In this work, a liquid crystal (LC)-based aptasensor for okadaic acid (OA) detection was developed with a novel aptamer mechanism for enhancing the optical signals of LCs. In this molecular strategy, a short linker aptamer was utilized to immobilize on the sensing platform to form a double-stranded structure with OA specific aptamer. The duplex forming disrupted the orientation of LCs and led to bright LC images under polarized light. The brightness of the LC images was enhanced by integrating a signal amplifier aptamer linked with gold nanoparticles (SA-AuNPs) to form an enlarged double-stranded aptamer structure. In the presence of OA, the specific binding between aptamer and OA led to dissociation of double-stranded aptamer structure and released the specific aptamer and SA-AuNPs from the substrate. As a result, the orientation of LC cannot be disrupted and dark LC images were observed. By measuring the brightness of the LC images, the limit of detection of the developed LC-based aptasensor for OA was 0.42 pM with good linearity and selectivity. In addition, we also demonstrated the applicability of this LC-based aptasensor to detect OA in clam samples with good recoveries.
