Objectives A major obstacle to be overcome for oral drug delivery is that drug absorption/release must be avoided before the drug reaches the target site. In an attempt to overcome this challenge, we selected synthetic hydroxyapatite (HA) as a drug carrier for the hydrophobic drug indomethacin (IDM) used in local treatment of the colon, exploring the loaded drug and in vitro release characteristics of IDM/HA.
Methods An easy one-step hydrothermal method was employed to prepare micro-hydroxyapatite (HA) spheres. Infrared spectroscopy, X-ray diffraction and scanning electron microscopy further confirmed the composition, structure and morphology of the obtained sample. In vitro release of the anti-inflammatory drug (IDM) was performed successively under simulated conditions. The loading and release profiles of the drug were analysed by UV-spectrophotometry.
Results The use of ethanol enhances solubilization, and the drug loading rate is about 62.21% at 37° C for 12 hours when the mass ratio of IDM/HA is 2:1. The in vitro release of IDM/HA is dependent on solution pH. There is almost no release of IDM (only 0.159%) at pH 1.0, poor release (about 10.55%) at pH 6.8, and a cumulative release rate of up to 84.95% at pH 7.8. These results suggest that HA particles can be used as a pH responsive vehicle for delivering drugs.
Conclusions The as-synthesized micro-hydroxyapatite spheres may act as a promising drug delivery system due to their good biocompatibility, pH sensitivity and high drug loading/release efficiency. The IDM/HA drug delivery system satisfies the basic demand of oral site-specific delivery.
Acknowledgments This work was financially supported by a college students’ innovative training project (Grant No. 4041906168).