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

Abstract 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/dSiO₂), 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/dSiO₂ is captured on the electrode surface via a sandwich immunoreaction, which enhances the ECL signal by decreasing the distance between PEI‐Ru/dSiO₂ 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 1–10⁴ 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.