MIPs-graphene nanoplatelets-MWCNTs modified glassy carbon electrode for the determination of cardiac troponin I.

An electrochemical sensor with high selectivity in addition to sensitivity was developed for the determination of cardiac troponin I (cTnI), based on the modification of cTnI imprinted polymer film on a glassy carbon electrode (GCE). The sensor was fabricated by layer-by-layer assembled graphene nanoplatelets (GS), multiwalled carbon nanotubes (MWCNTs), chitosan (CS), glutaraldehyde (GA) composites, which can increase the electronic transfer rate and the active surface area to capture a larger number of antigenic proteins. MWCNTs/GS based imprinted polymers (MIPs/MWCNTs/GS) were synthesized by means of methacrylic acid (MAA) as the monomer, ethylene glycol dimethacrylate (EGDMA) as the cross linker α,α'-azobisisobutyronitrile (AIBN) as the initiator and cTnI as the template. In comparison with conventional methods, the proposed electrochemical sensor is highly sensitive for cTnI, providing a better linear response range from 0.005 to 60 ng cm-3 and a lower limit of detection (LOD) of 0.0008 ng cm-3 under optimal experimental conditions. In addition, the electrochemical sensor exhibited good specificity, acceptable reproducibility and stability. Moreover, satisfactory results were obtained in real human serum samples, indicating that the developed method has the potential to find application in clinical detection of cTnI as an alternative approach.

Synthesis, characterization, and photocatalytic activities of titanate nanotubes surface-decorated by zinc oxide nanoparticles.

Nanoscaled zinc oxide (ZnO) particles with different amounts are coated on titanate nanotubes (TNTs) by a facile chemical method at room temperature. The characterizations of XPS, TEM, XRD and UV-vis spectra confirm that pure hexagonal wurtzite ZnO nanoparticles with an average size of about 9nm are distributed on the surfaces of TNTs evenly and attached strongly. The photocatalytic activities of the ZnO-TNTs nanocomposite are superior to those of P25, ZnO, TNTs and ZnO-anatase TiO2 (TNP) nanocomposite in the oxidation of rhodamine B under UV light irradiation. A comparison of the photocatalytic activities between different catalysts is discussed. Furthermore, we also find that the ZnO-TNT nanocomposite shows very favorable recycle use potential, because they have a high sedimentation rate and their photocatalytic activity is only slightly decreased even after five times of repeated uses.

Sensitive electrochemical detection of gp120 based on the combination of NBD-556 and gp120.

As is known, the employment of molecular imprinting polymer (MIP) as specific sensing materials in sensors, namely MIP-based sensors. In this contribution, we devised a MIP electrochemical sensor for the detection of variable-format conformations protein gp120. The sensor was constructed by using a grapheme-like carbon nanfragment (CNF) and bismuth oxides composites (CNF-Bi) as decoration material, small-molecule entry inhibitor NBD-556 and gp120 conjugates NBD-556@gp120 instead of gp120 as the template, and pyrrole as an electropolymerization monomer. Cyclic voltammetry, differential pulse voltammetry, scanning electron microscopy and transmission electron microscope were used to characterize the preparation process of the sensor. Results showing that, under optimized conditions, the introduction of NBD-556 make the specific recognition and analytical properties of the MIP sensor towards gp120 more efficient. The response currents were proportional to the NBD-556@gp120 concentrations in the range of 0.0002 ng mL-1 to 200 ng mL-1 with the detection limit of 0.0003 ng mL-1 based on S/N = 3. Meanwhile, the NBD-556@gp120 based MIP sensor also shows acceptable stability and reproducibility. When used for the detection of gp120 in human plasma, it also showed good accuracy. This research idea is in great promising for the early diagnosis of HIV-1 virus and can also be extended to the detection of other conformationally unstable proteins.

[Using Fourier transform to analyse differential optical absorption spectrum].

According to the theory of differential optical absorption spectral technique, the differential optical absorption spectral monitoring equipment was designed. Aiming at two kinds of main pollutants, SO2 and NO2, in the atmosphere, this technique was used to monitor them. The present article puts forward the signal analysis method of Fourier transformation to process the above-mentioned two kinds of absorption spectra. The two approaches contain the removeal of noise and the fitting of the slow variety. On the frequency chart after the spectrum was transformed, the low frequency corresponded to the slow variety part and the high frequency corresponded to the noise part of the original spectrum, so through intercepting a certain frequency segment and using inverse Fourier transformation the slow variety part of the low frequency and the noise part of the high frequency of the absorption spectrum could be subtracted. After farther processing we can get a higher resolution differential absorption spectrum of the gas. According to the strength of the spectrum, we can calculate the concentration of the gas. After analysis and comparison with the conventional method, it is considered a new processing method of differential optical absorption spectral technique, and the method can fit the slow variety much better.

[Using Fourier transform to calculate gas concentration in DOAS].

Being an analysis tool of high sensitivity, high resolution, multicomponents, real-time and fast monitoring, the differential optical absorption spectrometry (DOAS) is becoming a new method in atmosphere pollution monitoring. In the DOAS technique, many gases spectra have periodicity evidently, such as those from SO2, NO, NH3 and NO2. Aiming at three kinds of main air-polluted gases, i.e., SO2, NO and NO2 in atmosphere, the DOAS technique is used to monitor them, and Fourier transform is used to analyse the above-mentioned absorption spectra. Under the condition of Hanning Windows, Fourier transforma is used to process various gases spectra which have periodicity. In the process, the value of the characteristic frequency has a linearity relation to the gas concentration. So a new analysis method of DOAS is proposed, which is utilizing the relation between the value of the characteristic frequency and the gas concentration to deduce a linearity formula to calculate the gas concentration. So the value of the characteristic frequency can be used to get the gas concentration. For the gases with evident spectrum periodicity, such as SO2 and NO, this method is good. But for some gases with periodicity not evident, the error in the calculated concentration is beyond the allowable value. So in this method, the important process is frequency separation. It is also the main part in the future study. In a word, this method frees itself from the basic theory in the DOAS technique, cuts down on the process of the concentration calculation and the spectral analysis, and deserves further study.

A multi-walled carbon nanotubes based molecularly imprinted polymers electrochemical sensor for the sensitive determination of HIV-p24.

To develop a rapid, simple and sensitive method for the determination of human immunodeficiency virus p24 (HIV-p24), a novel molecularly imprinted polymers (MIPs) electrochemical sensor was constructed on the surface of a multi-walled carbon nanotubes (MWCNTs) modified glassy carbon electrode (GCE) by surface polymerization using acrylamide (AAM) as functional monomer, N,N'-methylenebisacrylamide (MBA) as cross-linking agent and ammonium persulphate (APS) as initiator. Each modification step was carefully examined by cyclic voltammetry (CV), differential pulse voltammetry (DPV) and scanning electron microscope (SEM). The proposed MIPs electrochemical biosensor exhibited specific recognition to HIV-p24 and displayed a broad linear detection range from 1.0×10-4 to 2ngcm-3 with a low detection limit of 0.083pgcm-3 (S/N=3). This performance is superior to most HIV-p24 sensors based on other methods. Meanwhile, this sensor possessed of good selectivity, repeatability, reproducibility, stability and was successfully applied for the determination of HIV-p24 in real human serum samples, giving satisfactory results. The accuracy and reliability of the sensor is further confirmed by enzyme-linked immunosorbent assay (ELISA).

An enhanced sensitive electrochemical immunosensor based on efficient encapsulation of enzyme in silica matrix for the detection of human immunodeficiency virus p24.

We report a new electrochemical immunosensor for enhanced sensitive detection of human immunodeficiency virus p24 (HIV-p24) based on graphene oxide (GO) as a nanocarrier and enzyme encapsulated in carbon nanotubes-silica as a matrix in a multienzyme amplification strategy. Greatly enhanced sensitivity was achieved by using the bioconjugates featuring horseradish peroxidase-HIV-p24 signal antibody (HRP-HIV-p24) linked to functionalized GO and thionine (TH) as well as efficient encapsulation of enzyme (HRP) in the silica matrix with retained bioactivity. After a sandwich immunoreactions, the HRP in carbon nanotubes-silica matrix and the HRP-HIV-p24-TH/GO captured onto the electrode surface produced an amplified electrocatalytic response by the reduction of enzymatically oxidized thionine in the presence of hydrogen peroxide. The increase of response current was proportional to the HIV-p24 concentration in the range of 0.5 pg/mL-8.5 ng/mL with the detection limit of 0.15 pg/mL, which was lower than that of the traditional sandwich electrochemical measurement for HIV-p24. The amplified immunoassay developed in this work shows acceptable stability and reproducibility, and the assay results for HIV-p24 spiked in human plasma also show good accuracy. This simple and low-cost immunosensor shows great promise for detection of other proteins and clinical applications.

Electrochemical immunoassay for procalcitonin antigen detection based on signal amplification strategy of multiple nanocomposites.

Procalcitonin, as a medium of inflammation, has become a new marker of the identification of severe bacterial infections in recent years and has received high attention due to its most ideal diagnostic indicators of specificity with major types of organism systemic inflammation of bacterial infection in the early stages. Thus, a novel method for the determination of procalcitonin (PCT) was developed based on a sandwich-type electrochemical immunosensor, which combined a simple immunosensor array as well as an effectively designed trace tag. The immunosensor was fabricated by layer-by-layer coating graphene (GC), carbon nanotubes (MWCNTs), chitosan (CS), glutaraldehyde (GA) composite on the working electrode, which can increase the electronic transfer rate and improve the surface area to capture a large number of primary antibodies (Ab1). The trace tag was prepared by loading high-content signal horseradish peroxidase labeled secondary PCT antibody (HRP-Ab2) with AuNPs, which were coated with mesoporous silica nanoparticles (MCM-41) through thionine linking. In comparison with conventional methods, the proposed immunosensor for PCT provided a better linear response range from 0.01 to 350 ng/mL and a lower limit of detection (LOD) of 0.5 pg/mL under optimal experimental conditions. In addition, the immunosensor exhibited convenience, low cost, rapidity, good specificity, acceptable stability and reproducibility. Moreover, satisfactory results were obtained for the determination of PCT in real human serum samples, indicating that the developed immunoassay has the potential to find application in clinical detection of PCT and other tumor markers as an alternative approach.

Simple approach for ultrasensitive electrochemical immunoassay of Clostridium difficile toxin B detection.

Clostridium difficile toxin B (Tcd B), as one of the primary contributing factors to the pathogenesis of C. difficile-associated diseases, has raised serious public concerns due to its virulence, spore-forming ability and persistence with major types of infectious diarrhea diseases, and been used as a potential biomarker in clinical diagnoses. Thus, a simple method for the determination of Tcd B was developed based on a sandwich-type electrochemical immunosensor. Greatly enhanced sensitivity was achieved based on fabricating the immunosensor by layer-by-layer coating carbon nanotubes (MWCNTs), Prussian blue (PB), Chitosan (CS), Glutaraldehyde (GA) composite on the working electrode as well as using graphene oxide (GO) as a nanocarrier in a multienzyme amplification strategy. In comparison with conventional methods, the proposed immunoassay exhibited high sensitivity and selectivity for the detection of Tcd B, providing a better linear response range from 0.003 to 320 ng/mL and a lower limit of detection (LOD) of 0.7 pg/mL (S/N=3) under optimal experimental conditions. The immunosensor exhibited convenience, low cost, rapidity, good specificity, acceptable stability and reproducibility. Moreover, satisfactory results were obtained for the determination of Tcd B in real human stool samples, indicating that the developed immunoassay has the potential to find application in clinical detection of Tcd B and other tumor markers as an alternative approach.

High-sensitivity C-reactive protein is a strong risk factor for death after acute ischemic stroke among Chinese.

BACKGROUND AND PURPOSE: Elevated plasma C-reactive protein (CRP) has been suggested as a risk factor for ischemic stroke (IS) and coronary ischemic disease. Evidence has shown that high-sensitivity CRP (hs-CRP) is related to a worsening prognosis after IS, but hs-CRP was rare in a large-sample study in a Chinese population. We investigated the associations between hs-CRP and outcome of Chinese patients after acute IS. METHODS: Seven hundred and forty-one consecutive acute IS patients (74.9% male, mean age 60.9 years), with baseline characteristics and hs-CRP measured within 24 h after hospitalization, were admitted in this study. We also prospectively followed up for clinical outcome and death 3 months after disease onset. hs-CRP was divided into two categories: hs-CRP >3 mg/L and hs-CRP ≤3 mg/L. Survival analysis using multivariable Cox regression was performed to analyze the association between hs-CRP and stroke outcomes after adjusting for potential confounding factors. RESULTS: Compared with low hs-CRP, patients with high hs-CRP (>3 mg/L) had a significantly higher rate of all-cause death (0.71% vs. 10.00%; P < 0.001) at 3 months after stroke onset. High hs-CRP was an independent risk factor for all-cause death (HR, 6.48; 95% CI, 1.41 to 29.8; P= 0.016), as well as history of atrial fibrillation (HR, 5.24; 95% CI, 1.83 to 15.0; P= 0.002), no statin therapy during hospitalization (HR, 4.56; 95% CI, 2.18 to 9.55; P < 0.001), high homocysteine (>15.1 mmol/L) (HR, 2.66; 95% CI, 1.26 to 5.60; P= 0.01); fasting glucose (>6.1 mmol/L) (HR, 9.14; 95% CI, 3.34 to 25.0; P < 0.001), NIHSS at admission (HR, 2.35; 95% CI, 1.35 to 4.09; P= 0.003) and history of coronary heart disease (CHD) (HR, 2.34; 95% CI, 1.06 to 5.17; P= 0.035). Kaplan-Meier survival curves showed a higher risk of death for patients with hs-CRP >3 mg/L (P= 0.016). CONCLUSION: Elevated plasma hs-CRP independently predicted risk of all-cause death within 3 months after acute IS in Chinese patients.

Running buffers for determination of chromium(VI)/(III), cobalt(II) and zinc(II) in complex matrices by capillary electrophoresis with contactless conductivity detection.

Complex matrices and rather high acidity in environmental samples are often the impelling challenges for the used running buffers of capillary electrophoresis. Twelve binary acid-base buffers were evaluated for separation of Cr(VI)/Cr(III), Co(2+) and Zn(2+) in a sample containing various salts by capillary electrophoresis with contactless conductivity detector. The malic acid (MA) systems including MA-His (histidine), MA-Arg (arginine) and MA-Tris (tris(hydroxymethyl)aminomethane) were selected as the candidates with powerful separation efficiency and good response sensitivity. In the MA-Tris buffer, optimization were further carried out in terms of the pH value and the concentration of MA, and the optimal conditions were obtained as 6mM MA-Tris and 2mM 18-crown-6 at pH 3.5. Furthermore, a real application was demonstrated by analyzing the plating rinse water (pH 0.8), in which the Ca(2+), Na(+), Cr(VI)/Cr(III), Co(2+) and Zn(2+) were all detected by adjusting at pH 3.5 with 5% (v/v) diluent ammonia. Both the cations, e.g., K(+), Ca(2+), Na(+), Mg(2+), and the common high concentration anions in the sample, e.g., Cl(-), SO(4)(2-) and NO(3)(-) did not cause any disturbance to the concerned analytes.