Low-energy laser peening induces surface microtopography and enhances early osteoblastic cell attachment on commercially pure titanium

Low-energy laser peening (LELP) was applied to commercially pure titanium (JIS Class 2) immersed in water using a Q-switched Nd: YAG microchip laser with a wavelength of 1064 nm, a pulse energy of 2.4 mJ, a pulse duration of 0.43 ns and a nominal spot diameter of 0.20 mm. MC3T3-E1 murine pre-osteoblastic cells were cultured on the LELP-treated specimens to evaluate early osteoblastic cell responses. LELP formed periodic microtopographic patterns with peaks reflecting the laser-scanning sequence and pulse density. As the laser pulse density increased from 100 to 400 /mm 2 , the arithmetical mean roughness, Ra , increased from approximately 0.1 to 0.25 μm and the arithmetical mean waviness, Wa , increased from approximately 0.6 to 1.5 μm, while the mean width of the profile elements, WSm , corresponding to the pitch between adjacent peaks, decreased from approximately 80 to 50 μm. SEM observations at 6 h after seeding showed more extensive cell coverage on the LELP-treated specimens, particularly at 400 /mm 2 , than on the untreated surface. After 72 h, the number of cells on the specimens treated at 100 and 400 /mm 2 were 2.9 and 2.8 times higher, respectively, than that on the untreated surface. These findings indicate that LELP-induced surface microtopography enhanced early cell attachment and increased cell numbers after 72 h, highlighting LELP as a promising technique for the development of biomedical components, such as implants, with favorable cell responses.