No abstract

Ultrashort pulse lasers have significant advantages over conventional continuous wave and long pulse lasers for the texturing of metallic surfaces, especially for nanoscale surface structure patterning. Furthermore, ultrafast laser beam polarization allows for the precise control of the spatial alignment of nanotextures imprinted on titanium-based implant surfaces. In this article, we report the biological effect of beam polarization on human mesenchymal stem cell differentiation. We created, on polished titanium-6aluminum-4vanadium (Ti-6Al-4V) plates, a laser-induced periodic surface structure (LIPSS) using linear or azimuthal polarization of infrared beams to generate linear or radial LIPSS, respectively. The main difference between the two surfaces was the microstructural anisotropy of the linear LIPSS and the isotropy of the radial LIPSS. At 7 d post seeding, cells on the radial LIPSS surface showed the highest extracellular fibronectin production. At 14 days, qRT-PCR showed on the same surface an increase in osteogenesis-related genes, such as alkaline phosphatase and osterix. At 21 d, mineralization clusters indicative of final osteoinduction were more abundant on the radial LIPSS. Taken together, we identified that creating more isotropic than linear surfaces enhances cell differentiation, resulting in an improved osseointegration. Thus, the fine tuning of ultrashort pulse lasers may be a promising new route for the functionalization of medical implants.

Precise weight measurements of stainless steel, PZT and PMMA samples were performed after groove machining with femtosecond laser pulses (150 fs, 800 nm, 5 kHz) to determine volume ablation rates and ablation threshold with good accuracy. Weighing clearly enables faster determination of such phenomenological parameters without any methodological issue compared to other methods. Comparisons of the three types of materials reveal similar monotonous trends depending on peak fluences from 0.2 to 15 J/cm². The metallic target exhibits both the lowest volume ablation rate under the highest irradiation conditions with almost 400 µm³/pulse and the lowest ablation threshold with 0.13 J/cm². Ceramic PZT reaches 3.10³ µm³/pulse with a threshold fluence of 0.26 J/cm² while polymer PMMA attains 10⁴ µm³/pulse for a 0.76 J/cm² threshold. Pros and cons of this method are also deduced from complementary results obtained on microscopic and confocal characterizations.

No abstract

Titanium alloys are widely used in bio-medical applications for their excellent bio-compatibility and superior mechanical strength. On the other hand, femtosecond laser processing is a robust versatile and industrial method widely used for surface functionalization. In this work, laser-induced periodic surface structures (LIPSS) on titanium alloy (Ti6Al4V) using different laser wavelengths of 1030 nm (IR), 515 nm (Green) and 257 nm (UV) were created and their surface wettability (physical parameter correlated with cell adhesion) was studied, in relation to sterilization process. The contact angle over LIPSS was smaller than over polished samples, with Green and UV LIPSS presenting contact angles inferior to 20$$^\circ$$ ∘ and a superior stability to sterilization process.