title: In vitro evaluation of osteoblast responses to carbon nanotube-coated titanium surfaces.
abstract: BACKGROUND
  The effects of surface roughness and carboxyl functionalization of multi-walled carbon nanotubes (MWCNTs) mixed with collagen coated onto titanium (Ti) substrates on MC3T3-E1 osteoblasts were evaluated.
  
  
  METHODS
  The proliferation, differentiation, and matrix mineralization were investigated using (1) smooth-surfaced Ti discs, (2) Ti discs coated with collagen and MWCNT (Ti-MWCNT), and (3) Ti discs coated with collagen and MWCNT-COOH (Ti-MWCNT-COOH) for applications in orthodontic mini screw implants (MSIs). The coatings were uniform when analyzed using scanning electron microscopy (SEM), and surface roughness was evaluated by surface profilometry that demonstrated similar surface roughness (R a , mean ± SD) in the MWCNT (0.83 ± 0.02 μm) and MWCNT-COOH (0.84 ± 0.01 μm) groups. MTT (3-(4,5-dimethylthiazol-2-Yl)-2,5-diphenyltetrazolium bromide) assay was performed after days 1, 3, and 7 to assess proliferation. Alkaline phosphatase (ALP)-specific activity was assessed after day 7 to quantify differentiation. Alizarin red staining was measured after day 28 to quantify matrix mineralization. All data were analyzed with JMP Pro11 software (SAS, USA) with a statistical significance of p  < 0.05.
  
  
  RESULTS
  Surface profilometry demonstrated similar surface roughness (R a , mean ± SD) in the MWCNT (0.83 ± 0.02 μm) and MWCNT-COOH (0.84 ± 0.01 μm) groups. On day 7, ALP assay showed that MWCNT-COOH (mean ± SD 0.98 ± 0.26 U/μg of protein) enhanced cell differentiation when compared to the uncoated group (p = 0.05). Alizarin red staining after 28 days of cell culture revealed that MWCNT-COOH (mean ± SD 1.5 ± 0.2 OD405) increased (p = 0.03) matrix mineralization when compared to the uncoated group (0.9 ± 0.09 OD405).
  
  
  CONCLUSIONS
  This study showed that coatings containing MWCNT-COOH (increased hydrophilic surface chemistry) influence osteoblast proliferation, differentiation, and matrix mineralization and should be further studied for applications in orthodontic MSIs.
authors.affiliation: Division of Orthodontics, University of Kentucky, Lexington, KY, USA.
authors.forename: K
authors.initials: K
authors.lastname: Subramani
authors.affiliation: Division of Orthodontics, University of Kentucky, Lexington, KY, USA.
authors.forename: S N
authors.initials: SN
authors.lastname: Pandruvada
authors.affiliation: Department of Biomedical Engineering, University of Kentucky, Lexington, KY, USA.
authors.forename: D A
authors.initials: DA
authors.lastname: Puleo
authors.affiliation: Division of Orthodontics, University of Kentucky, Lexington, KY, USA.
authors.forename: J K
authors.initials: JK
authors.lastname: Hartsfield
authors.affiliation: Division of Orthodontics, University of Kentucky, Lexington, KY, USA. sarandeep.huja@uky.edu.
authors.forename: S S
authors.initials: SS
authors.lastname: Huja
mesh_terms: D000469:Alkaline Phosphatase / Q000378:metabolism; D000818:Animals; D000880:Anthraquinones; D002113:Calcification, Physiologic / Q000187:drug effects; D002454:Cell Differentiation / Q000187:drug effects; D002460:Cell Line; D049109:Cell Proliferation / Q000187:drug effects; D002478:Cells, Cultured; D003094:Collagen / Q000737:chemistry; D008422:Materials Testing; D051379:Mice; D008855:Microscopy, Electron, Scanning; D037742:Nanotubes, Carbon / Q000737:chemistry* / Q000648:ultrastructure*; D010006:Osteoblasts / Q000166:cytology* / Q000187:drug effects*; D013499:Surface Properties; D013778:Tetrazolium Salts; D013844:Thiazoles; D014025:Titanium / Q000737:chemistry*
chemical_list: D000880:Anthraquinones; D037742:Nanotubes, Carbon; D013778:Tetrazolium Salts; D013844:Thiazoles; C010078:alizarin; D003094:Collagen; D014025:Titanium; D000469:Alkaline Phosphatase; C022616:thiazolyl blue
keywords: Multi-walled carbon nanotubes; Orthodontic mini screw implants; Osteoblast response; Temporary anchorage devices; Titanium