Highly sensitive SERS-active substrate with uniform gold nanostructures on heat-treated Ni foam for detection of cardiovascular disease biomarker†

Surface-enhanced Raman scattering (SERS) immunoassays for biomarker detection have attracted considerable attention owing to their high sensitivity and selectivity. In this study, we fabricated hotspot-rich SERS-active substrates by depositing gold after forming a protruding structure on the surface via high-temperature heat treatment. The structure formed by the heat treatment enabled a more uniform and dense gold nanostructure, which provided more hotspots within the focal volume of the Raman laser, thereby enhancing the SERS signal. This was verified by calculating the electromagnetic field using a finite element method. The fabricated SERS-active substrates and 50 nm gold nanoparticles were used to perform a competitive assay for the detection of cardiac troponin I (cTnI). The assay demonstrated a cTnI detection range of 10⁰–10⁶ pg mL⁻¹ with a detection limit of 5.8 pg mL⁻¹. This indicates that the SERS-active substrate fabricated from the Ni foam has the potential to be used as a sensitive and selective tool for the detection of various biomarkers in complex biological samples.