title: Antioxidant multi-walled carbon nanotubes by free radical grafting of gallic acid: new materials for biomedical applications.
abstract: OBJECTIVE
  To prove the possibility of covalently functionalizing multi-walled carbon nanotubes (CNTs) by free radical grafting of gallic acid on their surface with the subsequent synthesis of materials with improved biological properties evaluated by specific in-vitro assays.
  
  
  METHODS
  Antioxidant CNTs were synthesized by radical grafting of gallic acid onto pristine CNTs. The synthesis of carbon nanotubes was carried out in a fixed-bed reactor and, after the removal of the amorphous carbon, the grafting process was performed. The obtained materials were characterized by fluorescence and Fourier transform infrared spectroscopy (FT-IR) analyses. After assessment of the biocompatibility and determination of the disposable phenolic group content, the antioxidant properties were evaluated in terms of total antioxidant activity and scavenger ability against 2,2'-diphenyl-1-picrylhydrazyl (DPPH), hydroxyl and peroxyl radicals. Finally the inhibition activity on acetylcholinesterase was evaluated.
  
  
  RESULTS
  The covalent functionalization of CNTs with gallic acid was confirmed and the amount of gallic acid bound per g of CNTs was found to be 2.1±0.2 mg. Good antioxidant and scavenging properties were recorded in the functionalized CNTs, which were found to be able to inhibit the acetylcholinesterase with potential improved activity for biomedical and pharmaceutical applications.
  
  
  CONCLUSIONS
  For the first time, a free radical grafting procedure was proposed as a synthetic approach for the covalent functionalization of CNTs with an antioxidant polyphenol.
authors.affiliation: Department of Pharmaceutical Sciences, University of Calabria, Arcavacata di Rende (CS), Italy. giuseppe.cirillo@unical.it
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Cirillo
authors.forename: Silke
authors.initials: S
authors.lastname: Hampel
authors.forename: Rüdiger
authors.initials: R
authors.lastname: Klingeler
authors.forename: Francesco
authors.initials: F
authors.lastname: Puoci
authors.forename: Francesca
authors.initials: F
authors.lastname: Iemma
authors.forename: Manuela
authors.initials: M
authors.lastname: Curcio
authors.forename: Ortensia Ilaria
authors.initials: OI
authors.lastname: Parisi
authors.forename: Umile Gianfranco
authors.initials: UG
authors.lastname: Spizzirri
authors.forename: Nevio
authors.initials: N
authors.lastname: Picci
authors.forename: Albrecht
authors.initials: A
authors.lastname: Leonhardt
authors.forename: Manfred
authors.initials: M
authors.lastname: Ritschel
authors.forename: Bernd
authors.initials: B
authors.lastname: Büchner
mesh_terms: D000818:Animals; D000975:Antioxidants / Q000138:chemical synthesis / Q000737:chemistry* / Q000494:pharmacology; D001713:Biphenyl Compounds / Q000737:chemistry; D002642:Chick Embryo; D002800:Cholinesterase Inhibitors / Q000737:chemistry / Q000494:pharmacology; D016166:Free Radical Scavengers / Q000138:chemical synthesis / Q000737:chemistry* / Q000494:pharmacology; D005707:Gallic Acid / Q000737:chemistry* / Q000494:pharmacology; D017665:Hydroxyl Radical / Q000737:chemistry; D015227:Lipid Peroxidation / Q000187:drug effects; D008422:Materials Testing / Q000379:methods; D037742:Nanotubes, Carbon / Q000737:chemistry* / Q000648:ultrastructure; D010545:Peroxides / Q000737:chemistry; D010851:Picrates / Q000737:chemistry; D017550:Spectroscopy, Fourier Transform Infrared / Q000379:methods
chemical_list: D000975:Antioxidants; D001713:Biphenyl Compounds; D002800:Cholinesterase Inhibitors; D016166:Free Radical Scavengers; D037742:Nanotubes, Carbon; D010545:Peroxides; D010851:Picrates; C049375:perhydroxyl radical; D017665:Hydroxyl Radical; D005707:Gallic Acid; C004931:1,1-diphenyl-2-picrylhydrazyl