Ultra-short Laser Surface Functionalization: from Modeling to Bioengineering

Abstract

International audienceFemtosecond laser texturing allows one to produce various surface relief ranging from nano- and micro ones to much more complex multi-scale pattern. In this context, the main advantages of using ultra-short laser pulses are known to be in a reduction of thermal effects, of debris, and of the surface contamination. Additionally, combinations of laser-induced micro- and nano- reliefs have strong capacities to alternate cell-surface interactions and even to guide cell behavior. Despite previously demonstrated link of cell behavior with wetting properties, the definition of the best laser treatment condition remains challenging. In particular, the difficulty arises from the change in surface wettability with time after laser treatment, but also due to annealing, sterilization, ultra-sound or cold plasma treatment. The reasons for these changes are not yet well understood. For this, femtosecond laser irradiation of titanium-based surfaces is used. As a result, multi-scale textures are produced with high precision. A series of simulations were also performed to determine the properties of these surfaces. Their wetting properties were tested and the capacities to guide stem cells were evaluated. Several templates with different sizes and motifs have been tested. In addition, human stem cell cultures (HSC) have been cultivated on several structured surfaces. The results reveal that HSCs preferentially place their nuclei in the pits with a diameter about the cell size, while the cell were looking for the hydrophilic areas for the attachment of their periphery. As a result, wetting maps can serve to predict cellular behavior. To better understand the involved mechanisms, wetting tests were performed for several surface reliefs and the results were compared to the results of our modeling. The obtained results are particular helpful in bioengineering, for cellular tests, for the treatment of various prosthesis, as well as of dental implants