A new method for fabricating porous monetite via phase transformation of porous calcium sulfate for bone graft applications

Porous monetite is a promising material for bone graft applications because of its ability to balance resorption with new bone formation. However, the methods for fabricating porous monetite are very limited. In this study, a novel method for fabricating porous monetite was developed. Porous monetite grafts were successfully fabricated through the phase transformation of porous calcium sulfate anhydrate (CS) in sodium dihydrogen phosphate (NaH₂PO₄) solution under hydrothermal conditions at temperatures of 150 °C and 180 °C, denoted as PM-150 and PM-180, respectively. The results demonstrated that porous CS underwent a phase transformation, as evidenced by X-ray diffraction and SEM-EDX analysis, resulting in the formation of porous monetite. The diametral tensile strengths (DTS) of the resulting porous monetite groups were 0.45 ± 0.04 MPa and 0.41 ± 0.10 MPa for PM-150 and PM-180, respectively, comparable to that of the porous calcium sulfate precursor. The porous monetite obtained through this fabrication method had an average porosity of 50–60 %. They also demonstrated enhanced solubility in acetate buffer: 94.30 ± 5.03 mg/L for PM-150 and 107.99 ± 12.53 mg/L for PM-180, compared to Tris-HCl: 16.07 ± 0.66 mg/L for PM-150 and 8.86 ± 0.66 mg/L for PM-180, suggesting their potential for resorption by osteoclasts. Additionally, through MTT assays, the material was found to be non-cytotoxic (cell viability >70 %), showing no adverse effects on cell viability. In conclusion, the new fabrication method is promising to produce porous monetite.