Hierarchical and porous calcium titanate hydroxide nanosheet nanoflower arrays for enhanced biocompatibility and drug delivery performance

In this study, a calcium-driven growth route was developed to induce in situ growth of calcium titanate hydroxide nanosheet nanoflower arrays on the sintered hydroxyapatite (HAp)/titania compacts as supporting substrates in a sodium hydroxide solution via a hydrothermal route. The microstructure, formation mechanism, biocompatibility and drug delivery performance of the nanosheet nanoflowers were investigated. The analyses of SEM and TEM observations indicated that each nanosheet nanoflower consisted of Ca, Ti, and O elements and was hierarchically assembled from the interlaced ultrathin nanosheets with thickness of 15-30 nm and exhibited a rose flower-like morphology with porous structure of 1-12 μm. XRD patterns showed that the nanosheet nanoflowers were assigned to calcium titanate hydroxide. This growth route was template-/additive-free and the formation of nanosheet nanoflower arrays was highly dependent on the release of Ca ions from HAp. In vitro biocompatibility evaluation indicated that those nanosheet nanoflowers grown on compacts were biocompatible and exhibited an enhanced cell attachment and proliferation compared with nanoflower array-free compacts. Those nanosheet nanoflowers could be also in situ decorated on the sintered HAp/titania microspheres to derive hierarchical HAp/titania/nanosheet nanoflower microspheres. Moreover, when soaked in the solution of tetracycline hydrochloride (TH) as model drugs, those nanosheet nanoflowers not only enabled HAp/titania microspheres with a sustained release behavior for TH, but also well maintained their biological efficacy against the growth of bacteria. Thus, the present nanosheet nanoflowers would have potentials as drug-laden and biocompatible materials/coatings in the biomedical fields.