Plasmon-Enhanced Quantum Dot Nanobeads-Based Lateral Flow Assay with Lower Background and Improved Sensitivity

Developing a quantum dot (QD) nanobeads-based lateral-flow assay (LFA) is of great importance for achieving ultrasen-sitive, quantitative, and rapid testing of clinical specimens at the point-of-care. However, the QD nanobeads currently used in LFA still have drawbacks such as large particle size, which leads to high background, easy aggregation, and poor fluidity. To address these issues, a promising strategy is to utilize plasmonic energy transfer from gold nanoparticles (AuNPs) to QDs in order to create smaller size and brighter fluorescent QD nanobeads, without simply increasing the amount of QDs encapsulated in the nanobeads. In this study, we prepared the plasmon-enhanced quantum dot nano-beads (PEQNB) by encapsulating AuNPs and QDs into polymer nanobeads using the versatile emulsion-solvent evapora-tion method. We were able to detect as low as ~4347 PEQNBs nanoparticles using a gel imager, which is 14.6 times brighter than the QD nanobeads of a similar size. Compared to QD nanobeads of similar size, the PEQNB-based LFA for interleukin-6 detection exhibited higher fluorescent signal and lower background. The detection limit of PEQNB-based LFA was 1.63-fold higher than that of QD nanobeads. Furthermore, compared to larger-sized QD nanobeads with aver-age diameter of 131.1nm, PEQNB with average diameter of 78.6 nm based LFA exhibited similar levels of fluorescence intensity, but 1.55-fold lower background signal and 1.44-fold lower detection limits. This work demonstrates that opti-mized plasmon-enhanced QD nanobeads can further increase the sensitivity and lower the background signals of ultra-sensitive QD nanobeads-based LFA for disease diagnosis at point-of-care.