Construction of aptamer-based liquid crystal-aqueous sensing interface for the sensitive detection of dopamine

Dopamine (DA) is an important neurotransmitter, playing significant roles in various psychological and physiological process of human body. However, the development of a simple, highly sensitive and cost-effective method for DA detection is still challenging. In this study, we report a simple, sensitive and label-free liquid crystal (LC)-based aptasensor for DA detection using a LC-aqueous interface with hexadecyltrimethylammonium bromide (CTAB) as a mediator. In the presence of DA, the specific DA-aptamer binding would weaken the electrostatic interaction between the aptamer and CTAB. This, in turn, promotes the assembly of CTAB at LC-aqueous interface and consequently induces a planar-to-homeotropic anchoring transition of LCs at the interface, which allows the detection of DA under polarized optical microscope (POM) with high sensitivity and specificity. By analysing the variation in dark pixel ratio in POM images of LC films, quantitative detection of DA can be achieved. The results show a linear detection range for DA from 10 pM to 1 μM with a detection limit as low as 2.51 pM (S/N = 3). Moreover, the feasibility of the LC-based aptasensor for DA detection in urine samples has been also validated.