scholarly journals A Cationic Surfactant-Decorated Liquid Crystal-Based Aptasensor for Label-Free Detection of Malathion Pesticides in Environmental Samples

Biosensors ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 92
Author(s):  
Duy Khiem Nguyen ◽  
Chang-Hyun Jang
Keyword(s):  
Liquid Crystal ◽  
Cationic Surfactant ◽  
Environmental Samples ◽  
Tap Water ◽  
High Specificity ◽  
Optical Image ◽  
Label Free ◽  
Optical Images ◽  
Label Free Detection ◽  
Homeotropic Orientation

We report a liquid crystal (LC)-based aptasensor for the detection of malathion using a cationic surfactant-decorated LC interface. In this method, LCs displayed dark optical images when in contact with aqueous cetyltrimethylammonium bromide (CTAB) solution due to the formation of a self-assembled CTAB monolayer at the aqueous/LC interface, which induced the homeotropic orientation of LCs. With the addition of malathion aptamer, the homeotropic orientation of LCs changed to a planar one due to the interactions between CTAB and the aptamer, resulting in a bright optical image. In the presence of malathion, the formation of aptamer-malathion complexes caused a conformational change of the aptamers, thereby weakening the interactions between CTAB and the aptamers. Therefore, CTAB is free to induce a homeotropic ordering of the LCs, which corresponds to a dark optical image. The developed sensor exhibited high specificity for malathion determination and a low detection limit of 0.465 nM was achieved. Moreover, the proposed biosensor was successfully applied to detect malathion in tap water, river water, and apple samples. The proposed LC-based aptasensor is a simple, rapid, and convenient platform for label-free monitoring of malathion in environmental samples.

scholarly journals A liquid-crystal-based DNA biosensor for pathogen detection

2016 ◽  
Vol 6 (1) ◽  
Author(s):  
Mashooq Khan ◽  
Abdur Rahim Khan ◽  
Jae-Ho Shin ◽  
Soo-Young Park
Keyword(s):  
Liquid Crystal ◽  
Pathogen Detection ◽  
Grid Cell ◽  
High Specificity ◽  
Erwinia Carotovora ◽  
Optical Microscope ◽  
Label Free ◽  
Label Free Detection ◽  
Homeotropic Orientation ◽  
Tem Grid

Abstract A liquid-crystal (LC)-filled transmission electron microscopy (TEM) grid cell coated with the cationic surfactant dodecyltrimethylammonium bromide (DTAB), to which a single-stranded deoxyribonucleic acid probe (ssDNAprobe) was adsorbed at the LC/aqueous interface (TEMDTAB/DNA), was applied for the highly specific detection of target DNA molecules. The DTAB-coated E7 (used LC mixture) in the TEM grid (TEMDTAB) exhibited a homeotropic orientation, and changed to a planar orientation upon adsorption of the ssDNAprobe. The TEMDTAB/DNA was then exposed to complementary (target) ssDNA, which resulted in a planar-to-homeotropic configurational change of E7 that could be observed through a polarized optical microscope under crossed polarizers. The optimum adsorption density (2 μM) of ssDNAprobe enabled the detection of ≥0.05 nM complementary ssDNA. This TEMDTAB/DNA biosensor could differentiate complementary ssDNA from mismatched ssDNA as well as double-stranded DNA. It also successfully detected the genomic DNAs of the bacterium Erwinia carotovora and the fungi Rhazictonia solani. Owe to the high specificity, sensitivity, and label-free detection, this biosensor may broaden the applications of LC-based biosensors to pathogen detection.

scholarly journals A Label-Free Liquid Crystal Biosensor Based on Specific DNA Aptamer Probes for Sensitive Detection of Amoxicillin Antibiotic

Micromachines ◽  
2021 ◽  
Vol 12 (4) ◽  
pp. 370
Author(s):  
Duy Khiem Nguyen ◽  
Chang-Hyun Jang
Keyword(s):  
Liquid Crystal ◽  
Specific Binding ◽  
Water Environment ◽  
Polarized Light ◽  
High Specificity ◽  
Dna Aptamer ◽  
Sensitive Detection ◽  
Label Free ◽  
Homeotropic Orientation ◽  
Optical Appearance

We developed a liquid crystal (LC) aptamer biosensor for the sensitive detection of amoxicillin (AMX). The AMX aptamer was immobilized onto the surface of a glass slide modified with a mixed self-assembled layer of dimethyloctadecyl [3-(trimethoxysilyl) propyl] ammonium chloride (DMOAP) and (3-aminopropyl) triethoxysilane (APTES). The long alkyl chains of DMOAP maintained the LC molecules in a homeotropic orientation and induced a dark optical appearance under a polarized light microscope (POM). In the presence of AMX, the specific binding of the aptamer and AMX molecules induced a conformational change in the aptamers, leading to the disruption of the homeotropic orientation of LCs, resulting in a bright optical appearance. The developed aptasensor showed high specificity and a low detection limit of 3.5 nM. Moreover, the potential application of the developed aptasensor for the detection of AMX in environmental samples was also demonstrated. Therefore, the proposed aptasensor is a promising platform for simple, rapid, and label-free monitoring of AMX in an actual water environment with high selectivity and sensitivity.

scholarly journals A cationic surfactant-decorated liquid crystal-based sensor for sensitive detection of quinoline yellow

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Fatemeh S. Mohseni-Shahri ◽  
Farid Moeinpour ◽  
Asma Verdian
Keyword(s):  
Liquid Crystal ◽  
Cationic Surfactant ◽  
Electrostatic Interactions ◽  
Simple Procedure ◽  
Label Free ◽  
Safety Control ◽  
Label Free Detection ◽  
Homeotropic Alignment ◽  
Quinoline Yellow ◽  
Control Application

AbstractQuinoline yellow (QY) is one of the popular synthetic food colorants and in food industry greatly used. Developing accurate and simple QY detection procedures is of major considerable importance in ensuring food safety. Hence, it is important to detect this food colorant effectively to reduce risk. Herein, an innovative liquid crystal (LC)-based sensor was designed for the label-free and ultra-sensitive detecting of the QY by means of a cationic surfactant-decorated LC interface. The nematic liquid crystal in touch with CTAB revealed a homeotropic alignment, when QY was injected into the LC-cell, the homeotropic alignment consequently altered to a planar one by electrostatic interactions between QY and CTAB. The designed LC-based sensor detected QY at the too much trace level as low as 0.5 fM with analogous selectivity. The suggested LC-based sensor is a rapid, convenient and simple procedure for label-free detection of QY in food industrial and safety control application.

scholarly journals Impedimetric Immunosensor Utilizing Polyaniline/Gold Nanocomposite-Modified Screen-Printed Electrodes for Early Detection of Chronic Kidney Disease

Sensors ◽  
2019 ◽  
Vol 19 (18) ◽  
pp. 3990 ◽  
Author(s):  
Muhammad Omar Shaikh ◽  
Boyanagunta Srikanth ◽  
Pei-Yu Zhu ◽  
Cheng-Hsin Chuang
Keyword(s):  
Chronic Kidney Disease ◽  
Kidney Disease ◽  
Early Detection ◽  
Electrochemical Impedance ◽  
High Specificity ◽  
Homogeneous Distribution ◽  
Label Free ◽  
Gold Nanocrystals ◽  
Working Electrode ◽  
Label Free Detection

The presence of small amounts of human serum albumin (HSA) in urine or microalbuminuria (30–300 µg/mL) is a valuable clinical biomarker for the early detection of chronic kidney disease (CKD). Herein, we report on the development of an inexpensive and disposable immunosensor for the sensitive, specific, and label-free detection of HSA using electrochemical impedance spectroscopy (EIS). We have utilized a simple one-step screen-printing protocol to fabricate the carbon-based three-electrode system on flexible plastic substrates. To enable efficient antibody immobilization and improved sensitivity, the carbon working electrode was sequentially modified with electropolymerized polyaniline (PANI) and electrodeposited gold nanocrystals (AuNCs). The PANI matrix serves as an interconnected nanostructured scaffold for homogeneous distribution of AuNCs and the resulting PANI/AuNCs nanocomposite synergically improved the immunosensor response. The PANI/AuNCs-modified working electrode surface was characterized using scanning electron microscopy (SEM) and the electrochemical response at each step was analyzed using EIS in a ferri/ferrocyanide redox probe solution. The normalized impedance variation during immunosensing increased linearly with HSA concentration in the range of 3–300 µg/mL and a highly repeatable response was observed for each concentration. Furthermore, the immunosensor displayed high specificity when tested using spiked sample solutions containing different concentrations of actin protein and J82 cell lysate (a complex fluid containing a multitude of interfering proteins). Consequently, these experimental results confirm the feasibility of the proposed immunosensor for early diagnosis and prognosis of CKD at the point of care.

Selective, Sensitive and Label-Free Detection of Fe3+ Ion in Tap Water Using Highly Fluorescent Graphene Quantum Dots

2019 ◽  
Vol 29 (3) ◽  
pp. 541-548 ◽  
Author(s):  
Yuanyuan Zhang ◽  
Xiangyue Yang ◽  
Yunxun Pu ◽  
Wei Cheng ◽  
Song Lin ◽  
...  
Keyword(s):  
Quantum Dots ◽  
Tap Water ◽  
Graphene Quantum Dots ◽  
Label Free ◽  
Label Free Detection

Anti-IgG-anchored liquid crystal microdroplets for label free detection of IgG

2016 ◽  
Vol 4 (4) ◽  
pp. 704-715 ◽  
Author(s):  
Kyubae Lee ◽  
Kailash Chandra Gupta ◽  
Soo-Young Park ◽  
Inn-Kyu Kang
Keyword(s):  
Liquid Crystal ◽  
Label Free ◽  
Label Free Detection

AIgG anchored LC microdroplets showing configurational transition from radial (a) to bipolar (b) upon interaction with IgG.

Fluorescent Carrier Ampholytes Assay for Portable, Label-Free Detection of Chemical Toxins in Tap Water

2010 ◽  
Vol 82 (5) ◽  
pp. 1858-1866 ◽  
Author(s):  
M. Bercovici ◽  
G. V. Kaigala ◽  
C. J. Backhouse ◽  
J. G. Santiago
Keyword(s):  
Tap Water ◽  
Label Free ◽  
Label Free Detection ◽  
Carrier Ampholytes

Electrokinetics-Based Microfluidic Technology for the Rapid Separation and Concentration of Bacteria/Cells/Biomolecules

2014 ◽  
Vol 911 ◽  
pp. 347-351 ◽  
Author(s):  
I Fang Cheng ◽  
Tzu Ying Chen ◽  
Hsien Chang Chang
Keyword(s):  
Cancer Cell ◽  
Electrochemical Impedance ◽  
High Sensitivity ◽  
High Specificity ◽  
Cell Detection ◽  
Label Free ◽  
Rapid Separation ◽  
Whole Cells ◽  
Highly Sensitive ◽  
Label Free Detection

Conventional techniques for detection of bacteria/cell and assessment of cancer cell typically use DNA techniques, Western blot and ELISA kits that are high cost, complicated processes and long time consuming. Our researches focus on rapid, portable, simple and highly sensitive separation and detection of cells/bacteria/biomolecules for field-use diagnosis. An ideal portable biosensor (molecular or whole cells detections) unit must have several important features: rapid detection time (<10 minutes), high sensitivity (pM level for molecular detection, 103 cells/ml for whole cell detection), high specificity, small and inexpensive instrumentation configuration. Electrochemical impedance/conductance sensing is preferred over optical detection because of cost and portability concerns. Cancer cell detection using heterogeneous medical samples require continuous isolation, sorting, and trapping of the target bioparticles and immunocolloids within a diagnostic chip. We have developed several electrokinetic strategies to rapid separation, concentration and detection of cells/bacteria/biomolecules in a microfluidic chip using such as dielectrophoresis (DEP), traveling-wave dielectrophoresis (twDEP) and electrohydrodynamics (EHD). Several key techniques we done, which on a rapid/simple/label-free detection platform for the highly sensitive on-chip separation/identification/quantification will be introduced in this paper.

scholarly journals Predicting Future Prospects of Aptamers in Field-Effect Transistor Biosensors

Molecules ◽  
2020 ◽  
Vol 25 (3) ◽  
pp. 680 ◽  
Author(s):  
Cao-An Vu ◽  
Wen-Yih Chen
Keyword(s):  
Small Molecules ◽  
Field Effect ◽  
Field Effect Transistor ◽  
Field Effect Transistors ◽  
High Specificity ◽  
Label Free ◽  
Sensing Technology ◽  
Wide Range ◽  
Label Free Detection ◽  
Effect Transistor

Aptamers, in sensing technology, are famous for their role as receptors in versatile applications due to their high specificity and selectivity to a wide range of targets including proteins, small molecules, oligonucleotides, metal ions, viruses, and cells. The outburst of field-effect transistors provides a label-free detection and ultra-sensitive technique with significantly improved results in terms of detection of substances. However, their combination in this field is challenged by several factors. Recent advances in the discovery of aptamers and studies of Field-Effect Transistor (FET) aptasensors overcome these limitations and potentially expand the dominance of aptamers in the biosensor market.

Graphene-Based Hall Effect Biosensor for Improved Specificity and Sensitivity of Label-Free DNA Detection

NANO ◽  
2020 ◽  
Vol 15 (07) ◽  
pp. 2050088
Author(s):  
Naiyuan Cui ◽  
Fei Wang ◽  
Hanyuan Ding
Keyword(s):  
Hall Effect ◽  
Dna Hybridization ◽  
Chemical Vapor ◽  
High Specificity ◽  
Label Free ◽  
Complementary Dna ◽  
Mismatched Dna ◽  
Specificity And Sensitivity ◽  
Label Free Detection ◽  
Detection Of Biomolecules

There is a broad interest in using graphene or graphene oxide (GO) sheets as a transducer for selective and label-free detection of biomolecules such as DNA, tumor marker, biological ions, etc. Here, a chemical vapor deposition (CVD) graphene-based Hall effect biosensor used for ultrasensitive label-free detection of DNA via DNA hybridization is reported. Hall effect measurements based on the Van der Pauw method are used to perform single-base sequence selective detection of DNA on graphene sheets, which are prepared by CVD. The mobility decreases and the sheet resistance increases with the adding of either complementary or one-base mismatched DNA to the graphene device. The hole carrier concentration of the graphene devices increases apparently with the addition of complementary DNA while it is hardly affected by the one-base mismatched DNA. The detection limit as low as 1[Formula: see text]pM was realized with a linear range from 1[Formula: see text]pM to 100[Formula: see text]nM. Moreover, the Hall effect biosensor was able to distinguish the complementary DNA from one-base mismatched DNA with a high specificity of [Formula: see text]6.2 which is almost two orders of magnitude higher than that of the previously reported graphene biosensors based on DNA–DNA hybridization.

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