Sr-Doped Zinc Phosphate Ceramic Nanoparticles for Bone Regeneration

Background: Synthetic bioceramic repair materials have a broad application prospect in bone defect repair because of their excellent bone conductivity and bone induction.Znic Phosphate ceramic particles are commonly used as bone repair material, but there are still problems such as insufficient osteogenesis and potential biological toxicity.Strontium (Sr) has the function of enhancing bone strength. Even in a wide range of ions concentration, they still have a positive impact on osteogenic differentiation.we made a novel type of Sr doped Znic Phosphate ceramic nanoparticles to explore its role in bone regeneration. Methods: : Bioactive nanoparticles with Zn and Sr and phosphate (Zn 2 Sr(PO 4 ) 2 ) were prepared through high temperature solid state method. The characterization analysis for Zn 2 Sr(PO 4 ) 2 nanoparticles was confirmed by TEM observation, EDS mapping ,FTIR, XRD, and XPS .The concentration of released Zn 2+ ,Sr 2+ and PO 4 3- was measured by ICP. In vitro,the toxic effect and osteogenic capacity of Zn 2 Sr(PO 4 ) 2 to MC 3 T 3 -E 1 cells was measured.In vivo ,the ability to promote new bone formation of nanoparticles was tested in rat criticalsized supracondylar femur defect models. Results: : In vitro degradation result revealed that the bioactive Zn 2+ ,Sr 2+ and PO 4 3- ions were released from nanoparticles in a sustained and stable manner in PBS at 25 o C up to 4 weeks. In vitro osteogenic promotive result showed that the 1/8-1/2 Zn 2 Sr(PO 4 ) 2 nanoparticles cell culture medium extraction,which was at a relatively low concentration, showed superior ability in promoting MC 3 T 3 -E 1 cell proliferation, osteogenic differentiation, and biomineralization compared to other diluted extract groups and control groups. Finally, 2mg-8mg Zn 2 Sr(PO 4 ) 2 nanoparticles promoted more new bone formation when implanted in the critical sized femoral bone defect (3 mm in diameter) in the rat. Conclusion: The data suggest that the fabricated Zn 2 Sr(PO 4 ) 2 nanoparticles could act as an attractive candidate for bone regeneration.Zn and Sr play a synergistic role in this process,which avoids potential toxic reactions.