Background
Fluorescent-labeled peptides are being developed to improve the endoscopic detection
of colonic dysplasia.
Objective
To demonstrate a near-infrared peptide multimer that functions as a phage mimic for
in vivo detection of colonic adenomas.
Design
A peptide multimer was synthesized by using trilysine as a dendritic wedge to mimic
the presentation of peptides on phage, and all peptides, including the multimer, were
fluorescent-labeled with Cy5.5.
Setting
Small-animal imaging facility.
Animal Subjects
Genetically engineered CPC;Apc mice that spontaneously develop colonic adenomas.
Intervention
Near-infrared-labeled AKPGYLS peptide multimer was administered topically into the
distal colons of the mice, and endoscopic images of adenomas were captured. Fluorescence
intensities were quantified by target-to-background (T/B) ratios, and adenoma dimensions
were measured with calipers after imaging. Validation of specific peptide binding
was performed on cryosectioned specimens and cells by using confocal microscopy and
flow cytometry.
Main Outcome Measurements
Fluorescence T/B ratios from colonic adenomas and adjacent normal-appearing mucosa.
Results
AKP-multimer, monomer, trilysine core, and Cy5.5 resulted in mean (± SD) T/B ratios
of 3.85 ± 0.25, 2.21 ± 0.13, 1.56 ± 0.12, and 1.19 ± 0.11, respectively, P < .01 on in vivo imaging. Peptide multimer showed higher contrast and greater specificity
for dysplastic crypts as compared with other probes. Peptide multimer demonstrated
significantly greater binding to HT29 cells on flow cytometry and fluorescence microscopy
in comparison to monomer and trilysine core. A binding affinity of 6.4 nm/L and time
constant of 0.1136 minutes−1 (8.8 minutes) was measured for multimer.
Limitations
Only distal colonic adenomas were imaged.
Conclusion
Peptide multimers combine strengths of multiple individual peptides to enhance binding
interactions and demonstrate significantly higher specificity and affinity for tumor
targets.
Abbreviations:
FITC (fluorescein isothiocyanate), HPLC (high-performance liquid chromatography), NIR (near-infrared), PBS (phosphate-buffered saline), T/B (target-to-background), TFA (trifluoroacetic acid)To read this article in full you will need to make a payment
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Article info
Publication history
Published online: October 01, 2012
Accepted:
July 8,
2012
Received:
April 15,
2012
Footnotes
DISCLOSURE: This research was supported in part by National Institutes of Health grants U54 CA13642, P50 CA93990, and R01 CA142750 to T. Wang. The University of Michigan has filed a provisional patent on behalf of authors B. Joshi and T. Wang on the peptide presented in this study. No other financial relationships relevant to this publication were disclosed.
Identification
Copyright
© 2012 American Society for Gastrointestinal Endoscopy. Published by Elsevier Inc. All rights reserved.
