On-Paper Enzyme-Linked and Metal-Linked Immunosorbent Assays for Low-Cost Decentralized Testing of Carcinoembryonic Antigen

Abstract

This work reports two simplified paper-based approaches for immunosensing of carcinoembryonic antigen (CEA) in serum. On-paper enzyme-linked immunosorbent assay (p-ELISA) (using enzymatic generation of a colored product) and metal-linked immunosorbent assay (p-MeLISA) (using gold nanoparticles (AuNPs) as labels) were implemented using low-cost diagnostic bio-conjugated paper mini disks as platforms for the fast colorimetric immunosensing of CEA in human serum. The colour intensity was captured with a commercial scanner and analyzed using an open-source software. Different parameters of the preparation of the bioconjugated disks and of the immunoassays were studied and, under the selected conditions, LODs of 0.4 ng mL⁻¹ with p-ELISA and 0.1 ng mL⁻¹ with p-MeLISA were achieved while recoveries of CEA in serum samples were in the range from 88 to 112 % with coefficient of variation of <12 %. The assay time was 90 s for p-ELISA and 85 s for p-MeLISA. The immunoassays exhibited satisfactory selectivity in the presence of other cancer biomarkers and good stability under storage. Thanks to simple and rapid fabrication and modification, simple analysis protocol, affordability (<0.05 € per device), equipment-free quantification, low sample and reagents requirments, stability and satisfactory analytical characteristics, these approaches are fit-for-purpose for assay of CEA in serum at the point-of care in resource-limited settings.