Nanoporous PtCo-based ultrasensitive enzyme-free immunosensor for zeranoldetection

Recent advances in electrochemical monitoring of zearalenone in diverse matrices

The current manuscript summarizes different electrochemical sensing systems developed within the last 5 years for the detection of zearalenone (ZEN) in diverse matrices such as food, feed, and biofluids. ZEN is one of the most prevalent non-steroidal mycotoxins that is often found in pre- and post-harvest crops. Crops contamination with ZEN and animal exposure to it via contaminated feed, is a global health and economic concern. The European Union has established various preventive programs to control ZEN contamination, and regulations on the maximum levels of ZEN in food and feed. Electrochemical (bio)sensors are a very promising alternative to sensitive but sophisticated and expensive chromatographic techniques. In the current review, recent developments towards electrochemical sensing of ZEN, sorted by type of transducer, their design, development, and approbation/validation are discussed, and the use of specialized electrochemical instrumentation is highlighted.

Metallic Woodpile Nanostructures for Femtomolar Sensing of Alzheimer's Neurofilament Lights

Alzheimer's disease (AD), the most common age-related neurodegenerative disorder, accompanies a massive degradation of neurons including axonal injury. Being an axonal neuron-specific protein, neurofilament light (NfL) is a blood biomarker that reflects the neurodegeneration in AD, but no attempt has been made yet to develop sensing platforms that target NfLs in blood serum or plasma. Here, we report three-dimensional cross-stacked Pt nanowire arrays for the ultrasensitive photoelectrochemical (PEC) detection of NfLs. We constructed a woodpile-like Pt nanowire array (PtWP)-based biocathode by printing multilayer Pt nanowire arrays in an orthogonal configuration and conjugating them with NfL-specific DA2 antibodies. According to our collective electrochemical analyses, the five-layered PtWP electrode modified with DA2 antibodies exhibited high oxygen reduction activities due to the large electrochemical active surface area and the effective electron transfer properties. We have combined the DA2-PtWP biocathode with a water-oxidizing, iron oxyhydroxide-deposited bismuth vanadate (FeOOH/BiVO₄) photoanode to assemble a bias-free PEC detection system. Powered by a white-light-emitting diode, the unbiased PEC platform accurately recognizes NfLs in blood plasma with the limit-of-detection of 38.2 fg/mL and limit-of-quantification of 853 fg/mL, which is 40 times lower than the NfL levels in AD patients' blood.

Construction of Electrochemical Immunosensor Based on Gold-Nanoparticles/Carbon Nanotubes/Chitosan for Sensitive Determination of T-2 Toxin in Feed and Swine Meat

T-2 toxin (T-2) is one of major concern mycotoxins acknowledged as an unavoidable contaminant in human foods, animal feeds and also agriculture products. Thus, a facile and sensitive method is essential for accurate T-2 toxin detection. In our work, a specific electrochemical immunosensor based on gold nanoparticles/carboxylic group-functionalized single-walled carbon nanotubes/chitosan (AuNPs/cSWNTs/CS) composite was established. The mechanism of the electrochemical immunosensor was an indirect competitive binding to a given amount of anti-T-2 between free T-2 and T-2-bovine serum albumin, which was conjugated on covalently functionalized cSWNTs decorated on the glass carbon electrode. Afterwards, the alkaline phosphatase labeled anti-mouse secondary antibody was bound to the electrode surface by reacting with the primary antibody. Lastly, alkaline phosphatase catalyzed the hydrolysis of the substrate α-naphthyl phosphate, which produced an electrochemical signal. Compared with conventional methods, the established immunosensor was more sensitive and simpler. Under optimal conditions, this method could quantitatively detect T-2 from 0.01 to 100 μg·L-1 with a detection limit of 0.13 μg·L-1 and favorable recovery 91.42⁻102.49%. Moreover, the immunosensor was successfully applied to assay T-2 in feed and swine meat, which showed good correlation with the results obtained from liquid chromatography-tandem mass spectrometry (LC-MS/MS).

Recent advances in mycotoxins detection

Mycotoxins contamination in both food and feed is inevitable. Mycotoxin toxicity in foodstuff can occur at very low concentrations necessitating early availability of sensitive and reliable methods for their detection. The present research thrust is towards the development of a user friendly biosensor for mycotoxin detection at both academic and industrial levels to replace conventional expensive chromatographic and ELISA techniques. This review critically analyzes the recent research trend towards the construction of immunosensor, aptasensor, enzymatic sensors and others for mycotoxin detection with a reference to label and label free methods, synthesis of new materials including nano dimension, and transuding techniques. Technological aspects in the development of biosensors for mycotoxin detection, current challenges and future prospects are also included to provide a overview and suggestions for future research directions.

A novel electrochemical immunosensor based on the rGO-TEPA-PTC-NH₂ and AuPt modified C₆₀ bimetallic nanoclusters for the detection of Vangl1, a potential biomarker for dysontogenesis

The aberrant expression of Vangl1 is highly correlated with dysontogenesis, especially for neural tube defects. Therefore, the ultrasensitive detection of Vangl1 would provide a new approach for the specific early diagnostics in dysembryoplasia. However, no quantitative detection method is currently available. Herein, we describe the development of a new approach to fill this assay gap. We utilized C60-templated AuPt bimetallic nanoclusters for signal amplification because the promising C60 nanomaterial provides a large surface area for the in site reduction of bimetallic nanocomposites as well as excellent conductivity. To further amplify the electrochemical signal, reduced graphene oxide-tetraethylene pentamine (rGO-TEPA) and a derivative of 3,4,9,10-perylenetetracarboxylicdianhydride (PTC-NH2) were selected for modification of the electrode to provide more amino groups for the immobilization of antibodies and to enhance the conductivity. The electrochemical signal was primarily derived from the catalysis of H2O2 by C60-AuPt. Chronoamperometry was applied to record the electrochemical signals. Under optimal conditions, the prepared immunosensor exhibited a wide linear range from 0.1 pg mL(-1) to 450 pg mL(-1) and a low detection limit of 0.03 pg mL(-1). Moreover, the proposed method exhibited good stability and recovery, suggesting its potential for use in clinical research.

3D sandwich-type prostate specific antigen (PSA) immunosensor based on rGO–MWCNT–Pd nanocomposite

A signal amplifying sandwich-type immunosensor with a wide linear range and a low detection limit is developed with potential clinical and diagnostic applications.

A sandwich electrochemical immunoassay for Salmonella pullorum and Salmonella gallinarum based on a AuNPs/SiO2/Fe3O4adsorbing antibody and 4 channel screen printed carbon electrode electrodeposited gold nanoparticles

A: The synthesis of Fe₃O₄/SiO₂–SH; B: AuNPs and the Ab₁link with Fe₃O₄/SiO₂–SH; C: functions of IMB for antigen enrichment and separation from the sample, and HRP-antibody for the immunoreaction; D: the principle of the electrochemical detection.

An ultrasensitive electrochemical immunosensor for determination of estradiol using coralloid Cu2S nanostructures as labels

Ultrasensitive electrochemical immunoassay based on coralloid Cu₂S nanostructure for determination of estradiol.

Copper-doped titanium dioxide nanoparticles as dual-functional labels for fabrication of electrochemical immunosensors

Constructions of versatile electroactive labels are key issues in the development of electrochemical immunosensors. In this study, copper-doped titanium dioxide nanoparticle (Cu@TiO2) was synthesized and used as labels for fabrication of sandwich-type electrochemical immunosensors on glassy carbon electrode (GCE). Due to the presence of copper ions, Cu@TiO2 shows a strong response current when coupled to an electrode. The prepared nanocomposite also shows high electrocatalytic activity towards reduction of hydrogen peroxide (H2O2). The dual functionality of Cu@TiO2 enables the fabrication of immunosensor using different detection modes, that is, square wave voltammetry (SWV) or chronoamperometry (CA). While Cu@TiO2 was used as labels of secondary antibodies (Ab2), carboxyl functionalized graphene oxide (CFGO) was used as electrode materials to immobilize primary antibodies (Ab1). Using human immunoglobulin G (IgG) as a model analyte, the immunosensor shows high sensitivity, acceptable stability and good reproducibility for both detection modes. Under optimal conditions, a linear range from 0.1 pg/mL to 100 ng/mL with a detection limit of 0.052 pg/mL was obtained for SWV analysis. For CA analysis, a wider linear range from 0.01 pg/mL to 100 ng/mL and a lower detection limit of 0.0043 pg/mL were obtained. The proposed metal ion-based enzyme-free and noble metal-free immunosensor may have promising applications in clinical diagnoses and many other fields.

A novel signal amplification strategy of an electrochemical immunosensor for human chorionic gonadotropin, based on nanocomposites of multi-walled carbon nanotubes–ionic liquid and nanoporous Pd

A novel electrochemical immunosensor using MWCNTs–BMIMPF₆/NP-Pd as a sensor platform to sequentially immobilize antibodies was developed for hCG detection.

Food safety control of zeranol through voltammetric immunosensing on Au–Pt bimetallic nanoparticle surfaces

This study reports an accurate and sensitive strategy for zeranol (ZER) determination in bovine urine samples.

Ultrasensitive dual amplification sandwich immunosensor for breast cancer susceptibility gene based on sheet materials

A new electrochemical dual amplification sandwich immunosensor (DASI) was designed for ultrasensitive and accurate detection of the breast cancer susceptibility gene based on the combination of N-doped graphene, hydroxypropyl chitosan and Co₃O₄ mesoporous nanosheets.

Cathodic electrochemiluminescence immunosensor based on nanocomposites of semiconductor carboxylated g-C3N4 and graphene for the ultrasensitive detection of squamous cell carcinoma antigen

A novel label-free electrochemiluminescence (ECL) immunosensor was developed for the detection of squamous cell carcinoma antigen (SCCA) based on nanocomposites of semiconductor carboxylated graphitic carbon nitride (g-C3N4) and graphene (g-C3N4-graphene). The ECL intensity of carboxylated g-C3N4 was much enhanced after being combined with graphene which had excellent electron-transfer ability. The sensing platform was constructed by depositing g-C3N4-graphene on electrodes and immobilizing antibodies on the surface of carboxylated g-C3N4 through amidation. The specific immunoreaction between SCCA and antibody resulted in the decrease of ECL intensity and the intensity decreased linearly with the logarithm of SCCA concentration in the range of 0.025-10 ng mL(-1) with a detection limit of 8.53 pg mL(-1). The developed ECL immunosensor exhibited high sensitivity, good reproducibility and long-term stability, which possessed great potential for cancer detection in clinical laboratory diagnosis.

Metal ions-based immunosensor for simultaneous determination of estradiol and diethylstilbestrol

Environmental estrogens (EEs) can cause various endocrine diseases. Herein, we designed an ultrasensitive electrochemical immunosensor for simultaneous detection of two typical EEs, estradiol and diethylstilbestrol. These two analytes were immobilized on graphene sheet (GS) modified glassy carbon electrode (GCE). Amino-group functionalized mesoporous Fe3O4 (Fe3O4-NH2) was loaded with Pb(2+) or Cd(2+), and then incubated with estradiol and diethylstilbestrol antibodies, respectively. Using an electrochemical analysis technique, two well-separated peaks were generated by the redox reaction of Pb(2+) or Cd(2+), making the simultaneous detection of two analytes on the electrode possible. Subsequently, square wave anodic stripping voltammetry (SWASV) and electrochemical impedance spectroscopy (EIS) were used to investigate the electrochemical behaviors of the immunosensor. Under optimized conditions, the SWASV peak currents were proportional to the concentrations of estradiol and diethylstilbestrol in the range from 0.050 pg mL(-1) to 100 ng mL(-1) and 1.0 pg mL(-1) to 100 ng mL(-1), respectively. The immunosensor exhibited highly sensitive response to estradiol with a detection limit of 0.015 pg mL(-1) and diethylstilbestrol with a detection limit of 0.38 pg mL(-1). Furthermore, the immunosensor was satisfactorily employed to detect estradiol and diethylstilbestrol simultaneously in water samples.