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Plasmonic Enzyme-Linked Immunosorbent Assay Using Nanospherical Brushes as a Catalase Container for Colorimetric Detection of Ultralow Concentrations of Listeria monocytogenes
journal contribution
posted on 2015-12-30, 00:00 authored by Rui Chen, Xiaolin Huang, Hengyi Xu, Yonghua Xiong, Yanbin LiPlasmonic 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.