The detection and quantification of low-abundance molecular biomarkers in biological samples is challenging. Here, we show that a plasmonic nanoscale construct serving as an ‘add-on’ label for a broad range of bioassays improves their signal-to-noise ratio and dynamic range without altering their workflow and readout devices. The plasmonic construct consists of a bovine serum albumin scaffold with approximately 210 IRDye 800CW fluorophores (with a fluorescence intensity approximately 6,700-fold that of a single 800CW fluorophore), a polymer-coated gold nanorod acting as a plasmonic antenna and biotin as a high-affinity biorecognition element. Its emission wavelength can be tuned over the visible and near-infrared spectral regions by modifying its size, shape and composition. It improves the limit of detection in fluorescence-linked immunosorbent assays by up to 4,750-fold and is compatible with multiplexed bead-based immunoassays, immunomicroarrays, flow cytometry and immunocytochemistry methods, and it shortens overall assay times (to 20 min) and lowers sample volumes, as shown for the detection of a pro-inflammatory cytokine in mouse interstitial fluid and of urinary biomarkers in patient samples.
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The main data supporting the results in this study are available within the paper and its Supplementary Information. Raw imaging data (collected and analysed via the software indicated in the Reporting Summary) are available from figshare with the identifier https://doi.org/10.6084/m9.figshare.11888055.
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We acknowledge support from National Science Foundation (award nos. CBET-1512043 and CBET-1900277), National Institutes of Health (R01DE027098 and R01CA141521), Center for Multiple Myeloma Nanotherapy (U54 CA199092) and a grant from the Barnes-Jewish Hospital Research Foundation (no. 3706). We thank K. Naegle for providing access to a LI-COR Odyssey CLx scanner, L. Setton for the flow cytometer, J. Rudra and T. Pietka for Luminex readers, and the Nano Research Facility (NRF) and Institute of Materials Science and Engineering (IMSE) at Washington University for providing access to electron microscopy facilities. We also thank G. Genin for inspiring discussions and suggestions.
J.L., J.J.M. and S.S. are inventors on a provisional patent related to this technology. The technology has been licensed by the Office of Technology Management at Washington University in St. Louis to Auragent Bioscience LLC, which is developing plasmonic-fluor products. J.L., J.J.M. and S.S. are co-founders/shareholders of Auragent Bioscience LLC. These potential conflicts of interest have been disclosed and are being managed by Washington University in St. Louis. The remaining authors declare no competing interests.
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Luan, J., Seth, A., Gupta, R. et al. Ultrabright fluorescent nanoscale labels for the femtomolar detection of analytes with standard bioassays. Nat Biomed Eng 4, 518–530 (2020). https://doi.org/10.1038/s41551-020-0547-4