The effect of coated nano-hydroxyapatite concentration on scaffolds for osteogenesis

In this study, we fabricated a silk scaffold containing nano-hydroxyapatite (nano-HAp) for bone tissue engineering applications. The sericin-extracted silk scaffolds were coated with 0.30, 0.15, and 0.03g of nano-HAp. The scaffolds were soaked in a 1% type I atelocollagen solution and lyophilized. Scaffolds were crosslinked with 0.02% carbodiimide and lyophilized for 48h, followed by sterilization with gamma-irradiation at 10 kGy. The scaffold properties were investigated by energy-dispersive X-ray spectroscopy and atomic force microscope. A typical spectrum of the inorganic crust and the electron diffraction patterns revealed peaks for calcium, phosphorus, and oxygen atoms. Root mean square values of the control and experimental group surfaces were 5.60 and 40.32nm. The width of nano-HAp was in the approximate range 100-150nm, and the height was approximately 350nm. Dental pulp cells were seeded at a density of 2.8x10(4) cells/cm(2) and cultured for 3weeks in a growth medium. The cells were then cultured for 4weeks in differentiation medium and were transplanted into a nude mouse. The biopsy was processed at 8weeks. The use of 0.15g of nano-HAp led to the greatest collagen type III, fibronectin, osteocalcin, osteopontin, osteonectin, osteoprotegerin, and BMP-2 mRNA levels in vitro after 4weeks in differentiation medium. Western blotting analysis to elucidate signaling pathways was performed. beta-Catenin, phosphorylated-ERK, p38 phosphorylation most increased when 0.15g of nano-HAp was used compared with the control group. In the histological comparison, osteocalcin and osteopontin synthesis were higher for the silk scaffold that contained 0.15g of nano-HAp. Among the scaffolds, samples containing 0.15g of nano-HAp were the most effective for osteogenesis. Therefore, this will be a suitable substrate as a biomaterial for bone tissue engineering applications.