Diagnostic and therapeutic potential of poly(benzyl L-glutamate)

Development of 68Ga-glycopeptide as an imaging probe for tumor angiogenesis

Objective. This study was aimed to study tissue distribution and tumor imaging potential of ⁶⁸Ga-glycopeptide (GP) in tumor-bearing rodents by PET. Methods. GP was synthesized by conjugating glutamate peptide and chitosan. GP was labeled with ⁶⁸Ga chloride for in vitro and in vivo studies. Computer outlined region of interest (counts per pixel) of the tumor and muscle (at the symmetric site) was used to determine tumor-to-muscle count density ratios. To ascertain the feasibility of ⁶⁸Ga-GP in tumor imaging in large animals, PET/CT imaging of ⁶⁸Ga-GP and ¹⁸F-FDG were conducted in New Zealand white rabbits bearing VX2 tumors. Standard uptake value of tumors were determined by PET up to 45 min. To determine blood clearance and half-life of ⁶⁸Ga-GP, blood samples were collected from 10 seconds to 20 min. Results. Radiochemical purity of ⁶⁸Ga-GP determined by instant thin-layer chromatography was >95%. Tumor uptake values (SUV) for ⁶⁸Ga-GP and ¹⁸F-FDG in New Zealand white rabbits bearing VX2 tumors were 3.25 versus 7.04. PET images in tumor-bearing rats and rabbits confirmed that ⁶⁸Ga-GP could assess tumor uptake. From blood clearance curve, the half-life of ⁶⁸Ga-GP was 1.84 hr. Conclusion Our data indicate that it is feasible to use ⁶⁸Ga-GP to assess tumor angiogenesis.