title: Visualization of internalization of functionalized cobalt ferrite nanoparticles and their intracellular fate.
abstract: In recent years, nanoparticles (NPs) and related applications have become an intensive area of research, especially in the biotechnological and biomedical fields, with magnetic NPs being one of the promising tools for tumor treatment and as MRI-contrast enhancers. Several internalization and cytotoxicity studies have been performed, but there are still many unanswered questions concerning NP interactions with cells and NP stability. In this study, we prepared functionalized magnetic NPs coated with polyacrylic acid, which were stable in physiological conditions and which were also nontoxic short-term. Using fluorescence, scanning, and transmission electron microscopy, we were able to observe and determine the internalization pathways of polyacrylic acid-coated NPs in Chinese hamster ovary cells. With scanning electron microscopy we captured what might be the first step of NPs internalization - an endocytic vesicle in the process of formation enclosing NPs bound to the membrane. With fluorescence microscopy we observed that NP aggregates were rapidly internalized, in a time-dependent manner, via macropinocytosis and clathrin-mediated endocytosis. Inside the cytoplasm, aggregated NPs were found enclosed in acidified vesicles accumulated in the perinuclear region 1 hour after exposure, where they stayed for up to 24 hours. High intracellular loading of NPs in the Chinese hamster ovary cells was obtained after 24 hours, with no observable toxic effects. Thus polyacrylic acid-coated NPs have potential for use in biotechnological and biomedical applications.
authors.affiliation: Faculty of Electrical Engineering, University of Ljubljana, Ljubljana, Slovenia.
authors.forename: Vladimir B
authors.initials: VB
authors.lastname: Bregar
authors.forename: Jasna
authors.initials: J
authors.lastname: Lojk
authors.forename: Vid
authors.initials: V
authors.lastname: Suštar
authors.forename: Peter
authors.initials: P
authors.lastname: Veranič
authors.forename: Mojca
authors.initials: M
authors.lastname: Pavlin
mesh_terms: D000180:Acrylic Resins / Q000737:chemistry; D000818:Animals; D016466:CHO Cells; D002462:Cell Membrane / Q000378:metabolism; D049109:Cell Proliferation / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D003035:Cobalt / Q000032:analysis* / Q000737:chemistry / Q000493:pharmacokinetics / Q000494:pharmacology; D006224:Cricetinae; D003412:Cricetulus; D022162:Cytoplasmic Vesicles / Q000737:chemistry / Q000378:metabolism; D004705:Endocytosis / Q000187:drug effects; D005290:Ferric Compounds / Q000032:analysis* / Q000737:chemistry / Q000493:pharmacokinetics / Q000494:pharmacology; D042541:Intracellular Space / Q000737:chemistry* / Q000378:metabolism; D053768:Metal Nanoparticles / Q000737:chemistry*; D008854:Microscopy, Electron
chemical_list: D000180:Acrylic Resins; D005290:Ferric Compounds; C001215:ferrite; D003035:Cobalt; C006903:carbopol 940
keywords: internalization; intracellular fate; magnetic nanoparticles; scanning electron microscopy; transmission electron microscopy