Nanocarriers can be useful tools for delivering drugs to the central nervous system (CNS). Their distribution within the brain and their interaction with CNS cells must be assessed accurately before they can be proposed for therapeutic use. We investigated these issues by employing poly-lactide-co-glycolide nanoparticles (NPs) specifically engineered with a glycopeptide (g7) conferring to NPs the ability to cross the blood brain barrier (BBB) at a concentration of up to 10% of the injected dose. g7-NPs display increased in vitro uptake in neurons and glial cells, in vivo administration of g7-NPs leads to a region- and cell type-specific enrichment of NPs within the brain. Moreover, g7-NPs are endocytosed in a clathrin-dependent manner and transported into a specific subset of early endosomes positive for Rab5 in vitro and in vivo. Moreover, in order to understand the journey of NPs, we demonstrated that g7-NPs can be transported intra- and intercellularly inside vesicles. Cell-to-cell transport is mediated by tunneling-nanotube (TNT)-like structures in cell lines and most interestingly in glial as well as neuronal cells in vitro. These in vitro findings were in part confirmed by in vivo evidence after i.p. administration in mice. We also tested Ab-modified g7-NPs both in vitro and in vivo to investigate the possibility of a specific targeting.
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