Self-assembly and bioactive response of a crystalline metal oxide in a simulated blood fluid.

In this study we report on the bioactive response of self-assembled niobium oxide microstructures when immersed in a supersaturated solution emulating mineral content in blood. The structures were formed via electrochemical anodization in an electrolyte comprised of HF and NaF. The slow oxide formation kinetics associated with the presence of NaF in the electrolyte enabled microscopic examinations during microstructure evolution as shown via scanning electron microscopy (SEM). Apparently the slow growth kinetics encourage the development of bioactive sites on the microstructures, as these structures induced mineral formations. On the other hand, microstructures grown in the absence of salt were ineffective mineral nucleators. Analysis of nucleated mineral deposits was performed using X-ray diffraction and Raman spectroscopy. Both long-range and short-range order experiments verified the nucleated mineral phase was hydroxyapatite (HAP). Further characterization of the mineral phase was observed using SEM and revealed effective nucleation sites were predominantly isolated to loci on the ordered microbodies as opposed to locations lying within the amorphous strata.