Interfacial galvanic replacement strategy for Pd-doped NiFe MOF nanosheets with highly efficient dopamine detection.

An interfacial galvanic replacement strategy to controllable synthesize palladium nanoparticles (Pd NPs)-modified NiFe MOF nanocomposite on nickel foam, which served as an efficient sensing platform for quantitative determination of dopamine (DA). Pd NPs grown in situ on the nanosheets of NiFe MOF via self-driven galvanic replacement reaction (GRR) and well uniform distribution was achieved. This method effectively reduced the aggregation of metallic nanoparticles and significantly promoted the electron transfer rate during the electrochemical process, leading to improved electrocatalytic activity for DA oxidation. Remarkably, the precisely constructed biosensor achieved a low detection limit (LOD) of 0.068 µM and recovery of 94.1% (RSD 6.7%, N = 3) for simulated real sample detection and also exhibited superior selectivity and stability. The results confirmed that the as-fabricated Pd-NiFe/NF composite electrode could realize the quantitative determination of DA and showed promising prospects in real sample biosensing.

Synthesis of porous Co3S4 for enhanced voltammetric nonenzymatic determination of glucose.

Porous Co3S4 was synthesized by a two-step hydrothermal method, and its morphology and structure were characterized by transmission electron microscopy and X-ray diffraction. Electrochemical investigations showed that a glassy carbon electrode modified with Co3S4 exhibits high electrocatalytic activity toward glucose in 0.2 M NaOH solution. Figures of merit for this sensor include (i) a wide linear range (2.0 µM to 1.1 mM), (ii) a working potential near 0.52 V (vs. Ag/AgCl), (iii) high sensitivity (346.7 µA mM-1 cm-2), and (iv) a 0.17 µM detection limit. Graphical abstractPorous Co3S4 was explored as electrocatalyst for glucose oxidation. It exhibits distinctly higher electrocatalytic activity toward glucose oxidation than Co3O4.

Wide electrochemical window of screen-printed electrode for determination of rapamycin using ionic liquid/graphene composites.

A disposable screen-printed carbon electrode (SPCE) modified with an ionic liquid/graphene composite (IL/G) exhibits a wider potential window, excellent conductivity, and specific surface area for the improvement in the voltammetric signal of rapamycin detection. The modified composite was characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), and electrochemical impedance spectroscopy (EIS). The electrochemical behavior of rapamycin at the modified SPCE was investigated by cyclic and square wave voltammetry in 60:40 EtOH: 0.1 M LiClO4 at pH 5.0. A high reproducible and well-defined peak with a high peak current were obtained for rapamycin detection at a position potential of + 0.98 V versus Ag/AgCl. Under the optimized conditions, the rapamycin concentration in the range 0.1 to 100 µM (R2 = 0.9986) had a good linear relation with the peak current. The detection limit of this method was 0.03 µM (3SD/slope). The proposed device can selectively detect rapamycin in the presence of commonly interfering compounds. Finally, the proposed method was successfully applied to determine rapamycin in urine and blood samples with excellent recoveries. These devices are disposable and cost-effective and might be used as an alternative tool for detecting rapamycin in biological samples and other biological compounds. Graphical abstract Schematic presentation of wide electrochemical window and disposable screen-printed sensor using ionic liquid/graphene composite for the determination of rapamycin. This composite can enhance the oxidation current and expand the potential for rapamycin detection.

A magnetic electrode modified with hemoglobin for determination of hydrogen peroxide: distinctly improved response by applying a magnetic field.

A facile and highly sensitive biosensor was developed for the determination of hydrogen peroxide (H2O2) via electrochemical catalytic reduction of H2O2 by hemoglobin (Hb). Hb was enriched and immobilized simply in a chitosan (Chit) membrane on a magnetic electrode to construct an enzyme-like biosensor. The biosensor catalyzes the electrochemical reduction of H2O2 under an external magnetic field. The response improved roughly twice as Hb was adsorbed by Chit in an alkaline medium. The response of the biosensor under the magnetic field increased by 16% owing to the paramagnetism of Hb. The effect of pH values on Hb adsorption by Chit, as well as the effect of an external magnetic field on Hb configuration were investigated by UV-vis spectroscopy. The reduction peak current has linear and log-linear relationships with H2O2 concentration in the range of 5-250 µmol∙L-1 and 0.01-1 µmol∙L-1, respectively. The detection limit was 0.003 µmol∙L-1, with a good sensitivity of 0.227 µA∙µM-1∙cm-2. The biosensor was successfully applied to the determination of H2O2 in milk samples and in disinfectant solutions. Recoveries ranged from 96.3 to 105.4%, and from 95.3 to 107.7%, respectively. Graphical abstractConstruction of the biosensor, and principle of H2O2 determination based on Hb bioelectrocatalysis.

Electrodeposited poly(3,4-ethylenedioxythiophene) doped with graphene oxide for the simultaneous voltammetric determination of ascorbic acid, dopamine and uric acid.

Poly(3,4-ethylenedioxythiophene) (PEDOT) films were electrodeposited by cyclic voltammetry on a glassy carbon electrode (GCE) in aqueous solution. Three kinds of supporting electrolytes were used, viz. graphene oxide (GO), phosphate buffered saline (PBS), and GO in PBS, respectively. The surface morphology of the modified electrodes was characterized by scanning electron microscopy. The electrochemical performance of the modified electrodes was investigated by cyclic voltammetry and electrochemical impedance spectroscopy by using the hexacyanoferrate redox system. The results demonstrate that the PEDOT-GO/GCE, which was electropolymerized in aqueous solutions containing EDOT and GO, shows the best electrochemical activities compared with other modified electrodes. The electrochemical behaviors of ascorbic acid (AA), dopamine (DA) and uric acid (UA) were investigated by cyclic voltammetry. The PEDOT-GO/GCE exhibits enhanced electrocatalytic activities towards these important biomolecules. Under physiological pH conditions and in the mixed system of AA, DA and UA, the modified GCE exhibits the following figures of merit: (a) a linear voltammetric response in the concentration ranges of 100-1000 µM for AA, 6.0-200 µM for DA, and 40-240 µM for UA; (b) well separated oxidation peaks near 31, 213 and 342 mV (vs. saturated Ag/AgCl) for AA, DA and UA, respectively; and (c) detection of limits (at S/N = 3) of 20, 2.0 and 10 µM. The results demonstrate that GO, based on its relatively large number of anionic sites, can be used as the sole weak electrolyte and charge balance dopant for the preparation of functionally doped conducting polymers by electrodeposition. Graphical abstractSchematic representation of a nanostructure composed of hybrid conducting polymer PEDOT-GO nanocomposites, and its application to simultaneous determination of ascorbic acid, dopamine and uric acid.

A poly(acrylic acid)-modified copper-organic framework for electrochemical determination of vancomycin.

A copper(II) benzene-1,3,5-tricarboxylate (BTC) metal-organic framework (MOF) was modified with poly(acrylic acid) (PAA) and then used in an electrochemical sensor for vancomycin. The MOF, synthesized via a single-pot method, has enhanced solubility and dispersibility in water as compared to HKUST-1 but without compromising its crystallinity and porosity. The MOF was placed on a glassy carbon electrode (GCE) where it shows enhanced electrocatalytic properties. This is assumed to be due to the presence of the poly(acrylic acid) that forms a network between various HKUST-1 crystals through dimer formation between the carboxy groups of BTC and PAA. This also led to better dispersion of the MOF and to improved interaction between MOF and vancomycin. The structural, spectral and electrochemical properties of the MOFs and their vancomycin complexes was characterized. The modified GCE is shown to be a viable tool for electrochemical determination (best at a working potential of 784 mV vs. Ag/AgCl) of the antibiotic vancomycin in spiked urine and serum samples. Response is linear in the 1-500 nM vancomycin concentration range, and the detection limit is 1 nM, with a relative standard deviation of ±4.3%. Graphical abstractSchematic representation of a method for determination of vancomycin. Poly(acrylic acid) modified HKUST-1 (P-HKUST-1) forms a complex with vancomycin [Van-P-HKUST-1] which is coated over glassy carbon electrode (GCE). The decrease in peak current is recorded as response to vancomycin via cyclic voltammetry.

An electrochemical aptasensor for amyloid-ß oligomer based on double-stranded DNA as "conductive spring".

In order to overcome the antibody-based sensor's shortcomings, an electrochemical aptamer (Apt)-based sensor was developed for amyloid-ß40 oligomer (Aß40-O). The aptasensor was constructed by locating Apt and ferrocence (Fc) on streptavidin-modified gold (SA-gold) nanoparticles. The obtained AptFc@SA-gold nanoparticles were linked onto the Au electrode via the connection of double-stranded DNA (dsDNA) as a "conductive spring." The determination of Aß40-O was performed with square-wave voltammetry (SWV). Upon bio-recognition between Apt and Aß40-O, the conformation of Apt changed and the formed Apt/Aß40-O complex separated from the SA-gold surface. As a result, the surface charge of SA-gold positively shifted, weakening the electrostatic attraction between the SA-gold and the positively charged Au electrode surface (at potential range of 0.1~0.5 V, corresponding to the Fc redox transformation), and stretching the dsDNA chain. Based on the exponential decay of dsDNA's electron transfer efficiency on its chain stretching, the oxidation current density from Fc decreased and displayed linear correlation to the concentration of Aß40-O. A wide linear range of 0.100 nM to 1.00 µM with a low detection limit of 93.0 pM was obtained. The aptasensor displayed excellent selectivity toward Aß40-O in contrast to other possible interfering analogs (Aß40 monomer, Aß42 monomer, and oligomer) at × 100 higher concentrations. The recoveries for Aß40-O-spiked artificial cerebrospinal fluid and healthy human serum were 94.0~104% and 92.8~95.4%, respectively. The electrochemical aptasensor meets the demands of clinic determination of Aß40-O, which is significant for the early diagnosis of AD. Graphical abstract Schematic representation of the electrochemical aptasensor for amyloid-ß oligomer based on the surface charge change induced by target binding.

Target induced framework nucleic acid nanomachine with doxorubicin-spherical nucleic acid tags for electrochemical determination of human telomerase activity.

A stable and enzyme-free method is described for highly sensitive determination of telomerase activity. It is based on the use of a framework nucleic acid (FNA) nanomachine and doxorubicin-spherical nucleic acid (DSNA) tags. Upon incubation with telomerase, the primer-tetrahedron becomes elongated to form the handed swing arm. The extended swing arm autonomously moves along the predefined track consisting of entropy-tetrahedron by consecutive strand displacement under the aid of fuel-tetrahedron. As a result, many (entropy-tetrahedron)-(fuel-tetrahedron) complexes are assembled for combining the DSNA tags. This results in an amplified electrochemical signal, typically measured at around -0.63 V (Ag/AgCl). The use of an enzyme-free FNA nanomachine and of DSNA tags warrants outstandingly high stability and sensitivity. The method shows a broad dynamic correlation of telomerase activity in cell extracts. The analytical range extends from 10 to 1.0 × 104 HeLa cells mL-1 with a lower detection limit of 2 cells mL-1. The differences in telomerase activity between different cancer cells can be easily evaluated. The method was further verified by quantifying telomerase activity of cancer cells in accumulated normal cells. Therefore, the sensing method has great potential for clinical application. Graphical abstractSchematic representation of the electrochemical biosensor based on target induced framework nucleic acid nanomachine with doxorubicin-spherical nucleic acids (DSNA) tags, which can be used to the determination of telomerase activity in accumulated normal cells. dNTP: Deoxynucleotide triphosphates; FT: Fuel-tetrahedron.

Multiwalled carbon nanotubes coated with cobalt(II) sulfide nanoparticles for electrochemical sensing of glucose via direct electron transfer to glucose oxidase.

Multiwalled carbon nanotubes coated with cobalt(II) sulfide nanoparticles were prepared and used for immobilization of glucose oxidase (GOx) to obtain an electrochemical glucose biosensor. The nanocomposite was synthesized through an in-situ hydrothermal method and characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and electrochemical impedance spectroscopy. The results show that the nanocomposite possesses a large specific surface area and apparently enhances the direct electron transfer between GOx and the surface of the electrode, best at a potential near -0.43 V (vs. SCE). The immobilized GOx retains its good bioactivity even at a high surface coverage of 30 pmol cm-2. Under the optimum conditions. The biosensor exhibits a wide linear range (from 8 µM to 1.5 mM), a high sensitivity (15 mA M -1 cm-2), and a 5 µM detection limit (at S/N = 3). The sensor is selective, acceptably repeatable, specific and stable. Graphical abstractMultiwalled carbon nanotubes coated with cobalt(II) sulfide nanoparticles (CoS-MWCNTs) were synthesized through in situ hydrothermal method for the construction of a sensitive electrochemical glucose biosensor.

Ultrasensitive amperometric immunosensor for the prostate specific antigen by exploiting a Fenton reaction induced by a metal-organic framework nanocomposite of type Au/Fe-MOF with peroxidase mimicking activity.

To increase the sensitivity of electrochemical sensor, Fe-MIL-88B-NH2 (Fe-MOF) with peroxidase-like activity is designed for the construction of immunoprobe. The Fe-MOF was prepared by one-step hydrothermalf method using 2-aminoterephthalic acid and iron(III) chloride. For the immunoprobe, it was fabricated by gold nanocomposite/Fe-MOF (Au/Fe-MOF) for the immobilization of labeling antibody (the antibody was used to conjuncting with label materials). The thin layer of Methylene Blue (MB) covered by reduced graphene oxide-gold nanocomposites (Au-rGO) serves as a substrate to covalently fix coating antibodies. The MB as a redox-active species was modified on the glass carbon electrode that can give a strong amperometric signal at 0.18 V (vs. Ag/AgCl). With the participation of H2O2, Fe-MOF can induce the Fenton reaction which degrades MB covered by Au-rGO on the substrate. The rest of MB on the surface of electrode becomes oxidized thereby generating a current signal. Square wave voltammetry (SWV) was used to quantify PSA. Under optimal conditions, the immunoassay is stable, specific and reproducible. It has a lower detection limit of 0.13 pg mL-1 (S/N = 3) and a wide analytical range that extends from 0.001 to 100 ng mL-1. Graphical abstractA sandwich-type amperometric immunoassay based on Fe-MOF-induced Fenton reaction was designed for sensitive determination of prostate specific antigen.

Ultrasensitive Electrochemiluminescent Sensor for MicroRNA with Multinary Zn-Ag-In-S/ZnS Nanocrystals as Tags.

For the screening of novel toxic-element-free and biocompatible electrochemiluminophores, electrochemiluminescence (ECL) of multinary nanocrystals (NCs) was investigated for the first time with Zn-Ag-In-S (ZAIS) NCs as model. Aqueous soluble ZAIS NCs could bring out efficient reductive-oxidation ECL with tri- n-propylamine as coreactant, while coating the ZAIS NCs with a ZnS shell could reduce the surface defects of ZAIS NCs, and enable 6.7-fold enhanced ECL of ZAIS/ZnS NCs as compared to ZAIS NCs. ECL of ZAIS/ZnS NCs was about 4.2-fold that of ternary CuInS2/ZnS NCs, spectrally similar to that of Ru(bpy)32+ with maximum emission around 605 nm, and favorable for less electrochemical interference with a lowered triggering potential (∼0.95 V) than that of Ru(bpy)32+. An ultrasensitive ECL microRNA sensor was fabricated with ZAIS/ZnS NCs as tags, which could sensitively and selectively determine microRNA-141 with a wide linearity range from 0.1 fmol/L to 20 pmol/L and a low limit of detection at 50 amol/L ( S/ N = 3). Multinary NCs might provide a promising alternative to the traditional binary NCs for both electrochemiluminophore screening and NC ECL modulating.

An aptamer biosensor for leukemia marker mRNA detection based on polymerase-assisted signal amplification and aggregation of illuminator.

A novel electrochemical luminescence (ECL) aptamer biosensor via polymerase amplification is constructed for label-free detection of leukemia marker mRNA (miR-16). In order to achieve the ultrasensitive detection of the target mRNA, the cyclic target chain displacement polymerization of leukemia marker mRNA assisted with Klenow fragment of DNA polymerase is employed. The determination is carried out by recording the ECL emission of pyridine ruthenium (Ru(bpy)32+) complexes embedded into the assistance DNA (ADNA) loaded on the nanogold surface, after the hybridization reaction between the probe DNA (PDNA) and the remaining sequence of the CP's stem part, and the formation of a core-shell sun-like structure. The mercapto-modified capture DNA (CP) is immobilized on the surface of a magneto-controlled glassy carbon electrode by Au-S bond. The CP is opened and hybridized with the target mRNA to form double-stranded DNA. In the presence of polymerase, primer DNA, and bases (dNTPs), the primer chain gets access to its complementary sequence of the stem part and then triggers a polymerization of the DNA strand, leading to the release of mRNA and starting the next polymerization cycle. Finally, the composite of PDNA-covered and ADNA-covered (embedded with Ru(bpy)32+) gold nanoparticles (hereafter called AuNPs@(PDNA+ADNA-Ru(bpy)32+) is added, and the ECL intensity is recorded. Because of the polymerization cycle and the aggregation of the illuminator of Ru(bpy)32+, the detected signal is amplified significantly. The results showed that the corresponding ECL signal has a good linear relationship with a logarithm of target mRNA concentration in the range of 1 × 10-16 to 1 × 10-7 mol/L, with a detection limit of 4.3 × 10-17 mol/L. The mRNA spiked in the human serum sample is determined, and the recoveries are from 97.2 to 102.0%. This sensor demonstrates good selectivity, stability, and reproducibility. Graphical abstract ᅟ.

Electrochemical skin conductance: a systematic review.

PURPOSE: Currently available techniques for the evaluation of small fiber neuropathy and related sudomotor function remain suboptimal. Electrochemical skin conductance (ESC) has recently been introduced as a simple noninvasive and fast method for the detection of sudomotor dysfunction. The purpose of this review is to synthesize and appraise research using ESC measurements for sudomotor evaluation in adults. METHODS: Electronic databases including MEDLINE and Google Scholar were searched (up to March 13, 2017). The search strategy included the following terms: "electrochemical skin conductance," "Sudoscan," and "EZSCAN." Evidence was graded according to defined quality indicators including (1) level of evidence; (2) use of established tests as reference tests (e.g., quantitative sudomotor axon test [QSART], sympathetic skin responses [SSR], thermoregulatory sweat test [TST], and skin biopsies to assess sudomotor and epidermal small fibers); (3) use of consecutive/non-consecutive subjects; and (4) study design (prospective/retrospective). RESULTS: A total of 24 studies met the inclusion criteria. These were classified into preclinical, normative, comparative/diagnostic, or interventional. ESC measurement properties, diagnostic accuracy, and similarities to and differences from established tests were examined. CONCLUSIONS: ESC measurements expand the arsenal of available tests for the evaluation of sudomotor dysfunction. The advantages and disadvantages of ESC versus established tests for evaluating sudomotor/small fiber function reviewed herein should be used as evidence to inform future guidelines on the assessment of sudomotor function.

Sudomotor function testing by electrochemical skin conductance: does it really measure sudomotor function?

OBJECTIVE: Electrochemical skin conductance (ESC) is a non-invasive test of sweat function developed as a potential marker of small fiber neuropathy. Here we systematically review the evolution of this device and the data obtained from studies of ESC across different diseases. METHODS: Electronic databases, including MEDLINE, and Google Scholar were searched through to February 2018. The search strategy included the following terms: "electrochemical skin conductance," "EZSCAN," and "Sudoscan." The data values provided by each paper were extracted, where available, and input into tabular and figure data for direct comparison. RESULTS: Thirty-seven studies were included this systematic review. ESC did not change by age or gender, and there was significant variability in ESC values between diseases, some of which exceeded control values. Longitudinal studies of disease demonstrated changes in ESC that were not biologically plausible. Of the 37 studies assessed, 25 received support from the device manufacturer. The extracted data did not agree with other published normative values. Prior studies do not support claims that ESC is a measure of small fiber sensory function or autonomic function. CONCLUSIONS: Although many papers report significant differences in ESC values between disease and control subjects, the compiled data assessed in this review raises questions about the technique. Many of the published results violate biologic plausibility. A single funding source with a vested interest in the study outcomes has supported most of the studies. Normative values are inconsistent across publications, and large combined data sets do not support a high sensitivity and specificity. Finally, there is insufficient evidence supporting the claim that Sudoscan tests sudomotor or sensory nerve fiber function.

Photodeposition of palladium nanoparticles on a porous gallium nitride electrode for nonenzymatic electrochemical sensing of glucose.

A nonenzymatic electrochemical glucose sensor is described that was obtained by in situ photodeposition of high-density and uniformly distributed palladium nanoparticles (PdNPs) on a porous gallium nitride (PGaN) electrode. Cyclic voltammetric and chronoamperometric techniques were used to characterize the performance of the modified electrode toward glucose. In 0.1 M NaOH solution, it has two linear detection ranges, one from 1 µM to 1 mM, and another from 1 to 10 mM, and the detection limit is 1 µM. The electrode is repeatable, highly sensitive, fast and long-term stable. It was applied to the quantitation of serum glucose where it displayed accurate current responses. Graphical abstract A novel nonenzymatic electrochemical glucose sensor was developed by in situ photodeposition of palladium nanoparticles on the porous gallium nitride electrode.

Amperometric sensing of hydrazine in environmental and biological samples by using CeO2-encapsulated gold nanoparticles on reduced graphene oxide.

CeO2-encapsulated gold nanoparticles (AuNPs) were anchored to reduced graphene oxide (RGO/Au@CeO2) by an interfacial auto-redox reaction in a solution containing tetrachloroauric acid and Ce(III) on a solid support. The resulting material was placed on a glassy carbon electrode (GCE) and used as an electrochemical hydrazine sensor at trace levels. The electrocatalytic activity of the modified GCE towards hydrazine oxidation was significantly enhanced as compared to only RGO/CeO2, or CeO2-encapsulated AuNPs, or AuNPs loaded on CeO2 modified with RGO. This enhancement is attributed to the excellent conductivity and large surface area of RGO, and the strong interaction between the reversible Ce4+/Ce3+ and Auδ+/Au0 redox systems. The kinetics of the hydrazine oxidation was studied by electrochemical methods. The sensor, best operated at a peak voltage of 0.35 V (vs. saturated calomel electrode), had a wide linear range (that extends from 10 nM to 3 mM), a low detection limit (3.0 nM), good selectivity and good stability. It was successfully employed for the monitoring of hydrazine in spiked environmental water samples and to in-vitro tracking of hydrazine in cells with respect to its potential cytotoxicity. Graphical abstract CeO2-encapsulated gold nanoparticles anchored on reduced graphene oxide with the strong interaction between the reversible Ce4+/Ce3+ and Auδ+/Au0 reductions can be used for sensitive detection of hydrazine with detection limit of 3 nM and good selectivity in environmental and biological samples.

Gold nanoparticles conjugated to bimetallic manganese(II) and iron(II) Prussian Blue analogues for aptamer-based impedimetric determination of the human epidermal growth factor receptor-2 and living MCF-7 cells.

An aptamer-based assay is described for the determination of trace levels of the cancer marker human epidermal growth factor receptor-2 (HER2) and living MCF-7 cells. The method is based on the use of a bimetallic MnFe Prussian blue analogue coupled to gold nanoparticles (MnFePBA@AuNP). Compared to pristine MnFe PBA nanocubes, the series of MnFePBA@AuNP exhibits a core-shell spherical nanostructure, and the shell thickness decreases from 99.9 nm down to 49.3 nm on increasing the fraction of AuNPs. The composite was placed on a gold electrode and incubated with the aptamer solution through electrostatic interaction. Then the modified electrode was employed to detect HER2 and MCF-7 cells using [Fe(CN)6]3-/4- as redox probe and displays good responses to both of them. Electrochemical impedance spectroscopy data show that the signal variation between each step during the whole procedure for the HER2 and MCF-7 cells detection can be embodied as the resistance value change between the [Fe(CN)6]3-/4- and electrode surface. The assay has a very low detection limit (0.247 pg∙mL-1) and works in the 0.001-1.0 ng∙mL-1 HER2 concentration range. It was also used to sense HER2 in MCF-7 cells, and this results in an assay that works within the 500-5 × 104 cell∙mL-1 cell concentration range and a 36 cell∙mL-1 detection limit. Furthermore, the aptamer-based assay is selective, acceptably reproducible, stable, and well feasible for the detection of HER2 and living MCF-7 cells in human serum. Graphical abstract Schematic of an electrochemical aptasensor based on the bimetallic MnFe Prussian blue analogue (MnFe PBA) coupling with gold nanoparticles (represented by MnFePBA@AuNPs). It was employed as the aptasensor for human epidermal growth factor receptor-2 (HER2), and living MCF-7 cells.

Voltammetric kanamycin aptasensor based on the use of thionine incorporated into Au@Pt core-shell nanoparticles.

A signal-on aptasensor is described for the voltammetric determination of kanamycin (KANA). Au@Pt core-shell nanoparticles with large surface and good electrical conductivity were synthetized and act as both a conductive material and as the carrier for complementary strands (CS2) and thionine (TH). In the presence of KANA, the electrochemical response of TH changes due to hybridization between CS1 immobilized on the electrode and the Au@Pt-CS2/TH system. The peak current increases linearly with the logarithm of the KANA concentration in the range from 1 pM to 1 µM, and the limit of detection is 0.16 pM. The sensor was characterized in terms of selectivity, reproducibility and stability, and satisfactory results were obtained. It was also utilized for the determination of KANA in (spiked) chicken samples. The recoveries (95.8-103.2%) demonstrate the potential of the method for KANA detection in real samples. Graphical abstract A signal-on aptasensor for kanamycin (KANA) was developed by using Au@Pt core-shell nanoparticles as nanocarrier for probe aptamer and as a sensing probe.

Gold nanoparticles anchored onto three-dimensional graphene: simultaneous voltammetric determination of dopamine and uric acid.

An electrochemical sensor is described for simultaneous voltammetric determination of dopamine (DA) and uric acid (UA). It is based on the use of a nanomaterial composed of gold nanoparticles and 3-dimensional graphene (Au NP@3D GR). The 3D GR was prepared by chemical vapor deposition using nickel nanoparticles as the template at a temperature of around 900 °C. The surface of 3D GR contains oxygen-functional groups after treatment with acid. Carboxylated Au NP were self-assembled and anchored onto the surface of 3D GR. The nanomaterial was placed on a ITO electrode. The few-layer graphene on the ITO glass has a porous structure and the distribution of Au NP is uniform. The electrode shows a high sensitivity and a low detection limit for DA and UA. Figures of merit include detection limits of 0.1 M for DA and of 0.1 µM for UA, and well separated peaks at potentials of 0.18 and 0.30 V (vs. Ag/AgCl), respectively, at pH 7.0. The electrode has good repeatability and stability. Graphical abstract Carboxylated gold nanoparticles were self-assembled and immobilized on 3-dimensional graphene by chemical vapor deposition for simultaneous determination of dopamine (DA) and uric acid (UA).

Serum prolactin levels across pregnancy and the establishment of reference intervals.

BACKGROUND: Reference intervals (RIs) play key roles in clinical diagnosis, treatment and prognosis. However, RIs for clinical testing tend to be confined to the general population, and RIs for pregnant women are not very comprehensive. In this study, we establish RIs for prolactin (PRL) in healthy pregnant and postpartum women in the Chinese population. METHODS: Healthy pregnant women (n=378) were divided into groups according to whether they were in the first, second or third trimester of pregnancy. Healthy postpartum women (n=493) were separated into four groups according to mode of delivery as follows: postvaginal (24 and 48 h) or postcesarean (24 and 48 h). Healthy, non-pregnant women (n=123) were enrolled as a control group. Serum PRL levels were measured by electrochemiluminescence immunoassay, and RIs were established for each group. RESULTS: The RIs for PRL were as follows: healthy non-pregnant women, 178.89-757.52 µIU/mL; first trimester, 621.20-3584.00 µIU/mL; second trimester, 1432.00-5349.68 µIU/mL; third trimester, 4087.33-9733.65 µIU/mL; 24 and 48 h postvaginal delivery (combined), 7865.36-10998.86 µIU/mL; and 24 and 48 h postcesarean delivery, 4556.41-7675.99 and 6578.45-9980.45 µIU/mL, respectively. CONCLUSIONS: PRL RIs for pregnant women were established according to trimester, days postpartum and mode of delivery, thus providing a clinical reference for medical staff.