Trans-endothelial transport of nanoparticles remains poorly characterized in live organisms. The zebrafish is a well-established model for direct in vivo imaging; however, standardized controls have not been consistently applied across studies. Here, we developed a standardized protocol to assess nanoparticle trans-endothelial trafficking in live zebrafish. We identified 2000 kDa dextran as an optimal coinjection control for standardizing microinjections and quantifying nanoparticle transport in a systematic, unbiased manner. Using the standardized protocol, we profiled early physiological trans-endothelial transport pathways in zebrafish embryos using dextran solutes as extravasation markers, showing that steady-state solute extravasation is characterized by paracellular routes selective for solutes cavin1b knock-in zebrafish line. Using cavin1a/cavin1b double knockout zebrafish and tumor-bearing Cavin1 null mice, we showed that caveolae do not contribute to the transvascular transport of these PEG-based nanoparticles. This work demonstrates the rigor of the standardized protocol for assessing trans-endothelial transport in the live zebrafish and provides fundamental cell biology insight into the in vivo behavior of PEG-based nanoparticles.
Lim et al. (Wed,) studied this question.