Effect of capillary action on bone regeneration in micro-channeled ceramic scaffolds

Abstract A new scaffold design was introduced with macro-pores and micro-channels, which greatly assisted in the initial bone marrow absorption and uniform cell distribution. Unfortunately, the underlying scientific reasons for the new scaffold׳s efficiency are currently unknown. Hence, we approached using a mathematical and experimental method to elucidate the new scaffold׳s efficiency. The mathematical formula describe rising fluid height in a narrow cylindrical vessel due to capillary action. Through the mathematical simulation, the maximum fluid heights at equilibrium for scaffold tubes of diameters 50, 150, 350, and 750 µm were 156.6, 52.7, 22.6, and 10.5 mm, respectively. The fluid would theoretically reach 90% of the maximum height at 900, 30, 3, and 0.3 s, respectively. In the experiment, the fluid heights were observed from 30 to 600 s. All the scaffolds had 50 µm micro-channels with different macro-pore sizes of 150, 350, and 750 µm. The media rose through macro-pores of the three scaffolds until 40, 15, and 10 mm, respectively. The fluid heights were observed at about 2 s and 0.5 s after being immersed for the 350 µm and 750 µm macro-pore scaffolds. In the case of the 150 µm sample, the fluid height was 30 mm at about 30 s and 40 mm at about 75 s. Since all samples had 50 µm micro-channels, the fluid reached to the top of the scaffolds, eventually. The results showed that capillary action was highly dependent on the size of the tubes within the scaffold. They also confirmed the simulated data in both equilibrium height and the time trajectory. The data from both the experiment and the mathematical simulation proved our hypothesis that capillary action was the cause for the improvement in cell immigration in the new scaffold since the data matched each other in both equilibrium height and the time trajectory.