Comparative in vitro Study on Immunomodulatory Effects of Nano-Hydroxpatite Powders on Human Immune Cells

Significant advancement was recently achieved in the field of hydroxyapatite nanoparticles, contributing to their implementation in numerous biomedical applications, including bone tissue reconstruction. Nevertheless, the influence of these materials on the immune system still remains an unresolved issue.

Here, we managed to reveal a direct in vitro impact of nano-hydroxyapatite particles on immunological, cellular and humoral components. Further, we analyzed the effect of nanoparticle size and shape on healthy human immune cells residing in the peripheral blood. Special attention was given to particles produced using the microwave hydrothermal synthesis method and precisely controlled size. Viability, phenotypes, activation status, cytokine production and release were assessed using flow cytometry and immunoenzymatic techniques.

We showed that large-sized nanoparticles caused significant induction of immune response associated with innate and acquired immunity, in size-dependent manner. The synthesized nanoparticles allowed for avoidance of the immunogenicity, with no changes in inflammatory cytokines, supporting high biocompatibility. Various effects suggest a different potential use of examined nanoparticles, whether proinflammatory or neutral conditions are required in the field of anticancer therapy or transplantology respectively.

Obtained results indicate that precise selection of nano-hydroxyapatites with specific immunomodulatory properties might be crucial for application in the clinical setting. Subsequent studies would establish most suitable therapeutic approaches where selected nano-hydroxyapatites could be implemented.