Simple, sensitive technique for α-amylase detection facilitated by liquid crystal-based microcapillary sensors

Abstract

Here, we describe a novel sensor that uses microcapillary-confined liquid crystals (LC) and a host-guest inclusion complex, β-cyclodextrin/sodium dodecyl sulfate (β-CD/SDS), to detect α-amylase. All LC droplets confined within the microcapillaries were planar-oriented at the LC-aqueous interface where they came into contact with the non-surfactant solution. In contrast, when the LC droplets come into contact with a surfactant solution (SDS aqueous solution), the surfactant molecules anchor the LC droplets and induce a homeotropic orientation. The degradation of β-CD in the host-guest inclusion complex by α-amylase releases free SDS molecules and facilitates a change in LC orientation, from planar to homeotropic, which corresponds with the development of two bright lines and four petal-shaped optical images. This LC-based microcapillary sensor has a limit of detection (LOD) of 100 ng/mL for α-amylase in aqueous solutions and 500 ng/mL in urine samples. Our sensor exhibits good specificity, sensitivity, and long-term stability for α-amylase, and it provides an uncomplicated, cost-competitive, and non-labeled technique for the detection of α-amylase in both aqueous solutions and human urine samples. Furthermore, the results show an effective detection of α-amylase in human urine samples, demonstrating the feasibility of this sensor in practical applications.