Porous hollow hydroxyapatite microspheres synthesized by spray pyrolysis using a microalga template: preparation, drug delivery, and bioactivity

Hollow hydroxyapatite microspheres (HHMs) are known to be an excellent drug storage and delivery vehicle. A representative microalga, Chlorella sp. 227, was used as a template to synthesize porous HHMs using spray pyrolysis. This method offers a one-step process for producing HHMs while simultaneously removing the template. As compared to non-HHMs synthesized without microalga, the HHMs described in this paper exhibit 2.7 and 2.2 times greater surface area and pore volume, respectively. The highest drug loading capacity was 0.893 g g(-1) for HHMs, which is an improvement of 52% compared to the capacity of non-HHMs. Ibuprofen release was shown to be slower in HHMs, and the release kinetics fit the Higuchi model. This finding suggests that ibuprofen was released via diffusion mechanisms. Immersion in simulated body fluid results in the formation of apatite on the surface of the HHM samples, and the Ca/P ratio is close to the stoichiometric composition. Therefore, HHMs represent an attractive candidate system for sustained drug delivery.