Search

Neuron-specific enolase (NSE) has gained extensive attention as a reliable target for detecting small cell carcinoma of lungs. In this paper, an electrochemical immunoassay method based on molybdenum disulfide (MoS2) is proposed to detect NSE sensitively. By an in-situ growth method, MoS2 and Au nanoclusters (Au NCs) were composited to form a MoS2@Au nanozyme, and then the secondary antibodies were modified. Primary antibodies were immobilized on amino-reduced graphene oxides to capture NSE. The flower-like MoS2 nanozyme provided abundant sites to load Au NCs and catalyze the decomposition of H2O2, which were beneficial to amplify an amperometric response as well as build up sensitivity. Under optimum conditions, the detection range of this strategy was 0.1 pg·mL−1–10 ng·mL−1 and the limit of detection was 0.05 pg·mL−1. This sensing strategy achieved the prospect of sensitively detecting NSE. Moreover, the prepared electrochemical immunosensor provides a theoretical basis and technical support for the detection of other disease markers. [ABSTRACT FROM AUTHOR]

In this study, a sensitive label-free electrochemical immunosensor was designed based on nanoporous Fe3O4 and a biotin–streptavidin system to specifically detect zearalenone (ZEN). Herein, nanoporous Fe3O4 was employed to carry streptavidin to prepare the highly sensitive immunosensor. The application of nanoporous Fe3O4 and the biotin–streptavidin reaction provided large amounts of antibodies on each conjugate, thus amplifying the detected signal. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were conducted to characterize the modification with ZEN. Factors which might influence the properties of the immunosensor, including concentration of nanoporous Fe3O4, pH of the buffer, incubation time and temperature were studied. Under the best conditions, the immunosensor displayed a highly sensitive response toward ZEN, ranging in concentration from 10.0 pg mL−1 to 3.00 ng mL−1 and 3.00 ng mL−1 to 12.0 ng mL−1, with a low detection limit of 3.7 pg mL−1. The results for analysis of human urine samples were satisfactory. Furthermore, this proposed method may find promising applications in the detection of other mycotoxins. [ABSTRACT FROM AUTHOR]

An ultrasensitive label-free photoelectrochemical (PEC) immunosensor was developed to detect amyloid β-protein (Aβ) based on CdS/CdTe-cosensitized SnO2 nanoflowers. Specifically, SnO2 with a flower-like porous nanostructure was utilized as a perfect substrate for the construction of PEC immunosensors, and the SnO2-modified electrode was first coated with CdTe quantum dots (QDs) and then further deposited with CdS by successive ionic layer adsorption and reaction techniques. The formed SnO2/CdS/CdTe-cosensitized structure exhibited excellent photocurrent intensity and was employed as an excellent photoactive matrix to immobilize Aβ antibody to further construct the immunosensor. Under optimal conditions, the as-constructed PEC immunosensor was used to detect Aβ and exhibited a wide linear concentration range from 0.5 pg mL−1 to 10 ng mL−1, with a low limit of detection (LOD, 0.18 pg mL−1, S/N = 3). Meanwhile, it also presented good reproducibility, specificity, and stability and may open a new promising platform for the clinical detection of Aβ or other biomarkers. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Ultrasensitive electrochemical aptasensor was developed for detecting Pb2+. • Au@p-rGO was applied as support for immobilizing the aptamer. • Au NPs@GO as signal probe exhibited high electrocatalytic activity towards H 2 O 2. • The aptasensor displayed low detection limit of 1.67 pmol/L for Pb2+. Abstract A sensitive electrochemical aptasensor was designed based on gold modified graphene nanocomposite with different morphologies for the detection of lead ion (Pb2+). Specifically, a sulfydryl-labeled substrate strand (Apt1) and a sulfydryl-labeled catalytic strand (Apt2) were devised in fabricating the electrochemical aptasensor. Gold modified porous reduced graphene oxide (Au@p-rGO) was synthesized and applied as support for immobilizing the Apt1. And gold modified graphene oxide (Au NPs@GO) was employed as signal probe and connected with Apt2 to realize the immobilization of it on the electrode by means of the principle of complementary base pairing. The current signal can be obtained by recording the electrocatalytic conditions toward H 2 O 2. The Pb2+-dependent DNAzyme could play a role when Pb2+ existed. With the increase of the concentration of Pb2+, the current response revealed a diminishing signal, thus realizing the sensitive detection of Pb2+. Under the optimal conditions, the fabricated electrochemical aptasensor exhibited a linear response toward Pb2+ ranging from 5 pmol/L to 1 μmol/L, together with a low limit of detection of 1.67 pmol/L. Moreover, the prepared aptasensor displayed outstanding selectivity, acceptable stability and superior reproducibility for detecting Pb2+. This proposed tactics may provide reference and potential applications for detecting some other heavy metal ions. [ABSTRACT FROM AUTHOR]

Based on the necessity and urgency of detecting infectious disease marker procalcitonin (PCT), a novel unlabeled photoelectrochemical (PEC) immunosensor was prepared for the rapid and sensitive detection of PCT. Firstly, SnO2 porous nanoflowers with good photocatalytic performance were prepared by combining hydrothermal synthesis and calcining. BiOI nanoflowers were synthesized by facile ultrasonic mixed reaction. Ag2S quantum dots were deposited on SnO2/BiOI composites by in situ growth method. The SnO2/BiOI/Ag2S composites with excellent photoelectric properties were employed as substrate material, which could provide significantly enhanced and stable signal because of the energy level matching of SnO2, BiOI and Ag2S and the good light absorption performance. Accordingly, a PEC immunosensor based on SnO2/BiOI/Ag2S was constructed by using the layered modification method to achieve high sensitivity analysis of PCT. The linear dynamic range of the detection method was 0.50 pg·mL−1~100 ng·mL−1, and the detection limit was 0.14 pg·mL−1. In addition, the designed PEC immunosensor exhibited satisfactory sensitivity, selectivity, stability and repeatability, which opened up a new avenue for the analyzation of PCT and further provided guidance for antibiotic therapy. [ABSTRACT FROM AUTHOR]

• Ultrasensitive electrochemical aptasensor was fabricated for detecting Pb2+. • AuPd@Fe-MOFs labeled DNA was firstly applied to produce the electrical signal. • Au@MoS 2 /rGO was utilized as sensing platform to construct the aptasensor. • The aptasensor displayed low detection limit of 0.07 pmol/L for Pb2+ detection. In this work, an electrochemical aptasensor was proposed by using gold-modified molybdenum disulfide/reduced graphene oxide (Au@MoS 2 /rGO) nanocomposite and gold-palladium (AuPd)-modified MIL-88 (Fe) metal-organic frameworks (AuPd@Fe-MOFs) for sensitive detection of lead ions (Pb2+). The 8–17 DNAzyme consisting of a substrate strand (Apt1) and a catalytic strand (Apt2) was used to construct the aptasensor. Au@MoS 2 /rGO nanocomposite was applied as the sensing platform to immobilize the mercapto-group-labeled Apt1. Meanwhile, AuPd@Fe-MOFs was employed to label Apt2, which showed excellent catalytic ability toward H 2 O 2. In the presence of Pb2+, the Apt1 of the DNAzyme was catalytically cut off, decreasing the amount of AuPd@Fe-MOFs. The current response was correlated to the Pb2+concentration, thereby achieving Pb2+ detection. Under the optimal experimental conditions, the fabricated aptasensor showed a highly linear response for Pb2+ in the range from 5.0 pmol/L to 2.0 μmol/L, with a detection limit of 0.07 pmol/L. Additionally, the proposed electrochemical aptasensor exhibited excellent selectivity, stability and reproducibility. Moreover, the proposed aptasensor demonstrated good performance in real water sample analysis, making it promising for use in Pb2+ detection in environmental monitoring. [ABSTRACT FROM AUTHOR]

Self-supported Fe3N-Co2N nanoarray with high electric conductivity and large surface area was prepared for growth of MIPs and further constructing a sensitive and stable electrochemical sensor. For the evaluation of its performance, Fe3N-Co2N is used as sensing electrode material, and AMP is used as template molecule to construct the MIP electrochemical sensor. Under the optimized conditions, the developed MIPs electrochemical sensor detects AMP with a low detection limit of 3.65 × 10−10 mol L−1 and shows outstanding reproducibility and stability. When the MIPs electrochemical sensor was applied to detect AMP in milk samples via standard addition method, the recovery within 97.06–102.43% with RSD of 1.05–2.11% was obtained. The fabrication of MIPs electrochemical sensor is highly promising for sensitive and selective electrochemical measurement and food safety testing. This work can provide theoretical guidance for truly challenging problems. [ABSTRACT FROM AUTHOR]

A sensitive electrochemical aptasensor was prepared on the basis of gold modified thiol reduced graphene (Au@HS-rGO) and thymine-Hg2+-thymine (T-Hg2+-T) constitution for the checkout of Hg2+. Firstly, Au@HS-rGO was fabricated as the substrate onto the glassy carbon electrode (GCE) surface, which facilitated the subsequent introduction of single-stranded DNA onto the electrode. Following that, thionine (Th) was immobilized on the electrode surface depend on the physical size effect of T and Hg2+. Finally, the amount of Hg2+ was determined by differential pulse voltammetry (DPV) of Th. Under the best conditions, the linear range of the aptasensor to Hg2+ was in the range of 1–200 nmol/L and the detection limit was as low as 0.38 nmol/L. Simultaneously, good selectivity and acceptable reproducibility were revealed in the designed aptasensor. Moreover, the design thought may provide an idea for the detection of other substances in the water sample. [ABSTRACT FROM AUTHOR]

Abstract A sandwich-type electrochemical immunosensor for prostate-specific antigen (PSA) detection was constructed. In this sensing platform, palladium nanoparticles (Pd NPs) loaded electroactive amino-zeolitic imidazolate framework-67 (Pd/NH 2 -ZIF-67) nanocomposite is utilized as a novel redox mediator. Pd NPs, as the labeling signal molecule, owns good biocompatibility and excellent catalytic performance. Meanwhile, the electroactive ZIF-67 with lamellar structures serves not only as a carrier of Pd NPs but also as a synergistic catalyst of palladium to decompose H 2 O 2. Amperometric method is used to determine the current signal generated on the electrode surface, which is conducive to achieve the quantitative determination of PSA. Under optimum conditions, the proposed immunosensor shows a wide detection range from 100 fg mL–1 to 50 ng mL–1 with a low detection limit of 0.03 pg mL–1, featuring favorable selectivity, repeatability and stability. This proposed immunosensor is expected to be a powerful tool for realizing quantitative detection of PSA and other biomarkers in actural sample analysis. Highlights • Electrochemical immunoassay is proposed for detection of PSA based on Pd/NH 2 -ZIF-67. • The response signal is amplified by the synergetic effect between Pd and Co2+/3+. • The immunosensor exhibits a low detection limit of 0.03 pg mL-1 for PSA detection. [ABSTRACT FROM AUTHOR]

• An enzyme-free colorimetric immunosensor was designed for detection PCT. • MgFe 2 O 4 @Cys was first used as the sacrificial probe of the immunosensor. • MgFe 2 O 4 @Cys released Fe3+ under acidic condition and reacted with [Fe(CN) 6 4− can generate soluble PB. • PCT determination was established by measuring absorbance of generated PB. • It achieved an excellent result in human serum sample analysis. An enzyme-free immunosorbent assay using MgFe 2 O 4 modified with cysteine (MgFe 2 O 4 @Cys) as sacrificial probe for the detection of procalcitonin (PCT) was developed. MgFe 2 O 4 @Cys was linked with second antibody of PCT (Ab 2) by cysteine amino group and released Fe3+ under acidic conditions. Taking advantage of Fe3+ and [Fe(CN) 6 4− generating soluble Prussian blue (PB), a novel method of PCT determination was established by measuring the absorbance of the generated PB. Different from the traditional immunosensor detection mode, the enzyme-free colorimetric immunosensor in this work can not only avoid the interference of nano-enzymes or enzymes, but also has the advantages of rapid detection, low cost, high selectivity and sensitivity. Therefore, the developed immunosensor for PCT detection exhibited a wide linear response (0.0001–50 ng/mL) and a low detection limit (44.9 fg/mL). Additionally, the immunosensor exhibits satisfactory performance in human serum testing, which indicated its good application value in clinical diagnoses. [ABSTRACT FROM AUTHOR]

In this paper, we constructed a sandwich-type photoelectrochemical (PEC) immunosensor for the quantitative detection of procalcitonin (PCT) based on the sensitization of Mn2+ doped CdS (CdS:Mn) nanocomposites to Bi 2 WO 6 and the signal amplification effect of an upconversion material NaYF 4 :Yb,Tm. Bi 2 WO 6 was synthesized with a three-dimensional flowered structure. CdS:Mn reduced the recombination of photogenerated carriers, and significantly improved photocurrent response. Lanthanide-doped upconversion nanomaterials were used as the label of secondary antibody. NaYF 4 :Yb,Tm have two functions, not only connected with the secondary antibody, but also can further amplify the photocurrent response. The proposed immunosensor for detecting PCT provided a desired linear range of 0.5 pg mL−1-100 ng mL−1 and a detection limit of 0.13 pg mL−1 under optimal experimental conditions. Besides, the PEC immunosensor demonstrated good reproducibility, specificity and stability. The results of determination of PCT in real human serum samples were satisfactory. Thus, the immunosensor may be applied in the clinical diagnosis of PCT and other biomarkers. [Display omitted] [ABSTRACT FROM AUTHOR]