Highly bright aggregation-induced emission nanoparticle-based ratiometric lateral flow immunoassay for sensitive and user-friendly detection of carcinoembryonic antigen

The development of ultrasensitive and visually recognizable point-of-care testing (POCT) sensors for carcinoembryonic antigen (CEA) is of great importance. Advanced ratiometric strategies have been developed to improve visual recognition capability. However, most existing ratiometric methods rely on inorganic materials, which raise concerns regarding long-term biological and environmental impact. To address this, we developed an organic ratiometric fluorescent lateral flow immunoassay (FLFIA) based on matched aggregation-induced emission nanoparticles (AIENPs) for CEA detection and systematically evaluated its visual readout capability, sensitivity, accuracy, and robustness. By transforming the mono fluorescent brightness signal into a clearer green-to-red shift signal, the AIENP-based ratiometric FLFIA achieved a visual limit of detection (vLOD) of 1.25 ng/mL for CEA, representing a 3.28-fold more sensitive than the mono-response LFIA. Preliminary clinical serum measurements show a positive correlation with a commercial enzyme-linked immunosorbent assay (ELISA) (R² = 0.97), while non-expert color-card matching achieved an accuracy exceeding 92%. This work provides a promising solution for visual, sensitive, and user-friendly POCT.