Analytical Sciences

Magnetic Nanoparticles-based Aptasensor Using Gold Nanoparticles as Colorimetric Probes for the Detection of Salmonella typhimurium

Nuo DUAN,* Baocai XU,** Shijia WU,* and Zhouping WANG**

*State Key Laboratory of Food Science and Technology, Synergetic Innovation Center of Food Safety and Nutrition, School of Food Science and Technology, Jiangnan University, Wuxi 214122, China
**State Key Laboratory of Meat Processing & Quality Control, Yurun Group, Nanjing 210041, China

This paper presents a sensitive and convenient visual methodology for Salmonella typhimurium detection using gold nanoparticles (AuNPs) as colorimetric probes and magnetic nanoparticles (MNPs) as concentration elements. In the protocol, the aptamers were first immobilized onto the surface of AuNPs and MNPs, respectively. Then, S. typhimurium were added into the above solution and incubated for 45 min. During the incubation, aptamer on the surface of nanoparticles could specifically bind to the target and form a MNPs-aptamer-S. typhimurium-aptamer-AuNPs sandwich structure complex. In a magnetic field, the formed complexes were easily separated from the solution, resulting in a fading of the AuNPs suspension and a decrease of the ultraviolet visible (UV/Vis) signal. The assay shows a linear response toward S. typhimurium concentration through a range of 25 to 10⁵ cfu/mL, and the detection limit was improved to 10 cfu/mL. The applicability of the bioassay in real food samples was also investigated; the results were consistent with the experimental results obtained from plate-counting methods. It is believed that the developed aptasensor will broaden the application in bioassays.

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