Exogenous-Label-Free Colorimetric/SERS Dual-Mode Immunosensing Platform Driven by Au NCs@Pt Nanozyme for Ultrasensitive and Rapid Detection of the Pancreatic Cancer Biomarker CA19-9.

Early diagnosis of pancreatic cancer is critical for improving survival rates, yet conventional CA19-9 immunoassays and labeled surface-enhanced Raman scattering (SERS) methods are often limited by slow processing, complex fabrication, or instability. Herein, we report a rapid, exogenous-label-free colorimetric/SERS dual-mode sandwich immunoassay utilizing coral-like gold nanocores decorated with platinum clusters (Au NCs@Pt). This unique nanozyme architecture synergistically integrates high-density electromagnetic hotspots with efficient peroxidase-like activity to catalyze the oxidation of TMB. The resulting oxidized product (oxTMB) acts as an intrinsic Raman reporter, eliminating the need for exogenous labels and enabling catalysis-amplified signal reporting. The proposed platform achieves quantitative CA19-9 detection within 15 min, featuring a linear range of 1-200 IU/mL and an ultralow limit of detection (LOD) of 0.16 IU/mL. Clinical validation using 60 serum samples demonstrated 100% diagnostic accuracy (AUC = 1.00 in this cohort study). This strategy successfully overcomes the limitations of traditional SERS tags, offering a robust, ultrasensitive tool for the point-of-care screening of digestive system malignancies.