4TH International Congress on Technology - Engineering & SCIENCE - Kuala Lumpur - Malaysia (2017-08-05)

Detection Of Catalase Activity With Aldehyde-doped Liquid Crystal Confined In Microcapillaries
In this study, a simple sensor using liquid crystal (LC) to detect enzymatic activity of catalase (CAT) was developed. CAT is an enzyme that decomposes hydrogen peroxide (HP), which has strong oxidative reactivity, into water and oxygen. CAT is produced in nearly all aerobic organisms not to accumulate HP in the cells, avoiding the oxidative damage. Consequently, it is possible to track where HP is being produced by detecting and chasing the activity of CAT. To detect CAT, we used aldehyde-doped LC confined in the microcapillaries which were functionalized to control the orientation of LC. In normal state, LC molecules inside the microcapillary aligned parallel to the interface, resulting in radial orientation of LC. This state was observed under polarized optical microscope (POM) as two bright straight lines. However, in the presence of HP, aldehyde doped in LC was oxidized into carboxylic acid which has a surface activity and, thus, caused orientational change of LC at the interface: parallel to homeotropic. This state was observed under POM as two crossed lines, drawing a pattern of four petals. With these two distinct patterns, we could detect enzymatic activity of CAT in the solution of interest. The mixture of HP and the solution of interest was incubated for 1 h, followed by the injection to the LC-loaded microcapillary. When the solution contained enough level of CAT, significant amount of HP in the mixture was decomposed; the aldehyde doped in LC was not oxidized into carboxylic acid, so that the orientation of LC was parallel to the interface between LC mesogen and the mixture, which was observed as the pattern of two parallel lines under POM. When the solution contained little or no CAT, or contained proteins which have no activity to decompose HP, the optical appearance of the system under POM was the pattern of four petals as described above, because HP remained undecomposed oxidized aldehyde doped in LC to carboxylic acid. The limit of detection of this system for CAT was determined as 0.8 fM. From the result, a simple, rapid, and label-free sensor was developed. It showed a feasibility of LC-based detecting system to be applied further to broad biochemical interactions.
Keywords: Catalase, 4-Cyano-4’-pentylbiphenyl (5CB), Hydrogen peroxide, Liquid crystals, Microcapillary
Jinseob Rim, Chang-Hyun Jang