Heat accumulation during femtosecond laser treatment at high repetition rate – A morphological, chemical and crystallographic characterization of self-organized structures on Ti6Al4V

This study presents a detailed characterization of self-organized nano- and microstructures on Ti6Al4V evoked by different scanning strategies and fluences with a 300 fs laser operating at a laser wavelength of 1030 nm. The resulting surface morphology was visualized via field emission scanning electron microscopy (FEG-SEM) images of the surface and cross-sections. X-ray diffraction (XRD)-analysis was performed to analyse changes in crystal structures. The chemical surface composition of the near-surface layer was determined by X-ray photoelectron spectroscopy (XPS). Results show a significant influence of heat accumulation while processing with high laser repetition rates on the formation, crystallinity and chemical composition of self-organized structures depending on the scanning strategy. The ablation with different laser scanning strategies led to varying dynamics of growth-mechanisms of self-organized structures, formation of intermetallic phases (Ti3Al), sub-oxides and oxides (Ti6O, TiO) as well as ions (Ti3+, Ti4+) in surface layer reliant on applied fluence. Furthermore, investigations revealed a heat-affected zone up to several micrometers in non-ablated material. © 2021 The Author

Utilization of a highly adaptable murine air pouch model for minimally invasive testing of the inflammatory potential of biomaterials

Introduction: The biocompatibility of an implanted material strongly determines the subsequent host immune response. After insertion into the body, each medical device causes tissue reactions. How intense and long-lasting these are is defined by the material properties. The so-called foreign body reaction is a reaction leading to the inflammation and wound healing process after implantation. The constantly expanding field of implant technology and the growing areas of application make optimization and adaptation of the materials used inevitable.Methods: In this study, modified liquid silicone rubber (LSR) and two of the most commonly used thermoplastic polyurethanes (TPU) were compared in terms of induced inflammatory response in the body. We evaluated the production of inflammatory cytokines, infiltration of inflammatory cells and encapsulation of foreign bodies in a subcutaneous air-pouch model in mice. In this model, the material is applied in a minimally invasive procedure via a cannula and in one piece, which allows material testing without destroying or crushing the material and thus studying an intact implant surface. The study design includes short-term (6 h) and long-term (10 days) analysis of the host response to the implanted materials. Air-pouch-infiltrating cells were determined by flow cytometry after 6 h and 10 days. Inflammation, fibrosis and angiogenesis markers were analyzed in the capsular tissue by qPCR after 10 days.Results: The foreign body reaction was investigated by macroscopic evaluation and scanning electron microscopy (SEM). Increased leukocyte infiltration was observed in the air-pouch after 6 h, but it markedly diminished after 10 days. After 10 days, capsule formations were observed around the materials without visible inflammatory cells.Discussion: For biocompatibility testing materials are often implanted in muscle tissue. These test methods are not sufficiently conclusive, especially for materials that are intended to come into contact with blood. Our study primarily shows that the presented model is a highly adaptable and minimally invasive test system to test the inflammatory potential of and foreign body reaction to candidate materials and offers more precise analysis options by means of flow cytometry

Transfer activities for cardiovascular, ophthalmologic and otolaryngologic medical device innovations

The consortium RESPONSE is a cooperation of partners from science and industry within the BMBFProgram “Twenty20 - Partnership for Innovation”, 2014- 2021. Current efforts are being made towards the transfer of new products, technologies and processes in the field of medical devices. Here, RESPONSE is focusing on novel concepts of implantable medical devices for cardiovascular, ophthalmologic and otolaryngologic application. Platform technology approaches, such as drug delivery systems for responsive functionalized implants or smart implant technologies, are being used to enable new applications

Medical device innovations for cardiovascular, ophthalmologic and otolaryngologic applications

The consortium RESPONSE is a cooperation between partners from science and industry within the BMBF-Program “Twenty20 - Partnership for Innovation”, 2014-2021. RESPONSE gives its partners opportunities to put medical device innovations into practice more efficiently. In order to accelerate innovation processes, joint efforts are being made along the entire translation chain. RESPONSE is focusing on the development of novel concepts of implantable medical devices for cardiovascular, ophthalmologic and ENT application. Platform technology approaches are being used to extend the range of device applications. See also: www.response.uni-rostock.d

Computed fiber evaluation of SEM images using DiameterJ

Fiber materials offer a high potential for improving the surface characteristics of medical implants. For quality assurance of nano- and microfiber structures the morphology is inspected by Scanning Electron Microscopy (SEM) as a standard method. Vast quantities of image data have to be evaluated. Usual practice for obtaining the fiber diameters is the manually setting of measurement points. The software DiameterJ which runs as plugin in ImageJ automatically computes fiber diameters. Here we investigated its capabilities and limitations by comparing the evaluation of selected sample SEM images of electrospun fibers. In this study the fibers of three examplary images specified by different contrast and fiber morphology were analyzed by using varied segmentation algorithms. The results are displayed in bar charts of frequency distribution. Additionally the computed fiber diameters were compared to manual measurements. Depending on various image properties the segmentation process works more or less reliable, and fault data of incomplete segmented fibers are computed. Often the results are eligible, but frequently DiameterJ generates data resembling to thin fibers, which are not present in the image. In some cases the peaks of fault data are much higher than peaks of real fibers. In consequence misinterpretation of data cannot be avoided. DiameterJ is a validated tool with the ability to generate reliable results. Future work on improving the segmentation algorithms can refine computed evaluation

Water uptake of various electrospun nonwovens

In recent years, nanofiber based materials have emerged as especially interesting for several biomedical applications, regarding their high surface to volume ratio. Due to the superficial nano- and microstructuring and the different wettability compared to nonstructured surfaces, the water absorption is an important parameter with respect to the degradation stability, thermomechanic properties and drug release properties, depending on the type of polymer [1]. In this investigation, the water absorption of different non- and plasma modified biostable nanofiber nonwovens based on polyurethane, polyester and polyamide were analysed and compared. Also, the water absorption by specified water wetting, the contact angle and morphology changes were examined. The results show that the water uptake is highly dependent on the surface modification and the polymer composition itself and can therefore be partially changed

Optimized Gingiva Cell Behavior on Dental Zirconia as a Result of Atmospheric Argon Plasma Activation

Several physico-chemical modifications have been developed to improve cell contact with prosthetic oral implant surfaces. The activation with non-thermal plasmas was one option. Previous studies found that gingiva fibroblasts on laser-microstructured ceramics were hindered in their migration into cavities. However, after argon (Ar) plasma activation, the cells concentrated in and around the niches. The change in surface properties of zirconia and, subsequently, the effect on cell behavior is unclear. In this study, polished zirconia discs were activated by atmospheric pressure Ar plasma using the kINPen®09 jet for 1 min. Surfaces were characterized by scanning electron microscopy, X-ray photoelectron spectroscopy (XPS), and water contact angle. In vitro studies with human gingival fibroblasts (HGF-1) focused on spreading, actin cytoskeleton organization, and calcium ion signaling within 24 h. After Ar plasma activation, surfaces were more hydrophilic. XPS revealed decreased carbon and increased oxygen, zirconia, and yttrium content after Ar plasma. The Ar plasma activation boosted the spreading (2 h), and HGF-1 cells formed strong actin filaments with pronounced lamellipodia. Interestingly, the cells’ calcium ion signaling was also promoted. Therefore, argon plasma activation of zirconia seems to be a valuable tool to bioactivate the surface for optimal surface occupation by cells and active cell signaling