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    Detection of Methicillin-Resistant Staphylococcus Aureus Bacteria Using Liquid Crystals
    (Gazi Univ, 2022) Kemiklioglu, Emine; Tuncgovde, Ebru Busra
    Methicillin-resistant Staphylococcus aureus (MRSA) is an essential pathogen for public health and this bacteria commonly cause serious infectious in humans. In recent years, MRSA bacteria are detected by the bacterial culture and nucleic acid-based methods which are time-consuming and labor-intensive. In this study, a novel liquid crystal (LC)-based biosensing system was developed to overcome these limitations. The objective of this study was to detect the presence of MRSA bacteria which prepared within the isotonic water and phosphate buffer saline (PBS). In this system, the binding of MRSA bacteria to the dimettw loctadecyl [3-(trimethoxysilyl) propyl] ammonium chloride (DMOAP)-coated surface disrupted the orientation of I Cs. triggering a transition from a homeotropic orientation to a random one. This transition in the orientation of the LCs was observed as a change from a dark optical LC image to a bright one under a polarized light microscope (POM) and the reflection values of LC molecules were determined by using a spectrometer. Through this sensing mechanism, MRSA bacteria prepared within the isotonic water was detected ranging from the 9.2x10(3) CFU/mL to 9.2x10(7) CFU/mL concentration. Furthermore. Ni RSA bacteria prepared in PBS was detected in the concentration range of 7.1x10(4) CFU/mL to 7.1x10(8) CFU/ml by using this system.
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    Development an optical sensor using lyotropic cholesteric liquid crystals for the detection of toxic gases
    (Elsevier Gmbh, 2021) Kemiklioglu, Emine; Gurboga, Berfin; Tuncgovde, Ebru Busra
    In the current study, a lyotropic cholesteric liquid crystal (ChLC) based sensor for the identification of vapors of polar (toluene and phenol) and apolar (1,2 dicholoropropane) toxic gases was investigated. The lyotropic ChLC sample including cholesteryl oleyl carbonate, cholesteryl pelargonate, and cholesteryl benzoate was supported on the chemically modified glass surfaces as an optical sensor for the detecting of these toxic gases vapors. The glass surfaces were modified by coating Dimethyloctadecyl [3-(trimethoxysilyl) propyl] ammonium chloride (DMOAP). The optical signal generated by the incorporation of different toxic gases vapors in the lyotropic ChLC layers which disturbs the pitch length. These toxic gases were evaporated at different temperatures and the exposure time was differentiated. Increasing solvent evaporation temperature lead a shift in the wavelength maximum to smaller wavelengths which can be observed by a naked eye.
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    Development of liquid crystal biosensor for the detection of amyloid beta-42 levels associated with Alzheimer's disease
    (Soc Bioscience Bioengineering Japan, 2021) Kemiklioglu, Emine; Tuncgovde, Ebru Busra; Ozsarlak-Sozer, Gonen
    This study represents the development of a biosensor which is based on the liquid crystal (LC) orientation as a function of the peptide concentration to detect an amyloid-beta-42 (A beta 42) antibody-antigen binding events. The A beta 42 peptide binds to the A beta 42 antibody forming an immunocomplex which is immobilized on the Dimethyloctadecyl[3-(trimethoxysilyl)propyl] ammonium chloride (DMOAP) coated surface. The disturbed orientation of LCs as a result of the binding of the formed immunocomplex was observed using the polarized optical microscope (POM) as a function of decreasing A beta 42 peptide concentration from 1000 to 1 pg/ml. The concentration, as low as 1 pg/ml of A beta 42 peptide was able to be successfully detected in our system. Apolipoprotein E4 (ApoE4), that specifically bound to the A beta 42 peptide, was added into the system and a remarkable change in reflection spectra of samples was observed with increasing A beta 42 peptide concentration. The concentration of ApoE4 protein was detected in the range of 0.1-30 nM by this system due to the interaction between the two proteins. (C) 2021, The Society for Biotechnology, Japan. All rights reserved.