Smart modification of magnetron sputtered TiN surfaces for stimulated differentiation

The surface electrical properties of TiN films are revisited in this work aiming at a controlled surface modification of their in vitro behaviour. A plasma oxidation process is used to tune the originally high electrical conductance of TiN to that of a wide band gap semiconductor. A capacitively coupled plasma reactor with Ar:O mixtures was used to oxidize the surfaces of thin (250 nm) magnetron sputtered TiN films deposited onto Si substrates. Both optical (UV–Vis reflectance spectroscopy) and structural (X-ray diffraction diagrams) properties were traced to follow a graded modification. Pluripotent human mesenchymal stem cells (hMSCs) were exposed to the resulting TiN surfaces in both proliferation and osteoblastic differentiation biomolecular environments. HMSCs response was evaluated by fluorescence microscopy (double staining with 594 and 488 nm emissions). Cells adhered to TiN and modified TiNO show that, completely oxidized surfaces are better adapted for proliferation purposes while unmodified surfaces are ideal for differentiation as denoted by the development of characteristic cytosolic prolongations.