title: Synthesis and antibacterial evaluation of calcinated   Ag-doped nano-hydroxyapatite with dispersibility.
abstract: OBJECTIVE
  Dispersible hydroxyapatite (HAp) nanoparticles are very useful for applying a monolayer to implantable medical devices using the nano-coating technique. To improve tolerance to infection on implanted medical devices, silver-doped HAp (Ag-HAp) nanoparticles with dispersiblity and crystallinity were synthesized, avoiding calcination-induced sintering, and evaluated for antibacterial activity.
  
  
  METHODS
  The Ca10-xAgx(PO4)6(OH)2 with x = 0 and 0.2 were prepared by wet chemical processing at 100°C. Before calcination at 700°C for 2 h, two kinds of anti-sintering agents, namely a Ca(NO3)2 (Ca salt) and a polyacrylic acid/Ca salt mixture (PAA-Ca), were used. Escherichia coli was used to evaluate the antibacterial activity of the nanopowder.
  
  
  RESULTS
  When PAA-Ca was used as an anti-sintering agent in calcination to prepare the dispersible nanoparticles, strong metallic Ag peaks were observed at 38.1° and 44.3° (2θ) in the X-ray diffraction (XRD) profile. However, the Ag peak was barely observed when Ca salt was used alone as the anti-sintering agent. Thus, using Ca salt alone was more effective for preparation of dispersible Ag-HAp than PAA-Ca. The particle average size of Ag-HAp with 0.5 mol% of Ag content was found to be 325 ± 70 nm when the formation of large particleaggregations was prevented, as determined by dynamic light scattering instrument. The antibacterial activity of the Ag-HAp nanoparticles possessing 0.5 mol% against E. coli was greater than 90.0%.
  
  
  CONCLUSIONS
  Dispersible and crystalline nano Ag-HAp can be obtained by using Ca salt alone as an anti-sintering agent. The nanoparticles showed antibacterial activity.
authors.forename: Tsutomu
authors.initials: T
authors.lastname: Furuzono
authors.forename: Mazumder
authors.initials: M
authors.lastname: Motaharul
authors.forename: Yasumichi
authors.initials: Y
authors.lastname: Kogai
authors.forename: Yoshinao
authors.initials: Y
authors.lastname: Azuma
authors.forename: Yoshiki
authors.initials: Y
authors.lastname: Sawa
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D017886:Durapatite / Q000737:chemistry*; D004926:Escherichia coli / Q000187:drug effects*; D053758:Nanoparticles / Q000737:chemistry*; D010316:Particle Size; D012834:Silver / Q000494:pharmacology*
chemical_list: D000900:Anti-Bacterial Agents; D012834:Silver; D017886:Durapatite