Quantitative assessment of AD markers using naked eyes: point-of-care testing with paper-based lateral flow immunoassay

Liding Zhang,Xuewei Du,Ying Su,Shiqi Niu,Haiming Luo,Xiaohan Liang,Yanqing Li

doi:10.1186/s12951-021-01111-z

Abstract

Aβ42 is one of the most extensively studied blood and Cerebrospinal fluid (CSF) biomarkers for the diagnosis of symptomatic and prodromal Alzheimer’s disease (AD). Because of the heterogeneity and transient nature of Aβ42 oligomers (Aβ42Os), the development of technologies for dynamically detecting changes in the blood or CSF levels of Aβ42 monomers (Aβ42Ms) and Aβ42Os is essential for the accurate diagnosis of AD. The currently commonly used Aβ42 ELISA test kits usually mis-detected the elevated Aβ42Os, leading to incomplete analysis and underestimation of soluble Aβ42, resulting in a comprised performance in AD diagnosis. Herein, we developed a dual-target lateral flow immunoassay (dLFI) using anti-Aβ42 monoclonal antibodies 1F12 and 2C6 for the rapid and point-of-care detection of Aβ42Ms and Aβ42Os in blood samples within 30 min for AD diagnosis. By naked eye observation, the visual detection limit of Aβ42Ms or/and Aβ42Os in dLFI was 154 pg/mL. The test results for dLFI were similar to those observed in the enzyme-linked immunosorbent assay (ELISA). Therefore, this paper-based dLFI provides a practical and rapid method for the on-site detection of two biomarkers in blood or CSF samples without the need for additional expertise or equipment.Graphical

Highlights

Alzheimer’s disease (AD) is a chronic neurodegenerative disorder, which may begin to develop 20–30 years before clinical onset, accompanied by progressive neuropathology, brain atrophy, and lead to cognitive decline [1,2,3]
As shown in Scheme 1a, the blood samples were firstly enriched with magnetic nanoparticle (MNP) modified by monoclonal antibodies (mAbs) 1F12, and the Aβ42 monomers (Aβ42Ms) or/and Aβ42 oligomers (Aβ42Os) were eluted for lateral flow immunoassay (LFI) analysis
The Aβ42Os–1F12–AuNP complex was first fixed by 1F12 coated on the NC membrane to form the test line 1, due to Aβ42Os were aggregated by multiple monomers, exposing several same epitopes that could be recognized by the same detection antibody (Scheme 1b)

Summary

Introduction

Alzheimer’s disease (AD) is a chronic neurodegenerative disorder, which may begin to develop 20–30 years before clinical onset, accompanied by progressive neuropathology, brain atrophy, and lead to cognitive decline [1,2,3]. The diagnosis of AD is still mainly based on clinical cognitive assessment and physical examination. Magnetic resonance imaging (MRI) for measuring brain volume and neuronal connections, and Aβ- or taubased positron-emission tomography (PET) for detecting pathological protein deposition in the brain have been used in AD diagnosis [10,11,12,13]. MRI and PET imaging tools with good diagnostic performances of brain diseases are approved for clinical use, the economic burden of imaging hinders their wide application in the identification of AD [14]. Limited MRI or PET equipment is difficult to meet the growing number of AD patients. Expect for imaging diagnosis tools, it has developed the detection of cerebrospinal fluid (CSF) biomarkers, such Aβ1-40 (Aβ40), Aβ1-42 (Aβ42), and the phosphorylation of tau (p-Tau) for AD diagnosis. The Aβ-based ELISA methods have been used as a reference for clinical diagnosis [15,16,17]

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