Liquid crystal-based capillary sensory platform for the detection of bile acids

Bile acids directly related to liver and intestinal function are used as indicators of hepatobiliary and intestinal diseases. Here, we have designed and realized a capillary sensory platform for the detection of bile acids using liquid crystals (LCs). LC droplets confined in micro-capillaries are homeotropically aligned at the surfactant-packed LC/aqueous interface. However, the competitive adsorption of bile acids disrupts the surfactant packing at this interface and triggers the orientational transition of the LC droplets from homeotropic to planar at the interface, followed by changes in optical images captured by polarized light microscopy. With this sensing system, we could successfully detect three main types of bile acids and further examine the effects of the pH of the solution and chain-length of the surfactant molecules on the detection of bile acids. Interference experiment with ascorbic acid confirms the feasibility of this bile acids detection approach. Our research suggests that this LC-based capillary sensor is a sensitive, simple, and potential tool for the detection of bile acids without the need for complicated processes and expensive equipment.