Colorimetric, Quantitative, and Portable Liquid Crystal Elastomer Biosensing of Cholesterol and Malathion

Cholesteric liquid crystal elastomers (CLCEs) possess a unique characteristic that allows the manipulation of the reflected color by adjusting the spacing between layers. This attribute can create a reliable and cost-effective colorimetric sensing platform for the on-site detection of various substances. In this study, CLCE films were coupled with cross-linked poly(acrylic acid) (CLCE-PAA) or poly(dimethylaminoethyl methacrylate) (CLCE-PDA) films to monitor cholesterol and malathion levels, respectively. In both cases, the color change is recorded by a mobile phone camera, and the reflectance wavelength is measured spectrophotometrically. For on-site detection, a smartphone application was used to capture the film's image, process the color data into hue (H) values, and calculate the corresponding concentration of the tested analyte via an analysis program. Cholesterol and malathion can be detected within a linear range of 0.2-1.0 mM and 1-10,000 ng/mL, respectively. The corresponding recoveries for actual sample analysis were 86-115% and 87-122% for cholesterol and malathion, respectively. This system offers a practical solution for on-site testing of cholesterol and malathion in biological and environmental samples.