Osteoblast interaction with DLC-coated Si substrates

Diamond-like carbon (DLC) coating is a convenient means of modifying material surfaces that are sensitive to wear, such as titanium and silica substrates. This work aims to evaluate the osteoblast-like cells’ response to DLC-coated Si (Si-DLC), which was treated under different conditions. DLC and deuterated DLC films were deposited by plasma-enhanced chemical vapor deposition to obtain a 200-nm-thick layer on all the samples. Three types of precursor gas were applied for deposition: pure methane (CH4), pure deuterated methane (CD4) and their half/half mixture. All surface treatments were performed under two different self-bias voltages (Vsb): −400 and −600 V. The modified surfaces were characterized by X-ray photoelectron spectroscopy, Raman spectroscopy, Rutherford backscattering spectroscopy, elastic recoil detection analysis, X-ray reflectometry and the sessile-drop method. MC3T3-E1 osteoblasts were cultured on the Si-DLC wafers for 3 and 6 days. Biological tests to measure cell proliferation, cell vitality, cell morphology and cell adhesion were performed. All DLC coatings produced a slightly more hydrophobic state than non-treated Si. Certain types of amorphous DLC coating, such as the surface treated under the Vsb of −600 V in pure methane (600CH4) or in pure deuterated methane (600CD4), offered a significantly higher cell proliferation rate to Si substrate. Scanning electron microscopy observations confirmed that the optimal cell adhesion behavior, among all the treated surfaces, occurred on the surface of the 600CH4 and 600CD4 groups, which showed increased amounts of filopodia and microvilli to enhance cell–environment exchange. In conclusion, DLC coating on Si could produce better surface stability and improved cellular responses.