Colorimetric immunoassay for Listeria monocytogenes by using core gold nanoparticles, silver nanoclusters as oxidase mimetics, and aptamer-conjugated magnetic nanoparticles
The authors describe a rapid colorimetric assay for Listeria monocytogenes (L. monocytogenes) based on the o-phenylenediamine-mediated deaggregation of gold nanoparticles. Silver nanoclusters are used as an artificial enzyme that can oxidize o-phenylenediamine to form o-benzoquinone diamine. Aptamer and IgY antibodies were chosen to conjugate with magnetic beads and silver nanoclusters, respectively, which can recognize and bind L. monocytogenes at different specific binding sites. This results in the disassembly of colloidal gold nanoparticles which is accompanied by a color change from blue to red, with peaks at 730 and 525 nm, respectively. The method allows L. monocytogenes to be colorimetrically determined in the 10 to 106 cfu·mL−1 concentration range without pre-enrichment, and the limit of detection is as low as 10 cfu·mL−1. Recoveries ranging from 97.4 to 101.3% are found when analyzing spiked food samples. The assay is rapid, sensitive and specific.
KeywordsFood safety Visual detection de-aggregation Immunomagnetic separation Nanozyme o-phenylenediamine
This study was supported by the Chinese National Natural Science Foundation (Grant No. 81602894, 81602895, and 81473018), China Postdoctoral Science Foundation (Grant No. 2017 T100214 and 2016 M591492), the Development Foundation of Science and Technology in Jilin Province of China (Grant No. 20170204003SF) and Graduate Innovation Fund of Jilin University (Grant No. 2017084).
Compliance with ethical standards
The author(s) declare that they have no competing interests.