Fig. 6.

Tracking biotinylated cytotoxic T lymphocytes in vivo targeting brain gliomas. a Position emission tomography-computed tomography (PET/CT) imaging of CTLs targeting brain gliomas at 3 and 20 h after [⁸⁹Zr]Zr-deferoxamine-biotin injection. Biotinylated CTLs with streptavidin were injected 24 h prior to the PET agent. The targeted [biotin acceptor peptide-transmembrane (BAP-TM)+] glioma expressed surface biotin, while the control tumor did not. The initial intensity of the control tumor appeared higher at the 3 h image due to the much larger size of the tumor compared to the targeted tumor, representing non-specific uptake of the PET agent due to leakage across a disrupted blood–brain barrier. However, over time, the control tumor showed a rapid loss of the PET signal while the targeted tumor showed only a minimal decrease in signal over time. b Quantification of the PET signal (tumor/normal brain, normalized to the 3-h time point)