Sensitive colorimetric detection of ochratoxin A by a dual-functional Au/Fe3O4 nanohybrid-based aptasensor

Rong Huang; Lu Lu Xiong; Hui Hui Chai; Jing Jing Fu; Zhisong Lu; Ling Yu

doi:10.1039/c9ra07899a

Sensitive colorimetric detection of ochratoxin A by a dual-functional Au/Fe₃O₄ nanohybrid-based aptasensor

RSC Adv. 2019 Nov 25;9(66):38590-38596. doi: 10.1039/c9ra07899a.

Authors

Rong Huang¹, Lu Lu Xiong¹, Hui Hui Chai¹, Jing Jing Fu¹, Zhisong Lu¹, Ling Yu¹

Affiliation

¹ Key Laboratory of Luminescent and Real-Time Analytical Chemistry, Ministry of Education, Institute for Clean Energy and Advanced Materials, School of Materials and Energy, Southwest University Chongqing 400715 PR China lingyu12@swu.edu.cn zslu@swu.edu.cn.

Abstract

A novel colorimetric aptasensor based on a Au/Fe₃O₄ nanohybrid was developed to detect ochratoxin A (OTA). The aptasensor is composed of a free OTA aptamer, a Au/Fe₃O₄ nanohybrid coated with biotinylated complementary DNA of the OTA aptamer (biotin-cDNA-Au/Fe₃O₄), and free alkaline-phosphatase-labeled streptavidin (SA-ALP). The Au/Fe₃O₄ nanohybrid not only immobilizes biotin-cDNA but also magnetically separates SA-ALP from the sample solution. One part of the OTA aptamer sequence hybridizes with biotin-cDNA immobilized on Au/Fe₃O₄, and the left part of the OTA aptamer sequence covers the biotin and blocks the specific interaction between biotin and SA-ALP. OTA can interrupt the interaction of OTA aptamer binding to biotin-cDNA-Au/Fe₃O₄ and can inhibit the shielding effect of the OTA aptamer on biotin. The amount of SA-ALP that can be captured by biotin-cDNA-Au/Fe₃O₄ thus increases with increasing OTA concentration. Through a simple magnetic separation, the collected SA-ALP-linked Au/Fe₃O₄ can produce a yellow-colored solution in the presence of p-nitrophenyl phosphate (p-NPP). This colorimetric aptasensor can detect OTA as low as 1.15 ng mL^-1 with high specificity.