In vivo targeting of colonic dysplasia on fluorescence endoscopy with near-infrared octapeptide

Abstract

Objective To demonstrate a near-infrared peptide that is highly specific for colonic adenomas on fluorescence endoscopy in vivo. Design A 3 mm diameter endoscope was adapted to deliver 671 nm illumination and collect NIR fluorescence (696–736 nm). Target (QPIHPNNM) and control (YTTNKH) peptides were labeled with Cy5.5, a near-infrared dye, and characterized by mass spectra. The peptides were topically administered separately (100 µM) through the endoscope’s instrument channel into the distal colon of CPC;Apc mice, genetically-engineered to spontaneously develop adenomas. After 5 minutes for incubation, the unbound peptides were rinsed off, and images were collected at a rate of 10 per second. Regions-of-interest were identified around the adenoma and adjacent normal-appearing mucosa on white light. Intensity measurements were made from these same regions on fluorescence, and the target-to-background ratio (TBR) was calculated. Results We achieved an image resolution of 9.8 µm and field-of-view of 3.6 mm at a distance of 2.5 mm between the distal end of the instrument and the tissue surface. On mass spectra, the experimental mass-to-charge ratio for the Cy5.5-labeled target and control peptides agreed with expected values. The near-infrared fluorescence images of adenomas revealed individual dysplastic crypts with distorted morphology. By comparison, only amorphous surface features could be visualized from reflected near-infrared light. The average TBR for adenomas was found to be 3.42±1.30 and 1.88±0.38 for the target and control peptides, respectively, p=0.007. Conclusion We demonstrate a near-infrared peptide that is highly specific for colonic adenomas on fluorescence endoscopy in vivo and achieved sub-cellular resolution images.

Detection of colorectal polyps in humans using an intravenously administered fluorescent peptide targeted against c-Met

“…The exact target for this heptapeptide has yet to be determined, so any potential downstream signaling due to peptide binding has not been evaluated. This study made use of endoscopic confocal microscopy, in which only a few square millimeters of colon can be examined, and fluorescein, a suboptimal fluorophore for use in the colon 26 .…”

Mitigating fluorescence spectral overlap in wide-field endoscopic imaging

“…14, and the T∕B increased from 4 to ≥ 10. This enhancement elevates the performance of UV-blue excited fluorophores (e.g., FITC) to the level achieved with red and NIR dyes, 16,28 which are excited and fluorescence in spectral regions considered more immune from AF. 6 Indocyanine green, the only FDA-approved NIR fluorescent dye, 55,56 has a hydrophobic, large heptamethine interior that is surrounded by a negatively charged surface shell.…”

“…9 It was also shown that topically administered fluorescent molecular probes combined with endoscopic imaging can readily identify cancerous lesions. [8][9][10]27,28 In the diagnosis of HGD and early cancerous lesions in BE, multiple overexpressed cell surface targets, such as epidermal growth-factor receptor (EGFR and ErbB2), hepatocyte growth-factor receptor gene (MET), vascular endothelial growth-factor receptor 2 (VEGFR2), have been reported. 29,30 As a result, the coincident emission signature from multiple fluorescent-labeled probes is expected to provide a more sensitive and a specific disease state diagnosis than a single molecular target for HGD and early cancer detection in BE.…”

Target-to-background enhancement in multispectral endoscopy with background autofluorescence mitigation for quantitative molecular imaging

“…However, a low T/B (≤3) is often reported and is caused by a combination of confounding factors, including the abundant tissue background AF. 8,[13][14][15][16]36,37 Sometimes the background AF signal can be as high as the target signal. It blocks out diagnostic information and reduces the net sensitivity of the molecular probe imaging.…”

“…[1][2][3][4][5][6] Numerous endoscopic applications for tracking exogenous targeted fluorescence are under investigation, such as detection and diagnosis of early cancerous lesions in Barrett's esophagus, 7 navigation and demarcation of tumor margins during brain surgery, 8,9 and detection of early neoplasia in oral tissue, 10 lung, 11 bladder, 12 and smaller gastrointestinal (GI) ducts. 13 Moreover, translational studies for first-in-human application of fluorescence molecular targets have been demonstrated in colonic dysplasia detection as well as surgical guidance for ovarian cancer. 14,15 Compared to other optical contrast imaging techniques such as narrow band imaging and autofluorescence (AF) imaging, fluorescence molecular imaging with exogenous probes improves specificity for the detection of diseased tissues by targeting specific molecular entities such as overexpressed cell surface proteins at the cellular level.…”