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Accurately delivering antisense oligonucleotides (ASOs) to tumor cells for gene therapy poses a significant challenge. To address this issue, we develop a NIR light-activable DNA nanodevice to target survivin mRNA and simultaneously release ASOs in tumor cells, which allows high-precision spatiotemporal imaging with high sensitivity and efficient gene therapy. The concept is based on upconversion nanoparticles, which can convert NIR light into UV emissions to activate an entropy-driven DNA walking system that further determines mRNA in tumor cells. The intramolecular toehold-mediated entropy-driven catalytic reaction generates a large amount of Bcl-2 ASOs, which allows accurate delivery of ASOs for gene therapy due to the specific targeting of mRNA in tumor cells. Both in vitro and in vivo results show that the NIR light induced-DNA nanodevice can detect mRNA with high sensitivity by DNA walking amplification system and high precision in gene delivery. Moreover, the released ASOs from DNA walking system deregulate the expression of Bcl-2 anti-apoptosis protein and induce tumor cell apoptosis, thereby suppressing tumor growth without a transfection reagent. The NIR-light-controlled DNA nanodevice holds great potential for precise gene therapy in clinical applications.

As two main types of liquid biopsy markers, both circulating tumor cells (CTCs) and small extracellular vesicles (sEVs) play important roles in the diagnosis and prognosis of cancers. CTCs are malignant cells that detach from the original tumor tissue and enter the circulation of body fluids. sEVs are nanoscale vesicles secreted by normal cells or pathological cells. However, CTCs and sEVs in body fluids are scarce, leading to great difficulties in the accurate analysis of related diseases. For the sensitive detection of CTCs and sEVs in body fluids, various types of nucleic acid and nanomaterial-assisted signal amplification strategies have been developed. In this review, we summarize the recent advances in fluorescent detection of CTCs and sEVs in liquid biopsy based on nucleic acid and nanomaterial-assisted signal amplification strategies. We also discuss their advantages, challenges, and future prospects.

Herein, a ratiometric fluorescent method was developed for alkaline phosphatase (ALP) detection based on near-infrared (NIR) Ag2S quantum dots (QDs) and calcein through the competitive approach. The system based on Ag2S QDs and calcein shows green (maximum emission at 512 nm from calcein) and near infrared (NIR) fluorescence (maximum 798 nm from Ag2S QDs) under the same excitation wavelength (468 nm). In the presence of Ce3+, the fluorescence intensity of calcein is decreased due to static quenching, while the fluorescence intensity of Ag2S QDs is enhanced through aggregation induced emission (AIE). The p-nitrophenyl phosphate is hydrolyzed by ALP, and the yield phosphate ions bind with Ce3+ with higher affinity than these of Ag2S QDs and calcein. Therefore, the green fluorescence from calcein is recovered while NIR fluorescence from Ag2S QDs is decreased. On the basis of these findings, a ratiometric fluorescence assay was developed for the measurement of ALP activity. The ratio of fluorescence intensity at 512 and 798 nm (F512/F798) was well associated with the ALP concentration ranging from 2 to 100 mU/mL with the detection limit of 1.28 mU/mL. The method was successfully applied for detecting ALP in human serum with an acceptable recovery and bioimaging intracellular ALP with good performance. In addition, the approach was also employed for the screening ALP inhibitor.

Elevated hydrogen sulfide (H2S) level is closely associated with various diseases. So the sensing of H2S is noteworthy for divulging its role in diagnosing these diseases. Herein, we proposed poly(acrylic acid)-modified upconversion nanoparticles assembled with cationic near-infrared cyanine chromophores (Cy7-Cl) as the nanoprobe (Cy7-UCNPs) for monitoring H2S based on thiolation reactions. The presence of H2S resulted into about five-fold enhancement in the luminescence intensity of Cy7-UCNPs and the nanoprobe showed a good linearity (R2 =0.9952) over the range of 1.0 − 90 μM. Furthermore, Cy7-UCNPs were successfully employed in sensing and imaging of exogenous and endogenous H2S in live cells and zebrafish. The system shows great potential in the field of nanobiomedicine because of the many excellent properties including high sensitivity, good selectivity, and low cytotoxicity.

An efficient near-infrared fluorescence probe has been developed for the sequential detection of Cu2+, pyrophosphate (P2O74-, PPi), and alkaline phosphatase (ALP), which is based on the "off-on-off" fluorescence switch of branched polyethyleneimine (PEI)-capped NaGdF4:Yb/Tm upconversion nanoparticles (UCNPs). The fluorescence is quenched via energy transfer from UCNPs to Cu2+ for the coordination of PEI with Cu2+. The strong affinity between Cu2+ and PPi leads to the formation of Cu2+-PPi complex and results in the detachment of Cu2+ from the surface of UCNPs, thus the fluorescence is triggered on. ALP-directed hydrolysis of PPi causes the disassembly of Cu2+-PPi complex and re-conjugation between Cu2+ with PEI, which leads to the switch-off fluorescence of UCNPs. The system allows sequential analysis of Cu2+, PPi, and ALP by modulating the switch of the fluorescence of UCNPs with detection limits of 57.8nM, 184nM, and 0.019U/mL for Cu2+, PPi, and ALP, respectively. By virtue of the NIR feature and excellent biocompatibility, the UCNPs-based probes are suitable for bioimaging. Taking Cu2+ visualization as a model, the nanoprobes have been successfully applied for intracellular imaging of Cu2+ in living cells.

Herein, a ratiometric fluorescent method was developed for alkaline phosphatase (ALP) detection based on near-infrared (NIR) Ag

Elevated hydrogen sulfide (H

Reduced graphene oxide (rGO) nanosheets decorated with tunable magnetic nanoparticles (MNPs) were synthesized by a simple co-precipitation method and employed for recyclable removal of bisphenol A (BPA) from aqueous solution. The morphological characterization shows that Fe3O4 nanoparticles are uniformly deposited on rGO sheets. The magnetic characterization demonstrates that composites with various amounts of Fe3O4 nanoparticles are superparamagnetic. Due to the superparamagnetism, rGO-MNPs were used as recyclable adsorbents for BPA removal in aqueous solution. The kinetics of the adsorption process and the adsorption isotherm were investigated. The results indicate that the adsorption process is fitted to Langmuir model and the composites with lower density of MNPs represent better adsorption ability. In addition, its kinetics follows pseudo-second-order rate equation. Moreover, the adsorbents could be recovered conveniently by magnetic separation and recyclable used because of the easy desorption of BPA.

An efficient near-infrared fluorescence probe has been developed for the sequential detection of Cu

In this paper, a simple, facile and general strategy was proposed for the covalent biofunctionalization of Au surface with hemoglobin (Hb). Structurally well-defined azide-terminated organic self-assembled monolayers (SAMs) were formed on Au surface from a mixture solution of azidoundecanethiol and dilute thiol. 4-Pentynoic acid was used as a bifunctional linker to immobilized Hb via a selective, reliable, robust click reaction and a widely used carbodiimide reaction. The surface modification was characterized by reflectance absorption infrared (RAIR) spectroscopy, electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). The experimental data indicate that the proposed methodology is a highly versatile strategy for quantitative, stable and covalent attachment of biomacromolecules onto solid interface. The Hb functionalized Au electrode shows a pair of well-defined and quasi-reversible peaks at about -0.210 V (vs. SCE) in 0.1 mol/L pH 5.0 buffers, which stands for the reduction and oxidation of Hb Fe(III)/Fe(II) redox couple. The electron transfer rate constant (k(s)) was estimated to be 0.78 s(-1). The maximal surface coverage (Gamma) of the immobilized Hb was 8.3 x 10(-12) mol cm(-2), indicating the formation of a monolayer. Moreover, the biocatalytic activity of the Hb biofunctonalized electrode was investigated and an excellent electrocatalytic reduction toward O(2) and H(2)O(2) was observed.

ZnO nanorods/Au hybrid nanocomposites (ZnO/Au) with Au nanocrystals growing on the surface of ZnO nanorods were synthesized via a simple and facile hydrothermal route. The prepared ZnO/Au nanocomposites were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) and transmission electron microscopy (TEM) for the morphology study. The composites had a good electron transferring and biocompatibility. The glucose biosensor was fabricated by entrapping glucose oxidase (GOx) in this composite matrix using cross-linking method with glutaraldehyde and Nafion solutions. The proposed biosensor responded to glucose linearly over concentration range of 0.1–33.0 μM (R2 = 0.9956), and the detection limit was 10 nM (S/N = 3) at an operating potential of +0.55 V in pH 7.4 phosphate buffered solution (PBS). The biosensor exhibited a high and reproducible sensitivity, short response time (within 5 s), good storage stability and high affinity to GOx ( K M app = 0.41 mM ) . The effects of electroactive interferents at the testing conditions can be negligible which showed a good selectivity of the biosensor. It is estimated that this ZnO/Au is an attractive material for the fabrication of efficient amperometric biosensors.

The “click” chemistry, Cu(I)-catalyzed azide–alkyne cycloaddition reaction, was applied to covalently functionalize the poly(3,4-ethylenedioxythiophene) (PEDOT) conducting polymer film with an excellent electron transfer mediator (ferrocene). Scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), and Raman spectroscopy were used to characterize the ferrocene-grafted PEDOT conducting polymer film, and it was proved that the grafting procedure via click reaction had a high efficiency. The ferrocene groups covalently grafted in the polymer films turned out to own a relatively fast electron transfer rate and show multi-color states via adjusting applied potential. Keywords: Click reaction, Ferrocene, Conducting polymer, Electrochemistry, Electrochromic property

In this paper, we described a simple and facile method for the covalent functionalization of Au surface with nitrophenyl group via stepwise strategy. Structurally well-defined azide-terminated organic self-assembled monolayers (SAMs) were formed on Au surface from a commercially available mixture solution of azidoundecanethiol and dilute thiol. Subsequent, derivatization of the azide-terminated monolayers was conducted in aqueous environments with ethynyl nitrobenzene via a selective, reliable, robust click reaction. By this way, the nitrophenyl group was covalently and quantitatively grafted on Au surface, which was confirmed by Raman Spectrometry and electrochemical methods. These results demonstrated the efficiency of using click chemistry in assembling covalently linked nanostructures. Keywords: Click reaction, Covalent grafting, Self-assembled monolayers, Nitrophenyl group, Azidoundecanethiol

A novel method for the oxidative determination of trace arsenic(III) was investigated on highly ordered platinum-nanotube array electrodes (PtNTAEs). The PtNTAEs with a highly organized structure were fabricated by electrochemical deposition of platinum in a 3-aminopropyltrimethoxysilane-modified porous anodic alumina template (PAA). The morphologies and structures of PtNTAEs were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). Electrochemical experiments proved that the PtNTAEs exhibited better performance for As(III) analysis in comparison with platinum nanoparticles-coated GCE (Ptnano/GCE) or Pt foil electrode. The PtNTAEs showed to provide higher reproducibility and lower detection limit. The relative standard deviation (RSD) was 3.5% for 50 repeated measurements of 20 μM As(III), and the limit of detection (LOD) was 0.1 ppb, which was typically 1–2 orders of magnitude lower than that of Ptnano/GCE or Pt foil electrode. Keywords: Highly ordered platinum-nanotube array, Arsenic, Voltammetry, Porous anodic alumina template, Heavy metals

Gold nanoparticles/carbon nanotubes (Au-NPs/CNTs) composites were rapidly synthesized by microwave radiation, and firstly applied for the determination of trace mercury(II) by anodic stripping voltammetry (ASV). The structure and composition of the synthesized Au-NPs/CNTs nanocomposites were characterized by transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDX), UV–vis absorption spectroscopy and cyclic voltammetry. Au-NPs/CNTs nanocomposites modified glassy carbon electrode (Au-NPs/CNTs/GCE) exhibited excellent performance for Hg(II) analysis. A wide linear range (5 × 10−10–1.25 × 10−6 mol/L) and good repeatability (relative standard deviation of 1.84%) were obtained for Hg(II) detection. The limit of detection was found to be 3 × 10−10 mol/L (0.06 μg/L) at 2 min accumulation, while the World Health Organization’s guideline value of mercury for drinking water is 1 μg/L, suggesting the proposed method may have practical utility. Keywords: Microwave-irradiated synthesis, Gold nanoparticles, Carbon nanotubes, Voltammetry, Mercury

Platinum nanoparticles/carbon nanotubes (Ptnano/CNTs) were rapidly synthesized by microwave radiation, and applied for the oxidative determination of arsenic(III). The transmission electron microscopy (TEM) revealed the size of synthesized Pt nanoparticles with nominal diameter of 15 ± 3 nm. Ptnano/CNTs modified glassy carbon electrode (Ptnano/CNTs/GCE) exhibited better performance for arsenic(III) analysis than that of Pt nanoparticles modified GCE (Ptnano/GCE) by electrochemical deposition or Pt foil electrode. Excellent reproducibility of the Ptnano/CNTs/GCE was obtained with the relative standard deviation (RSD) of 3.5% at 20 repeated analysis of 40 μM As(III), while the RSD was 9.8% for Ptnano/GCE under the same conditions. The limit of determination (LOD) of the Ptnano/CNTs/GCE was 0.12 ppb, which was 1–2 orders of magnitude lower than that of Ptnano/GCE or Pt foil electrode. Keywords: Microwave-irradiated synthesis, Platinum nanoparticles, Voltammetry, Carbon nanotubes, Arsenic

A novel method based on electric field directed layer-by-layer assembly (EFDLA) and template synthesis is successfully developed to fabricate horseradish peroxidase (HRP) nanotubes. It provides a rapid and general strategy for functional protein nanoarrays. The alternative deposition of poly(diallyldimethylammonium chloride) (PDDA) and HRP are characterized by SEM, TEM, UV–vis and electrochemical impedance spectroscopy (EIS). Moreover, the UV–vis spectrometry and electrochemistry of HRP indicate that immobilization of PDDA/HRP via EFDLA coupled with template synthesis could retain the conformations and bioactivities of HRP. Keywords: Horseradish peroxidase, Nanotubes, Layer-by-layer assembly, Anodic aluminum oxide, Direct electrochemistry

Porous sol–gel (PSG) film has been utilized as a template for the electrochemical polymerization of aniline in presence of poly(acrylic acid) (PAA). The presence of electroactive polyaniline (PAn)/PAA within the porous skeleton of the sol–gel films has been confirmed using cyclic voltammetry, UV–vis spectrometry and atomic force microscopic measurements. The densities and the sizes of the nanoelectrodes can be controlled easily using electrochemical methods. The conductive polymer “wires” of PAn/PAA formation in PSG matrix can behave as an ensemble of closely-spaced but isolated nanoelectrodes. Moreover, the nanoelectrode ensembles based on conductive PAn/PAA for glucose biosensing are fabricated by immobilization of glucose oxidase (GOx) and Nafion onto the surface of conductive polymer. Owing to the biocompatibility of PSG and electro-activity of PAn/PAA at neutral pH regions, the glucose biosensor shows excellent characteristics and performance, such as low detection limit and fast response time. Keywords: Nanoelectrode ensembles, Polyaniline/poly(acrylic acid), Porous sol–gel film, Template synthesis, Glucose biosensor

A new method for determining chemical oxygen demand (COD) value in water using ion chromatography coupled with nano TiO2-K2S2O8 co-existing system was described. The photocatalytic oxidation system and nano TiO2-K2S2O8 co-existing system could degrade the organic compounds in water. All sulfur-containing species in the reactive solution were eventually transformed to sulfate which could be determined by conductivity detector in ion chromatography. The change of conductivity of sulfate was proportional to COD value. The optimal experimental conditions and the mechanism of the detection were discussed. The application range was 10.0–300.0 mg·L−1 and the lowest limit of detection was 3.5 mg·L−1. It was considered that the value obtained could be reliably correlated with the COD value obtained using the conventional methods.

The encapsulation of hemoglobin (Hb) on the mesoporous silicas SBA-15 and Au-doped SBA-15 (Au-SBA-15) has been studied as a model protein adsorption system. The influences of solution pH, structure of mesoporous silicas and gold nanoparticles incorporation on Hb immobilization are investigated in detail. The spectral characteristics of Hb/SBA-15 and Hb/Au-SBA-15 nanoconjugate show an absorption curve quite similar to that of native Hb, indicating that Hb retains its higher-order structure in the mesopores of SBA-15. Direct electrochemistry of Hb is obtained when Hb is adsorpted by mesoporous silicas SBA-15 or Au-SBA-15. Moreover, Hb/Au-SBA-15 exerts enhancing electron transfer ability because of the Au incorporation. Additionally, the Hb/Au-SBA-15 displays good electrocatalytic reduction of hydrogen peroxide with a detection limit of 1.0 μM, about 3 times as low as that for the Hb/SBA-15. The Hb/Au-SBA-15 exhibits higher peroxidase-like activity with the apparent Michaelis–Menton constant (Km) of 2.87 mM, significantly lower than the 7.78 mM value for the Hb/SBA-15. Keywords: SBA-15, Au-SBA-15, Hemoglobin, Direct chemistry, Hydrogen peroxide

In this work, the colloid of Au nanoparticles (AuNPs)/reduced graphene oxide (rGO) was synthesized by growth AuNPs on rGO via the reduction of HAuCl 4 on graphene oxide (GO) nanosheets. The nanoarchitecture of the colloid could be controllably regulated through in-situ Pb 2+ -enhanced gold leaching reaction, which made the colloid be a flexible surface-enhanced Raman scattering (SERS) platform for Pb 2+ detection. Upon the addition of Pb 2+ , the Raman signal of graphene underwent significant descent due to the decrease of the amount of the “hot spots”, which was originated from Pb 2+ -accelerated dissolution of AuNPs on the graphene surface in the present of thiosulfate (S 2 O 3 2− ). Based on the change of SERS signal through in situ regulation the nanoarchitecture of the colloid, a sensitive and selective strategy for Pb 2+ measurement was developed with a linear range from 5 nM to 4 μM as well as a low detection limit of 1 nM. Furthermore, the SERS-based method was applied for the determination of Pb 2+ in water samples with satisfactory results.

In this paper, we report a novel glucose biosensor based on composite of Au nanoparticles (NPs)–conductive polyaniline (PANI) nanofibers. Immobilized with glucose oxidase (GOx) and Nafion on the surface of nanocomposite, a sensitive and selective biosensor for glucose was successfully developed by electrochemical oxidation of H 2 O 2 . The glucose biosensor shows a linear calibration curve over the range from 1.0 × 10 −6 to 8.0 × 10 −4 mol/L, with a slope and detection limit (S/N = 3) of 2.3 mA/M and 5.0 × 10 −7 M, respectively. In addition, the glucose biosensor system indicates excellent reproducibility (less than 5% R.S.D.) and good operational stability (over 2 weeks).

A novel reagentless amperometric uric acid biosensor based on functionalized multi-wall carbon nanotubes (MWCNTs) with tin oxide (SnO2) nanoparticles has been developed. This was successfully applied to assay uric acid levels from an in vivo microdialysis sampling. Compared with unfunctionalized or traditional carboxylic acid (-COOH)-functionalized MWCNTs, the MWCNTs-SnO2 electrode exhibited higher electrocatalytic oxidation to uric acid. Here, MWCNTs-SnO2 may act as an efficient promoter, and the system exhibited a linear dependence on the uric acid concentration over the range from 1.0 x 10(-7) to 5.0 x 10(-4) mol L(-1). In addition, there was little ascorbic acid interference. The high sensitivity of the MWCNTs-SnO2 modified enzyme electrode enabled the monitoring of trace levels of uric acid in dialysate samples in rat striatum.

A novel method for fabricating a nanoarray electrode combining the template technique with the self-assembled approach was developed. The glassy carbon electrode was modified with the Au nanoarray using micropores of aluminum anodic film as template. Then, the Au nanoarray electrode was self-assembled with l-cysteine (l-Cys) and gold colloid, respectively. In order to evaluate the electrochemical characteristics of l-Cys–Au colloid self-assembled nanoarray electrode, Fe(CN)63- was chosen as molecule probe and cyclic voltammetry was used. In addition, the functional nanoarray electrode was applied to measuring dopamine (DA). The resulting l-Cys–Au colloid self-assembled nanoarray electrode demonstrated that the linear calibration range extended over three orders of magnitude of DA concentrations (1.0 × 10−9–1.0 × 10−6 mol/L) and the detection limit was 5.0 × 10−10 mol/L. Keywords: Nanoarray electrode, Aluminium anodic oxide film, Self-assemble, l-Cysteine, Gold colloid, Dopamine

This paper summarizes the results of a degradation test of bromopyrogallol red (BPR) and textile dye wastewater (TDW) with a conventional three-electrode potentiostatic system in the presence of cobalt ions (electro Co 2+ –H 2 O 2 system). H 2 O 2 , produced by the two-electron reduction of O 2 at the cathode, would react with Co 2+ ions, leading to the generation of hydroxyl radicals ( OH), which caused the degradation of the organic pollutants. With BPR degradation process as the reference point, the optimal conditions (pH=4.0 and the concentration of Co 2+ is 0.1 mM) and the treating capacity of the system were both studied and compared with electro-Fenton’s reagent. Many benefits were shown by the electro Co 2+ –H 2 O 2 system, such as less metal ions consumption, more moderate conditions and faster reaction process. Treated with the system for 0.5 h, chemical oxygen demand and biological oxygen demand of TDW (pH=5.2), without pH adjustment, were reduced by 95.7% and 92.7%, respectively. These characteristics make the method another appropriate solution for wastewater treatment, especially for those contaminated by organic pollutants.

Horseradish peroxidase (HRP) was successfully immobilized on vertically oriented TiO 2 nanotube arrays (NTAs), which was prepared by a seeded-growth mechanism. The nanotubular structure of TiO 2 was characterized by scanning electron microscope (SEM). After encapsulated HRP on TiO 2 nanotube arrays, the direct electron transfer of HRP was observed. Owing to the redox reaction of electroactive center of HRP, the HRP/TiO 2 NTAs modified electrode exhibited a pair of quasi-reversible peaks with the peak-to-peak separation of 70 mV and the formal potential of −0.122 V (vs. SCE) in 0.2 mol L −1 phosphate buffer solution (PBS, pH 7.0). The number of transference electron was 0.84 and the direct electron transfer (ET) constant ( k s ) was 3.82 s −1 . The HRP/TiO 2 NTAs modified electrode displayed an excellent electrocatalytic performance for H 2 O 2 and the formal Michaelis–Menten constant ( K m app ) was 1.9 mmol L −1 . The response currents had a good linear relation with the concentration of H 2 O 2 from 5.0 × 10 −7 mol L −1 to 1.0 × 10 −5 mol L −1 and 5.0 × 10 −5 mol L −1 to 1.0 × 10 −3 mol L −1 , respectively.

In this paper, we propose a strategy to form nanoelectrode arrays by electrochemical deposition of the Prussian blue (PB) through highly ordered porous anodic alumina (PAA) membrane. The structure and morphology of the nanoarrays were characterized by scanning electron microscopy (SEM). As the highly ordered PB arrays can behave as an ensemble of closely spaced but isolated nanoelectrodes, the nanostructured PB arrays are successfully applied to improve the analytical performances of glucose by electrocatalytic reduction enzymatically liberated H 2 O 2 . The resulting PB based nanoelectrode arrays show a wide linear calibration range over three orders of magnitude of glucose concentrations (5.0 × 10 −6 to 8.0 × 10 −3 M) and a low detection limit of 1 μM. Moreover, the biosensor exhibits other good characteristics, such as short response time, high selectivity, excellent operation stability. In addition, effects of the glucose oxidase (GOx) loading, applied potential and pH on the biosensor performance were also discussed.

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.

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.