Optical birefringence of liquid crystals for label-free optical biosensing diagnosis.
OBJECTIVE
We present a polarization-sensitive optical detection platform for label-free quantitative optical biosensing diagnosis using liquid crystals (LCs). This is capable of determining quantitatively the optical birefringence of optical cells containing LCs, whose orientation depends on the immobilized biomolecules.


METHODS
This technique uses a polarization-dependent double-port detection without any polarizer at a single wavelength and removes the need of aligning optical cells of LCs in the azimuthal direction, with respect to the light path through the optical cell. Thus, this technique enables a stand-alone detection in a relatively compact format without an additional optical instrument, such as a retardation compensator, a Michael-Levy chart, and a spectrophotometer, in order to determine the optical birefringence quantitatively.


RESULTS
We demonstrate that bovine serum albumin immobilized on the gold surface of the cell hybrid interfaces that support both homeotropic and planar anchoring of LCs causes optical phase retardation change which can be determined quantitatively. We also provide estimation of the zenithal orientation of LCs near the gold surface of the hybrid interfaces, based on the phase retardation determined. The estimated limit of bovine serum albumin detection is approximately 2.1 μM.


CONCLUSIONS
This optical technique with LCs can serve an optical platform for label-free quantitative diagnosis of proteins in a real time manner.
Department of Bionano Technology, Gachon University, Seongnam-City, South Korea.
Tan Tai
TT
Nguyen
Department of Nano-Chemistry, Gachon University, Seongnam-City, South Korea.
Gyeo-Re
GR
Han
Department of Bionano Technology, Gachon University, Seongnam-City, South Korea ; Department of Nano-Chemistry, Gachon University, Seongnam-City, South Korea.
Chang-Hyun
CH
Jang
Department of Bionano Technology, Gachon University, Seongnam-City, South Korea ; Department of Nano-Physics, Gachon University, Seongnam-City, South Korea ; Neuroscience Institute, Gil Hospital, Incheon, South Korea.
Heongkyu
H
Ju
D000818:Animals; D015374:Biosensing Techniques / Q000379:methods*; D001718:Birefringence; D002417:Cattle; D006046:Gold; D055767:Immobilized Proteins / Q000737:chemistry; D050866:Liquid Crystals / Q000737:chemistry*; D012710:Serum Albumin, Bovine / Q000737:chemistry; D013499:Surface Properties
D055767:Immobilized Proteins; D012710:Serum Albumin, Bovine; D006046:Gold
LC orientation; biological sensors; protein sensing; tag-free diagnosis