Although Titanium and its alloys are generally used for the manufacturing of dental implant abutments, they are typically prone to bacterial infection, due to their implantation in the transgingival region. In close contact with the soft surrounding tissue, the surface may be functionalized in order to improve connective tissue cells adhesion while preventing bacterial penetration at the interface. Ultrafast laser processing of dental implants has demonstrated the potential to obtain unique surface features, down to the nanoscale. With this study, we introduce the possibility to generate laser-induced periodic surface structures (LIPSS) by picosecond laser processing, with periodicity of about 500 nm on large-scale surfaces, in a contamination-free approach. By changing the applied laser dose, different surface coloring of TiAl6V4 samples is obtained due to a gradual surface oxidation, as revealed by depth-profile compositional analyses. In the same time, an increase of the irradiation dose induced the formation of thicker oxide layers, the oxygen content increasing up to ten times. The response of human mesenchymal stem cells (hMSCs) in contact with laser processed surfaces was evaluated to assess samples cytocompatibility. It was demonstrated that large-scale, uniform LIPSS distributed on whole TiAl6V4 surface are beneficial to hMSCs viability and proliferation.
We fabricated hierarchical glass biochips with interior characteristics that can be tailored by adjusting process parameters. By a new derived processing method, termed Femtosecond Laser Assisted chemical Etching Nanoscale Glass Deformation (FLAE-NGD), we have developed graded and hierarchical configurations with dimensions from several hundred micrometers to several hundred nanometers as relevant glass model platforms that mimic cancer cell intravasation-extravasation processes. We were able to control the dimensions of both the widths and lengths of the channels as well as shape and curvatures of interior glass pillars. Various curvatures were successfully prepared for the study of the migration and invasion processes of cancer. We have further evaluated the effect of x-ray exposure on melanoma cells grown in glass biochips and determined the increase of intracellular reactive oxygen species production and cellular DNA breaks with the applied irradiation dose.
Three dimensionally (3D) engineered scaffolds are a viable alternative to investigate cells in physiologically relevant configurations. Two photon polymerization (TPP) is a 3D maskless laser direct writing technology that employs a focused femtosecond (fs) laser beam to produce a localized chemical reaction with high precision that ultimately leads to polymerization of a photosensitive material inside the focal volume. TPP has the capability of creating synthetic polymer constructs with 3D complex architectures and high resolution far beyond the diffraction limit. TPP was demonstrated to fulfill technical requirements necessary for fabricating personalized 3D scaffolds for tissue engineering and regenerative medicine applications. Herein, we propose the use of polymeric scaffolds fabricated by TPP for cancer research, specifically as model structures for cancer cell invasion assessment in 3D environments. In particular, the aim is to evaluate cancer cell interaction with confined spaces developed in a woodpile-like polymeric scaffold with pore dimensions less than 1 μm in microchannel cross-section. TPP of negative photoresist SU-8 was conducted using a 3D Lithography platform produced by Nanoscribe GmbH. Scaffolds with uniform networks of pores with sizes down to 0.66 μm were successfully produced, which were then used for melanoma cancer cell invasion assays. The scaffolds demonstrated potential for use in testing the invasion potential of melanoma cancer cells in comparison to normal melanocytes. Time-lapse microscopy observations were carried out to assess the optimal intervals for cell analysis in interaction with scaffolds. Preliminary in vitro tests suggested that melanoma-melanocytes co-culture may exhibit a more invasive potential in narrower spaces as compared to normal melanocytes alone, while an inhibitory effect on melanocyte invasion may be attributed to melanoma cells present in co-culture.
Cladding waveguides have been realized in Nd:YAG by direct writing with a femtosecond-laser beam. A classical
method that inscribes many tracks around the waveguide circumference with step-by-step translations of the laser
medium, and a new technique in which the laser medium is moved on a helical trajectory and that delivers waveguides
with well-defined walls were employed. Laser emission on the 1.06 μm 4F3/2→4I11/2 transition and at 1.3 μm on the
4F3/2→4I13/2 line was obtained under the pump with a fiber-coupled diode laser. Thus, laser pulses at 1.06 μm with energy
of 1.3 mJ for the pump at 807 nm with pulses of 12.5-mJ energy were recorded from a circular waveguide of 100-μm
diameter that was inscribed in a 5-mm long, 0.7-at.% Nd:YAG single crystal by the classical translation technique. A
similar waveguide that was realized in a 5-mm long, 1.1-at.% Nd:YAG ceramic increased the 1.06-μm laser pulse energy
to 2.15 mJ for the pump pulses of 13.1-mJ energy. Furthermore, a circular waveguide of 100-μm diameter that was
inscribed in the Nd:YAG ceramic by the helical-movement method yielded pulses at 1.06 μm with increased maximum
energy of 3.2 mJ; the overall optical-to-optical efficiency was 0.24, and the laser operated with a slope efficiency of 0.29.
The same device outputted laser pulses at 1.3 μm with energy of 1.15 mJ.
Nonlinear optical phenomena which dominate the interaction of tightly focused femtosecond laser beams with materials are discussed. Different femtosecond laser based techniques for material processing such as laser ablation, two-photon photo-polymerization, and material surface nano-structuring are described. For the computer controlled micro-processing of materials, near-infrared Ti:sapphire femtosecond lasers, with nano-Joule/micro-Joule pulse energy, were coupled with direct laser writing workstations. Laser fabricated micro-nanostructures and their applications are presented.
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