One-Step Coassembly of Quantum Dots and Amphiphilic Polymer into Superparticles for Highly Sensitive Lateral Flow Immunoassay

Submicron nanobeads encapsulated with hundreds of quantum dots (QDs) exhibit ultrahigh brightness, signal amplification for biosensing, and excellent photostability, making them ideal labels for lateral flow immunoassay at point-of-care. Nevertheless, their assembly into QD superparticles remains hampered by tedious multistep surface chemistries and by fluorescence losses arising from interdot energy transfer and surface defect-mediated quenching. Here we report a one-step coassembly route that directly produces QD superparticles in the presence of an amphiphilic polymer. Interdot spacing within the superparticles is dictated by the QDs/polymer feed ratio, while the size of the superparticles is tuned through the aqueous surfactant concentration. After optimization of the superparticle preparation, different-sized superparticle-based immunological labels were evaluated using lateral flow immunoassays for cardiac troponin I (cTnI) detection, and a size of 167 ± 31 nm demonstrated optimized sensitivity. Finally, the analytical performance of the superparticle-based lateral flow immunoassay (LFIA) was compared with that of assays using time-resolved fluorescent nanoparticles and traditional quantum dot nanobeads (QDNBs). For the detection of cardiac troponin I (cTnI), the limits of detection of LFIA employing superparticles, time-resolved fluorescent nanoparticles, and traditional QDNBs were 0.35, 3.05, and 0.23 ng/mL, respectively. These results demonstrate that the superparticle system, formed by coassembling quantum dots with amphiphilic polymers, offers a versatile and straightforward strategy for enhancing the sensitivity of fluorescent lateral flow immunoassays.