Nano‑calcium phosphate bone cement based on Si-stabilized α-tricalcium phosphate with improved mechanical properties

- Nano‑calcium phosphate cement of Si-stabilized α-TCP nanopowder was developed.
- The injectability of nano-cement was reached 87.90 ± 2.60%.
- The compressive strength of nano-cement enhanced to 18.70 ± 2.23 MPa.
- Nano-cement enhanced proliferation and spreading of osteoblast like cells.

This study aimed to develop nano‑calcium phosphate cement (nCPC) and evaluate the effect of nanosized precursors on mechanical, physical and handling properties (injectability and setting time) as well as conversion rate of nano-reactants into nano-hydroxyapatite (nHA). In this study, while alpha tricalcium phosphate (α-TCP, 98 wt%) and HA (2 wt%) were applied as the powder phase, 2.5 wt% NaH2PO4 solution was used as liquid phase of cement. Before nano-CPC preparation, Si-stabilized α-TCP nanopowder with particle size of 10 ± 3.6 nm was firstly synthesized in a two-step process of sol-gel followed by mechanical alloying. Moreover, HA nanopowder with particle size of 32 ± 3.6 nm was synthesized using sol-gel process. Our results revealed that after 3 days of immersion in ringer's solution, reactants almost completely converted to nHA. Moreover, the initial and final setting time of nano-CPC was obtained 6.3 ± 2.1 min and 14.3 ± 4.0 min, respectively. Furthermore, injectability of this formulation was reached 87.90 ± 2.60%. In addition, our results confirmed that the compressive strength and modulus of nano-CPC enhanced with increasing immersion time in ringer's solution from 9.50 ± 1.27 MPa and 0.38 ± 0.07 GPa (at 1 day) to 18.70 ± 2.23 MPa and 0.57 ± 0.15 GPa (at 5 days), respectively. Finally, in order to evaluate cellular responses to nano-CPC, MG63 cells were cultured on it and cell morphology and cytotoxicity were evaluated. Results revealed that nano-CPC enhanced proliferation and spreading of osteoblast like cells compared to control (tissue culture plate) which could be due to both appropriate physical and chemical properties of nano-CPC which stimulate cell proliferation. Our findings suggest the formation of an injectable nano-CPC with appropriate mechanical, physical and degradation rate which can potentially utilized for filling bone defects.