Protein assay and immunoassay based on nematic thermotropic and lyotropic liquid crystals quantitated by haze measurement

Abstract

Haze measurement is the cornerstone for assessing the transparency or opaqueness of liquid crystals (LCs) in applications such as smart windows and display technologies. In this study, we present a novel application of haze measurement as the quantitative approach for LC-based biosensing. Protein assay with bovine serum albumin (BSA) as the protein standard and immunoassay of the cancer biomarker CA125 were performed with the thermotropic LC 5CB and the nematic phase of the lyotropic chromonic LC sunset yellow. We observed that the brightness of LC optical texture increased with increasing analyte concentration due to enhanced light leakage caused by the attenuation of the vertical anchoring force of the surface alignment reagent coated on the glass surface. On the other hand, the haze value decreased as the amount of BSA or CA125 at the LC–glass interface increased, indicating that the scattering angle of the incident light was reduced. By calculating the percent difference in haze value, W (%), which gave rise to a positive correlation between the result of haze analysis and analyte concentration, a limit of detection (LOD) of 1.2 × 10⁻³ and 5.6 × 10⁻⁵ g/mL for BSA and CA125, respectively, was achieved by detection with 5CB, whereas the LOD values for BSA and CA125 were 1.0 × 10⁻¹² and 1.9 × 10⁻⁹ g/mL, respectively, when detected with nematic sunset yellow. To the best of our knowledge, this study provides the first demonstration of the feasibility and simplicity of quantitative analysis by haze measurement in LC-based biosensing.