The work described in this dissertation contributes to a better mechanistic understanding of nanoparticles in vivo. To achieve that goal, we used the zebrafish as a highly predictive pre-screening... Show moreThe work described in this dissertation contributes to a better mechanistic understanding of nanoparticles in vivo. To achieve that goal, we used the zebrafish as a highly predictive pre-screening model of nanoparticles. This approach enables the investigation of the fundamental behavior of nanoparticles, correlation of the physicochemical properties of the formulated nanoparticles with their biodistribution and identification of important nano-bio interactions. Zebrafish established transgenic lines were used to study specific interactions. In addition, genetically modified zebrafish applying CRISPR/Cas9 were generated. These strategies not only show key mechanistic features of nanoparticles in circulation, but also promote the rational design of more efficient nanoparticles systems.After understanding the fundamental behavior of nanoparticles, this thesis describes the identification of a key interaction between stabilins receptors (expressed in liver sinusoidal endothelial cells) and nanoparticles. Next, the scope is changed to design nano-systems that target specific cell types showing liposomes capable of switching the surface charge in situ and in vivo using light as an external trigger and a rationally designed lipid nanoparticle formulation containing mRNA able to preferentially target the hepatic reticuloendothelial system. In addition, a phase-separated liposomes hijacking a lipase mediated transport to selectively target endothelial lipase in vivo was studied. Show less