Search

Label-free electrochemiluminescence (ECL) immunoassays ( lf -ECLIA), based on biomarker-induced ECL signal changes, have attracted increasing attention due to the simple, rapid, and low-cost detection of biomarkers without secondary antibodies and complicated labeling procedures. However, the interaction rule and mechanism between analytical interfaces and biomarkers have rarely been explored. Herein, the interactions between biomarkers and analytical interfaces constructed by assembly of a nanoluminophore and antibody-functionalized gold nanoparticles on an indium tin oxide electrode were studied. The nanoluminophore was synthesized by mixing Cu 2+ /l-cysteine chelate and N-(4-Aminobutyl)-N-ethylisoluminol-bifunctionalized gold nanoparticles with chitosan. It was found that positively charged biomarkers increased the ECL intensity, whereas negatively charged biomarkers decreased the ECL intensity. The assembly pH influenced the biomarker charges, which determined the ECL enhancement or inhibition. The detection pH only affected the ECL intensity but not the ECL changing trends. Based on the ECL signal changes, a charge-dependent lf -ECLIA was established, which exhibited inhibition responses to negatively charged human immunoglobulin G and copeptin and enhancement responses to positively charged cardiac troponin I, heart-type fatty acid binding protein, brain natriuretic peptide, and SARS-CoV-2 N protein. The linear range was 0.1-1000 pg/mL, and the detection limits were distributed in 0.024-0.091 pg/mL. Besides, a mechanism of the charge-dependent ECL enhancement and inhibition effects is proposed, which is very important for the development of new lf -ECLIA methodologies.

A novel electrochemiluminescence (ECL) immunosensor was developed for the determination of N-terminal pro-brain natriuretic peptide (NT-proBNP) by using N-(aminobutyl)-N-(ethylisoluminol) (ABEI)-functionalized gold nanodots/chitosan/multiwalled carbon nanotubes (ABEI/GNDs/chitosan/COOH-MWCNTs) hybrid as nanointerface. First, ABEI/GNDs/chitosan/COOH-MWCNTs hybrid nanomaterials were grafted onto the surface of ITO electrode via the film-forming property of hybrid nanomaterials. The anti-NT-proBNP antibody was connected to the surface of modified electrode by virtue of amide reaction via glutaraldehyde. The obtained sensing platform showed strong and stable ECL signal. When NT-proBNP was captured by its antibody immobilized on the sensing platform via immunoreaction, the ECL intensity decreased. Direct ECL signal changes were used for the determination of NT-proBNP. The present ECL immunosensor demonstrated a quite wide linear range of 0.01-100 pg/mL. The achieved low detection limit of 3.86 fg/mL was about 3 orders of magnitude lower than that obtained with electrochemistry method reported previously. Because of the simple and fast analysis, high sensitivity and selectivity, and stable and reliable response, the present immunosensor has been successfully applied to quantify NT-proBNP in practical plasma samples. The success of the sensor in this work also confirms that ABEI/GNDs/chitosan/COOH-MWCNTs hybrid is an ideal nanointerface to fabricate a sensing platform. Furthermore, the proposed strategy could be applied in the detection of other clinically important biomarkers.

A novel nanoparticle-based electrochemiluminescence (ECL) immunosensor was designed for highly sensitive and selective detection of human cardiac troponin I (cTnI), an important Acute Myocardial Infarction (AMI)-related biomarker, by using N-(aminobutyl)-N-(ethylisoluminol)-functionalized gold nanoparticles (ABEI-AuNPs) as labels. ABEI-AuNPs were successfully synthesized via a simple seed growth method. A great number of luminescence molecules ABEI as stabilizers were coated on the surface of the AuNPs, which exhibited better ECL activities than previously reported luminol functionalized gold nanoparticles. ABEI-AuNPs were used as new ECL labels to build bio-probes by conjugation with secondary antibodies, which showed good ECL activity, immunological activity, and stability. Another kind of AuNPs functionalized with streptavidin was modified on the electrode surface for biotinylated antibodies capture through the specific interaction of biotin/streptavidin and enhancing the electrical connectivity. By combining with the novel ECL labels and amplification of AuNPs and biotin-streptavidin system, a high sensitive sandwich-type electrochemiluminescence immunoassay was developed for detecting human cTnI with a low detection limit of 2 pg/mL. The immunosensor showed good precision, acceptable stability and reproducibility and could be used for the detection of cTnI in real samples, which was of great potential application in clinical analysis. Importantly, the sensitive detection would have far more diagnostic value than would absolute measurements during the early stage of AMI., (Copyright © 2011 Elsevier B.V. All rights reserved.)

Gold nanoprisms with average edge size of approximately 140 nm and thickness of approximately 8 nm were achieved in high-purity ( approximately 97%) by exploiting the electrostatic aggregation and shape effects through a modified seed-mediated approach. The proposed strategy lies in the dramatically different stability and aggregation potential between the produced gold nanoprisms and spherical gold nanoparticles, which can be modulated by varying the anion concentration in the reaction solution. Hence, the gold nanoprisms spontaneously aggregated into precipitate whereas most of the spherical ones were still kept in the solution. Moreover, this strategy is also flexible enough that ultra-small gold nanoprisms with average width less than 50 nm can be collected in good-purity. The structure and optical properties of these nanoprisms have been studied by TEM, SAED, XRD and UV-vis-NIR spectroscopy, respectively. These high-purity colloidal gold nanoprisms exhibit remarkably enhanced surface plasmon resonance (SPR) as well as strong near-infrared absorption. Furthermore, we have also investigated their potential for biosensing based on the sensitive changes of SPR band induced by the antibody-antigen recognition events. The experimental results clearly suggest that gold nanoprisms can be a promising nanostructured system for plasmonic sensor applications., (Copyright (c) 2010 Elsevier Inc. All rights reserved.)