A Fluorescent Imaging Probe Based on a Macrocyclic Scaffold That Binds to Cellular EpCAM
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Here, we report a fluorescent probe based on a macrocyclic peptide scaffold that specifically stains EpCAM-expressing MCF7 cells. The 14-mer macrocyclic peptide binding to the extracellular domain of EpCAM with a dissociation constant in the low nM range (1.7 nM) was discovered using the random non-standard peptide-integrated discovery system. Notably, this probe containing a fluorescence tag is less than 3000 Da in total and able to visualize nearly every live cell under high cell-density conditions, which was not achieved by the conventional mAb staining method. This suggests that the molecular probe based on the compact macrocyclic scaffold has great potentials as an imaging tool for the EpCAM biomarker as well as a delivery vehicle for drug conjugates.
KeywordsIn vitro selection Macrocyclic peptide EpCAM Fluorescent imaging probe Cancer cell imaging
We thank Drs. M. Ohuchi and T. Yoshitomi for supporting in the preparation of the manuscript. This work was supported by Ministry of Health, Labor and Welfare Grants-in-aid for Scientific Research programs from 2010 to 2012 to H. S., Y. T., and S. K., Grants-in-Aid for JSPS Fellows (7734) to K. I., and partly grants of Japan Society for the Promotion of Science Grants-in-Aid for Young Scientists (A) (24681047) to T. K., and Challenging Exploratory Research (15K12739) to Y. G.
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