Tri-modal lateral flow immunoassay for highly sensitive and reliable detection of C-reactive protein using Prussian...

Lateral flow assays (LFAs) are widely used for point-of-care biomarker detection; however, conventional gold nanoparticle (AuNP)-based LFAs suffer from insufficient sensitivity and poor quantitative reliability due to their single-mode colorimetric readout. In particular, reliable quantification of clinically relevant protein biomarkers such as C-reactive protein (CRP) remains challenging, as it requires not only signal amplification but also analytical robustness across complex biological matrices.

Here, we report a Prussian blue-coated gold nanozyme (Au@PB NZ) that integrates intrinsic coloration, catalytic amplification, and surface-enhanced Raman scattering (SERS) within a single probe for sensitive and quantitative detection of CRP. The Au@PB NZs exhibit a deep-blue coloration for direct visual readout, strong peroxidase-like activity enabling catalytic signal amplification via 3,3',5,5'-tetramethylbenzidine (TMB) oxidation, and a distinct Raman signature further enhanced by the plasmonic Au core. When incorporated into antibody-functionalized LFA strips, the probe enabled tri-modal detection, markedly improving analytical performance across visual, catalytic, and SERS modes. The assay achieved limits of detection of 10 ng mL^-1 (visual), 0.6 ng mL^-1 (catalytic), and 0.1 ng mL^-1 (SERS), with enhanced analytical sensitivity and reliable quantitative performance in human serum samples.

This work establishes a tri-modal nanozyme-based LFA platform that combines signal amplification and spectroscopic readout for improved analytical reliability. The proposed strategy provides a robust and versatile framework for quantitative point-of-care detection of clinically relevant protein biomarkers and advances the development of multi-signal nanozyme-enabled diagnostic systems.