Plasmonic Enzyme-Linked Immunosorbent Assay Using Nanospherical Brushes as a Catalase Container for Colorimetric Detection of Ultralow Concentrations of Listeria monocytogenes

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• 作者：Rui Chen ; Xiaolin Huang ; Hengyi Xu ; Yonghua Xiong ; Yanbin Li
• 刊名：ACS Applied Materials & Interfaces
• 出版年：2015
• 出版时间：December 30, 2015
• 年：2015
• 卷：7
• 期：51
• 页码：28632-28639
• 全文大小：495K
• ISSN：1944-8252

文摘

Plasmonic enzyme-linked immunosorbent assay (pELISA) based on catalase (CAT)-mediated gold nanoparticle growth exhibits ultrahigh sensitivity for detecting disease-related biomarkers using sandwich formats. However, the limit of detection (LOD) of this strategy for Listeria monocytogenes is only around 10³ CFU/mL, which considerably exceeds the amount of L. monocytogenes commonly present in food products (<100 CFU/g). Herein, we report an improved pELISA method for detection of L. monocytogenes at ultralow concentrations with the sandwich formats using silica nanoparticles carrying poly(acrylic acid) brushes as a “CAT container” to increase enzyme loading for enhancing the detection signal. Under optimal conditions, the proposed pELISA exhibits good specificity and excellent sensitivity for L. monocytogenes with a LOD of 8 × 10¹ CFU/mL in 0.01 M phosphate-buffered saline, via a reaction that can be discriminated by the naked eye. The LOD obtained by this method was 2 and 5 orders of magnitude lower than that of conventional CAT-based pELISA and horseradish peroxidase (HRP)-based conventional ELISA, respectively. Coupled with large-volume immunomagnetic separation, the LOD for L. monocytogenes-spiked lettuce samples reached 8 × 10¹ CFU/g. The improved pELISA also exhibited a great potential in detecting a single cell of L. monocytogenes in 100 μL of solution.