Figure 5. PET/CT tracking of B cells after application to the wound bed.

A1–8 Representative maximum intensity projection (MIP) images of PET/CT scans from a WT animal at various intervals after application of ⁸⁹Zr-protamine-nanoparticle-labeled B cells or equal amounts of nanoparticle control. Note the highly restricted localization of the radioactive signal to the treated wound bed and edges (arrows) in the cell-treated condition (A1, A3, A5, A7), while substantial diffusion of the radioactivity was observed in the absence of cells (A2, A4, A6, A8; nanoparticle alone). Virtually no signal can be detected in the contralateral wound (open arrows) or in other organs of the body at this signal intensity. B. ⁸⁹Zr-decay-corrected radioactivity at the treated wound site (n = 4 animals per condition) indicates that the leakage of activity from the wound site is much more pronounced if the nanoparticle is applied in the absence of cells. ⁸⁹Zr decay is set at 1 and shown for comparison. C. Gamma counter measurements of residual radioactivity at the end point of the experiments in various organs confirms the localization of the signal in the B cell treated wounds and the increased distribution to liver and lymph nodes after free nanoparticle application. CPM/g = counts per minute per gram tissue. D1–5. B cell survival at the wound site. Intravital imaging of a WT mouse at multiple time points after application of B^luc cells (right-side wound, arrow) or saline control (left-side wound, open arrow). E. Light emission from the wound site treated with luciferase-expressing B cells (n = 6 animals per condition) indicates that the cells survive in situ up to approximately 14 days after application, with numbers of viable cells decreasing markedly after day 6. [p/s] = photons per second.