Fig. 5: Vascular differences in nanoparticle motility and subcellular distribution.
a Time-lapse imaging of the vessel wall surface (left panel) and across the vessel (right panel). Arrowheads indicate moving nanoparticles. See also Supplementary Movie 4. b Nanoparticle tracking. Left panel: circles outline selected nanoparticles. Middle panel: nanoparticle movement during 30 min of continuous imaging. Right panel: isolated movement traces (black) with contours delineating microvessels (gray). See also Supplementary Movie 5. c Upper left inset: vessel hierarchy and color-coding. Lower left inset: translation of nanoparticle movement from (x,y) to a (v) coordinate aligned with the vessel long symmetry axis and direction of the blood flow. Right panels: Nanoparticle traces in (x,y) and corresponding (v) coordinate. v > 0 indicates the movement along, and v < 0 against the blood flow direction. d Nanoparticles traverse longer distances in post-capillary venules (orange), compared to pial venules and capillaries (red, yellow; *p = 0.0302, ****p < 0.0001, respectively; two-tailed t-tests with Bonferroni post hoc correction). Time span = 30 min. Data are means ± SEM. e Blood flow direction does not affect the nanoparticle displacement. Boxplots show medians with IQR, whiskers extend between 5th and 95th percentile range. f Deviation of MSDv(Δt) from linearity indicates movement inconsistent with diffusion predicted by the linear fit (all groups ****p < 0.0001, Wald–Wolfowitz runs test). Data are means ± SEM. c–f n = number of nanoparticles, where npV = 90; npcV = 200; ncap = 380 across 5 mice. g In venules, nanoparticles distribute preferentially to perinuclear areas. Images collected 3 h post-injection. h Capillaries do not exhibit a preferential perinuclear distribution of nanoparticles. i Measurement of nanoparticles location in relation to nucleus perimeter 3 h post-injection. j Kernel density map of nanoparticle distribution in relation to the geometric center of the nucleus. Kernel = 2σ (=0.58 µm). The heat-map represents the probability of nanoparticle presence at a given coordinate. k Percentage distribution of nanoparticles in relation to nucleus perimeter. Non-classified are nanoparticles overlapping with the nucleus. j, k n = 3534 nanoparticles across 5 mice. l Nanoparticles do not distribute to the endothelial cells boundaries or contact sites (dashed lines). All panels: Image insets denote the imaging plane in relation to a vessel perimeter. pV pial venule, pcV post-capillary venule, cap capillary, nuc nucleus, MSDv(Δt) mean squared displacement in (v) coordinate.
