Polydopamine nanoparticle-based colorimetric-photothermal dual-mode lateral flow immunoassay for thromboembolism...

Lateral flow immunoassay (LFIA) using gold nanoparticles (AuNPs) as signal labels is widely utilized for point-of-care diagnostics. However, it is typically limited by a single colorimetric readout and insufficient sensitivity. To address these limitations, polydopamine nanoparticles (PDANs) were introduced as alternative signal labels to enhance LFIA sensitivity. Owing to their high molar extinction coefficient and broadband absorption spanning the ultraviolet to near-infrared region, PDANs provide strong visual contrast and efficient photothermal conversion capability. Based on these advantages, a dual-mode colorimetric-photothermal LFIA platform was successfully constructed for the detection of thrombosis-related biomarkers, including thrombomodulin (TM) and α₂-plasmin inhibitor-plasmin complex (PIC), in clinical serum samples. Under optimized conditions, the visual limits of detection (vLOD) for TM and PIC were 5 ng mL^-1 and 50 ng mL^-1, respectively. Subsequently, a convenient photothermal readout was introduced, and photothermal signal amplification further improved the sensitivity by approximately 10-fold for TM and 2.5-fold for PIC, achieving dual-mode detection. Clinical validation using 48 serum samples demonstrated good agreement with the clinical method. Overall, this PDANs-based LFIA platform enhances analytical sensitivity and reliability, providing a feasible strategy for the advancement of LFIAs.