Enhanced cell proliferation on biomedical titanium surfaces by laser ablation-induced micro- And nanoscale hybrid structures

The cell proliferation performance of pure titanium substrates was enhanced by modifying the surface morphology using an ultraviolet laser with a wavelength of 355 nm and travel speeds ranging from 10³300 mm/sec. Rat calvarial osteoblast cells were cultured on the sample surfaces for 1³7 days. The cell proliferation was investigated via 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assays. Scanning electron microscopy observations showed that the laser ablation (LA) surfaces had a hybrid micro- and nanoscale structure consisting of microscale grooves with nanoscale agglomerations on their surface. For a low laser travel speed of 10 mm/sec, the grooves had a width of approximately 5.44³10.03 µm. For the maximum travel speed of 300 mm/sec, the grooves reduced in height, but increased in width to around 10.97³20.06 µm. The agglomerations on the grooves had a size of around 30³100 nm; with larger agglomerations being formed at a lower laser travel speed. The XRD analysis results revealed the presence of titanium compounds (TiO and TiN_0.3) on the LA surfaces ablated at lower travel speeds of 10 mm/sec and 50 mm/sec, respectively. The MTT measurements showed that the LA samples yielded a better cell proliferation rate than a sandblasted acid-etched titanium sample or a machined titanium sample. Furthermore, the cell proliferation rate increased with a decreasing laser travel speed. In general, the present results confirm the feasibility of laser ablation surface modification as a means of promoting the cell proliferation rate on titanium bioimplants.