Detection of bitter limonin in citrus samples using plasmonic gold nanobipyramid-based dual-mode lateral flow immunoassay.

The detection of limonin, a bitter compound in citrus samples, is crucial for maintaining product quality, safety, and marketability and ultimately benefits both producers and consumers. In this assay to effectively modify the monoclonal antibody on gold nanobipyramids (AuNBPs), we replaced the original hexadecyltrimethylammonium bromide coating (CTAB) with SH-PEG2000-NHS. Then AuNBPs were modified with a limonin-specific monoclonal antibody (mAb) to create an AuNBP@mAb immunoprobe. We present a novel plasmonic AuNBP-based lateral flow immunoassay (LFIA) for colorimetric and photothermal assay of limonin. The limit of detection for the colorimetric mode of AuNBPs is 4.8 ng mL. The limit of detection for the photothermal mode of AuNBPs is 3.8 ng mL. Validation experiments using citrus samples demonstrate the robustness and reliability of the LFIA in real-world applications. Comparative analysis with ultra-high performance liquid chromatography tandem mass spectrometry confirms the accuracy of our LFIA.