Amperometric sandwich immunoassay for the carcinoembryonic antigen using a glassy carbon electrode modified with iridium nanoparticles,polydopamine and reduced graphene oxide

The authors describe a sandwich-type electrochemical immunoassay for sensitive determination of the carcinoembryonic antigen (CEA). It is based on the use of iridium nanoparticles (Ir NPs) acting as electrochemical signal amplifier on the surface of a glassy carbon electrode. At first, polydopamine-reduced graphene oxide (PDA-rGO) was employed to immobilize primary antibody (Ab₁) against CEA. Secondly, Ir-NPs were used as a support for the immobilization of secondary antibody (Ab₂) to afford signal labels. The large surface area of PDA-rGO and the excellent electro-oxidative H₂O₂-sensing properties of Ir NPs result in a sensitive assay for CEA. Operated best at a working voltage of ?0.6 V (vs. SCE), the assay has a linear range that extends from 0.5 pg?mL^?1 to 5 ng·mL^?1, and the lower detection limit is 0.23 pg?mL^?1. The immunosensor displays satisfactory reproducibility and stability, thus demonstrating a reliable immunoassay strategy for tumor biomarkers. It was applied to the determination of CEA in spiked serum samples.

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Graphical abstract Schematic of an amperometric sandwich immunoassay for the carcinoembryonic antigen using a glassy carbon electrode modified with polydopamine, reduced graphene oxide and iridium nanoparticles

     

Electrochemical DNA impedance biosensor for the detection of DNA hybridization with polymeric film, single walled carbon nanotubes modified glassy carbon electrode

In this work, we report the fabrication of a sensitive electrochemical DNA impedance biosensor for the detection of sequence-specific target DNA. p-Aminobenzoic acid was first immobilized on the surface of the electrode modified with single walled carbon nanotubes with carboxylic acid groups (SWCNTs) by cyclic voltammetry (CV). A single-stranded DNA probe with a NH₂ group at the end (H₂N-ssDNA) was then covalently immobilized on the surface of polymeric film at room temperature. The impedance measurement was performed in a solution containing 5 mM K₃[Fe(CN)₆]/K₄[Fe(CN)₆]. The change of interfacial charge transfer resistance (R _CT) was confirmed the hybrid formation. The difference of R _CT was linear with the logarithm of complementary oligonucleotides concentrations in the range of 1.0 × 10^?12 to 1.0 × 10^?7 M, with a detection limit of 3.5 × 10^?13 M (S/N = 3).     

Electrochemical immunosensor for prostate-specific antigen using a glassy carbon electrode modified with a nanocomposite containing gold nanoparticles supported with starch-functionalized multi-walled carbon nanotubes

We report on a simple, rapid, and efficient method for the extraction of volatile organic compounds (VOCs; including methanol, tetrahydrofuran, 2-hexanone and benzene) from air and solid samples. The system is based on the use of a laboratory-made syringe as the extractor. The needle of the syringe is placed in a chamber cooled by liquid nitrogen. The tip of the needle is placed in the headspace of a vial containing the sample. The headspace components then are circulated with a pump to pass the needle, and this results in freeze-trapping of the VOCs on the inner surface of the needle. The circulation of the headspace components is continued for 15 min, and the syringe is then removed and placed in a GC injector. The effects of volume of the sample vial, headspace flow rate, temperature and time of extraction and desorption were optimized. The overall time for sampling and analysis is <30 min. The method displays an extraction efficiency of >80%) and a good sample transfer efficiency into the GC column due to the absence of a sorbent inside the needle. No carry-over was observed after 30?s desorption at 260?°C. An external standard method was used for quantitative analysis. The relative standard deviation values are below 10% and the limits of detection range from 1.3 to 4.6?ng?g^?1.

维生素B6在纳米金/石墨烯修饰电极上的电化学行为

将金纳米粒子电沉积在石墨烯修饰的玻碳电极表面,研究了维生素B6(VB6)在该修饰电极上的电化学行为。扫描电镜用于该修饰电极组装过程的形貌表征。实验结果表明:VB6在此修饰电极上出现一个良好的氧化峰,在最佳实验条件下,其氧化峰电流与VB6浓度在5.0×10-8～2.0×10-5 mol/L范围内呈线性关系,其线性回归方程为I(μA)=0.5697c(μmol/L)+0.06275,R=0.9992,检出限为2.0×10-8 mol/L(S/N=3)。一些常见的干扰物质如抗坏血酸不干扰VB6的检测。方法已用于片剂中VB6的含量的检测。     

Electrochemical oxidation and nanomolar detection of acetaminophen at a carbon-ceramic electrode modified by carbon nanotubes: a comparison between multi walled and single walled carbon nanotubes

Carbon-ceramic electrodes (CCE) modified with carbon nanotubes were prepared, and the electrochemical behavior towards acetaminophen (ACOP) was investigated using both a bare CCE and electrodes modified with either single walled carbon nanotubes (SWCNT) or multi walled carbon nanotubes (MWCNT) in an effort to understand which of them is the better choice in terms of electrocatalyzing the oxidation of ACOP, and thus for sensing it. The SWCNT are found to be the better material in significantly enhancing the oxidation peak current and improving the reversibility of the oxidation. Under optimal conditions, linearity between the oxidation peak current and the concentration of ACOP is obtained for the concentration range from 40?nM to 85???M, with a detection limit of 25?nM. Finally, ACOP was successfully determined with the SWCNT modified electrode in pharmaceutical samples.

Impedimetric immunoassay for aflatoxin B1 using a cysteine modified gold electrode with covalently immobilized carbon nanotubes

The authors describe a label-free electrochemical biosensor based on CNTs for picogram range detection of the food carcinogen aflatoxin B1 (AFB1). A gold electrode was modified with a cysteine (Cys) self-assembled layer, and carboxyl-functionalized carbon nanotubes were covalently attached to Cys for the subsequent tethering of antibody against AFB1 (anti-AFB1). Topographical images of the biosensor surface were acquired by atomic force microscopy throughout the modification and assay procedure. Upon exposure to samples containing AFB1, its binding to anti-AFB1 will result in a change in electrical conductivity. The use of CNT warrants enhanced electrical properties, and the charge-transfer resistance (Rct) can be related to the concentration of AFB1. Biosensor selectivity was tested by using samples containing ochratoxin A. The electrode displays a limit of detection as low as 0.79 pg·g^?1, and response is linear in the 0.1 to 20 pg·g^?1 concentration range. The assay was applied to the determination of AFB1 in contaminated corn flour at concentrations so low that they cannot be quantified by established ELISAs. In our perception, this method represents a viable point-of-care probe for detection of AFB1.

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Graphical abstract A gold electrode was modified with a cysteine self-assembled layer, and carboxyl-functionalized carbon nanotubes were covalently attached to cysteine for the subsequent tethering of antibody against AFB1. The assay was applied to the determination of AFB1 in contaminated corn flour.

     

Electrochemiluminescent detection of the hybridization of oligonucleotides using an electrode modified with nanocomposite of carbon nanotubes and gold nanoparticles

We report on an electrochemiluminescent (ECL) sensing technique for the detection of the hybridization between oligonucleotides. A glassy carbon electrode was first functionalized with a composite prepared from gold nanoparticles and carbon nanotubes, and a sensor was then constructed by immobilizing the probing oligonucleotide. The ECL of luminol acts as the sensing signal. It is quenched, to a different degree, by the hybridized double strands of the oligonucleotide depending on the match status. The slope of the ECL response as a function of the status of hybridization drops with increasingly matched hybridization. The response is attributed to the interaction between luminol and the strands of oligomers, and also related to the reduction of reactive oxygen species.

Biosensor for bisphenol A leaching from baby bottles using a glassy carbon electrode modified with DNA and single walled carbon nanotubes

We have developed a biosensor for highly sensitive and selective determination of the endocrinic disruptor bisphenol A (BPA). It is based on glassy carbon electrode modified with calf thymus DNA and a composited prepared from single walled carbon nanotubes (SWNT) and Nafion. The interaction between BPA and DNA was studied by voltammetry. The binding constant was determined to be 3.55?×?10³ M^?1, and the binding site has a length of 4.3 base pairs. These electrochemical studies provide further information for a better understanding of the toxicity and carcinogenicity of BPA. Under optimal conditions, the biosensor displays a linear electrochemical response to BPA in the 10 nM to 20 μM concentration range, with a detection limit as low as 5.0 nM (at an S/N of 3). The method was successfully applied to the quantification of BPA in leachates from plastic baby bottles. Recoveries range from 94.0 % to 106.0 % which underpins the excellent performance of this SWNT-based DNA sensor.

Ultrasensitive determination of hydrazine using a glassy carbon electrode modified with Pyrocatechol Violet electrodeposited on single walled carbon nanotubes

A glassy carbon electrode (GCE) was modified with pyrocatechol violet (PCV) that was electrodeposited on single walled carbon nanotubes (SWCNTs) via continuous cycling between 0 and 0.9 V (vs. SCE). The resulting electrode exhibits excellent electrocatalytic activity towards the oxidation of hydrazine at 0.3 V. The apparent surface coverage of the electrode is at least 24 times higher (2.7?×?10^?10 mol cm^?2) than that obtained with a bare GCE (1.1?×?10^?11 mol cm^?2). This is attributed to a remarkably strong synergistic effect between the acid-pretreated SWCNTs and the electrodeposited PCV coating. Response is fast (2 s) and sensitive (281 mA M^?1 cm^?2). Other features include a wide linear range (150 nM to 0.4 mM) and a low detection limit (150 nM at an SNR of 3). The sensor has been successfully applied to the determination of hydrazine in water and cigarette samples with good accuracy and precision. In addition, the morphology and the wetting properties of the coating were studied by scanning electromicroscopy and contact angle measurements.

Chemical and biochemical sensing with modified single walled carbon nanotubes

The nano dimensions, graphitic surface chemistry and electronic properties of single walled carbon nanotubes make such a material an ideal candidate for chemical or biochemical sensing. Carbon nanotubes can be nondestructively oxidized along their sidewalls or ends and subsequently covalently functionalized with colloidal particles or polyamine dendrimers via carboxylate chemistry. Proteins adsorb individually, strongly and noncovalently along nanotube lengths. These nanotube-protein conjugates are readily characterized at the molecular level by atomic force microscopy. Several metalloproteins and enzymes have been bound on both the sidewalls and termini of single walled carbon nanotubes. Though coupling can be controlled, to a degree, through variation of tube oxidative pre-activation chemistry, careful control experiments and observations made by atomic force microscopy suggest that immobilization is strong, physical and does not require covalent bonding. Importantly, in terms of possible device applications, protein attachment appears to occur with retention of native biological structure. Nanotube electrodes exhibit useful voltammetric properties with direct electrical communication possible between a redox-active biomolecule and the delocalized pi system of its carbon nanotube support.     

Immunoassay for netrin 1 via a glassy carbon electrode modified with multi-walled carbon nanotubes,thionine and gold nanoparticles

We describe a nanostructured immunosensor for the cardiovascular biomarker netrin 1. A glassy carbon electrode was consecutively modified with multi-walled carbon nanotubes (MWCNTs), nafion (to retain the MWCNTs), thionine-coated gold nanoparticles (Thi@AuNPs), and monoclonal antibodies against netrin 1. The modified electrode was characterized by transmission electron microscopy, cyclic voltammetry, differential pulse voltammetry, UV-visible spectrophotometry and X-ray diffraction. The presence of Thi@AuNPs warrants direct and convenient immobilization of the antibody. This immunoelectrode enables netrin 1 to be determined, best at a voltage of −300 mV (vs. SCE), with a limit of detection of 30 fg mL⁻¹ (at an S/N ratio of 3) after a 50 min incubation time. The detection range extends from 0.09 to 1800 pg∙mL⁻¹. The method is simple, sensitive, specific and reproducible. We presume this stable and reproducible biosensor to be useful for the early detection of cardiovascular diseases.

A high sensitivity immunoassay was developed for the detection of netrin 1 based on multi-walled carbon nanotubes, thionine and gold nanoparticles. Its excellent performance is ascribed to the good conductivity of MWCNTs and the combination of materials.

     

Ultrasensitive electrochemiluminescent immunoassay for morphine using a gold electrode modified with CdS quantum dots, polyamidoamine, and gold nanoparticles

We report on a novel electrochemiluminescent (ECL) immunoassay for the ultrasensitive determination of morphine by making use of a gold electrode which was modified with a nanocomposite film containing self-assembled polyamidoamine (PAMAM) CdS quantum dots and electrodeposited gold nanoparticles (Au-NPs). The highly uniform and well-dispersed quantum dots were capped with PAMAM dendrimers. Due to the synergistic effect of the modified quantum dots and the electrodeposited Au-NPs, the ECL response is dramatically enhanced. Under optimal experimental conditions, the immunoreaction between morphine and anti-morphine antibody resulted in a decrease of the ECL signal because of steric hindrance. The calibration plot is linear in the morphine concentration range from 0.2 to 180 ng?mL^?1, with a detection limit as low as 67 pg?mL^?1. The sensor was successfully applied to the determination of morphine in blood plasma. This kind of assay is expected to pave new avenues in label-free drug assays.

Electrochemical behavior of adriamycin at an electrode modified with silver nanoparticles and multi-walled carbon nanotubes, and its application

An electrochemical sensor has been constructed for the determination of adriamycin (ADM) that is based on a glassy carbon electrode modified with silver nanoparticles and multi-walled carbon nanotubes with carboxy groups. The modified electrode was characterized by scanning electron microscopy and exhibits a large enhancement of the differential pulse voltammetric response to ADM. Signals are linear with the concentrations of ADM in the range from 8.2?×?10^?9 M to 19.0?×?10^?9 M, with a detection limit of 1.7?×?10^?9 M. The sensor is highly reproducible and exhibits excellent stability. It was to detect calf thymus DNA.     

Sensing Lorazepam with a glassy carbon electrode coated with an electropolymerized-imprinted polymer modified with multiwalled carbon nanotubes and gold nanoparticles

We report on an electrode for the amperometric determination of lorazepam. A glassy carbon electrode was coated with a molecular imprint made by electropolymerization of ortho-phenylenediamine and filled with multiwalled carbon nanotubes and gold nanoparticles, which enhances the transmission of electrons. The sensor was studied with respect to its response to hexacyanoferrate (III) as a probe and by electrochemical impedance spectroscopy, cyclic voltammetry and square wave voltammetry. The linear response range to Lorazepam is from 0.5 nM to 1.0 nM and from 1.0 nM to 10.0 nM, with a detection limit of 0.2 nM (at an S/N of 3). The electrode was successfully applied to determine Lorazepam in spiked human serum.

Electrochemiluminescence based determination of micro-RNA using target-guided assembly of gold nanoparticles on an electrode modified with Nafion,carbon nanotubes and polyvinylpyrrolidone

Microchimica Acta - The authors describe a sensing interface that is capable of selectively adsorbing gold nanopartices (AuNPs). It was applied to electrochemiluminescent (ECL) detection of...     

Electrochemical behavior and voltammetric determination of norfloxacin at glassy carbon electrode modified with multi walled carbon nanotubes/Nafion

A simple and rapid electrochemical method is developed for the determination of trace-level norfloxacin, based on the excellent properties of multi-walled carbon nanotubes (MWCNTs). The MWCNTs/Nafion film-coated glassy carbon electrode (GCE) is constructed and the electrochemical behavior of norfloxacin at the electrode is investigated in detail. The results indicate that MWCNTs modified glassy carbon electrode exhibited efficiently electrocatalytic oxidation for norfloxacin (NFX) with relatively high sensitivity, stability and life time. Under conditions of cyclic voltammetry, the current for oxidation of selected analyte is enhanced significantly in comparison to the bare GCE. The electrocatalytic behavior is further exploited as a sensitive detection scheme for the analyte determinations by linear sweep voltammetry (LSV). Under optimized condition in voltammetric method the concentration calibration range and detection limit (S/N=3) are 0.1-100 micromol/L and 5 x 10(-8)mol/L for NFX. The proposed method was successfully applied to NFX determination in tablets. The analytical performance of this sensor has been evaluated for detection of the analyte in urine as a real sample.