Black palladium nanoparticle-based lateral flow immunoassay for cardiovascular disease diagnosis†

Lateral flow immunoassay (LFIA) based on gold nanoparticles (AuNPs) has emerged as a rapid and cost-effective tool for point-of-care diagnostics, yet it remains limited by its low sensitivity in colorimetric detection. Herein, we report a black palladium nanoparticle (PdNP)-based LFIA system for the detection of lipoprotein-associated phospholipase A2 (Lp-PLA2), a key biomarker of cardiovascular diseases. The intrinsic black color of PdNPs provided higher visual discriminability at low concentrations compared with AuNPs. Moreover, PdNP probes synthesized through chemical covalent conjugation with antibodies had the advantages of enhancing the target recognition ability. The PdNP-based LFIA achieved a 12-fold lower visual detection limit and a 100-fold wider linear range compared with AuNP-based LFIA. Moreover, clinical validation detection results using 57 serum samples were in strong accordance with the clinical methods. This work not only establishes PdNP-based LFIA to address the long-standing sensitivity limitations of colorimetric LFIA, but also offers a robust diagnostic tool for early cardiovascular disease diagnosis in resource-limited settings.