Fe3O4@CuS-based immunochromatographic test strips and their application to label-free and dual-readout detection of Escherichia coli O157:H7 in food

• Published in: Food chemistry 2020-12, Vol.332, p.127398-127398, Article 127398
• Main Authors: Zhang, Meng, Bu, Tong, Tian, Yongming, Sun, Xinyu, Wang, Qinzhi, Liu, Yingnan, Bai, Feier, Zhao, Shuang, Wang, Li
• Format: Article
• Language: English
• Subjects: Escherichia coli O157:H7; Fe3O4@CuS NSs; Immunochromatographic test strip; Label-free; Photothermal effects; Sensitive detection
• ISSN: 0308-8146; 1873-7072
• DOI: 10.1016/j.foodchem.2020.127398

•A label-free and dual-readout biosensor was constructed to detect E. coli O157:H7.•The Fe3O4@CuS could capture targets directly and possessed PTEs to amplify signals.•An ideal analytical performance with high sensitivity and specificity was achieved.•The sensor were successfully used in food samples for E. coli O157:H7 detection. Herein, a label-free and dual-readout immunochromatographic test strip (ITS) for the sensitive detection of Escherichia coli (E. coli) O157:H7 by taking advantages of the strong capture ability of Fe3O4@CuS nanostructures (NSs) towards bacteria and their ultrahigh photothermal effects (PTEs) was reported. Especially, without the customarily antibody (Ab)-labeled probe, Fe3O4@CuS NSs could be adsorbed onto the surfaces of bacteria to form Fe3O4@CuS-bacteria conjugates and then trapped by immobilized Abs on the test line (T-line), forming a characteristic yellow band. After direct immunoreactions, the PTEs of Fe3O4@CuS NSs endowed T-line to be irradiated by an 808 nm infrared light, obtaining satisfactory sensitivity and accuracy. Under optimal conditions, E. coli O157:H7, as low as 103 and 102 CFU/mL, could be monitored in colorimetric and photothermal modes. Additionally, E. coli O157:H7 was successfully detected in beef, chicken, milk and honey samples by this proposed platform with a recovery of 80–120%.