Analytical Sciences

Direct Labeling of Protein Nanoparticles with Fluorescent Compounds for Immunoassay Applications

Tsutomu SUGIHARA,*,** Masayasu MIE,* and Eiry KOBATAKE*

*School of Life Science and Technology, Tokyo Institute of Technology, 4259 Nagatsuta, Midori, Yokohama 226-8502, Japan
**Bio Process Research and Development Laboratories, Production Division, Kyowa Kirin Co., Ltd., 100-1 Hagiwara-machi, Takasaki, Gunma 370-0013, Japan

A fusion protein, designated ELP-D-C, comprised of a hydrophobic elastin-like polypeptide unit, a hydrophilic aspartic acid-rich peptide unit, and an antibody-binding domain as a functional unit, was constructed. Upon heat induction, ELP-D-C forms micellar nanoparticles displaying antibody-binding domains on their surfaces. The protein nanoparticles were able to incorporate hydrophobic fluorescent compounds and subsequently detect target molecules via antibody binding by the resulting fluorescence intensity, which was proportional to the log of the concentration of the target molecule.

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