A sandwich electrochemical immunosensor for Salmonella pullorum and Salmonella gallinarum based on a screen-printed carbon electrode modified with an ionic liquid and electrodeposited gold nanoparticles

This article describes an electrochemical immunosensor for rapid determination of Salmonella pullorum and Salmonella gallinarum. The first step in the preparation of the immunosensor involves the electrodeposition of gold nanoparticles used for capturing antibody and enhancing signals. In order to generate a benign microenvironment for the antibody, the ionic liquid (IL) 1-butyl-3-methylimidazolium hexafluorophosphate was used to modify the surface of a screen-printed carbon electrode (SPCE). The single steps of modification were monitored via cyclic voltammetry and electrochemical impedance spectroscopy. Based on these findings, a sandwich immunoassay was worked out for the two Salmonella species by immobilizing the respective unlabeled antibodies on the SPCE. Following exposure to the analytes, secondary antibody (labeled with HRP) is added to form the sandwich. After adding hydrogen peroxide and thionine, the latter is oxidized and its signal measured via CV. A linear response to the Salmonella species is obtained in the 10⁴ to 10⁹ cfu · mL⁻¹ concentration range, and the detection limits are 3.0 × 10³ cfu · mL⁻¹ for both species (at an SNR of 3). This assay is sensitive, highly specific, acceptably accurate and reproducible. Given its low detection limit, it represents a promising tool for the detection of S. pullorum, S. gallinarum, and - conceivably - of other food-borne pathogens by exchanging the antibody.

We describe an electrochemical sandwich assay based on a screen-printed carbon electrode, gold nanoparticles and ILs and capable of detecting Salmonella pullorum and Salmonella gallinarum. The preparation is outlined in the Schematic.

     

Multilayer structured immunosensor based on a glassy carbon electrode modified with multi-wall carbon nanotubes, polythionine, and gold nanoparticles

An immunosensor for determination of salbutamol was developed. It based on glass carbon electrode (GCE) modified with a conductive multilayer film comprised of multi-wall carbon nanotubes, polythionine and gold nanoparticles. Salbutamol antibody was immobilized on the surface of the modified GCE which then was blocked with bovine serum albumin (BSA). The stepwise self-assembly process of the immunosensor was studied by cyclic voltammetry. The detection scheme is based on competitive binding of salbutamol to the sensor surface whose differential pulse voltammetric signal decreases after competitive binding of the salbutamol-BSA conjugate and free salbutamol to the salbutamol antibody. The sensor responds to salbutamol in 5 to 150 nM concentration range, with a detection limit of 1 nM. This method was applied to the precise and sensitive determination of salbutamol in spiked feed samples.

A novel lable-free electrochemical immunosensor for carcinoembryonic antigen based on gold nanoparticles-thionine-reduced graphene oxide nanocomposite film modified glassy carbon electrode

In this paper, gold nanoparticle-thionine-reduced graphene oxide (GNP-THi-GR) nanocomposites were prepared to design a label-free immunosensor for the sensitive detection of carcinoembryonic antigen (CEA). The nanocomposites with good biocompatibility, excellent redox electrochemical activity and large surface area were coated onto the glassy carbon electrode (GCE) surface and then CEA antibody (anti-CEA) was immobilized on the electrode to construct the immunosensor. The morphologies and electrochemistry of the formed nanocomposites were investigated by using scanning electron microscopy (SEM), ultraviolet-visible (UV-vis) spectrometry, electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). CV and differential pulse voltammetry (DPV) studies demonstrated that the formation of antibody-antigen complexes decreased the peak current of THi in the GNP-THi-GR nanocomposites. The decreased currents were proportional to the CEA concentration in the range of 10-500 pg/mL with a detection limit of 4 pg/mL. The proposed method was simple, fast and inexpensive for the determination of CEA at very low levels.     

Chronocoulometric DNA biosensor based on a glassy carbon electrode modified with gold nanoparticles, poly(dopamine) and carbon nanotubes

We describe a sensitive chronocoulometric biosensor for the sequence-specific detection of DNA. It is based on a glassy carbon electrode modified with multi-walled carbon nanotubes, polydopamine, and gold nanoparticles. The ruthenium(III)hexammine complex acts as the electrochemical indicator. Electrochemical impedance spectra and scanning electron microscopy are employed to investigate the assembly of the electrode surface. The signals of the ruthenium complex electrostatically bound to the anionic phospho groups of the DNA strands are measured by chronocoulometry before and after hybridization. The difference in signal intensity is linearly related to the logarithm of the concentration of the target DNA in the range of 1.0 nM to 10 fM with a detection limit of 3.5fM (S/N?=?3) under optimal conditions. This biosensor exhibits excellent sensitivity and selectivity and has been used for an assay of complementary target DNA in human serum sample with satisfactory results.

Electrocatalytic oxidation of methanol on carbon ceramic electrode modified by platinum nanoparticles incorporated in poly (o-phenylenediamine) film

Carbon ceramic electrode, a new electrode substrate, was prepared by sol–gel procedure and used for the electropolymerization of o-phenylenediamine and incorporation of platinum nanoparticles into the resulting poly(o-phenylenediamine) (PoPD) film. The modified electrode was used for electrooxidation of methanol in 0.3 M H₂SO₄ as supporting electrolyte. The presence of PoPD film increased considerably the efficiency of deposited Pt nanoparticles toward the electrocatalytic oxidation of methanol. The effective parameters on the electrooxidation of methanol, i.e., amounts of polymer and Pt catalyst, medium temperature, working potential limit in anodic direction, and potential scan rate, were investigated, and the results were discussed.     

Amperometric immunosensing using an indium tin oxide electrode modified with multi-walled carbon nanotube and poly(ethylene glycol)-silane copolymer

We describe a sensitive electrochemical immunosensor that takes advantage of the low background current of an indium tin oxide electrode, the good electrocatalytic properties of multi-walled carbon nanotubes, and the low biofouling properties of poly(ethylene glycol)-silane copolymer.     

Sensing epinephrine with an ITO electrode modified with an imprinted chitosan film containing multi-walled carbon nanotubes and a polymerized ionic liquid

We report on a sensor for epinephrine (EP) that is based on an ITO electrode modified with multi-walled carbon nanotubes pre-coated with a polymerized ionic liquid (PIL-MWNTs). A chitosan film was then electrodeposited on the ITO electrode in the presence of EP (the template) and the PIL-MWNTs. This film acts as an excellent recognition matrix due to its excellent film-forming ability and the many functional groups that favor hydrogen bond formation with the target (EP). The PIL-MWNTs, in turn, can improve the sensing performance due to their good electrical conductivity, high dispersity, and large surface area. The imprinted films were characterized by scanning electron microscopy, X-ray diffraction, Fourier transform IR spectroscopy, and thermogravimetric analysis. The electrochemistry of the imprinted electrode was investigated by cyclic voltammetry, electrochemical impedance spectroscopy, differential pulse voltammetry and chronoamperometry. The response to EP is linear in the 0.2 μM to 0.67 mM concentration range, and the detection limit is as low as 60 nM (at an S/N of 3). The electrode is reusable and offers good reproducibility and stability.

Copper oxide nanoparticles and ionic liquid modified carbon electrode for the non-enzymatic electrochemical sensing of hydrogen peroxide

The direct electrocatalytic reduction of hydrogen peroxide in alkaline medium at a carbon ionic liquid electrode modified with copper oxide nanoparticles was investigated. The electrode was prepared by mixing graphite particles, ionic liquid (n-octylpyridium hexafluorophosphate) and copper oxide nanoparticles. Unlike the film-modified electrode, the fabrication of this electrode is simple and highly reproducible. The combination of the good conductivity of the ionic liquid and the high catalytic activity of the nanoparticles resulted in an electrode with attractive properties for the determination of hydrogen peroxide. The concentration of NaOH and the loading of copper oxide nanoparticles were optimized. The linear range for the determination of hydrogen peroxide is from 1.0 μM to 2.5 mM, the detection limit is 0.5 μM. High stability, sensitivity, selectivity and reproducibility, fast response, the ease of preparation, and surface renewal made the electrode well suitable for the determination of hydrogen peroxide in real samples.     

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.

Label-free amperometric immunobiosensor based on a gold colloid and Prussian blue nanocomposite film modified carbon ionic liquid electrode

A novel experimental methodology based on a Prussian blue (PB) and gold nanoparticles (AuNPs) modified carbon ionic liquid electrode (CILE) was developed for use in a label-free amperometric immunosensor for the sensitive detection of human immunoglobulin G (HIgG) as a model protein. The CILE was fabricated by using the ionic liquid 1-octyl-3-methylimidazolium hexafluorophosphate as binder. Controllable electrodeposition of PB on the surface of the CILE and coating with 3-aminopropyl triethylene silane (APS) formed a film with high electronic catalytic activity and large surface area for the assembly of AuNPs and further immobilization of HIgG antibody. The electrochemistry of the formed nanocomposite biofilm was investigated by electrochemical techniques including cyclic voltammetry, differential pulse voltammetry, and electrochemical impedance spectroscopy. The HIgG concentration was measured through the decrease of amperometric responses in the corresponding specific binding of antigen and antibody. The decreased differential pulse voltammetric values were proportional to the HIgG concentration in two ranges, 0.05–1.25 ng mL⁻¹ and 1.25–40 ng mL⁻¹, with a detection limit of 0.001 ng mL⁻¹ (S/N = 3). This electrochemical immunoassay combined the specificity of the immunological reaction with the sensitivity of the AuNPs, ionic liquid, and PB amplified electrochemical detection and would therefore be valuable for clinical immunoassays.     

Direct electron transfer of cytochrome c and its biosensor based on gold nanoparticles/room temperature ionic liquid/carbon nanotubes composite film

A robust and effective composite film based on gold nanoparticles (GNPs)/room temperature ionic liquid (RTIL)/multi-wall carbon nanotubes (MWNTs) modified glassy carbon (GC) electrode was prepared by a layer-by-layer self-assembly technique. Cytochrome c (Cyt c) was successfully immobilized on the RTIL-nanohybrid film modified GC electrode by electrostatic adsorption. Direct electrochemistry and electrocatalysis of Cyt c were investigated. The results suggested that Cyt c could be tightly adsorbed on the modified electrode. A pair of well-defined quasi-reversible redox peaks of Cyt c was obtained in 0.10 M, pH 7.0 phosphate buffer solution (PBS). RTIL-nanohybrid film showed an obvious promotion for the direct electron transfer between Cyt c and the underlying electrode. The immobilized Cyt c exhibited an excellent electrocatalytic activity towards the reduction of H₂O₂. The catalysis currents increased linearly to the H₂O₂ concentration in a wide range of 5.0 × 10⁻⁵– 1.15 × 10⁻³ M. Based on the multilayer film, the third-generation biosensor could be constructed for the determination of H₂O₂.     

Highly sensitive deoxynivalenol immunosensor based on a glassy carbon electrode modified with a fullerene/ferrocene/ionic liquid composite

We describe a sensitive electrochemical immunosensor for the detection of deoxynivalenol (DON). It is based on a glassy carbon electrode modified with a composite made from fullerene (C₆₀), ferrocene and the ionic liquid. The components were immobilized on the surface of the electrode using chitosan cross-linked with epichlorohydrin. Then, the antibody to DON was covalently conjugated to the surface which then was blocked with serum albumin. The performance of the immunosensor was investigated by cyclic voltammetry and electrochemical impedance spectroscopy. It offers good repeatability (RSD?=?1.2%), selectivity, a stability of more than 180?days, an impedimetric response to DON in the range of 1?pgmL^?1 to 0.3?ng?mL^?1, and a detection limit (at S/N?=?3) of 0.3?pgmL^?1. The limit of detection is better than that of GC, HPLC, GC-MS, HPLC-MS and LC-MS-MS. The effects of omitting C₆₀ or the ionic liquid were also examined. The results indicate that the sensitivity of the biosensor is 2-fold better if C₆₀ and ionic liquids are used. This demonstrates that C₆₀ facilitates electron transfer on the surface of the modified electrode due to its unique electrochemical properties, while the ionic liquid provides a biocompatible microenvironment for the antibody. This results in increased sensitivity and stability. The method was satisfactorily applied to the determination of DON in food samples.

Direct electrodeposition of gold nanoparticles onto indium/tin oxide film coated glass and its application for electrochemical biosensor

A novel electrochemical deposition method for growth of gold nanoparticles (GNPs) on indium tin oxide (ITO) thin film coated glass was investigated. The resulting electrode surface was characterized by SEM, UV–Vis spectroscopy and electrochemical methods. The GNPs directly attached on the electrode surface with a quasi-spherical shape and their sizes of diameters were in the range of 20–35 nm with a quite symmetric distribution. With increasing electrodeposition cycles of cyclic voltammetry, the density of GNPs on ITO electrode surface was increased. The potential utility of the GNPs modified ITO electrode was investigated. Superoxide dismutase (SOD) was successfully immobilized on GNPs modified ITO electrode and the direct electron transfer between enzyme and electrode surface realized. The enzyme electrode exhibited a rapid and high response to superoxide anion.     

Voltammetric myoglobin sensor based on a glassy carbon electrode modified with a composite film consisting of carbon nanotubes and a molecularly imprinted polymerized ionic liquid

The ionic liquid 1-{3-[(2-aminoethyl)amino]propyl}-3-vinylimidazole bromide was synthesized and used to fabricate a molecularly imprinted film for electrochemical sensing of myoglobin (Myo). This film was deposited on a glassy carbon electrode modified with multi-walled carbon nanotubes by using the ionic liquid as the functional monomer, Myo as the template, N,N′-methylenebisacrylamide as the crosslinker, and a redox system containing ammonium persulfate and N,N,N′,N′-tetramethylethylenediamine as the initiator. The sensing performance of the modified electrode was investigated by using the hexacyanoferrate system as an electrochemical redox probe. The results demonstrated that the sensor possesses good selectivity and high sensitivity. The oxidation peak current at the potential of ~0.3 V (vs. SCE) was found linearly related to the myoglobin concentration in the range from 60.0 nM to 6.0 μM, with a 9.7 nM detection limit at an S/N ratio of 3. The sensor was applied to the determination of Myo in spiked serum samples where it showed average recoveries (for n = 5) of 96.5 %.

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Graphical abstract By using a polymerizable ionic liquid as the functional monomer, a myoglobin imprinted polymer was fabricated on a multi-walled carbon nanotube modified glassy carbon electrode. The sensing performances of the molecularly imprinted sensor towards myoglobin demonstrated good selectivity, sensitivity and accuracy.

     

Simultaneous determination of guanosine and guanosine-5'-triphosphate in biological sample using gold nanoparticles modified indium tin oxide electrode

A nanogold modified indium tin oxide (ITO) electrode was used for the simultaneous determination of guanosine and GTP at pH 7.2. The electrode exhibited an effective catalytic response towards their oxidation and lowered the oxidation potential of guanosine by ∼120 mV and GTP by ∼183 mV. Linear concentration curves were obtained for guanosine with a detection limit of 9.8 × 10⁻⁸ M and 5.5 × 10⁻⁸ M for GTP. The concentration of guanosine and GTP were also estimated in the human blood plasma samples using gold nanoparticles modified ITO electrode with good reproducibility.     

Study on an immunosensor based on gold nanoparticles and a nano-calcium carbonate/Prussian blue modified glassy carbon electrode

An amperometric carcinoembryonic antigen (CEA) immunosensor was fabricated based on Prussian blue (PB), nano-calcium carbonate (nano-CaCO₃) and nano-gold modified glassy carbon electrode. First, PB as a mediator was deposited on glassy carbon electrode to obtain a negatively charged surface. Then, positive nano-CaCO₃ was adsorbed on the PB modified electrode through electrostatic interaction. Subsequently, gold nanoparticles were deposited on the nano-CaCO₃/PB modified electrode. The use of two kinds of nanomaterials (nano-CaCO₃ and nano-gold) with good biocompatibility as immobilization matrixes not only provides a biocompatible surface for protein loading but also avoids the leaking of PB. The size of nano-CaCO₃ was characterized by transmission electron microscopy (TEM). The factors influencing the performance of the immunosensor presented were studied in detail. Under the optimized conditions, cyclic voltammograms (CV) determination of CEA showed a specific response in two concentration ranges from 0.3 to 20 ng mL^?1 and from 20 to 100 ng mL^?1 with a detection limit of 0.1 ng mL^?1 at a signal-to-noise ratio of 3. The immunosensor presented exhibited high selectivity, sensitivity and good stability.     

A direct electrochemical biosensing platform constructed by incorporating carbon nanotubes and gold nanoparticles onto redox poly(thionine) film.

A direct electrochemical biosensing platform has been fabricated by covalent incorporation of carbon nanotubes (CNT) and gold nanoparticles (GNP) onto the poly(thionine) (PTH) film deposited by electropolymerization. With the synergic effects of the composite nanomaterials together with the excellent mediating redox polymer, the proposed platform could allow for faster electron transfer and higher enzyme immobilization efficiency than the platforms designed by using CNT or GNP alone. Comparison studies indicated that the as-developed H(2)O(2) sensor could show greatly improved performances of amperometric responses.     

Self-assembly of ultra-small gold nanoparticles on an indium tin oxide electrode for the enzyme-free detection of hydrogen peroxide

A novel enzyme-free electrochemical sensor for H₂O₂ was fabricated by modifying an indium tin oxide (ITO) support with (3-aminopropyl) trimethoxysilane to yield an interface for the assembly of colloidal gold. Gold nanoparticles (AuNPs) were then immobilized on the substrate via self-assembly. Atomic force microscopy showed the presence of a monolayer of well-dispersed AuNPs with an average size of ~4 nm. The electrochemical behavior of the resultant AuNP/ITO-modified electrode and its response to hydrogen peroxide were studied by cyclic voltammetry. This non-enzymatic and mediator-free electrode exhibits a linear response in the range from 3.0?×?10^?5 M to 1.0?×?10^?3 M (M?=?mol?·?L^?1) with a correlation coefficient of 0.999. The limit of detection is as low as 10 nM (for S/N?=?3). The sensor is stable, gives well reproducible results, and is deemed to represent a promising tool for electrochemical sensing.