Safety evaluation of needle-like hydroxyapatite nanoparticles in female rats

Objective The present study was designed to evaluate the safety of synthesized needle-like hydroxyapatite (HAp) nanoparticles ranging from 3 to 7 nm in diameter and from 27 to 46 nm in length when administered in female rats orally or subcutaneously at different concentrations. Methods Animals in different treatment groups were maintained on their respective diets as follows: group 1, untreated control; group 2, treated orally with HAp (300 mg/kg body weight) for 3 weeks; group 3, treated orally with a low dose of HAp (150 mg/kg body weight) for 3 weeks; and group 4, implanted subcutaneously with HAp (600 mg/kg body weight) once and left for 5 weeks. At the end of the experimentation period, blood samples were collected from all animals for biochemical analysis (alanine aminotransferase, aspartate aminotransferase, alkaline phosphatase, uric acid, urea, and creatinine). After sacrifice, histopathological examination of the liver and kidney was carried out. Results and conclusion The biochemical results showed an increase in alanine aminotransferase and aspartate aminotransferase in the groups treated orally and those treated subcutaneously. There was an increase in alkaline phosphatase only in the group receiving the high oral dose; however, animals treated with the low dose or those treated subcutaneously were comparable with the control group. All the rats showed normal kidney function because of normal levels of creatinine, urea, and uric acid. The histopathological results indicated that the liver and kidney of all rats treated with HAp (oral or subcutaneously) had a normal structure. The previous results confirmed the safety of the synthesized nanoneedle HAp when administered orally or subcutaneously at the suggested dose.