The authors report on a method for the determination of ractopamine (RAC) via liquid crystal (LC) optical imaging and gold nanoparticle-induced signal enhancement. The gold nanoparticles (AuNPs) were blended with the desired concentrations of RAC, and this is found to strongly improve the performance of the assay. The RAC aptamers were immobilized on the self-assembled film of a glass slide for specific recognition of RAC. This causes a homeotropic re-orientation of the LCs. Notably, the aptamers need not be immobilized on the nanoparticles like in other methods. The addition of RAC causes the formation of an AuNP-RAC-aptamer conjugate on the sensing interface. This disrupts the orientation of LCs and results in a change of the polarized images of the LCs. The method has a detection limit as low as 1 pM of RAC. Graphical abstract Schematic presentation of a method for the determination of ractopamine (RAC) using liquid crystal (LC) optical imaging and gold nanoparticle-induced signal enhancement. The aptamers need not be immobilized on the nanoparticles like in other methods.
Keywords: Aptamer; Biosensor; Conjugate; Glass slide; Homeotropic re-orientation; Orientation; Polarized image; Recognition; Self-assembled film; Sensing interface.