M. Vistak, V. Dmytrach, Z. Mykytyuk, V. Petryshak, L. Kobylinska
Danylo Halytsky Lviv National Medical University,
Keywords: liquid crystal, optical sensor, cholesterol
Summary:Increasing of cholesterol concentrations or hypercholesterolemia is one of the important reasons for cardiovascular disease growing in worldwide. Therefore, the control of cholesterol level in biological objects is an urgent task. Currently, a number of biosensors for qualitative and quantitative control of cholesterol levels are developed. The significant attention to design the liquid crystal (LC) compounds as the sensitive elements are increased. For the cholesterol detection the nematic liquid crystal (NLC) are used. The NLC molecular orientation is changed from planar to homeotropically at the presence of cholesterol molecules [1-3]. Cholesterol is organic, fat-like substance from the sterols group and presented in all body tissues and blood plasma. As it is known the normal cholesterol in human blood is 150-250 mg per 100 ml (0.2%). We propose to design an active medium on the base of cholesteric-nematic mixture (CNM) for cholesterol optical sensor. The sensor active medium is a CNM on the base of BLO-61 cholesteric liquid crystal (CLC) and 5CB nematic liquid crystal (NLC) (25 wt. %). In the CNM transmittance spectra the two minimum are observed. First of then are at 320 nm of wavelength and correspond to NLC minimum and the second wavelength minimum are depends of NLC concentration in CNM. At a 25 wt. % concentration of 5CB the wavelength is 520 nm at minimum transmittance . We investigated the transmittance spectrum of CNM with cholesterol dopant with 1-15 wt. % concentration range. It was found at the increasing of cholesterol concentrations in CNM the wavelength at minimum transmittance are shifted to long range of spectrum. The effect of long-wave shifting of wavelength at minimum transmittance of CNM at the cholesterol concentration increasing is enhanced at higher temperatures. It is also important to note the CNM with out cholesterol dopant at heating does not change the spectral characteristics in 10-70 °C temperature range. From obtained spectral dependences are make it possible to determine the coefficient of NCM spectral sensitivity to cholesterol and the maximum value are observed in the 1-5 wt.% cholesterol concentration range. On the based on the results analysis the interaction mechanism between cholesterol and multi-chiral liquid crystal mixture are proposed. REFERENCES 1. SundasMunir, Mashoog Khan, Soo-Young Park. Bienzyme liquid-crystal-based cholesterol biosensor. SensorsandActuators B: Chemical. 2015. Volume 220, Pages 1083-1100. 2. Hyun-Gyu Lee, SundasMunir, Soo-Young Park. Cholesteric liquid crystal droplets for biosensors. ACS Appl. Mater. Interfaces, 2016, 8 (39), pp 26407–26417. 3. Yibin Wei Chang-Hyun Jang. Detectionofcholesterolmoleculeswith a liquid crystal-based pH-drivensensor. Jurnal of Materials Science.July 2015, Volume 50, Issue 13, pp 4741–4748. 4. Mykytyuk Z. Optoelectronic multi-sensorof SO2and NO2gases / Z. Mykytyuk, A. Fechan, V. Petryshak, G. Barylo, O. Boyko // Proceedingsofthe 13th InternationalConference TCSET’2016 – Lviv-Slavske, Ukraine –2016 - pp. 402-405.