Efeitos dos nanotubos de carbono funcionalizados com hialuronato de sódio em reparos ósseos, na deposição de cristais inorgânicos no titânio e no comportamento de osteoblastos

Abstract

The sodium hyaluronate (HY) accelerates the repair of bone defects. However, the weak stability of HY has hindered its wide use in bone tissue reconstructions. Moreover, the functionalization of carbon nanotubes(CNT) with HY (HY-CNT) produces a reinforced hydrogel with improved mechanical and rheological properties when compared with HY alone. Thus, the main aim of this study was to evaluate in vivothe effects of CNT and HY-CNT in the healing process of tooth sockets of rats after extraction of upper first molars and, in vitro, on deposition of inorganic crystals on the titanium surface and in the behavior of osteoblasts in culture. Wistar male rats were subjected to the extraction of upper first molars and the sockets were treated with CNT, HY, HY-CNT or carbopol (vehicle). Histomorphometric analyses were performed, seven days after the surgeries, to assess the trabecular bone formation and the numberof cell nuclei. The expression of collagen types I and III was assessedby immunohistochemistry. Titanium discs treated with CNT, HY, HY-CNT or carbopol were immersed in an aqueous unsaturated solution containing CaCl2and Na2HPO4 during 14 and 28 days. The deposition of crystals over the titanium discs was analyzed utilizing SEM. Moreover, osteoblasts were plated on titanium discs treated with CNT or HY-CNT or plated directly on culture plates containing DMEN medium supplemented with CNT or HY-CNT.Analyses of alkaline phosphatase activity and cell viability were performed. Treatment with CNT did not alter the bone deposition as well as the counting of cell nuclei. On the other hand, both CNT and HY-CNT induced a similar and significant increase in bone formation and decreased the amount of cell nuclei. Moreover, the expression of type I collagen in sockets treated with 1% HY or HY-CNT (100µg/mL) was increased. No significant changes in the expression of type III collagen was observedamong any of the groups. The in vitroexperiments revealed that titanium discs coated with 100µg/mL HY-CNT showed a higher deposition of calcium, sodium and phosphorus ions. CNT and HY-CNT at higher concentrations (100-400µg/mL) induced death of osteoblasts, while lower concentrations (CNT and HY-CNT: 3.125-50µg/mL) resulted only in a slight decrease in activity of the alkaline phosphatase and cell viability. Altogether, these findings indicate that, like HY, HY-CNT accelerated the healing process when used in therapies for bone repair. In addition, HY-CNT induced a greater deposition of crystals in titanium discs, suggesting that this biomaterial could be used as an adjuvant agent in the bone repair in dental implants.