title: Synthesis of novel quaternary silica hybrid bioactive microspheres.
abstract: OBJECTIVE
  To survey the preparation of novel hybrid microspheres of quaternary silicate glassy composition (SiO2P2O5CaONa2O) and the prospect of using them as an osteogenic system with enhanced bioactive properties for the development of hydroxyapatite.
  
  
  METHODS
  In line with our previous synthetic procedure a two-step process was followed, wherein polystyrene (PS) microspheres were prepared by the emulsifier free-emulsion polymerization method and constituted the core for the sol-gel coating of the silicate inorganic shell. The development of the hybrid microspheres was based on silane and phosphate precursors and was assesses at different ratio of ethanol/water (of 9/1, 4/1, and 2/1, in mL) and at varied ammonia concentration of 4.8-1.0 mL.
  
  
  RESULTS
  The hybrid microspheres had an average size ranged between 350 and 550 nm according to SEM, depending on the ethanol/water solution rate and ammonia content. The final microspheres probably exhibited a porous-like structure through the formation of diffused voids along with the low carbon content of the EDX analysis, which could be regulated by the catalyst content. The hybrid microspheres exhibited effective in vitro bioactivity assessed in simulated body fluids (SBF).
  
  
  CONCLUSIONS
  Quaternary hybrid silica microspheres were effectively synthesized. The bioassay evaluation of the final microspheres revealed the rapid in vitro formation of a bone-like apatite layer. The results verify the bioactivity of the microspheres and promote further research of their suitability on regenerative treatment of bone abnormalities. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 112-120, 2018.
authors.affiliation: Laboratory for Sol-Gel, Institute of Nanoscience and Nanotechnology, NCSR, "Demokritos, 153 10 Ag. Paraskevi Attikis, Athens, Greece.|Department of Materials Science, School of Natural Sciences, University of Patras, 26 500, Patras, Greece.
authors.forename: A
authors.initials: A
authors.lastname: Angelopoulou
authors.affiliation: Laboratory for Sol-Gel, Institute of Nanoscience and Nanotechnology, NCSR, "Demokritos, 153 10 Ag. Paraskevi Attikis, Athens, Greece.
authors.forename: E Κ
authors.initials: EΚ
authors.lastname: Efthimiadou
authors.affiliation: Laboratory for Sol-Gel, Institute of Nanoscience and Nanotechnology, NCSR, "Demokritos, 153 10 Ag. Paraskevi Attikis, Athens, Greece.
authors.forename: G
authors.initials: G
authors.lastname: Kordas
mesh_terms: D000818:Animals; D018786:Bone Substitutes / Q000737:chemistry*; D006801:Humans; D008863:Microspheres; D010012:Osteogenesis; D011137:Polystyrenes / Q000737:chemistry*; D012822:Silicon Dioxide / Q000737:chemistry*
chemical_list: D018786:Bone Substitutes; D011137:Polystyrenes; D012822:Silicon Dioxide
keywords: PS; bioactivity; hybrid microspheres; hydroxyapatite; osteogenic; porous microspheres