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Detection of E. coli labeled with metal-conjugated antibodies using lateral-flow assay and laser-induced breakdown spectroscopy


This study explores the adoption of laser-induced breakdown spectroscopy (LIBS) for the analysis of lateral-flow immunoassays (LFIAs). Gold (Au) nanoparticles are standard biomolecular labels among LFIAs, typically detected via colorimetric means. A wide diversity of lanthanide-complexed polymers (LCPs) are also used as immunoassay labels but are inapt for LFIAs due to lab-bound detection instrumentation. This is the first study to show the capability of LIBS to transition LCPs into the realm of LFIAs, and one of the few to apply LIBS to biomolecular label detection in complete immunoassays. Initially, an in-house LIBS system was optimized to detect an Au standard through a process of line selection across acquisition delay times, followed by determining limit of detection (LOD). The optimized LIBS system was applied to Au-labeled Escherichia coli detection on a commercial LFIA; comparison with colorimetric detection yielded similar LODs (1.03E4 and 8.890E3 CFU/mL respectively). Optimization was repeated with lanthanide standards to determine if they were viable alternatives to Au labels. It was found that europium (Eu) and ytterbium (Yb) may be more favorable biomolecular labels than Au. To test whether Eu-complexed polymers conjugated to antibodies could be used as labels in LFIAs, the conjugates were successfully applied to E. coli detection in a modified commercial LFIA. The results suggest interesting opportunities for creating highly multiplexed LFIAs. Multiplexed, sensitive, portable, and rapid LIBS detection of biomolecules concentrated and labeled on LFIAs is highly relevant for applications like food safety, where in-field food contaminant detection is critical.

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The authors would like to acknowledge the Laser Technologies Group at Lawrence Berkeley National Laboratories and the Environmental Microbial & Food Safety Laboratory: Beltsville, MD. This research was partially supported by the US Department of Energy, Office of Defense Nuclear Nonproliferation Research and Development, under contract number DE-AC02-05CH11231 at the Lawrence Berkeley National Laboratory. We thank Dr. Gary Nolan’s group at Stanford University and the United States Department of Agriculture for their assistance in antibody conjugation chemistry. We also acknowledge support from the National Science Foundation (DGE-1333468) and funding from the U.S. Department of Agriculture, project 1935-42000-072-02G, Center for Food Safety Engineering at Purdue University.

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Gondhalekar, C., Biela, E., Rajwa, B. et al. Detection of E. coli labeled with metal-conjugated antibodies using lateral-flow assay and laser-induced breakdown spectroscopy. Anal Bioanal Chem 412, 1291–1301 (2020). https://doi.org/10.1007/s00216-019-02347-3

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  • Laser-induced breakdown spectroscopy
  • Lateral-flow immunoassay
  • Metal-conjugated antibodies
  • E. coli
  • Lanthanides