Colorimetric detection of Staphylococcus aureus using gold nanorods labeled with yolk immunoglobulin and urease, magnetic beads, and a phenolphthalein impregnated test paper
A colorimetric test is described for the rapid detection of Staphylococcus aureus (SA). Gold nanorods (AuNRs) are first labeled with urease and yolk immunoglobulin (IgY). This probe can specifically bind SA. In the next step, nonspecific magnetic beads and sample are added. This leads to the formation of the AuNR-IgY-SA-nMB immunocomplex which is then magnetically separated. Finally, a solution of urea is added to the supernatant. Ureases catalyzes the decomposition of urea which results in an increase in the pH value. The increase in the pH value is detected by using a phenolphthalein test paper which undergoes a color change from white to pink. The analytical process can be completed within 20 min. The method is highly specific and can detect as little as 476 cfu·mL−1. It was verified by analyzing contaminated Chinese cabbage and beef samples, and 1000 cfu·mL−1 of SA were accurately detected.
KeywordsFood safety Visual detection Nanoparticles Immunocomplex Magnetic separation Urea pH change Image analysis
This work was supported by the National Natural Science Foundation of China (Grant No.: 81872668, 81473018), Jilin Province Science and Technology Development Plan Item (Grant No.: 20170204003SF) and Graduate Innovation Fund of Jilin University (Grant No.: 101832018C061).
Compliance with ethical standards
The author(s) declare that they have no competing interests.
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