Label-free protein quantitation by dielectric spectroscopy of dual-frequency liquid crystal

•A novel method based on dual-frequency liquid crystal (DFLC) is developed for label-free protein assay.•The unique dielectric nature of DFLC is the key of the mechanism.•The frequency-dependent dielectric properties resolve the problem caused by cell-gap variations.•Dielectric analysis permits unambiguous quantitation of the model protein between 10−7 g/ml and 10−2 g/ml.•The method enables high sensitivity and high accuracy with a detection limit of 10 ng/ml for BSA. A dual-frequency-liquid-crystal (DFLC)-based biosensor was developed and its frequency-dependent dielectric properties were exploited to detect and quantitate a protein standard, bovine serum albumin (BSA). By analyzing the dielectric spectra of DFLC in the presence of BSA at various concentrations, we found that the difference in dielectric permittivity between the high- and low-frequency regimes is correlated to BSA concentration, thereby permitting a DFLC-based protein quantitative method. The dielectric properties of DFLCs are fundamental in the design of liquid crystal displays and fast-switching devices. Results from this study demonstrate the extended potential of the frequency-revertible dielectric anisotropy of DFLC in biosensing and protein quantitation.