title: Cell responses to two kinds of nanohydroxyapatite with different sizes and crystallinities.
abstract: BACKGROUND
  Hydroxyapatite (HA) is the principal inorganic constituent of human bone. Due to its good biocompatibility and osteoconductivity, all kinds of HA particles were prepared by different methods. Numerous reports demonstrated that the properties of HA affected its biological effects.
  
  
  METHODS
  Two kinds of nanohydroxyapatite with different sizes and crystallinities were obtained via a hydrothermal treatment method under different temperatures. It was found that at a temperature of 140°C, a rod-like crystal (n-HA1) with a diameter of 23 ± 5 nm, a length of 47 ± 14 nm, and crystallinity of 85% ± 5% was produced, while at a temperature of 80°C, a rod-like crystal (n-HA2) with a diameter of 16 ± 3 nm, a length of 40 ± 10 nm, and crystallinity of 65% ± 3% was produced. The influence of nanohydroxyapatite size and crystallinity on osteoblast viability was studied by MTT, scanning electron microscopy, and flow cytometry.
  
  
  RESULTS
  n-HA1 gave a better biological response than n-HA2 in promoting cell growth and inhibiting cell apoptosis, and also exhibited much more active cell morphology. Alkaline phosphatase activity for both n-HA2 and n-HA1 was obviously higher than for the control, and no significant difference was found between n-HA1 and n-HA2. The same trend was observed on Western blotting for expression of type I collagen and osteopontin. In addition, it was found by transmission electron microscopy that large quantities of n-HA2 entered into the cell and damaged the cellular morphology. Release of tumor necrosis factor alpha from n-HA2 was markedly higher than from n-HA1, indicating that n-HA2 might trigger a severe inflammatory response.
  
  
  CONCLUSIONS
  This work indicates that not all nanohydroxyapatite should be considered a good biomaterial in future clinical applications.
authors.affiliation: Center for Biomedical Materials and Tissue Engineering, Academy for Advanced Interdisciplinary Studies, Peking University, Beijing, People’s Republic of China.
authors.forename: Xiaochen
authors.initials: X
authors.lastname: Liu
authors.forename: Minzhi
authors.initials: M
authors.lastname: Zhao
authors.forename: Jingxiong
authors.initials: J
authors.lastname: Lu
authors.forename: Jian
authors.initials: J
authors.lastname: Ma
authors.forename: Jie
authors.initials: J
authors.lastname: Wei
authors.forename: Shicheng
authors.initials: S
authors.lastname: Wei
mesh_terms: D008841:Actin Cytoskeleton / Q000378:metabolism; D000469:Alkaline Phosphatase / Q000378:metabolism; D017209:Apoptosis / Q000187:drug effects; D002454:Cell Differentiation / Q000187:drug effects; D002460:Cell Line; D048430:Cell Shape / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D024042:Collagen Type I / Q000378:metabolism; D004355:Drug Stability; D017886:Durapatite / Q000737:chemistry* / Q000494:pharmacology*; D006801:Humans; D053758:Nanoparticles / Q000737:chemistry*; D010006:Osteoblasts / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D053495:Osteopontin / Q000378:metabolism; D010316:Particle Size; D013696:Temperature; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism
chemical_list: D024042:Collagen Type I; D014409:Tumor Necrosis Factor-alpha; D053495:Osteopontin; D017886:Durapatite; D000469:Alkaline Phosphatase