[Study on tailoring the nanostructured surfaces of cuttlefish bone transformed hydroxyapatite porous ceramics and its effect on osteoblasts].

OBJECTIVE: To investigate the formation of nanostructure on cuttlefish bone transformed hydroxyapatite (CB-HA) porous ceramics and the effects of different nanostructures on the osteoblasts adhesion, proliferation, and alkaline phosphatase (ALP) expression. METHODS: The cuttlefish bone was shaped as plate with diameter of 10 mm and thickness of 2 mm, filled with water, and divided into 4 groups. The CB-HA in groups 1-4 were mixed with different phosphorous solutions and then placed in an oven at 120℃ for 24 hours. In addition, the samples in group 4 were further sintered at 1 200℃ for 3 hours to remove nanostructure as controls. The chemical composition of CB-HA were analyzed by X-ray diffraction spectroscopy, Fourier transform infrared spectrum, and inductively coupled plasma (ICP). The physical structure was analyzed using scanning electron microscopy, specific surface tester, and porosity tester. The MC3T3-E1 cells of 4th generation were co-cultured with 4 groups of CB-HA. After 1 day, the morphology of the cells was observed under scanning electron microscopy. After 1, 3, and 7 days, the cell proliferation was analyzed by MTT assay. After 7 and 14 days, the ALP expression was measured by pNPP method. RESULTS: X-ray diffraction spectrum showed that the four nanostructures of CB-HA were made of hydroxyapatite. The infrared absorption spectrum showed that the infrared absorption peak of CB-HA was consistent with hydroxyapatite. ICP showed that the ratio of calcium to phosphorus of all CB-HA was 1.68-1.76, which was consistent with hydroxyapatite. Scanning electron microscopy observation showed that the nanostructure on the surface of CB-HA in groups 1-3 were large, medium, and small cluster-like structures, respectively, and CB-HA in group 4 had no obvious nanostructure. There were significant differences in the specific surface areas between groups ( P<0.05). There was no significant difference in the porosity between groups ( P>0.05). Compared with group 4, groups 1-3 have more pores with pore size less than 50 nm. After co-cultured with osteoblasts, scanning electron microscopy observation and MTT assay showed that the cells on groups 2 and 3 adhered and proliferated better and had more ALP expression than that on groups 1 and 4 ( P<0.05). CONCLUSION: The size of cluster-like nanostructure on the surface of CB-HA can be controlled by adjusting the concentration of ammonium ions in the phosphorous solution, and the introduction of small-sized cluster-like nanostructure on the surface of CB-HA can significantly improve the cell adhesion, proliferation, and ALP expression of the material which might be resulted from the enlarged surface area.