Considerable effort is being devoted to the surface engineering of biomaterials in order to improve and understand the material-cell interactions in various applications. Within this context, laser surface texturing presents an excellent alternative to other surface modification technologies, due to its flexibility, simplicity, precise control over the morphology and wettability of the modified surface, without affecting the properties of bulk material. The main idea of this study is to employ nanosecond Nd:YAG laser pulses at high fluences for texturing AISI 316L stainless steel aiming at improving and controlling material-cell interactions. Scanning electron microscopy (SEM), X-ray diffraction (XPS), optical 3D surface measuring system and contact angle goniometer were employed for surface characterization of non-treated and laser-textured samples. Results show that laser texturing greatly modifies surface morphology, topography, roughness, wetting properties, thickness and chemistry of the surface oxide layer. Subsequently we studied the effect of laser-texturing on human osteoblast-like cells (MG63) and their behaviour in vitro after 1, 3 and 7 days of exposure using fluorescence (viable staining) microscopy, cell cytotoxicity assays (Resazurin, NRU and CBB assay) and SEM microscopy for cell distribution and morphology evaluations. We observed higher number of attached viable cells on laser-textured surfaces in majority of samples. There was only one exception where surface exhibited cytotoxic effect already after 1 day, as seen by lower cell density (fluorescence and SEM microscopy) and by lower cell metabolic activity, the amount of cellular proteins and lysosomal integrity, based on cytotoxicity assessment test. SEM microscopy proved to be a very good method to study subtitle difference among samples in cell-surface interactions in terms of cell distribution, orientation, cell surface morphology and cell shape. Nanosecond laser surface texturing presents flexible, simple and chemical free approach that can be applied to most metallic materials without affecting the properties of bulk material.
B.04 Guest lecture
COBISS.SI-ID: 1514922In this study, steel samples are irradiated by 45 ns and 30 ps polarized laser pulses, emitted by nanosecond fiber laser (valovna dolžina 1060 nm) and Nd:YAG picosecond laser (valovna dolžina 1064 nm), respectively. Varying processing parameters in LIPSS production leads to different characteristics of the structures, formed in the top surface layer of material. The structures are mainly visible both under optical (OM) and scanning electron (SEM) microscope. In some cases, however, the color changing due to grating effect of the formed structures is visible by naked eye and LIPSS is easily examined under OM, but cannot be detected by observing secondary electrons (SEI) with SEM (Figure 1). The characteristics of the structures, obtained with different parameters, are therefore investigated and compared by using different microscopy techniques, including secondary electron imaging (SEI) and backscattered electrons detection (COMPO). For better understanding, cross-sections of the samples are prepared by focused ion beam (FIB) and analyzed by SEM.
B.04 Guest lecture
COBISS.SI-ID: 16823323Although stainless steel is widely used in medicine due to god combination of mechanical properties durability, ease of fabrication and low cost, it often exhibit insufficient biocompatibility. The mechanical performance of material is governed by its bulk properties, while bicompatibility is determined by the properties of its surface. Therefore considerable effort is being devoted to the surface engineering of biomaterials in order to improve the material cell interactions. Laser surface processing enables modification on micro- and nanoscale that significantly change surface properties and influence cellular adhesion. Within this context, the response of human osteoblast-like osteosarcoma cells (MG63) to laser textured 316L stainless steel was investigated. Surface texturing was carried out by Nd:YAG nanosecond laser at high fluences (DLT-HF). Surface properties of non-treated and laser textured samples were analysed using scanning electron microscopy (SEM), X-ray diffraction (XPS), optical 3D surface measuring system and contact angle goniometer was employed for surface wettability measurements. The influence of micro- and nanoscale transformation on MG63 cell behaviour was assessed by in vitro study using fluorescence (viable staining) and SEM microscopy after 24 h of exposure. Surface characterization revealed significant differences in surface morphology, chemistry and wettability after laser texturing. Non-treated sample exhibit hydrophobic grain like structured surface that transforms to hierarchical micro- and nanostructured surface covered with thick oxides super-hydrophilic nature. After 24 hours of exposure cells tend to attach in higher numbers to non-treated surface. On the other hand, we observed that cells respond to the laser-textured surfaces. Cells tend to attach and preferentially align to the laser-induced micro-grooves oriented in a specific direction. Furthermore, nanostructured oxide surface also induces changes in surface morphology of cells while no cytotoxic effects were observed. Nd:YAG nanosecond laser surface texturing presents flexible, simple and chemical free approach that can be applied to most metallic materials without affecting the properties of bulk material.
F.18 Transfer of new know-how to direct users (seminars, fora, conferences)
COBISS.SI-ID: 16285723Laser surface processing enables modification on micro-and nanoscale that significantly change surface properties and influence cellular adhesion. Within this context, the response of human osteoblast-likeosteosarcoma cells (MG63) to laser textured 316L stainless steel was investigated. Surface texturing was carried out by high-fluence, nanosecond laser pulses. Surface properties of non-treated and laser textured samples were analysed using scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), optical 3D surface measuring system and contact angle goniometer (surface wettability measurements). Biocompatibilty was studied by adhesion behaviour of MG63 cells using fluorescence and SEM microscopy. Laser texturing increases both surface area and the roughness (Sa) of the surface. Non-treated control sample exhibit typical smooth grain-structured like morphology with a network of subsurface crevices between the grain boundaries. Laser textured sample exhibit a hierarchical micro-and nanostructured (oxide layer) surface. Wettability measurements revealed hydrophobic behaviour of non-treated surface (?Y = 81.6°±5.7°) compared to superhydrophilic behaviour after laser texturing (?Y = 0°). After 24 hours of exposure cells tend to attach in higher numbers to non-treated surface. On textured surfaces, cells tend to attach and preferentially align on the surface between laser-induced micro-grooves oriented in a specific direction. Nanostructured oxide surface also affected cell morphology attachment pattern, while no cytotoxic effects were observed.
F.18 Transfer of new know-how to direct users (seminars, fora, conferences)
COBISS.SI-ID: 16358427