Single-domain antibodies: Next-generation targeting vectors for molecular imaging

Results: Tc-1 and Tc-2 exhibited high specific FR binding in vitro. Both Tc-1 and Tc-2 displayed high tumor uptake (8.55 ± 2.78% ID/g and 9.77 ± 1.54% ID/g at 1 h p.i., respectively) and rapid clearance from non-target organs. Micro-SPECT/CT imaging studies in KB tumor models showed that the tumor could be clearly visualized at 4 h p.i. Conclusion: The hydrophilic linkers exhibited a profound effect on the tumor uptake and pharmacokinetic properties of the radiotracers. The two Tc-labeled Pteroyl-lys derivatives are very promising SPECT radiotracers to detect the FR-positive tumors.