Background: There is still a big challenge to achieve a balance between mechanical characteristics and biological properties in biphasic calcium phosphate (BCP) ceramics.
Purpose: The present study focused on the in-situ whisker growth on BCP ceramics via different hydrothermal treatments and investigated the influences of these whiskers on the mechanical property and biological performance of the ceramics.
Methods: Five kinds of BCP ceramics with in-situ whisker growth, ie, BCP-C, BCP-HNO₃, BCP-Citric, BCP-NaOH, BCP-CaCl₂ and BCP-Na₃PO₄ were fabricated by different hydrothermal treatments. The phase compositions, morphologies, crystal structures and mechanical strengths of the obtained BCP ceramics were firstly characterized. Then, the in vitro cell adhesion, proliferation and alkaline  phosphatase (ALP) activity of bone marrow stromal cells (BMSCs) on the BCP ceramics were evaluated. Lastly, the effects of in-situ whisker growth on the bone-like apatite formation abilities of BCP ceramics were also investigated by immersing them in simulated body fluid (SBF).
Results: The results demonstrated that the hydrothermal conditions, especially the hydrothermal media, were crucial to determine the phase composition and morphology of the in-situ whisker. Especially among the five media used (HNO₃, Citric, NaOH, CaCl₂ and Na₃PO₄), the Na₃PO₄ treatment resulted in the shortest whisker with a unique hollow structure, and kept the original biphasic composition. All five kinds of whiskers increased the mechanical strength of BCP ceramics to some extent, and showed the good ability of bone-like apatite formation. The in vitro cell study demonstrated that the in-situ whisker growth had no adverse but even positive effect on the adhesion, proliferation and ALP activity of BMSCs.
Conclusion: Due to the growth of in-situ whiskers, the mechanical property and biological performance of the obtained BCP ceramics could increase simultaneously. Therefore, in-situ whiskers growth offers a promising strategy for the expanded application of BCP ceramics to meet the requirements of regenerative medicine.
Keywords: in-situ whisker, hydrothermal treatment, biphasic calcium phosphate, mechanical property, bioactivity