Effects of four types of hydroxyapatite nanoparticles with different nanocrystal morphologies and sizes on apoptosis in rat osteoblasts

J Appl Toxicol. 2012 Jun;32(6):429-35. doi: 10.1002/jat.1745. Epub 2011 Dec 8.


Hydroxyapatite nanoparticles (nano-HAP) have been reported to cause inflammatory reactions. Here, we aimed to compare the effects of four types of nano-HAP with different nanocrystal morphologies (short rod-like, long rod-like, spherical or needle-shaped crystals) and sizes (10-20, 10-30 or 20-40 nm) on growth inhibition and apoptosis in primary cultured rat osteoblasts. The osteoblasts was treated with the four types of nano-HAP at various concentrations (20, 40, 60, 80 or 100 mg l⁻¹). The nano-HAP specific surface area was detected using the Brunauer, Emmet and Teller method. The cell growth rate was detected using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay; apoptotic alterations and the level of reactive oxygen species in osteoblasts were measured using flow cytometry; and the amounts of apoptotic p53 and cytochrome c proteins were measured using western blotting. We observed that all four types of nano-HAP inhibited the growth of osteoblasts in a dose-dependent manner. These nano-HAP significantly induced apoptosis in osteoblasts. Nano-HAP with smaller specific surface areas induced lower apoptosis rates. The needle-shaped and the short rod-like particles induced greater cellular injury than the spherical and long rod-like particles, respectively. The increased apoptosis rates were accompanied by increased p53 and cytochrome c expression. These findings indicate that nano-HAP inhibit the activity of osteoblasts and also induce the apoptosis of osteoblasts in vitro. These findings also suggest that the nano-HAP-induced apoptotic pathway is mediated by a mitochondrial-dependent pathway. Moreover, the sizes, morphologies and concentrations of nano-HAP have significant effects on the apoptotic level.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Alkaline Phosphatase / metabolism
  • Animals
  • Animals, Newborn
  • Apoptosis / drug effects*
  • Blotting, Western
  • Cell Proliferation / drug effects
  • Cell Survival / drug effects
  • Cells, Cultured
  • Coloring Agents / metabolism
  • Crystallization
  • Cytochromes c / metabolism
  • Dose-Response Relationship, Drug
  • Durapatite / chemistry
  • Durapatite / toxicity*
  • Nanoparticles / chemistry
  • Nanoparticles / toxicity*
  • Nanoparticles / ultrastructure
  • Osteoblasts / drug effects*
  • Osteoblasts / metabolism
  • Osteoblasts / pathology
  • Oxidative Stress / drug effects
  • Particle Size
  • Rats
  • Rats, Sprague-Dawley
  • Reactive Oxygen Species / metabolism
  • Tetrazolium Salts / metabolism
  • Thiazoles / metabolism
  • Tumor Suppressor Protein p53 / metabolism


  • Coloring Agents
  • Reactive Oxygen Species
  • Tetrazolium Salts
  • Thiazoles
  • Tumor Suppressor Protein p53
  • Cytochromes c
  • Durapatite
  • Alkaline Phosphatase
  • thiazolyl blue