terminated silica coated superparamagnetic iron oxide nanoparticlesvia the copper(I)-catalyzed Huisgen azide-alkyne 1,3-dipolar cycloaddition (CuAAC) reaction. The course of the reaction was followed the use of powder X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectroscopy, fluoroscopy, and magnetics. The RhB labelled Fe3O4@SiO2 nanoparticles exhibit stable fluorescence and no detectable leakage of the fluorescent dye because the resulting 1,4-disubstituted 1,2,3-triazole ring formed via click reaction is thermally stable and relatively inert to hydrolysis, oxidation, and reduction. Due to the superparamagnetic property of the Fe3O4 and the RhB molecule covalently decorated in the Fe3O4@SiO2 framework, the nanoparticles are endowed with properties of a contrast agent in magnetic resonance imaging (MRI) and optical imaging modality. The cytotoxicity tests indicate the bifunctional nanoparticles could be applied in biomedical or bioengineering field.

In this paper, catechol, 1,4-dihydroxybenzene and dopamine are investigated as precursors of electrophiles for Michael addition reaction with the self-assembled monolayer (SAM) of 4-thiouracil (4-TU) via electrochemical triggering. All compounds can undergo Michael addition reaction with 4-TU; however, only catechol can react with 4-TU with high efficiency. The catechol-terminated SAMs, via electrochemically triggered Michael addition reaction, exhibit reversible redox response. In addition, we find that catechol-terminated SAMs can complex with Ni(2+) and Cu(2+) with different electrochemical behaviors. Moreover, the mechanism of complexation of Ni(2+)and Cu(2+) with catechol-terminated SAMs is also demonstrated with electrochemical and spectrometric methods. Based on the different electrochemical behaviors of Cu(2+) and Ni(2+) complex, the catechol-terminated SAMs provide a potential platform for metal ions recognition.