Ionic liquids functionalized Fe3O4-based colorimetric biosensor for rapid determination of ochratoxin A

A stainless steel mesh (SSM) with the feature of flexibility was employed as the colorimetric biosensor substrate, and aptamer was bond onto the surface of the SSM. Through the cross-linking of ionic liquids (ILs), AuPt nanoparticles were deposited onto the surface of Fe 3 O 4 material to obtain a magnetic nanozyme with high peroxidase catalytic activity and rapid color change. Through the competing interaction of OTA and cDNA with aptamer, AuPt@IL@Fe 3 O 4 signal probe was separated to catalyze the 3,3′,5,5′-tetramethylbenzidine/hydrogen peroxide (TMB/H 2 O 2 ) system to observe the color by bare eye and record the absorbance at 652 nm using a UV-spectrophotometer. Through the study of the catalytic properties on the basis of the Michaelis equation, AuPt@IL@Fe 3 O 4 nanozyme presented a V max of 3.85 × 10 −8 M s −1 and K m of 0.01 mM. Under the optimized conditions, the linear range of the colorimetric biosensor towards OTA was 5–100 ng mL −1 , and the detection limit was 0.078 ng mL –1 . This biosensor was applied to beer and corn samples with recoveries of 70.4–102.6% and 93.3–104.7%, respectively. Results showed that this sensor is a portable, rapid, economical, sensitive visual sensing platform towards mycotoxin in real samples. Graphical abstract