Distribution of hydroxylapatite nanoparticles via intramuscular administration in mouse

The present study was designed to investigate the distribution, accumulation and excretion of hydroxylapatite nanoparticles (nano-HAP) in mice with intramuscular administration. Mice were injected at 91 mg/kg with either nano-HAP or hydroxylapatite microparticles (micro-HAP) activated by neutrons, and then sacrificed at 1, 2, 4, 8, 12, 18, 24 week for getting samples, respectively. The main organs of the experimental animals were harvested for digestion, and then the counts of ⁴⁵Ca in every sample were measured by a liquid scintillation counter. The results indicated that 0-79 counts·min^-1·mg^-145Ca could be detected in all main organs after nano-HAP injection and 0-25 counts·min^-1·mg^-1 after micro-HAP injection. There were no significant differences between the SNP group and SMP group (p > 0.05) in the distribution in vivo. Bone is the only tissue for accumulation of nano-HAP and micro-HAP. Compared with micro-HAP, a larger amount of nano-HAP accumulated in bone. The results suggest that nano-HAP have a better osseointegration and bone inductivity. (authors)