Figure 1. In vivo phage screening in PBI.

(a) Schematic of the PBI mouse model, wherein a 5-mm craniotomy was performed in the right parietotemporal cortex and nine needle punctures were inflicted according to the grid shown. Right panel shows perfused brain, 6 h after the unilateral injury, from the top and in coronal view. (b) Representative immunofluorescence images show leakage through compromised BBB in PBI. Perfused PBI brain at 6 h was stained in the region around the corpus callosum (cc) for mouse IgG (red) and 4,6-diamidino-2-phenylindole (DAPI; blue). Scale bar, 50 μm. (c) Summary of peptide sequences recovered from phage screening in PBI mice. CAQK phage preferentially accumulated in brain injury after systemic injection of naïve phage library (1 × 10⁹ p.f.u.) in PBI animals; rescued first round phage pool sequenced with high-throughput sequencing showed CAQK and its variants (left pie chart). Sequences from second round of biopanning (right pie chart) show high CAQK recovery confirmed through Sanger sequencing. (d) CAQK phage frequency in brain as per cent of total phage recovered. Compared with PBI, CAQK was present at a lower percentage in the contralateral hemisphere in injured mice and absent in healthy, control mice.