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

• Published in: RSC advances 2019-11, Vol.9 (66), p.38590-38596
• Main Authors: Huang, Rong, Lu Lu Xiong, Hui Hui Chai, Jing Jing Fu, Lu, Zhisong, Yu, Ling
• Format: Article
• Language: English
• Subjects: Biotin; Chemistry; Colorimetry; Gold coatings; Iron oxides; Magnetic separation; Magnetic shielding
• ISSN: 2046-2069
• DOI: 10.1039/c9ra07899a

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.