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Abstract: Anatase is known to decompose organic material by photocatalysis and to enhance surface wettability once irradiated by ultraviolet (UV) light. In this study, pulse magnetron-sputtered anatase thin films were investigated for their suitability with respect to specific biomedical applications, namely superhydrophilic and biofilm degrading implant surfaces. UV-induced hydrophilicity was quantified by static and dynamic contact angle analysis. Photocatalytic protein decomposition was analyzed by quartz crystal microbalance with dissipation. The surfaces were characterized by X-ray diffraction, atomic force microscopy, scanning electron microscopy and X-ray photoelectron spectroscopy. The radical formation on anatase, responsible for photocatalytic effects, was analyzed by electron spin resonance spectroscopy. Results have shown that the nanocrystalline anatase films, in contrast to reference titanium surfaces, were sensitive to UV irradiation and showed rapid switching towards superhydrophilicity. The observed decrease in carbon adsorbents and the increase in the fraction of surface hydroxyl groups upon UV irradiation might contribute to this hydrophilic behavior. UV irradiation of anatase pre-conditioned with albumin protein layers induces the photocatalytic decomposition of these model biofilms. The observed degradation is mainly caused by hydroxyl radicals. It is concluded that nanocrystalline anatase films offer different functions at implant interfaces, e.g. bedside hydrophilization of anatase-coated implants for improved osseointegration or the in situ decomposition of conditioning films forming the basal layer of biofilms in the oral cavity. [ABSTRACT FROM AUTHOR]

RF excited gas discharges of hexamethyldisiloxane (HMDSO) with and without oxygen and methane (CH4) without further carrier gas were examined to identify reaction parameters determining deposition rate and film properties of SiOx and a-C:H films, respectively. This evaluation is supported by the used reactor type which enables well-defined deposition conditions. Both symmetrical and asymmetrical electrode configurations are investigated. It is found that the deposition rate depends on the reaction parameter power input per gas flow where the gas flows of monomer and reactive carrier gases are added. Thus, O2 in conjunction with HMDSO can be considered as a film-forming gas. Even in asymmetrical discharges the concept of the reaction parameter W/F holds, as long as the increasing ion bombardment allows a continuous film growth. While W/F controls the chemical composition of the films, the potential drop across the plasma sheath influences the mechanical film properties. With these findings SiOx and a-C:H plasma coatings can be designed. [Copyright &y& Elsevier]

Graphical abstract Highlights • Poly-3-hydroxybutyrate (PHB) films were plasma-treated in NH 3 , Ar and NH 3 /Ar mixtures. • Surface chemistry and topography changes were observed in PHB films. • A significant decrease in contact angle and an increase in free surface energy were observed. • Fibroblast cell adhesion was significantly improved after Ar plasma treatment. Abstract Poly-3-hydroxybutyrate (PHB) films were plasma-treated using pure NH 3 , pure Ar or mixtures of the two different proportions (20%, 30%, 40%, 50%, 70% NH 3 in Ar). Surface chemistry and surface topography changes of PHB films were observed after plasma processing in all plasma regimes. The XPS results confirmed the absence of chemical modification in the case of pure Ar plasma treatment. Nitrogen-containing groups (e.g., N C O) were detected on the surfaces of P3HB films treated with NH 3 -containing plasma. The surfaces of the untreated P3HB films were hydrophobic, and plasma treatment turned the surfaces hydrophilic, irrespective of the treatment. A significant decrease in the contact angle and an increase in the free surface energy were observed. An insignificant surface ageing effect was observed when P3HB samples were exposed to air for 10 days. In NIH 3T3 mice fibroblast cells, cell adhesion was significantly improved after plasma treatment in an Ar atmosphere, which is likely related to the fact that there was a surface ξ potential of 88.6 mV at neutral pH, causing a cleavage of the polymer chains and an increase in surface roughness. [ABSTRACT FROM AUTHOR]

In this paper, parylene C coating with the thickness of 2 μm was deposited on different magnesium alloy substrates (AZ31, WE43 and AZ91). The structure and phase composition of parylene C coating was analysed by Fourier transformed infrared (FTIR) spectroscopy and X-ray diffraction (XRD). In addition, extensive surface characterization was done using atomic force microscopy. The corrosion performance of polymer-coated magnesium alloys was investigated by electrochemical measurements in Hanks’ balanced salts solution that simulates bodily fluids at 37 ± 0.5 °C. The depth-dependent mechanical properties including Young’s modulus and nanohardness of parylene C films were investigated using nanoindentation technique. The effect of the penetration depth on the properties on nano- and microscale level have been described in detail. The percentage of elastic recovery was used to characterize the elastic properties of the polymeric coatings. The results of XRD showed (020) preferred orientation of the monoclinic unit cell of the alpha phase of parylene C. The parylene C revealed a semicrystalline structure with nanocrystalline blocks of 4.9 nm. The parylene C film shows a uniform surface morphology with a higher roughness level at micro and nanoscales compared to magnesium alloy surfaces. All of the uncoated substrates exhibited a low corrosion resistance compared to the coated samples, indicating that the corrosion resistance of the magnesium alloys could be improved by parylene C coating. The resulting average nanohardness and Young’s modulus of the parylene C coatings deposited onto different substrates were in the range of 0.18–0.25 GPa and 4.19–5.14 GPa, respectively. Furthermore, a higher percentage of elastic recovery of the polymer coating indicated a higher elasticity as compared to the magnesium alloy surface. The polymer coating has revealed the ability to recover elastically. Therefore, parylene C coating can not only improve corrosion resistance, but also provide the ability to recover elastically, expanding the potential applications of this material to include various biointerface platforms. [ABSTRACT FROM AUTHOR]

The surface properties of poly-3-hydroxybutyrate (P3HB) membranes were modified using oxygen and an ammonia radio-frequency (RF, 13.56 MHz) plasma. The plasma treatment procedures used in the study only affected the surface properties, including surface topography, without inducing any significant changes in the crystalline structure of the polymer, with the exception being a power level of 250 W. The wettability of the modified P3HB surfaces was significantly increased after the plasma treatment, irrespective of the treatment procedure used. It was revealed that both surface chemistry and surface roughness changes caused by the plasma treatment affected surface wettability. A treatment-induced surface aging effect was observed and resulted in an increase in the water contact angle and a decrease in the surface free energy. However, the difference in the water contact angle between the polymers that had been treated for 4 weeks and the untreated polymer surfaces was still significant. A dependence between cell adhesion and proliferation and the polar component of the surface energy was revealed. The increase in the polar component after the ammonia plasma modification significantly increased cell adhesion and proliferation on biodegradable polymer surfaces compared to the untreated P3HB and the P3HB modified using an oxygen plasma. [ABSTRACT FROM AUTHOR]

The effect of the pulsed electron beam (PEB) treatment on the structure and morphology of the hydroxyapatite (HA) coating deposited on the surfaces of titanium substrates by radio frequency magnetron sputtering was elucidated. The structure, composition and morphology of the samples were characterized by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). The results collected from SEM experiments demonstrated that the HA film was smooth and featureless. The samples were irradiated by PEB using an electron beam energy density of 0.1 J cm −2 , electron beam pulse duration of 50 μs, pulse repetition frequency of 5 Hz, and number of pulses N =50 and N =150. After PEB treatment with N =50, the coating exhibited a much finer uniform surface morphology, playing a crucial role in the enhancement of the mechanical properties of the HA-coated titanium substrate. The surface of the HA film treated with N =150 was still smooth and featureless. The XRD data demonstrated that PEB treatment of HA films produced only a slight decrease in the HA phase content. The combination of these two techniques opens the possibility of preparing high quality HA layers. [ABSTRACT FROM AUTHOR]

Silicon-doped hydroxyapatite-based (Si-HA) coatings were deposited via radio frequency (RF) magnetron sputtering on the surface of titanium that was treated with a pulsed electron beam. This study aimed to evaluate the effect of Si doping on the structure and mechanical properties of thin HA films. The content of the silicon was 1.2 and 4.6 at.% for the coatings prepared using the Si-HA precursor powders with a chemical formula Ca 10 (PO 4 ) 6 − x (SiO 4 ) x (OH) 2 − x where, x = 0.5 and 1.72. Pure HA (Ca 10 (PO 4 ) 6 (OH) 2 ) coatings were deposited for comparison. The as-deposited films were analysed with respect to their composition, state of chemical binding and microstructure using XPS, FTIR, XRD, and SEM. We hypothesized that the addition of Si would affect the mechanical features of the coatings due to microstructure changes. The effect of the introduction of Si on the nanohardness and the Young's modulus as well as the adhesion strength and scratch resistance of the HA coating was investigated using nanohardness testing and a scratch test, respectively. Examination of the coating microstructure using SEM and AFM revealed that Si doping influenced the surface morphology and led to a smaller grain size. The tendency to form an amorphous structure also increased with an increase in the Si content. A monotonous decrease in both the nanohardness and the elastic modulus was observed with an increase in the Si content. A maximum nanohardness of ~ 7 GPa was obtained for the Si-free HA coating, whereas the hardness decreased to ~ 4.3 GPa for the films with a Si content of 1.2 at.%. The addition of 4.6 at.% Si to the HA coating resulted in a reduction in the elastic modulus, whereas the nanohardness was very similar to that of the uncoated substrate. The adhesion behaviour of the coatings demonstrated different responses. In the case of pure HA coatings, failure occurred due to the low cohesion of the coating, whereas the crystalline Si-HA coatings with a Si content of 1.2 at.% deformed plastically without crack formation and without detaching from the titanium substrate, which resulted in a greater coating stability. [ABSTRACT FROM AUTHOR]