Biomimetic mineralization of nanocrystalline hydroxyapatites on aminated modified polylactic acid microspheres to develop a novel drug delivery system for alendronate

EPLA/nHAp composite microsphere, a novel drug delivery system potentially useful for the local delivery of alendronate (AL) to bone tissue was developed via the biomimetic mineralized deposition of nano-hydroxyapatite (nHAp) crystals on the surface of aminated modified polylactic acid (EPLA) microspheres. Scanning electron microscopy (SEM) observation showed that this system consisted of a polymer core with nanofiber network structure and inorganic coating composed of countless rod-like nanocrystalline particles, Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction analysis (XRD) confirmed that these particles were nHAp crystals. An efficient AL-loading can be realized by facile impregnation-adsorption method under suitable conditions due to the high adsorption capacity of EPLA/nHAp composite microspheres. The drug loading efficiency of microspheres was detected by indirect ultraviolet spectrophotometry. It was found that the adsorption capacity of EPLA/nHAp composite microsphere towards AL was increased nearly 5-fold compared with that of bare EPLA microspheres owing to the strong interaction between alendronate and hydroxyapatite. Meanwhile, in vitro release study showed that AL-loaded EPLA/nHAp microspheres had a more sustained drug release than AL-loaded EPLA microspheres, all these results demonstrated that the as-prepared EPLA/nHAp composite microsphere is an efficient carrier for the delivery and sustained release of AL. Furthermore, an in vitro cell culture study revealed that these composite microspheres presented a good biocompatibility, showing great potential for the applications in the biomedical field.