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

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 (alpha-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 alpha-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, inject ability 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.