Optical and flexoelectric biosensing based on a hybrid-aligned liquid crystal of anomalously small bend elastic constant

Tsung-Keng Chang; Yung-Yu Tseng; Po-Chang Wu; Mon-Juan Lee; Wei Lee

doi:10.1016/j.bios.2023.115314

Optical and flexoelectric biosensing based on a hybrid-aligned liquid crystal of anomalously small bend elastic constant

Biosens Bioelectron. 2023 Jul 15:232:115314. doi: 10.1016/j.bios.2023.115314. Epub 2023 Apr 12.

Authors

Tsung-Keng Chang¹, Yung-Yu Tseng², Po-Chang Wu³, Mon-Juan Lee⁴, Wei Lee⁵

Affiliations

¹ College of Photonics, National Yang Ming Chiao Tung University, Guiren Dist, Tainan, 711010, Taiwan; National Laboratory Animal Center, National Applied Research Laboratories, Taipei, 115202, Taiwan.
² Institute of Photonic System, National Yang Ming Chiao Tung University, Guiren Dist, Tainan, 711010, Taiwan.
³ Institute of Imaging and Biomedical Photonics, College of Photonics, National Yang Ming Chiao Tung University, Guiren Dist, Tainan, 711010, Taiwan.
⁴ Department of Bioscience Technology, Chang Jung Christian University, Guiren Dist, Tainan, 711301, Taiwan; Department of Medical Science Industries, Chang Jung Christian University, Guiren Dist, Tainan, 711301, Taiwan. Electronic address: mjlee@mail.cjcu.edu.tw.
⁵ College of Photonics, National Yang Ming Chiao Tung University, Guiren Dist, Tainan, 711010, Taiwan; Institute of Imaging and Biomedical Photonics, College of Photonics, National Yang Ming Chiao Tung University, Guiren Dist, Tainan, 711010, Taiwan. Electronic address: wei.lee@nycu.edu.tw.

PMID: 37086565
DOI: 10.1016/j.bios.2023.115314

Abstract

Liquid crystal (LC)-based biosensors rely on the response of the LC molecules to perturbation generated by analytes at the interface, leading to the susceptible change in molecular alignment or orientation. The sensitivity of these biosensors is primarily dependent on the LC's material properties and surface anchoring strength. By incorporation of an unconventional mesogenic compound (CB7CB) coupled with the hybrid-alignment cell configuration, this work presents a binary nematic LC for label-free biosensing, manifesting a novel sensing technology that takes advantage of CB7CB-induced flexoelectricity in the transducer. Herein, we prepared LC mixtures by blending a typical rod-like nematic LC (E7) with the bent-core mesogen CB7CB in various weight ratios and studied the effect of the CB7CB content on E7/CB7CB-based biosensing performance in vertically aligned and hybrid-aligned nematic (HAN) cells. Owing to the anomalously small bend elastic constant K₃₃ in CB7CB, the mixture designated CB45 with the highest CB7CB weight percentage (45 wt% in this study) was best applicable to biosensing in HAN cells. When observed under a polarizing optical microscope, CB45 in the HAN geometry showed the capability of detection of as low as 10^-10 g/mL for the protein standard bovine serum albumin (BSA). Moreover, the quantitation of the assay was fulfilled by both dielectric and light transmission measurements of the hybrid-aligned cholesteric CB45/R5011. The limit of detection of 7 × 10^-10 g/mL was achieved by spectrometric analysis. To the best of our knowledge, this work is the first to demonstrate flexoelectric biosensing on the basis of flexoelectric polarization associated with giant flexoelectricity in CB7CB partially constituting the LC transducer.

Keywords: Bovine serum albumin; Dielectric biosensor; Flexoelectric effect; Label-free biosensor; Liquid crystal; Optical biosensor.

MeSH terms

Biosensing Techniques*
Liquid Crystals* / chemistry
Serum Albumin, Bovine / chemistry

Substances

Serum Albumin, Bovine