Electrochemiluminescence Lateral Flow Immunoassay Using Ruthenium(II) Complex-Loaded Dendritic Mesoporous Silica Nanospheres for Highly Sensitive and Quantitative Detection of SARS-CoV-2 Nucleocapsid Protein

Lateral flow immunoassays (LFIA) are widely used for the cost-effective and rapid detection of diverse analytes. However, traditional LFIA suffers from difficulties in providing quantitative results and has low sensitivity. Herein, LFIA is combined with electrochemiluminescence (ECL), a leading transduction technique with high sensitivity and wide dynamic range, to achieve highly sensitive and quantitative detection of severe acute respiratory syndrome coronavirus nucleocapsid protein (SARS-CoV-2 N protein). Ruthenium(II)-based complexes are synthesized and loaded into dendritic mesoporous silica nanospheres (PEI-Ru/dSiO 2 ), which possessed central-radial pore channels and served as tags for ECL-LFIA. The electrodes are fabricated on a nitrocellulose (NC) membrane, which simplifies the structure of the ECL-LFIA. PEI-Ru/dSiO 2 is captured on the electrode surface via a sandwich immunoreaction, which enhances the ECL signal by decreasing the distance between PEI-Ru/dSiO 2 and the electrode surface. Using 2,2-bis(hydroxymethyl)-2,2′,2′'-nitrilotriethanol (BIS-TRIS) as coreactant, the ECL-LFIA is used for detecting SARS-CoV-2 N protein, with a linear range of 1–10 4 ng mL −1 and a limit of detection (LOD) of 0.52 ng mL −1 . ECL-LFIA can also be used to detect analytes in complex matrices. These results demonstrate that the prepared ECL-LFIA has great potential as a point-of-care testing platform for the rapid and quantitative detection of disease biomarkers.