title: Mechanism of PAMAM Dendrimers Internalization in Hippocampal Neurons.
abstract: Polyamidoamine (PAMAM) dendrimers are hyperbranched macromolecules which have been described as one of the most promising drug nanocarrier systems. A key process to understand is their cellular internalization mechanism because of its direct influence on their intracellular distribution, association with organelles, entry kinetics, and cargo release. Despite that internalization mechanisms of dendrimers have been studied in different cell types, in the case of neurons they are not completely described. Considering the relevance of central nervous system (CNS) diseases and neuropharmacology, the aim of this report is to describe the molecular internalization mechanism of different PAMAM-based dendrimer systems in hippocampal neurons. Four dendrimers based on fourth generation PAMAM with different surface properties were studied: unmodified G4, with a positively charged surface; PP50, with a substitution of the 50% of amino surface groups with polyethylene glycol neutral groups; PAc, with a substitution of the 30% of amino surface groups with acrylate anionic groups; and PFO, decorated with folic acid groups in a 25% of total terminal groups. Confocal images show that both G4 and PFO are able to enter the neurons, but not PP50 and PAc. Colocalization study with specific endocytosis markers and specific endocytosis inhibitor assay demonstrate that clathrin-mediated endocytosis would be the main internalization mechanism for G4, whereas clathrin- and caveolae-mediated endocytosis would be implicated in PFO internalization. These results show the existence of different internalization mechanisms for PAMAM dendrimers in neurons and the possibility to control their internalization properties with specific chemical modifications.
authors.affiliation: Laboratory of Molecular Neurobiology, Department of Physiology, Faculty of Biological Sciences, University of Concepcion , Concepcion, Chile.
authors.forename: Felipe
authors.initials: F
authors.lastname: Vidal
authors.affiliation: Laboratory of Molecular Neurobiology, Department of Physiology, Faculty of Biological Sciences, University of Concepcion , Concepcion, Chile.
authors.forename: Pilar
authors.initials: P
authors.lastname: Vásquez
authors.affiliation: Department of Organic Chemistry, Faculty of Chemical Sciences, University of Concepcion , Concepcion, Chile.
authors.forename: Carola
authors.initials: C
authors.lastname: Díaz
authors.affiliation: Laboratory of Molecular Neurobiology, Department of Physiology, Faculty of Biological Sciences, University of Concepcion , Concepcion, Chile.
authors.forename: Daniela
authors.initials: D
authors.lastname: Nova
authors.affiliation: Department of Organic Chemistry, Faculty of Chemical Sciences, University of Concepcion , Concepcion, Chile.
authors.forename: Joel
authors.initials: J
authors.lastname: Alderete
authors.affiliation: Laboratory of Molecular Neurobiology, Department of Physiology, Faculty of Biological Sciences, University of Concepcion , Concepcion, Chile.
authors.forename: Leonardo
authors.initials: L
authors.lastname: Guzmán
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D050091:Dendrimers / Q000378:metabolism*; D004705:Endocytosis / Q000502:physiology; D006624:Hippocampus / Q000166:cytology*; D007150:Immunohistochemistry; D051379:Mice; D008810:Mice, Inbred C57BL; D018613:Microscopy, Confocal; D009474:Neurons / Q000378:metabolism*
chemical_list: D050091:Dendrimers; C104700:PAMAM Starburst
keywords: PAMAM internalization; dendrimer; endocytosis; neuronal uptake; surface modification