Terahertz chemical microscope for label-free detection of protein complex

Abstract

A terahertz (THz) chemical microscope (TCM) has been proposed and developed for label-free analysis of the interactions of proteins, including immune reactions. A SiO2/Si/sapphire plate was fabricated and emitted THz pulses from the sapphire side using a femtosecond laser. The amplitude of a THz pulse depends on the chemical potential of the SiO2 surface. As an initial demonstration, a biotin–avidin complex was analyzed using TCM. Results indicate that biotin concentrations of up to 10−12 mol/l could be detected, suggesting that a high sensitivity immunoassay system can be realized using this method. The distribution of the THz peak amplitude was measured, reflecting the distribution of the biotin–avidin complex on the plate.