The adhesion and alignment of osteoblasts and fibroblasts on titanium alloy (Ti-6Al-4V) surfaces can be adjusted over a wide range by femtosecond laser treatment and anodization. The great differences in cell behavior between different experimental conditions raised further questions about the role of cell migration, which will be addressed in this study. For that, Ti-6Al-4V surfaces were laser-structured to obtain a surface covered with ripples, i.e., laser-induced periodic surface structures (LIPSS), or micro-cones superimposed with ripples. Then, cells were seeded either directly onto the non-structured or laser-structured areas on the titanium alloy samples or beside such samples where they can reach the surface by cell migration. After two weeks in culture, the cell coverage of the samples was evaluated by scanning electron microscopy (SEM). The results showed that cells directly seeded onto the non-structured or laser-structured areas covered the surface nearly completely and eventually aligned along the ripple direction for the laser-structured areas. In contrast, for cell-seeding beside the samples, the laser-structured areas remain nearly cell-free while the non-structured areas were covered with cells in a similar non-oriented manner as for direct cell-seeding. These results on reduced osteoblast migration due to laser structuring are in line with the findings in animal experiments. There, the new bone formation of laser-processed samples was 26.1% ± 16.9% lower in comparison to untreated samples of the same type, which can be explained by hindered cell migration on the laser-processed areas of the screws.

Laser-generated structures have a huge potential to induce an alignment of biological cells, which may be important for various fields in medicine and biotechnology. We describe the formation of fs-laser-induced micro- and nanostructures for achieving the directed growth of Schwann cells, a type of glial cell that can support the regeneration of nerve pathways by guiding the neuronal axons in the direction of their alignment. Polymer surfaces, i.e., polycarbonate (PC) or cellulose acetate butyrate (CAB), were exposed to the beam of a 1040 nm Yb-based amplified fs-laser system with a pulse length of about 350 fs. With appropriate parameters, the laser exposure resulted in a surface topography with oriented micro-grooves, which, for PC, were covered with nano-ripples. Schwann cell growth on these substrates was inspected after 3 to 5 days of cultivation by means of scanning electron microscopy (SEM). We show that Schwann cells can grow in a certain direction, predetermined by micro-groove or nano-ripple orientation. In contrast, cells cultivated on randomly oriented nanofibers or unstructured surfaces show an omnidirectional growth behavior. This method may be used in the future to produce nerve conduits for the treatment of injuries to the peripheral nervous system.

We describe the formation of LIPSS by fs laser irradiation on polished titanium or steel samples, from which polymer replicas can be produced. The irradiation of inclined samples allows a variation in the periodicity of the LIPSS in a range between about 500 and 1000 nm, depending on the angle of incidence and the orientation of the laser polarization relative to the plane of incidence, either parallel (p-polarization) or perpendicular (s-polarization). For p-polarization, a second larger-size LIPSS feature with periodicities between about 1300 and 2200 nm is observed at medium angles. LIPSS lines are oriented perpendicular to the light polarization, except for s-polarization on steel samples, where a rotation of up to 35° is observed. In a two-step process, the LIPSS are replicated in polymers. We investigate the attachment of Schwann cells and fibroblasts seeded thereon, which show no direct dependence on the variation in the LIPSS periodicities.

People with injuries to the peripheral nervous system, due to its poor functional regeneration, suffer from paralysis of the facial muscles, fingers and hands, or toes and feet, often for the rest of their lives. Therefore, to improve patients' quality of life, there is an urgent need for conduits that effectively support the healing of large defects in nerve pathways through specific guidance of nerve cells. This paper describes two specific methods for achieving directed growth of Schwann cells, a type of glial cells that can support the regeneration of the nerve pathway by guiding the neuronal axons in the direction of their alignment. One method implies the exposure of a poly(ethylene terephthalate) (PET) foil to a KrF* laser beam, that renders a nanorippled surface topography. The other method uses aligned polyamide-6 (PA-6) nanofibers produced via electrospinning on a very fast rotating structured collector, which enables easy nanofiber detachment, without additional effort. Schwann cells growth on these substrates was inspected after one week of cultivation by means of scanning electron microscope (SEM). For both methods we show that Schwann cells grow in a certain direction, predetermined by nanoripples and nanofibers orientation. In contrast, cells cultivated onto unstructured surfaces or randomly oriented nanofibers, show an omnidirectional growth behavior.

Pollutant emissions from vehicles form major sources of metallic nanoparticles entering the environment and surrounding atmosphere. In this research, we spectrochemically analyse the chemical composition of particle matter emissions from in-use diesel engine passenger vehicles. We extracted diesel particulate matter from the end part of the tail pipes of more than 70 different vehicles. In the laboratory, we used the high-resolution laser-induced breakdown spectroscopy (LIBS) spectrochemical analytical technique to sensitively analyse chemical elements in different DPM samples. We found that PM is composed of major, minor and trace chemical elements. The major compound in PM is not strictly carbon but also other adsorbed metallic nanoparticles such as iron, chromium, magnesium, zinc and calcium. Besides the major elements in DPM, there are also minor elements: silicon, nickel, titan, potassium, strontium, molybdenum and others. Additionally, in DPM are adsorbed atomic trace elements like barium, boron, cobalt, copper, phosphorus, manganese and platinum. All these chemical elements form the significant atomic composition of real PM from in-use diesel engine vehicles.