Optical approaches for the simple and sensitive detection of aflatoxin B 1 via a liquid crystal aptasensor

We report a direct observation method for the detection of aflatoxin B1 (AFB1), utilising the orientational properties of liquid crystals (LCs). The imaging principle is based on the orientation transition of an LC film, which can be influenced by an aptamer and AFB1. AFB1 is captured by aptamers fixed on a substrate, which causes a conformational change of the aptamers that induces a significant morphological change of the substrate. The AFB1–aptamer interaction induces an orientation transition of LCs from a homeotropic to a planar state at the LC – substrate interface, leading to changes from ‘dark’ to ‘bright’ responses that can be easily seen through crossed polarisers. The developed sensor exhibits high specificity for AFB1 determination and has a low detection limit of 5 fM. The sensor allows AFB1 to be determined in complex samples such as corn and rice powder. The sensing method is highly selective and sensitive for other toxins and common molecules in food. Also, the sensor is stable and easily regenerated. The proposed LC-based aptasensor is a simple, rapid, and convenient platform for label-free detection of AFB1 in real samples, and the design strategy may also provide a novel way for detecting multiple analytes.