title: Near-infrared-labeled peptide multimer functions as phage mimic for high affinity, specific targeting of colonic adenomas in vivo (with videos).
abstract: 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.
  
  
  METHODS
  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.
  
  
  METHODS
  Small-animal imaging facility. ANIMAL SUBJECTS: Genetically engineered CPC;Apc mice that spontaneously develop colonic adenomas.
  
  
  METHODS
  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.
  
  
  METHODS
  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.
  
  
  CONCLUSIONS
  Only distal colonic adenomas were imaged.
  
  
  CONCLUSIONS
  Peptide multimers combine strengths of multiple individual peptides to enhance binding interactions and demonstrate significantly higher specificity and affinity for tumor targets.
authors.affiliation: Department of Medicine, Division of Gastroenterology, University of Michigan, Ann Arbor, Michigan 48109-2200, USA.
authors.forename: Bishnu P
authors.initials: BP
authors.lastname: Joshi
authors.forename: Zhongyao
authors.initials: Z
authors.lastname: Liu
authors.forename: Sakib F
authors.initials: SF
authors.lastname: Elahi
authors.forename: Henry D
authors.initials: HD
authors.lastname: Appelman
authors.forename: Thomas D
authors.initials: TD
authors.lastname: Wang
mesh_terms: D000236:Adenoma / Q000175:diagnosis*; D000595:Amino Acid Sequence; D000818:Animals; D001435:Bacteriophages; D002232:Carbocyanines; D060326:Chemistry Techniques, Synthetic; D003110:Colonic Neoplasms / Q000175:diagnosis*; D003113:Colonoscopy / Q000379:methods*; D005434:Flow Cytometry; D005456:Fluorescent Dyes; D019073:HT29 Cells; D006801:Humans; D051379:Mice; D008822:Mice, Transgenic; D057054:Molecular Imaging / Q000379:methods*; D061848:Optical Imaging / Q000379:methods*; D019151:Peptide Library; D010455:Peptides / Q000138:chemical synthesis
chemical_list: C098793:CY5.5 cyanine dye; D002232:Carbocyanines; D005456:Fluorescent Dyes; D019151:Peptide Library; D010455:Peptides