Fig. 2

dSTORM imaging demonstrates super-resolution tracer permeability and validates the unique barrier properties of the CNS arteriole wall. Precise nano-scale localization of the sulfo-biotin tracer (443 Da), stained with Alexa-647 conjugated streptavidin. a Relatively low resolution TIRF mode imaging (Total Internal Reflection Fluorescence, similar to epi-fluorescence with TIRF illumination, presenting all the collected signals with no super-resolution analysis) of endothelium (anti-CD31), smooth-muscle (anti-SMA) in wild-type adult mouse brain sections, does not allow precise localization of tracer along the vascular wall due to diffraction limitation. Scale bar 10 µm. b dSTORM images of the same arteriole (as in a) shows that tracer signals are found passed both the endothelium and the smooth-muscle markers. Scale bar 10 µm. b’-b’’, Inset magnifications showing distances between the tracer and the cell markers (CD31 (b’, SMA signal omitted) and of SMA (b’’), scale bars b’ 2 µm, b’’ 1 µm). c Quantification of tracer signals beyond the smooth muscle marker (sulfo-biotin tracer images appear here, dextran and albumin tracers images appear in Additional file 1: Fig. S1). There are no significant differences in permeability of these three tracers of different size and molecular compositions (Kruskal–Wallis H test). (L) marks the vessel lumen. Dashed arrows marks tracer direction from the lumen towards the parenchyma. Images are representative of n = 18 arteriole profiles of n = 4 mice