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Research Papers: Imaging

Cy5.5-labeled Affibody molecule for near-infrared fluorescent optical imaging of epidermal growth factor receptor positive tumors

[+] Author Affiliations
Zheng Miao, Gang Ren, Hongguang Liu, Lei Jiang, Zhen Cheng

Stanford University, Stanford Cancer Center, Molecular Imaging Program at Stanford, Department of Radiology and Bio-X Program, 1201 Welch Road, Lucas Expansion, P095, Stanford, California 94305-5344

J. Biomed. Opt. 15(3), 036007 (June 23, 2010). doi:10.1117/1.3432738
History: Received October 22, 2009; Revised March 15, 2010; Accepted March 23, 2010; Published June 23, 2010; Online June 23, 2010
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Affibody protein is an engineered protein scaffold with a three-helical bundle structure. Affibody molecules of small size (7kD) have great potential for targeting overexpressed cancer biomarkers in vivo. To develop an Affibody-based molecular probe for in vivo optical imaging of epidermal growth factor receptor (EGFR) positive tumors, an anti-EGFR Affibody molecule, Ac-Cys-ZEGFR:1907(7kD), is site-specifically conjugated with a near-IR fluorescence dye, Cy5.5-mono-maleimide. Using fluorescent microscopy, the binding specificity of the probe Cy5.5-ZEGFR:1907 is checked by a high-EGFR-expressing A431 cell and low-EGFR-expressing MCF7 cells. The binding affinity of Cy5.5-ZEGFR:1907(KD) to EGFR is 43.6±8.4nM, as determined by flow cytometry. For an in vivo imaging study, the probe shows fast tumor targeting and good tumor contrast as early as 0.5h postinjection (p.i.) for A431 tumors, while MCF7 tumors are barely visible. An ex vivo imaging study also demonstrates that Cy5.5-ZEGFR:1907 has high tumor, liver, and kidney uptakes at 24h p.i.. In conclusion, Cy5.5-ZEGFR:1907 shows good affinity and high specificity to the EGFR. There is rapid achievement of good tumor-to-normal-tissue contrasts of Cy5.5-ZEGFR:1907, thus demonstrating its potential for EGFR-targeted molecular imaging of cancers.

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© 2010 Society of Photo-Optical Instrumentation Engineers

Citation

Zheng Miao ; Gang Ren ; Hongguang Liu ; Lei Jiang and Zhen Cheng
"Cy5.5-labeled Affibody molecule for near-infrared fluorescent optical imaging of epidermal growth factor receptor positive tumors", J. Biomed. Opt. 15(3), 036007 (June 23, 2010). ; http://dx.doi.org/10.1117/1.3432738


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