Fabrication and Characterization of Chitosan Based Injectable Thermosensitive Hydrogels Containing Silica/Calcium Phosphate Nanocomposite Particles

In this study, the effect of silica/calcium phosphate (SiCaP) nanocomposite particles on the properties of a novel chitosan-based thermosensitive hydrogel system was examined. SiCaP nanocomposite powder was fabricated using a sol-gel method and then used to fabricate nanocomposite hydrogels (Ch- β/7.5SiCaP and Ch-β/15SiCaP) including chitosan and β-glycerophosphate (Ch-β) as a matrix. Results revealed that compared to the Ch-β hydrogel without SiCaP, the presence of SiCaP particles in nanocomposite hydrogels maintained pH stability during the sol-gel transition, accelerated the gelation and improved the stiffness of nanocomposite hydrogels. Gelation time at 37℃ was reduced approximately 75% and stiffness was increased approximately 115%. Both of these changes are attributed to chemical and physical interactions of the SiCaP bioactive particles with chitosan. Furthermore, compared to the Ch-β hydrogel, the presence of SiCaP in the Ch-β/7.5SiCaP nanocomposite hydrogel did not affect biocompatibility negatively, but improved osteoblastic cell differentiation. Our studies suggest that these nanocomposite hydrogels may offer an innovative approach to bone regeneration strategies.

Polydopamine Coating on Titanium Affects Osteoblastic Differentiation to a Greater Degree than Does Surface Roughness

Biointerface design can greatly influence cell behavior. Therefore, in this study we examined the effects of three surface characteristics, roughness, chemistry, and wettability, on osteoblastic cell differentiation. We examined osteoblastic differentiation on titanium (Ti) samples with four levels of roughness (average roughness: 148.6 ± 23.1, 42 ± 6.2, 14.3 ± 5.5, 7.2 ± 1.6 nm) with or without a nanolayer coating of polydopamine (PDA). In vitro osteogenic differentiation was evaluated by quantifying alkaline phosphatase (AP) activity of human fetal preosteoblastic (hFOB 1.19) cells. The change in surface chemistry of Ti samples as a result of PDA coating was assessed by XPS analysis and water contact angle measurement. Results demonstrated that PDA treated samples were more hydrophilic, compared to untreated samples, and this was substrate roughness independent. Moreover, with the exception of the substrate with an oriented texture of surface nanotopography (RTi-4), the presence of a PDA nanolayer increased AP activity independent of substrate roughness. Our results suggest that surface chemistry and wettability, induced by a PDA nanolayer coating, had a greater effect on osteoblastic differentiation than did surface roughness.