title: Intracellular degradation of chemically functionalized carbon nanotubes using a long-term primary microglial culture model.
abstract: Chemically functionalized carbon nanotubes (f-CNTs) have been used in proof-of-concept studies to alleviate debilitating neurological conditions. Previous in vivo observations in brain tissue have suggested that microglia - acting as resident macrophages of the brain - play a critical role in the internalization of f-CNTs and their partial in situ biodegradation following a stereotactic administration in the cortex. At the same time, several reports have indicated that immune cells such as neutrophils, eosinophils and even macrophages could participate in the processing of carbon nanomaterials via oxidation processes leading to degradation, with surface properties acting as modulators of CNT biodegradability. In this study we questioned whether degradability of f-CNTs within microglia could be modulated depending on the type of surface functionalization used. We investigated the kinetics of degradation of multi-walled carbon nanotubes (MWNTs) functionalized via different chemical strategies that were internalized within isolated primary microglia over three months. A cellular model of rat primary microglia that can be maintained in cell culture for a long period of time was first developed. The Raman structural signature of the internalized f-CNTs was then studied directly in cells over a period of up to three months, following a single exposure to a non-cytotoxic concentration of three different f-CNTs (carboxylated, aminated and both carboxylated and aminated). Structural modifications suggesting partial but continuous degradation were observed for all nanotubes irrespective of their surface functionalization. Carboxylation was shown to promote more pronounced structural changes inside microglia over the first two weeks of the study.
authors.affiliation: Nanomedicine Lab, School of Medicine & National Graphene Institute, University of Manchester, AV Hill Building, Manchester M13 9PT, UK. kostas.kostarelos@manchester.ac.uk and Faculty of Life Sciences, University College London, Brunswick Square, London WC1N 1AX, UK.
authors.forename: Cyrill
authors.initials: C
authors.lastname: Bussy
authors.affiliation: Center of Excellence for Nanostructured Materials, Department of Chemical and Pharmaceutical Sciences, University of Trieste, Trieste, Italy and Carbon Nanobiotechnology Laboratory, CIC biomaGUNE, Paseo de Miramón 182, 20009 Donostia-San Sebastian, Spain.
authors.forename: Caroline
authors.initials: C
authors.lastname: Hadad
authors.affiliation: Center of Excellence for Nanostructured Materials, Department of Chemical and Pharmaceutical Sciences, University of Trieste, Trieste, Italy and Carbon Nanobiotechnology Laboratory, CIC biomaGUNE, Paseo de Miramón 182, 20009 Donostia-San Sebastian, Spain.
authors.forename: Maurizio
authors.initials: M
authors.lastname: Prato
authors.affiliation: CNRS, Institut de Biologie Moléculaire et Cellulaire, UPR 3572, Immunopathologie et Chimie Thérapeutique, Strasbourg, France.
authors.forename: Alberto
authors.initials: A
authors.lastname: Bianco
authors.affiliation: Nanomedicine Lab, School of Medicine & National Graphene Institute, University of Manchester, AV Hill Building, Manchester M13 9PT, UK. kostas.kostarelos@manchester.ac.uk and Faculty of Life Sciences, University College London, Brunswick Square, London WC1N 1AX, UK.
authors.forename: Kostas
authors.initials: K
authors.lastname: Kostarelos
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D017628:Microglia / Q000166:cytology / Q000378:metabolism*; D037742:Nanotubes, Carbon / Q000009:adverse effects / Q000737:chemistry*; D010084:Oxidation-Reduction; D051381:Rats; D017208:Rats, Wistar
chemical_list: D037742:Nanotubes, Carbon