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