Label-free detection of anti-estrogen receptor alpha and its binding with estrogen receptor peptide alpha by terahertz spectroscopy

Terahertz (THz) spectroscopic techniques were employed to study the hydration shell formation around anti-estrogen receptor alpha (AER-a), an important biomarker in breast cancer diagnosis, and to detect the binding reaction between AER-a and estrogen receptor peptide alpha (ERP-a), in aqueous solutions. A remarkable nonlinear relation between THz absorption and AER-a concentration was demonstrated, shedding some light on the formation process of the hydration shell around AER-a. THz spectroscopic properties of the AER-a were also shown to be significantly affected by the binding with the ERP-a, to the extent that THz transmission and attenuation could be used to investigate the dielectric properties of antibody–antigen binding reactions.