Abstract
As large amount of vasoactive intestinal peptide (VIP) receptors are expressed in various tumors and VIP-related diseases, radiolabeled VIP provides a potential PET imaging agent for VIP receptor. However, structural modification of VIP is required before being radiolabeled and used for VIP receptor imaging due to its poor in vivo stability. As a VIP analogue, [R8, 15, 21, L17]-VIP exhibited improved stability and receptor specificity in preliminary studies. In this study, F-18 labeled [R8,15,21, L17]-VIP was produced with the radiochemical yield being as high as 33.6% ± 3% (decay-for-corrected, n = 5) achieved within 100 min, a specific activity of 255 GBq/μmol, and a radiochemical purity as high as 99% as characterized by radioactive HPLC, TLC, and SDS-Page radioautography. A biodistribution study in normal mice also demonstrated fast elimination of F-18 labeled [R8,15,21, L17]-VIP in the blood, liver, and gastrointestinal tracts. A further micro-PET imaging study in C26 colon carcinoma bearing mice confirmed the high tumor specificity, with the tumor/muscle radioactivity uptake ratio being as high as 3.03 at 60 min following injection, and no apparent radioactivity concentration in the intestinal tracts. In addition, blocking experiment and Western Blot test further confirmed its potential in PET imaging of VIP receptor-positive tumor.
Highlights
As an advanced imaging technique, position emission tomography (PET) allows noninvasive detection and quantitative assay of the in vivo distribution profile of radioactive isotope-labeled probes and has been extensively used in the diagnosis and staging of various diseases [1, 2]
The target product [F-18]FB-[R8,15,21, L17]-vasoactive intestinal peptide (VIP) produced by F-18 labeling achieved the radiochemical yield as high as 33.6% ± 3% within 100 min, with a specific activity of 255 GBq/μmol and a radiochemical purity as high as 99% as characterized by radioactive HPLC, TLC, and SDS-Page radioautography
A novel VIP analogue was successfully labeled by F-18 and characterized by various methods, providing a detailed characterization methodology study of F-18 labeling polypeptides and antibodies
Summary
As an advanced imaging technique, position emission tomography (PET) allows noninvasive detection and quantitative assay of the in vivo distribution profile of radioactive isotope-labeled probes and has been extensively used in the diagnosis and staging of various diseases [1, 2]. Both advanced imaging devices and imaging agents are essential for such a functional imaging approach. VIP exerts physiological functions mainly through its receptor, which can be generally classified as VIP1 receptor
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