Label-free optical detection of aflatoxin by using a liquid crystal-based immunosensor

Aflatoxin is one of the most toxic mycotoxins and a severe threat to human health. Here, we report a novel liquid crystal (LC) cell system that can be used to visualize the immune competition reaction between an antibody and the target antigen aflatoxin. The sensing system involves co-immobilization of the antibody and N, N-dimethyl-N-octadecyl (3-aminopropyl) trimethoxysilyl chloride (DMOAP) on the surface of a glass slide, resulting in a random orientation of the LCs in the film on these surfaces. In this system, the LC molecules are disordered, producing bright optical signals upon binding of the antibody to the surface-immobilized antigen. In the presence of aflatoxin, the interaction between the target antigen and antibody results in an immune competition reaction, which disturbs the orientation of LCs. This change in orientation can be observed by the naked eye through a crossed polarizer. The results demonstrated that this method possesses high specificity with an antigen detection limit as low as 100 pg/mL. This method does not require laboratory-based instruments, and the test results can be observed with naked eyes through a polarized microscope.