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.
Zhang et al. (Mon,) studied this question.