Dual-Readout Sandwich Immunoassay for Device-Free and Highly Sensitive Anthrax Biomarker Detection

• Published in: Analytical chemistry (Washington) Vol. 92; no. 11; pp. 7845 - 7851
• Main Authors: Larkin, Isaac N, Garimella, Viswanadham, Yamankurt, Gokay, Scott, Alexander W, Xing, Hang, Mirkin, Chad A
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 02.06.2020
• Subjects: Anthrax; Anthrax - diagnosis; Antibodies; Antibodies, Monoclonal - chemistry; Antigens; Antigens, Bacterial - analysis; Bacterial Toxins - analysis; Biomarkers; Biomarkers - analysis; Chemistry; Colorimetry; Gold; Gold - chemistry; Immunoassay; Light scattering; Metal Nanoparticles - chemistry; Monoclonal antibodies; Platinum; Protective antigen; Signal transduction
• ISSN: 0003-2700; 1520-6882
• DOI: 10.1021/acs.analchem.0c01090

We report a dual-readout, AuNP-based sandwich immunoassay for the device-free colorimetric and sensitive scanometric detection of disease biomarkers. An AuNP-antibody conjugate serves as a signal transduction and amplification agent by promoting the reduction and deposition of either platinum or gold onto its surface, generating corresponding colorimetric or light scattering (scanometric) signals, respectively. We apply the Pt-based colorimetric readout of this assay to the discovery of a novel monoclonal antibody (mAb) sandwich pair for the detection of an anthrax protective antigen (PA ). The identified antibody pair detects PA down to 1 nM in phosphate-buffered saline and 5 nM in human serum, which are physiologically relevant concentrations. Reducing gold rather than platinum onto the mAb-AuNP sandwich enables scanometric detection of subpicomolar PA concentrations, over 3 orders of magnitude more sensitive than the colorimetric readout.