Studies on UVC Treatment of Polyamide Fibers for Improved Adhesion on TPU and TPA

We report about current work which is aimed to improve the adhesion of melt processable elastomers onto relevant reinforcement materials by means of short wave UVC （ultraviolet C） light. Results of laboratory tests regarding UVC surface activation ofpolyamide fiber materials in air using low-pressure mercury lamps with 185 nm and 254 nm emissions are shown. The effect of irradiation on fiber strength was studied to find out suitable process parameters for providing the UVC treatment efficient but as gentle as possible to avoid negative effects on reinforcement properties. Application of a laboratory process for UVC pretreatment leads to significantly increased adhesion strength between the fibers and the melt processable elastomers on the base of TPA （polyamide） respectively TPU （polyurethane）.

Enhancement of photocatalytic activity by femtosecond-laser induced periodic surface structures of Si

Laser induced periodic surface structures(LIPSS)represent a kind of top down approach to produce highly reproducible nano/microstructures without going for any sophisticated process of lithography.This method is much simpler and cost effective.In this work,LIPSS on Si surfaces were generated using femtosecond laser pulses of 800 nm wavelength.Photocatalytic substrates were prepared by depositing TiO2 thin films on top of the structured and unstructured Si wafer.The coatings were produced by sputtering from a Ti target in two different types of oxygen atmospheres.In first case,the oxygen pressure within the sputtering chamber was chosen to be high(3×10^–2 mbar)whereas it was one order of magnitude lower in second case(2.1×10^–3 mbar).In photocatalytic dye decomposition study of Methylene blue dye it was found that in the presence of LIPSS the activity can be enhanced by 2.1 and 3.3 times with high pressure and low pressure grown TiO2 thin films,respectively.The increase in photocatalytic activity is attributed to the enlargement of effective surface area.In comparative study,the dye decomposition rates of TiO2 thin films grown on LIPSS are found to be much higher than the value for standard reference thin film material Pilkington Activ^TM.

Ultraviolet Laser Based Gas Phase Fluorination of Polystyrene

A novel hybrid process for surface fluorination of polymers is being introduced. The process is based on ultra violet (UV) laser radiation, which on the one hand forms radicals out of an atmosphere of a partially fluorinated benzene, and on the other hand activates a polymer surface in the areas where the UV radiation hits the surface. The radicals can react with the polymer surface, hence altering the surface energy. With this process, a fluorine content of over 30% on the surface of bulk polystyrene can be achieved, while the smallest possible structure size was smaller than 1 mm.

Antibacterial Zinc Oxide Nanoparticle Coating of Polyester Fabrics

Polyester knitted fabrics have been equipped with antibacterial properties by coating with aqueous suspensions of zinc oxide (ZnO) with different particle diameters. It can be shown that the antibacterial efficacy against Staphylococcus aureus and Klebsiella pneumonia and the permanence of the coating after defined washing cycles depends on the composition of the ZnO dispersion. To improve the wettability of the textile, the combustion chemical vapor deposition (CCVD) is used to generate a hydrophilic nano layer of a hydroxyl terminated silicon network on the surface of the textiles. The comparison of CCVD-treated and untreated polyester samples does not show differences in the antibacterial activity. The influence of the coating in terms of amount and particle size of ZnO on the viability and proliferation of 3T3 mouse fibroblast cells is examined. A particle content of a maximum of 20 μg ZnO/cm2 is found to be cytocompatible for coating of textiles.

Manufacturing of Surface Nanostructured Fibers Featuring an Antibacterial Effect by Magnetic Field Transportation of Magnetite@Silver Core-Shell Nanoparticles

Magnetic core-shell nanoparticles of type Fe3O4@Ag were synthesized in gram scale following a combined co-precipitation phase-transfer method and afterwards, processed to nanoparticle polymer (polypropylene and polyamide) composites. These composites were used as sheath material for the fabrication of core-sheath fibers. During the melt spinning process, a magnetic field was applied around the roving, whereby the particles move in the still liquid sheath polymer towards the surface. The produced fiber materials were investigated by AFM showing a nanostructuring of the surface, which was indirectly confirmed by determination of a slight surface tension lowering. Nanoparticle movement was shown by cross-section SEM and EDX measurements. The antibacterial activity of the spun fibers was proven by contacting them with Escherichia coli. A long-term stability of this effect was observable by carrying out a standard washability test. In contrast to previous works this new approach uses no deposition technique to introduce surface changes. It rather applies a magnetic force to move appropriately equipped nanoparticles from the inside of the fiber to the surface. This leads in only one step to a strong superficial anchoring of the particles resulting in a unique combination of long-term stable antibacterial and improved anti-soiling effects.

Collagen/hyaluronan based hydrogels releasing sulfated hyaluronan improve dermal wound healing in diabetic mice via reducing inflammatory macrophage activity

Sustained inflammation associated with dysregulated macrophage activation prevents tissue formation and healing of chronic wounds.Control of inflammation and immune cell functions thus represents a promising approach in the development of advanced therapeutic strategies.Here we describe immunomodulatory hyaluronan/collagen(HA-AC/coll)-based hydrogels containing high-sulfated hyaluronan(sHA)as immunoregulatory component for the modulation of inflammatory macrophage activities in disturbed wound healing.Solute sHA downregulates inflammatory activities of bone marrow-derived and tissue-resident macrophages in vitro.This further affects macrophage-mediated pro-inflammatory activation of skin cells as shown in skin ex-vivo cultures.In a mouse model of acute skin inflammation,intradermal injection of sHA downregulates the inflammatory processes in the skin.This is associated with the promotion of an anti-inflammatory gene signature in skin macrophages indicating a shift of their activation profile.For in vivo translation,we designed HA-AC/coll hydrogels allowing delivery of sHA into wounds over a period of at least one week.Their immunoregulatory capacity was analyzed in a translational experimental approach in skin wounds of diabetic db/db mice,an established model for disturbed wound healing.The sHA-releasing hydrogels improved defective tissue repair with reduced inflammation,augmented pro-regenerative macrophage activation,increased vascularization,and accelerated new tissue formation and wound closure.

Covalent linkage of sulfated hyaluronan to the collagen scaffold Mucograft® enhances scaffold stability and reduces proinflammatory macrophage activation in vivo

Sulfated glycosaminoglycans(sGAG)show interaction with biological mediator proteins.Although collagen-based biomaterials are widely used in clinics,their combination with high-sulfated hyaluronan(sHA3)is unexplored.This study aims to functionalize a collagen-based scaffold(Mucograft®)with sHA3 via electrostatic(sHA3/PBS)or covalent binding to collagen fibrils(sHA3+EDC/NHS).Crosslinking without sHA3 was used as a control(EDC/NHS Ctrl).The properties of the sHA3-functionalized materials were characterized.In vitro growth factor and cytokine release after culturing with liquid platelet-rich fibrin was performed by means of ELISA.The cellular reaction to the biomaterials was analyzed in a subcutaneous rat model.The study revealed that covalent linking of sHA3 to collagen allowed only a marginal release of sHA3 over 28 days in contrast to electrostatically bound sHA3.sHA3+EDC/NHS scaffolds showed reduced vascular endothelial growth factor(VEGF),transforming growth factor beta 1(TGF-β1)and enhanced interleukin-8(IL-8)and epithelial growth factor(EGF)release in vitro compared to the other scaffolds.Both sHA3/PBS and EDC/NHS Ctrl scaffolds showed a high proinflammatory reaction(M1:CD-68+/CCR7+)and induced multinucleated giant cell(MNGC)formation in vivo.Only sHA3+EDC/NHS scaffolds reduced the proinflammatory macrophage M1 response and did not induce MNGC formation during the 30 days.SHA3+EDC/NHS scaffolds had a stable structure in vivo and showed sufficient integration into the implantation region after 30 days,whereas EDC/NHS Ctrl scaffolds underwent marked disintegration and lost their initial structure.In summary,functionalized collagen(sHA3+EDC/NHS)modulates the inflammatory response and is a promising biomaterial as a stable scaffold for full-thickness skin regeneration in the future.