In vitro/In vivo Evaluations of Hydroxyapatite Nanoparticles with Different Geometry

Hydroxyapatite-based nanoparticles have found diverse applications in drug delivery, gene carriers, diagnostics, bioimaging and tissue engineering, owing to their ability to easily enter the bloodstream and target specific sites. However, there is limited understanding of the potential adverse effects and molecular mechanisms of these nanoparticles with varying geometries upon their entry into the bloodstream. Here, we used two commercially available hydroxyapatite nanoparticles (HANPs) with different geometries (less than 100 nm in size each) to investigate this issue.

First, the particle size, Zeta potential, and surface morphology of nano-hydroxyapatite were characterized. Subsequently, the effects of 2~2000 μM nano-hydroxyapatite on the proliferation, migration, cell cycle distribution, and apoptosis levels of umbilical vein endothelial cells were evaluated. Additionally, the impact of nanoparticles of various shapes on the differential expression of genes was investigated using transcriptome sequencing. Additionally, we investigated the in vivo biocompatibility of HANPs through gavage administration of nanohydroxyapatite in mice.

Our results demonstrate that while rod-shaped HANPs promote proliferation in Human Umbilical Vein Endothelial Cell (HUVEC) monolayers at 200 μM, sphere-shaped HANPs exhibit significant toxicity to these monolayers at the same concentration, inducing apoptosis/necrosis and S-phase cell cycle arrest through inflammation. Additionally, sphere-shaped HANPs enhance SULT1A3 levels relative to rod-shaped HANPs, facilitating chemical carcinogenesis-DNA adduct signaling pathways in HUVEC monolayers. In vivo experiments have shown that while HANPs can influence the number of blood cells and comprehensive metabolic indicators in blood, they do not exhibit significant toxicity.

In conclusion, this study has demonstrated that the geometry and surface area of HANPs significantly affect VEC survival status and proliferation. These findings hold significant implications for the optimization of biomaterials in cell engineering applications.