Fig. 5: CD31-Mb-NPs specifically and efficiently accumulate throughout human renal endothelium during ex vivo organ perfusion.

a, b Representative kidney biopsy slices (10 µm thickness) taken from organs after a 4 h ex vivo perfusion with either CD31-Mb-NPs (a) or Isotype (iso)-Mb-NPs (b). Images show nanoparticles (NPs) in red with high levels of accumulation throughout the biopsy sample when NPs are targeted using CD31 (a). The biopsy perimeter is outlined in white, and the cortex- and medulla-facing-ends are labeled for orientation. Yellow boxes outline the location of the high magnification images defined in the rest of the figure and are labeled with the corresponding letter. Scale bar is 1 mm. c, d, f, g Representative high magnification images of microvasculature and glomeruli display NPs in red, vascular cells in cyan, cell nuclei in dark blue, and untargeted NPs in green. Each image is displayed with a color-merged view and accompanied with a red-only image below. Scale bar is 50 µm. Kidneys perfused with CD31-Mb-NPs have much higher NP coverage (61% in C and 92% in glomeruli of f) compared with kidneys perfused with isotype-Mb-NPs (1.8% in d and 3% in glomeruli of g). e, h Summary quantification of the red NP coverage on available microvascular structures (e) and glomeruli (h) with n = 3 tissue slices. Three biopsies were taken from each of six kidneys after the 4 h ex vivo perfusion, and are grouped together by the bars for representation. Three slices of 10 µm thickness, separated by 100 µm, were sampled from each biopsy. Each data point represents the area of available vasculature determined to have NP presence by fluorescence signal in a slice (~45 mm² area, or 300, 20× images) (e) or ~24 glomeruli (h), divided by the total area of available vasculature. Data points in green represent the data collected from the tissue slices shown in a and b. Statistical significance between treatments is denoted with ****p < 0.001, by an unpaired two-tailed T-test. Data are presented as mean values +/− SD. Source data are provided as a Source Data file. Mb monobody.