Cholesteric Liquid Crystal Droplets for Biosensors.
By utilizing a microfluidics approach, we prepared uniformly sized cholesteric liquid crystal (CLC) droplets from MLC-2132 doped with a chiral dopant (S)-4-cyano-4'-(2-methylbutyl)biphenyl (CB15). We studied the helical structures and reflecting color patterns of high- and low-dopant CLC droplets coated with poly(vinyl alcohol) (PVA) and sodium dodecyl sulfate (SDS). One central large spot with reflecting color in the CLC droplets (initially coated with PVA for planar anchoring) changed to many small spots with the same reflecting color (chicken-skin pattern) when an SDS aqueous solution was introduced to increase the homeotropic anchoring power. These small spots subsequently merged into several spots (flashlight pattern) with time. The CLC droplets coated with poly(acrylic acid)-b-poly(4-cyanobiphenyl-4'-oxyundecyl acrylate) (PAA-b-LCP) (CLCPAAdroplets) were pH-responsive. Their helical structure and the reflecting color pattern changed because of protonation (at low pH) and deprotonation (at high pH) of the carboxylic group of PAA, which causes the planar (tangential) and perpendicular (homeotropic) orientations, respectively. The CLCPAAdroplets immobilized with glucose oxidase (GOx) and cholesterol oxidase (ChO) (CLCPAA-GOxand CLCPAA-ChOdroplets, respectively), for glucose and cholesterol detection, exhibited high sensitivity (0.5 and 2.5 μM for the CLCPAA-GOxand CLCPAA-ChOdroplets, respectively), good selectivity, and fast response (≤4 s). Further optimization will enhance their performance as biosensors. With this novel approach, detection is possible by observing the coloring pattern of CLC droplets, without the crossed polarizers that are necessary for nematic LC biosensor systems.
Department of Polymer Science & Engineering, Polymeric Nanomaterials Laboratory, School of Applied Chemical Engineering, Kyungpook National University , 80 Daehak-ro, Buk-gu, Daegu 41566, Korea.
Hyun-Gyu
HG
Lee
Department of Polymer Science & Engineering, Polymeric Nanomaterials Laboratory, School of Applied Chemical Engineering, Kyungpook National University , 80 Daehak-ro, Buk-gu, Daegu 41566, Korea.
Sundas
S
Munir
Department of Polymer Science & Engineering, Polymeric Nanomaterials Laboratory, School of Applied Chemical Engineering, Kyungpook National University , 80 Daehak-ro, Buk-gu, Daegu 41566, Korea.
Soo-Young
SY
Park
D015374:Biosensing Techniques; D005947:Glucose; D005949:Glucose Oxidase; D050866:Liquid Crystals; D044085:Microfluidics
D005949:Glucose Oxidase; D005947:Glucose
biosensor; cholesteric liquid crystal; droplet; enzyme; microfluidics