title: Internalization of targeted quantum dots by brain capillary endothelial cells in vivo.
abstract: Receptors located on brain capillary endothelial cells forming the blood-brain barrier are the target of most brain drug delivery approaches. Yet, direct subcellular evidence of vectorized transport of nanoformulations into the brain is lacking. To resolve this question, quantum dots were conjugated to monoclonal antibodies (Ri7) targeting the murine transferrin receptor. Specific transferrin receptor-mediated endocytosis of Ri7-quantum dots was first confirmed in N2A and bEnd5 cells. After intravenous injection in mice, Ri7-quantum dots exhibited a fourfold higher volume of distribution in brain tissues, compared to controls. Immunofluorescence analysis showed that Ri7-quantum dots were sequestered throughout the cerebral vasculature 30 min, 1 h, and 4 h post injection, with a decline of signal intensity after 24 h. Transmission electron microscopic studies confirmed that Ri7-quantum dots were massively internalized by brain capillary endothelial cells, averaging 37 ± 4 Ri7-quantum dots/cell 1 h after injection. Most quantum dots within brain capillary endothelial cells were observed in small vesicles (58%), with a smaller proportion detected in tubular structures or in multivesicular bodies. Parenchymal penetration of Ri7-quantum dots was extremely low and comparable to control IgG. Our results show that systemically administered Ri7-quantum dots complexes undergo extensive endocytosis by brain capillary endothelial cells and open the door for novel therapeutic approaches based on brain endothelial cell drug delivery.
authors.affiliation: Faculty of Pharmacy, Université Laval, Quebec, Canada Centre de recherche du CHU de Québec, Neurosciences Axis, Quebec, Canada.
authors.forename: Sarah
authors.initials: S
authors.lastname: Paris-Robidas
authors.affiliation: Research and Development, Héma-Québec, Quebec, Canada.
authors.forename: Danny
authors.initials: D
authors.lastname: Brouard
authors.affiliation: Faculty of Pharmacy, Université Laval, Quebec, Canada Centre de recherche du CHU de Québec, Neurosciences Axis, Quebec, Canada.
authors.forename: Vincent
authors.initials: V
authors.lastname: Emond
authors.affiliation: Faculty of Medicine, Université Laval, Quebec, Canada Centre de recherche de l'Institut universitaire en santé mentale de Québec, Quebec, Canada.
authors.forename: Martin
authors.initials: M
authors.lastname: Parent
authors.affiliation: Faculty of Pharmacy, Université Laval, Quebec, Canada Centre de recherche du CHU de Québec, Neurosciences Axis, Quebec, Canada frederic.calon@crchul.ulaval.ca.
authors.forename: Frédéric
authors.initials: F
authors.lastname: Calon
mesh_terms: D000818:Animals; D001812:Blood-Brain Barrier / Q000648:ultrastructure; D002196:Capillaries / Q000166:cytology / Q000378:metabolism* / Q000648:ultrastructure; D002460:Cell Line; D002560:Cerebrovascular Circulation; D004705:Endocytosis; D042783:Endothelial Cells / Q000378:metabolism* / Q000648:ultrastructure; D004730:Endothelium, Vascular / Q000166:cytology / Q000378:metabolism* / Q000648:ultrastructure; D007074:Immunoglobulin G / Q000378:metabolism; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D053758:Nanoparticles; D045663:Quantum Dots / Q000378:metabolism*; D051381:Rats; D011990:Receptors, Transferrin / Q000096:biosynthesis / Q000235:genetics; D014018:Tissue Distribution
chemical_list: D007074:Immunoglobulin G; D011990:Receptors, Transferrin; C480029:Tfrc protein, mouse
keywords: Blood–brain barrier; brain capillary endothelial cells; drug targeting; monoclonal antibody; quantum dot nanocrystals