Autopore 4 9500

The pore structure of BCSA cement samples was measured on day 28 by Mercury intrusion porosimetry (MIP). MIP was measured by Micromeritics AutoPore IV9500 (Micromeritics Instrument Corporation) with a contact angle of 140° at 25 °C. The maximum and minimum pressures were set at 414 MPa and 1.4 kPa, respectively. The samples were cut into 5 mm cubes and stopped the cement hydration by the acetone-solvent exchange for 12 h.

Commercial osteoinductive CaP ceramics (Trade name: Osteoinductive artificial bone) were supplied by Engineering Research Center in Biomaterials, Sichuan University, China. This ceramic was composed of hydroxyapatite (HA) and β-tricalcium phosphate (β-TCP), and the ratio of HA to β-TCP was about 20/80. The sterilized samples (γ-ray irradiation) with the size of Φ 10 × 5 mm³ were used in this study. The morphology, porous structure and permeability were analyzed by field emission scanning microscopy (S4800, Hitachi, Japan) and automatic mercury porosimeter (AutoPore IV 9500, Micromeritics, America), respectively.

The gelatin/BGM scaffolds were fabricated using a freeze-drying method according to our previous report (Guo et al., 2017 (link); Zhao et al., 2018a (link)). Briefly, BGM (28 g) and gelatin (12 g, Aladdin) were dispersed in deionized water (200 ml), followed by stirring for 4 h at 40°C. Three milliliters of genipin solution (1 wt%) was added to the above solution, and the mixture was vigorously stirred for 20 min, frozen for 12 h at −20°C and then freeze-dried for another 24 h. SEM (Zeiss Sigma 300, Germany) and mercury intrusion porosimetry (MIP, Micromeritics AutoPore IV 9500, United States) were used to examine the morphology and porous structure of the scaffolds. To analyze the content of the BGM, thermogravimetric analysis (TGA, Mettler TGA/DSC3+, Switzerland) was used.

The pore size distribution and specific surface area of the anodes were determined using a mercury intrusion technique (Micromeritics AutoPore IV 9500). Mercury was pushed into the sample from 6.9 kPa (1 psia) to a maximum pressure of 206 843 kPa (30 000 psia). The relationship between this pressure (P) and the pore diameter (D) can be found through the Washburn equation assuming the pores are cylindrical,58 ,59
D = –4γ cos(θ)/P where γ is the surface tension of mercury (485 mN m^–1), θ is the contact angle (130°) acting along the parameter of the pore. The pore size diameter is plotted as a function of the differential intrusion (ml g^–1 Å^–1) which is found by dividing the incremental intrusion (ml g^–1) by the difference in pore diameter (Å). The specific pore area (A) is then calculated (A = 4V/D) assuming a cylinder pore volume (V = πD2h/4) and open cylinder pore area (A = πDh). For each specific surface area measurement the contribution from the macro (∼75 μm) and meso (∼1 μm) pores while the contribution from the micropores (∼10 nm) could not be determined as the foams collapsed at the higher pressures (∼400 psia), a known problem when examining soft foams with mercury porosimetry.58 ,59