Hydrogen plasma treatment confers enhanced bioactivity to silicon carbide-based nanowires promoting osteoblast adhesion

Nanomaterials play a pivotal role in modern regenerative medicine and tissue engineering, due to their peculiar physical, optical and biological properties once they are used in the nanometric size. Many evidences are showing the importance of biomaterial micro- and nano-topography on cellular adhesion, proliferation and differentiation, and hence, tissue regeneration. It is well known that nanowires (NWs) can mimic many different tissues as a result of their shape and their surface characteristics, and that surface hy- drophilicity affects early protein adsorption and cellular adhesion. Therefore a material able to induce bone regeneration might be obtained by combining optimal surface topography and hydrophilicity. Based on these evidence, we designed silicon carbide (SiC) and core/shell silicon carbide/silicon dioxide (SiC/ SiOx) nanowires with modified wettability in order to analyze cell behavior, using an in-vitro osteoblastic model. First, we synthetized SiC NWs and SiC/SiOx NWs through a chemical-vapour-deposition (CVD) process, and then we used hydrogen plasma to modify their hydrophilicity. Subsequently we evaluated the four types of NWs in terms of their morphology and contact angle, and we studied their behavior in the presence of MC3T3-E1 murine osteoblasts. Cell metabolic activity, viability, morphology and focal adhesions formation were considered. Morphological data showed different dimensions between SiC and SiC/SiOx NWs. SiC NWs before the hydrogen plasma treatment showed a very low contact angle, that was absent after the treatment. Osteoblastic cells appeared healthy on all of the samples. Interestingly, both hydrophilic SiC NWs and SiC/SiOx NWs generated a favorable distribution of focal adhesions around the cell body confirmed also by scanning electron microscopy images. Moreover, osteoblasts grown on hydrogen plasma treated SiC/SiOx NWs showed an increased metabolic activity testified by a significantly higher cell number. In conclusion, we are here demonstrating that hydrogen plasma treatment of SiC and SiC/SiOx NWs induce a better osteoblastic cellular adhesion by increasing NWs wettability. We are therefore suggesting that hydrogen plasma treatment of SiC/SiOx can offer a suitable method to develop scaffolds for bone tissue engineering applications.