Effects of single wall carbon nanotubes and its functionalization with sodium hyaluronate on bone repair

Sodium hyaluronate (HY) accelerates the repair of bone defects. However, the weak stability of HY formulations in aqueous environments has hindered its wide utilization. The functionalization of carbon nanotubes (SWCNT) with HY (HY-SWCNT) results in a reinforced hydrogel with an increased stability. Nevertheless, the biological effects of HY-SWCNT have not been explored. Thus, our objective was to evaluate whether this biomaterial preserves the bioactivity of the HY.

Wistar rats were subjected to molar extraction and the sockets were treated with SWCNT (50-400 microg/mL), 1% HY, HY-SWCNT (50-400 microg/mL) or carbopol (vehicle). After seven days of surgery, histological and morphometric analyses were performed to evaluate the trabecular bone formation and the number of cell nuclei in the sockets. Expression of collagen types I and III was determined by immunohistochemistry.

Treatment with SWCNT did not alter the bone deposition, as well as the cell nuclei counting. Additionally, no significant evidence of toxicity was observed in SWCNT-treated sockets. Contrastingly, both HY and HY-SWCNT induced a marked increase in the bone formation (HY: 10.10+/-1.99%; HY-SWCNT 100 microg/mL: 10.90+/-1.13%; control: 3.69+/-1.17%) and decreased the cell nuclei amount in the sockets. Moreover, collagen type I expression was more pronounced in HY- and HY-SWCNT-treated sockets. No significant differences were viewed in the expression of collagen type III.

Our results indicate that SWCNT is a feasible material to deliver HY to bone defects. Importantly, the functionalization of SWCNT with HY preserved the beneficial biological properties of HY in the healing process, thereby suggesting that HY-SWCNT scaffolds are potentially useful biomaterials for the restoration of bone defects.