Ultrabright NIR AIEgen nanoparticles-enhanced lateral flow immunoassay platform for accurate diagnostics of complex samples

Accurate and sensitive near-infrared (NIR) luminescent lateral flow immunoassay (LFIA) has attracted considerable attention in the field of point-of-care testing (POCT). However, the detection accuracy and sensitivity are often compromised by the low fluorescence quantum efficiency (<10%) of the NIR fluorescent probe. Herein, ultrabright NIR AIEgen nanoparticles (PS@AIE₈₃₀NPs) composed of polystyrene (PS) nanoparticles and NIR aggregation-induced emission luminogen (AIEgen) with the maximum emission at 830 nm (AIE₈₃₀) is reported, and its potential to promote an accurate and sensitive detection of complex samples by LFIA is described. The relative quantum yield (QY) of the PS@AIE₈₃₀NPs was 14.76%, which was superior to that of the polymer embedding method and indocyanine green (ICG)-based NIR nanoparticles. The PS@AIE₈₃₀NPs immunolabeled-LFIA combined with laboratory-built NIR-LFIA portable quantitative instruments (detected light range > 800 nm) completely eliminated background interference and allowed highly accurate and sensitive detection without any pre-treatment steps. The limits of detection (LODs) for aflatoxin B₁ (AFB₁) in soy sauce, alpha hemolysin (Hla) of Staphylococcus aureus biomarker in joint fluid, and C-reactive protein (CRP) in human haemolysed samples were 0.01 ng mL⁻¹, 0.02 µg mL⁻¹, and 0.156 mg L⁻¹, respectively, commensurating with those of the corresponding gold standard assays and covering the detection range of interests. It is anticipated that the ultrabright NIR AIEgen nanoparticles will serve as a universally applicable signal probe for NIR-LFIA diagnostics, promising to expand the range of applications for quantitative detection of complex samples.