One-Pot, Two-Stage Synthesis of Carboxylate-Functionalized Fluorescent Polymer Nanoparticles for Ultrasensitive Fluorescent Lateral Flow Immunoassays

We have developed a one-pot, two-stage method for the synthesis of highly monodispersed fluorescent polystyrene nanoparticles with surface carboxyl functional groups. The fluorescent nanoparticles have a tunable size range of 150−300 nm and excellent photo/chemical stability. Through conjugating antibodies to the surface carboxyl groups, various lateral flow immunoassays (LFIAs) using the fluorescent nanoparticles as the reporters have been developed, achieving a visual limit of detection (LOD) of 39 mIU mL−1 using human chorionic gonadotropin as the model sample. This LOD is 8-fold and 64-fold better as compared to LFIAs using AuNPs and free dye as reporters, respectively. The LODs of our optimized LFIAs are 3 pg mL−1 for HIV-1 p24, 4 ng mL−1 for Zika NS1, and 1 and 0.5 ng mL−1 for Staphylococcus aureus enterotoxin types A and B, respectively. These LOD values are below the clinical cutoffs and are comparable to ELISA results reported in the literature.