Highly sensitive electrochemical immunoassay for human IgG using double-encoded magnetic redox-active nanoparticles

Biosensors based on DNA-functionalized CdTe quantum dots for the enhanced electrochemical detection of human-IgG

Electrochemical detection of human-IgG via biosensors is vital in clinical diagnostics, owing to their simple equipment, facile operation, high selectivity, economical, short diagnostic time, fast response, and easy miniaturization, but the need to improve sensitivity for protein detection is still a barrier limiting its wider practical applications. A hypersensitized electrochemical biosensor based on steric effects for IgG detection was developed in this work. The results indicate that IgG-modified sig-DNA attached to CdTe quantum dots (CdTe-sig-DNA) limited the ability of CdTe-sig-DNA or CdTe-sig-DNA-IgG conjugate to hybridize through the captured DNA strand (cap-DNA) immobilized on a chitosan/nitrogen-doped carbon nanocomposite (CS/N-C) modified glassy carbon electrode surface (GCE). The concentration of IgG based on CdTe concentration was detected by differential pulse anode stripping voltammetry (DPASV) on the electrode surface. The efficiency for hybridizing CdTe-sig-DNA with cap-DNA was found to be logarithmically inverse to the concentration of IgG attached. A highly sensitive and selective detection of IgG from 5 pM to 50 μM with a relatively low detection limit of 1.7 pM was achieved. Therefore, the steric hindrance effect of IgG limited the quantity of DNA that could be functionalized on CdTe QDs, significantly improving the signal, and providing a practical strategy for the clinical analysis of IgG.

Prussian blue-doped PAMAM dendrimer nanospheres for electrochemical immunoassay of human plasma cardiac troponin I without enzymatic amplification

Rapid and accurate identification of cardiac troponin I (cTnl) in biological fluids is very essential for judging acute myocardial infarction (AMI).

New photothermal immunoassay of human chorionic gonadotropin using Prussian blue nanoparticle-based photothermal conversion

A new near-infrared-based photothermal immunosensing strategy was developed for the sensitive and feasible detection of human chorionic gonadotropin (HCG) by use of a Prussian blue nanoparticle-based photothermal conversion system. Prussian blue nanospheres synthesized by the one-pot method were used for the labeling of anti-HCG detection antibody. A sandwich-type immunoreaction was initially conducted on a monoclonal anti-HCG antibody-coated microplate with a nanoparticle-labeled signal antibody. Accompanying formation of the sandwiched immunocomplex, Prussian blue nanospheres caused photothermal conversion under 980-nm laser irradiation, thereby resulting in an increase of the temperature of the detection system measured by a portable digital thermometer. The properties and factors influencing the analytical performance of the photothermal immunoassay were studied in detail. Under the optimal conditions, the Prussian blue nanoparticle-based photothermal immunoassay exhibited good temperature responses relative to target HCG concentrations within the dynamic range of 0.01-100 ng mL^-1 at a low detection limit of 5.8 pg mL^-1. This system also displayed good anti-interference behavior with regard to other cancer biomarkers, good reproducibility, and relatively long storage stability. The method accuracy was evaluated for analysis of human serum specimens, giving results that matched well with those obtained with a commercial HCG enzyme-linked immunosorbent assay kit. Importantly, this protocol is promising for advanced development of photothermal immunoassays. Graphical abstract.

Label-free sensitive luminescence biosensor for immunoglobulin G based on Ag6Au6 ethisterone cluster-estrogen receptor α aggregation and graphene

A specific and label-free "on-off-on" luminescence biosensor based on a novel heterometallic cluster [Ag₆Au₆(ethisterone)₁₂]-estrogen receptor α (Ag₆Au₆Eth-ERα) aggregation utilizing graphene oxide (GO) as a quencher to lead a small background signal was firstly constructed to detect immunoglobulin G (IgG) with a simple process and high selectivity. The efficient photoluminescent (PL) Ag₆Au₆Eth-ERα aggregation is strongly quenched by GO. In the presence of IgG, the PL of this system will be restored, and perceivable by human eyes under UV lamp excitation (365 nm). The quenching mechanism of GO on Ag₆Au₆Eth-ERα and enhancement mechanism of IgG on Ag₆Au₆Eth-ERα-GO were investigated in detail. Under the optimum conditions, the biosensor for high sensitive IgG detection expressed a wider linear range of 0.0078-10 ng/mL and a lower detection limit of 0.65 pg/mL with good stability and repeatability, which provided a new approach for label-free IgG detection.

Fabrication of a label-free electrochemical immunosensor using a redox active ferrocenyl dendrimer

An amperometric immunosensor based on a redox active ferrocenyl end-grafted PAMAM dendrimer provides highly sensitive detection of immunoglobulin, down to 2 ng mL⁻¹.

Silver nanowire-based electrochemical immunoassay for sensing immunoglobulin G with signal amplification using strawberry-like ZnO nanostructures as labels

The quick development of nanoscience and nanotechnology has paved the way for ultrasensitive biosensing and analysis. In this work, an ultrasensitive electrochemical immunosensor was developed for the detection of human immunoglobulin G (IgG) by combining with a newly designed trace tag on a disposable immunosensor array. The array was prepared by immobilizing captured antibodies on ultralong Ag nanowires, whilst the trace tag was prepared by loading horseradish peroxidase (HRP)-labeled goat anti-human IgG (HRP-anti-IgG) on thionine (TH)-doped mesoporous ZnO nanostrawberries (MP-ZnO). With a sandwich-type immunoassay format, mainly due to crystalline framework and high surface area of the mesoporous (MP) materials, as well as the superconductivity of silver nanowires, the electrochemical signal was significantly amplified. The linear range of the developed immunosensor is 0.01-200 ng mL(-1) and the detection limit is 4 pg mL(-1) IgG, which make the hierarchically nanostructured composites very promising candidates for the next-generation sandwich-type electrochemical immunoassays.