Evaluation and effect of two co-ligand systems on optimization of the tumor-targeting ability of [^99mTc]Tc-HYNIC-KRWrNM

In this study, we compared in vitro and in vivo results of the ^99mTc-labeled HYNIC-KRWrNM in the presence of Tricine/EDDA and Tricine/Nicotinic acid (NA) as two co-ligand systems ([^99mTc]Tc-M-7 and [^99mTc]Tc-M-6, respectively). The dissociation constant (K_d) value of [^99mTc]Tc-M-6 was 7.1 ± 2.3 nM for U87-MG cell line (glioblastoma). Based on biodistribution studies, the tumor-to-muscle ratio of [^99mTc]Tc-M-6 was 8.77 and 11.33 at 1.5 and 4 h after injection, respectively. Finally, target-to-background ratio in the planar gamma image was 12.03 at 4 h after injection. By comparison, our experimental results showed that substitution of EDDA by Nicotinic acid in the ^99mTc-labeling of HYNIC-KRWrNM led to the formation of an improved tumor-targeting peptide. This improved radio-peptide can be a potential agent for the diagnosis of integrin α_vβ₃-positive tumors.