Fig. 5

IETP2 delivers MRI contrast agent across the BLB. a Schematic representation of the structure of IETP2-Gd-DOTA. Two GdDOTA molecules were attached to one peptide molecule. The red ribbon represents IETP2. b, c 7.0 T MRI images of isolated cochleae from mice injected with IETP2-Gd-DOTA or free Gd-DOTA at 5 min after injection. Dosage: 1.5 mmol gadolinium/kg. The color bar on the left shows the MRI signal intensity; red indicates high signal intensity, while blue indicates low signal intensity. d, e 7.0 T MRI images of isolated cochleae of mice injected with IETP2-Gd-DOTA or free GdDOTA at 2 h after injection. Dosage: 1.5 mmol gadolinium/kg. f, g In vivo cochlear MRI images (f coronal plane; g para-sagittal plane) of mice injected with free GdDOTA at 1 h after intravenous injection. Dosage: 1.5 mmol gadolinium/kg. f The scala tympani and scala vestibuli were clearly enhanced, while the scala media remained at low intensity without enhancement. g Cross modiolus plane image of cochleae. An apex turn and midturn were seen (white dotted region). The ROI was the scala media region (red dotted region). h, i In vivo cochlear MRI image (h coronal plane; i para-sagittal plane) of mice injected with IETP2-Gd-DOTA at 4 h after intravenous injection. Dosage: 1.5 mmol gadolinium/kg. h Scala tympani and scala vestibuli were clearly enhanced, and scala media were also enhanced. i Cross modiolus plane image of cochleae. An apex turn and a midturn were observed (white dotted region). The ROI was the scala media region (red dotted region). Images captured at 1 or 4 h are displayed in f–i due to the saturated signal intensity at these time points. j Time-course signal intensity of the endolymph and perilymph in mice injected with IETP2-Gd-DOTA or GdDOTA. k Quantitative representation of the MRI signal intensity of the perilymphatic regions in (g and i) 4 h after drug injection. Error bars represent the mean ± SD. N = 6. ****p < 0.0001