Morphological Tuning of Nanostructured Hydroxyapatite (HAp) Porous Microgranules by Evaporation-Induced Assembly

Porous biocompatible microgranules, such as hydroxyapatite (HAp), are potential candidates for various bio-medical applications including drug delivery and remediation. Using the principle of evaporation-induced assembly in contact free dispersion droplets, we have synthesized porous micrometric HAp granules consist of interlocked ellipsoidal nanoparticles. We have shown that the shape of the microgranules can be tuned from spherical to doughnut solely by controlling the drying temperature during assembly. The structure and interparticle correlation in the synthesized granules have been probed by electron microscopy and small-angle scattering. The observed morphological transition has been attributed to the buckling of elastic shell made of interlocked HAp nanoparticles. Alteration of granular morphology at higher drying rate does not affect the local packing fraction of the correlated HAp nanoparticles in the granules. The absorption of bovine serum albumin protein by the synthesized granules has been tested as a potential application.