Analytical Sciences

Interaction Analysis of the Carcinoembryonic Antigen (CEA) with Its Monoclonal Antibody Immobilized on a Gold Surface Using Fourier Transform Infrared Reflection-Absorption Spectroscopy (FT-IR RAS)

Keiichi OHTSUKA,* Masahide KUROKI,** Takahiko NOJIMA,* Michinori WAKI,* and Shigeori TAKENAKA*

*Department of Applied Chemistry, Faculty of Engineering, Kyushu University, Fukuoka 812-8581, Japan
**Department of Biochemistry, Faculty of Medicine, Fukuoka University, Fukuoka 814-0180, Japan

A monoclonal antibody for the carcinoembryonic antigen (CEA) was immobilized on a gold chip surface covered by a self-assembled monolayer of 11-mercaptoundecanoic acid. Upon the addition of CEA, a Fourier transform infrared reflection-absorption spectroscopy (FT-IR RAS) measurement showed an increased absorption at around 1500 - 1700 cm^-1, corresponding to its amide structures. Another addition of CEA polyclonal antibody on this chip caused a further increase of the absorption in this region only after a treatment with CEA. This result shows that an antibody-fixed gold surface coupled with an FT-IR RAS measurement provides a new tool for detecting the antibody-antigen interaction.

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