Ligand-assisted core-cavity-corona cubic plasmonic nanostructures amplify immunoassays for ultrasensitive triple-mode sensing of thrombomodulin

Thrombomodulin (TM) is a critical biomarker for endothelial dysfunction, yet there is currently no simple and rapid detection method, such as immunochromatographic assay (ICA). Conventional gold nanoparticles (AuNPs)-based ICA suffers from limited sensitivity, making it unsuitable for detecting trace biomarkers. Herein, we introduced a ligand-assisted core-cavity-corona cubic plasmonic nanostructure (RCmC) amplifying immunoassays for ultrasensitive triple-mode (visual/optical/surface-enhanced Raman spectroscopy) detection of TM. This unique design features a cubic nanocage framework encapsulating an anisotropic gold nanorod and p-mercaptobenzoic acid Raman reporters internally, and decorated with surface-roughened nanocoronas externally. By coupling with the hydrophobic interactions of cetyltrimethylammonium chloride ligand, RCmC further enhanced antibody coupling efficiency, leading to a 2.5-fold increase in antibody adsorption compared to AuNPs. The RCmC-based ICA achieved a quantitative limit of detection of 0.005 ng·mL⁻¹, providing a 346-fold enhancement in quantitative performance over AuNP-based ICA. Additionally, the detection process was drastically reduced to within 5 min, with recoveries ranging from 88.80% to 103.80% and coefficients of variation between 3.32% and 7.62% for serum and urine samples. These results were consistent with those from commercial enzyme-linked immunosorbent assay kits, demonstrating the significant potential of RCmC as a signal reporter for the ultrasensitive detection of trace biomarkers.