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The influence of H2 flooding on the development of surface roughness during time-of-flight secondary ion mass spectrometry (ToF-SIMS) depth profiling was studied to evaluate the different aspects of a H2 atmosphere in comparison to an ultrahigh vacuum (UHV) environment. Multilayer samples, consisting of different combinations of metal, metal oxide, and alloy layers of different elements, were bombarded with 1 and 2 keV Cs+ ion beams in UHV and a H2 atmosphere of 7 × 10-7 mbar. The surface roughness Sa was measured with atomic force microscopy (AFM) on the initial surface and in the craters formed while sputtering, either in the middle of the layers or at the interfaces. We found that the roughness after Cs+ sputtering depends on the chemical composition/structure of the individual layers, and it increases with the sputtering depth. However, the increase in the roughness was, in specific cases, approximately a few tens of percent lower when sputtering in the H2 atmosphere compared to the UHV. In the other cases, the average surface roughness was generally still lower when H2 flooding was applied, but the differences were statistically insignificant. Additionally, we observed that for the initially rough surfaces with an Sa of about 5 nm, sputtering with the 1 keV Cs+ beam might have a smoothing effect, thereby reducing the initial roughness. Our observations also indicate that Cs+ sputtering with ion energies of 1 and 2 keV has a similar effect on roughness development, except for the cases with initially very smooth samples. The results show the beneficial effect of H2 flooding on surface roughness development during the ToF-SIMS depth profiling in addition to a reduction of the matrix effect and an improved identification of thin layers.
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Stable chitosan thin films can be promising substrates for creating nanometric peptide-bound polyglucosamine layers. Those are of scientific interest since they can have certain structural similarities to bacterial peptidoglycans. Such films were deposited by spin coating from chitosan solutions and modified by acetylation and N-protected amino acids. The masses of deposited materials and their stability in aqueous solutions at different pH values and water interaction were determined with a quartz crystal microbalance with dissipation (QCM-D). The evolution of the surface composition was followed by X-ray photoelectron (XPS) and attenuated total reflectance infrared (ATR-IR) spectroscopy. Morphological changes were measured by atomic force microscopy (AFM), while the surface wettability was monitored by by static water contact angle measurements. The combination of the characterization techniques enabled an insight into the surface chemistry for each treatment step and confirmed the acetylation and coupling of N-protected glycine peptides. The developed procedures are seen as first steps toward preparing thin layers of acetylated chitin, potentially imitating the nanometric peptide substituted glycan layers found in bacterial cell walls.
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Quitosano , Quitosano/química , Microscopía de Fuerza Atómica , Tecnicas de Microbalanza del Cristal de Cuarzo , Técnicas de Síntesis en Fase Sólida , Propiedades de Superficie , Agua/químicaRESUMEN
Nanoporous ceramic coatings such as titania are promoted to produce drug-free cardiovascular stents with a low risk of in-stent restenosis (ISR) because of their selectivity towards vascular cell proliferation. The brittle coatings applied on stents are prone to cracking because they are subjected to plastic deformation during implantation. This study aims to overcome this problem by using a unique process without refraining from biocompatibility. Accordingly, a titanium film with 1 µm thickness was deposited on 316 LVM stainless-steel sheets using magnetron sputtering. Then, the samples were anodized to produce nanoporous oxide. The nanoporous oxide was removed by ultrasonication, leaving an approximately 500 nm metallic titanium layer with a nanopatterned surface. XPS studies revealed the presence of a 5 nm-thick TiO2 surface layer with a trace amount of fluorinated titanium on nanopatterned surfaces. Oxygen plasma treatment of the nanopatterned surface produced an additional 5 nm-thick fluoride-free oxide layer. The samples did not exhibit any cracking or spallation during plastic deformation. Cell viability studies showed that nanopatterned surfaces stimulate endothelial cell proliferation while reducing the proliferation of smooth muscle cells. Plasma treatment further accelerated the proliferation of endothelial cells. Activation of blood platelets did not occur on oxygen plasma-treated, fluoride-free nanopatterned surfaces. The presented surface treatment method can also be applied to other stent materials such as CoCr, nitinol, and orthopedic implants.
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Acero Inoxidable , Titanio , Materiales Biocompatibles Revestidos/farmacología , Células Endoteliales/metabolismo , Óxidos , Oxígeno , Plásticos , Stents , Propiedades de SuperficieRESUMEN
Ionizing radiation has been identified as an option for sterilization of disposable filtering facepiece respirators in situations where the production of the respirators cannot keep up with demand. Gamma radiation and high energy electrons penetrate deeply into the material and can be used to sterilize large batches of masks within a short time period. In relation to reports that sterilization by ionizing radiation reduces filtration efficiency of polypropylene membrane filters on account of static charge loss, we have demonstrated that both gamma and electron beam irradiation can be used for sterilization, provided that the respirators are recharged afterwards.
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In a proof-of-concept study, we assessed different analytical and spectroscopic parameters for stability screening of differently sized ß-NaYF4:20 molâ¯% Yb3+, 2 molâ¯% Tm3+ upconversion nanoparticles (UCNPs) exemplarily in the bioanalytically relevant buffer phosphate buffered saline (PBS; pH 7.4) at 37 and 50 °C. This included the potentiometric determination of the amount of released fluoride ions, surface analysis with X-ray photoelectron spectroscopy (XPS), and steady-state and time-resolved fluorescence measurements. Based on these results, the luminescence lifetime of the 800 nm upconversion emission was identified as an optimum parameter for stability screening of UCNPs and changes in particle surface chemistry.
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Water interaction with mineral surfaces is a complex living system decisive for any photocatalytic process. Resolving the atomistic structure of mineral-water interfaces is thus crucial for understanding these processes. Fibrous rutile TiO2 , grown hydrothermally on twinned rutile seeds under acidic conditions, is studied in terms of interface translation, atomic structure, and surface chemistry in the presence of water, by means of advanced microscopy and spectroscopy methods combined with structure modeling and density functional theory calculations. It is shown that fibers while staying in stable separation during their growth, adopt a special crystallographic registry that is controlled by repulsion forces between fully hydroxylated and protonated (110) surfaces. During relaxation, a turbulent proton transfer and cracking of OâH bonds is observed, generating a strong acidic character via proton jump from bridge âOHb to terminal âOHt groups, and spontaneous dissociation of interfacial water via a transient protonation of the âOHt groups. It is shown, that this specific interface structure can be implemented to induce acidic response in an initially neutral medium when re-immersed. This is thought to be the first demonstration of quantum-confined mineral-water interface, capable of memorizing its past and conveying its structurally encoded properties into a new environment.
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Nowadays, bacteria resistance to many antibiotics is a huge problem, especially in clinics and other parts of the healthcare system. This critical health issue requires a dynamic approach to produce new types of antibacterial coatings to combat various pathogen microbes. In this research, we prepared a new type of carbon quantum dots based on phloroglucinol using the bottom-up method. Polyurethane composite films were produced using the swell-encapsulation-shrink method. Detailed electrostatic force and viscoelastic microscopy of carbon quantum dots revealed inhomogeneous structure characterized by electron-rich/soft and electron-poor/hard regions. The uncommon photoluminescence spectrum of carbon quantum dots core had a multipeak structure. Several tests confirmed that carbon quantum dots and composite films produced singlet oxygen. Antibacterial and antibiofouling efficiency of composite films was tested on eight bacteria strains and three bacteria biofilms.
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The cost of treatment of antibiotic-resistant pathogens is on the level of tens of billions of dollars at the moment. It is of special interest to reduce or solve this problem using antimicrobial coatings, especially in hospitals or other healthcare facilities. The bacteria can transfer from medical staff or contaminated surfaces to patients. In this paper, we focused our attention on the antibacterial and antibiofouling activities of two types of photodynamic polyurethane composite films doped with carbon polymerized dots (CPDs) and fullerene C60. Detailed atomic force, electrostatic force and viscoelastic microscopy revealed topology, nanoelectrical and nanomechanical properties of used fillers and composites. A relationship between the electronic structure of the nanocarbon fillers and the antibacterial and antibiofouling activities of the composites was established. Thorough spectroscopic analysis of reactive oxygen species (ROS) generation was conducted for both composite films, and it was found that both of them were potent antibacterial agents against nosocomial bacteria (Klebsiela pneumoniae, Proteus mirabilis, Salmonela enterica, Enterococcus faecalis, Enterococcus epidermis and Pseudomonas aeruginosa). Antibiofouling testing of composite films indicated that the CPDs/PU composite films eradicated almost completely the biofilms of Pseudomonas aeruginosa and Staphylococcus aureus and about 50% of Escherichia coli biofilms.
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The present study introduces an advanced surface modification approach combining electrochemical anodization and non-thermal plasma treatment, tailored for biomedical applications on stainless steel grade 316L (SS316L) surfaces. Nanopores with various diameters (100-300 nm) were synthesized with electrochemical anodization, and samples were further modified with non-thermal oxygen plasma. The surface properties of SS316L surfaces were examined by scanning electron microscopy, atomic force microscopy, X-ray photoemission spectroscopy, and Water contact angle measurements. It has been shown that a combination of electrochemical anodization and plasma treatment significantly alters the surface properties of SS316L and affects its interactions with blood platelets and human coronary cells. Optimal performance is attained on the anodized specimen featuring pores within the 150-300 nm diameter range, subjected to subsequent oxygen plasma treatment; the absence of platelet adhesion was observed. At the same time, the sample demonstrated good endothelialization and a reduction in smooth muscle cell adhesion compared to the untreated SS316L and the sample with smaller pores (100-150 nm). This novel surface modification strategy has significant implications for improving biocompatibility and performance of SS316L in biomedical applications.
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Interaction of single γ-Al2O3 and γ-Ga2O3, and mixed γ-Al2O3/γ-Ga2O3 xerogels with CHF3 at intermediate temperatures results in partial fluorination. Fluorinated oxides remain amorphous and retain a considerable part of the initial surface area; for the fluorinated Al-based materials surface areas in all cases exceed 100 m2 g-1. Lewis acidity of mixed oxides, either before or after fluorination, is strongly influenced by the presence of surface Ga3+ ions, mainly due to their strong preference to replace highly acidic Al3+ ions in tetrahedral positions. Ion replacement leads to the formation of acidic sites with lower strengths what is confirmed by the model catalytic reaction, isomerisation of CCl2FCClF2. XPS investigations indicate that fluorination of mixed oxides is accompanied by substantial surface reconstructions and preferential formation of Al-F based phases with Ga remaining mainly in O environments. Further segregation processes, such as slow crystallisation of Al(F,OH)3·nH2O phases, are probably promoted by water adsorption.
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Óxido de Aluminio/química , Clorofluorocarburos de Metano/química , Galio/química , Geles/química , Halogenación , Catálisis , Espectroscopía de Fotoelectrones , Espectroscopía Infrarroja por Transformada de Fourier , Propiedades de Superficie , Difracción de Rayos XRESUMEN
This study reports on the successful conjugation of SARS-CoV-2 S1 spike protein fragments with gold nanoparticles (AuNPs) that were synthesised with Ultrasonic Spray Pyrolysis (USP). This method enables the continuous synthesis of AuNPs with a high degree of purity, round shapes, and the formation of a surface that allows various modifications. The conjugation mechanism of USP synthesized AuNPs with SARS-CoV-2 S1 spike protein fragments was investigated. A gel electrophoresis experiment confirmed the successful conjugation of AuNPs with SARS-CoV-2 S1 fragments indirectly. X-ray Photoelectron Spectroscopy (XPS) analysis confirmed the presence of characteristic O1s and N1s peaks, which indicated that specific binding between AuNPs and SARS-CoV-2 S1 spike protein fragments takes place via a peptide bond formed with the citrate stabiliser. This bond is coordinated to the AuNP's surface and the N-terminals of the protein, with the conjugate displaying the expected response within a prototype LFIA test. This study will help in better understanding the behaviour of AuNPs synthesised with USP and their potential use as sensors in colorimetric or electrochemical sensors and LFIA tests.
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In this study, MNPs were functionalized with pyrocatechol (CAT), pyrogallol (GAL), caffeic acid (CAF), and nitrodopamine (NDA) at pH 8 and pH 11. The functionalization of the MNPs was successful, except in the case of NDA at pH 11. The thermogravimetric analyses indicated that the surface concentration of the catechols was between 1.5 and 3.6 molecules/nm2. The saturation magnetizations (Ms) of the functionalized MNPs were higher than the starting material. XPS analyses showed only the presence of Fe(III) ions on the surface, thus refuting the idea of the Fe being reduced and magnetite being formed on the surfaces of the MNPs. Density functional theory (DFT) calculations were performed for two modes of adsorption of CAT onto two model surfaces: plain and adsorption via condensation. The total magnetization of both adsorption modes remained the same, indicating that the adsorption of the catechols does not affect the Ms. The analyses of the size and the size distribution showed an increase in the average size of the MNPs during the functionalization process. This increase in the average size of the MNPs and the reduction in the fraction of the smallest (i.e., <10 nm) MNPs explained the increase in the Ms values.
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Indium-zinc-oxide (IZO) films were prepared by spin coating an ethanol-ethylene-glycol precursor solution with a Zn/(In + Zn) ratio of 0.36 on glass. The effects of temperature on the structure, microstructure, electrical, and optical properties of the IZO thin films were investigated by thermal analysis, Fourier-transform infrared spectroscopy, X-ray diffraction, electron and atomic-force microscopy, X-ray photoelectron spectroscopy and variable-angle spectroscopic ellipsometry. The prepared IZO thin films heated at 500, 600, and 700 °C in air were transparent, without long-range ordering, and with an RMS surface roughness of less than 1 nm. The lowest electrical resistivity at room temperature, 0.0069 Ωcm, was observed for the 115-nm-thick IZO thin film heated at 600 °C in air and subsequently post-annealed in Ar/H2. The thin film exhibited a microstructure characterized by grains typically 20 nm in size and had no organic residues. This film exhibits uniaxial optical anisotropy due to its ultra-thin lamellae with a high electron density. The ordinary refractive index was fitted as a Tauc-Lorentz-Urbach function, which is typical of an indirect absorption edge occurring in amorphous semiconductor materials. The principal absorption peak with an onset at about 2.8 eV and a Tauc gap energy of â¼2.6 eV is similar to those observed for In2O3. The described process of chemical solution deposition and subsequent curing is promising for the low-cost fabrication of IZO thin films for transparent electronics, and can be used to tune the structure and microstructure of IZO thin films, as well as their electrical and optical properties.
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Development of a robust photocathode using low-cost and high-performing materials, e.g., p-Si, to produce clean fuel hydrogen has remained challenging since the semiconductor substrate is easily susceptible to (photo)corrosion under photoelectrochemical (PEC) operational conditions. A protective layer over the substrate to simultaneously provide corrosion resistance and maintain efficient charge transfer across the device is therefore needed. To this end, in the present work, we utilized pulsed laser deposition (PLD) to prepare a high-quality SrTiO3 (STO) layer to passivate the p-Si substrate using a buffer layer of reduced graphene oxide (rGO). Specifically, a very thin (3.9 nm â¼10 unit cells) STO layer epitaxially overgrown on rGO-buffered Si showed the highest onset potential (0.326 V vs RHE) in comparison to the counterparts with thicker and/or nonepitaxial STO. The photovoltage, flat-band potential, and electrochemical impedance spectroscopy measurements revealed that the epitaxial photocathode was more beneficial for charge separation, charge transfer, and targeted redox reaction than the nonepitaxial one. The STO/rGO/Si with a smooth and highly epitaxial STO layer outperforming the directly contacted STO/Si with a textured and polycrystalline STO layer showed the importance of having a well-defined passivation layer. In addition, the numerous pinholes formed in the directly contacted STO/Si led to the rapid degradation of the photocathode during the PEC measurements. The stability tests demonstrated the soundness of the epitaxial STO layer in passivating Si against corrosion. This study provided a facile approach for preparing a robust protection layer over a photoelectrode substrate in realizing an efficient and, at the same time, durable PEC device.
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Cardiovascular diseases are a pre-eminent global cause of mortality in the modern world. Typically, surgical intervention with implantable medical devices such as cardiovascular stents is deployed to reinstate unobstructed blood flow. Unfortunately, existing stent materials frequently induce restenosis and thrombosis, necessitating the development of superior biomaterials. These biomaterials should inhibit platelet adhesion (mitigating stent-induced thrombosis) and smooth muscle cell proliferation (minimizing restenosis) while enhancing endothelial cell proliferation at the same time. To optimize the surface properties of Ti6Al4V medical implants, we investigated two surface treatment procedures: gaseous plasma treatment and hydrothermal treatment. We analyzed these modified surfaces through scanning electron microscopy (SEM), water contact angle analysis (WCA), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD) analysis. Additionally, we assessed in vitro biological responses, including platelet adhesion and activation, as well as endothelial and smooth muscle cell proliferation. Herein, we report the influence of pre/post oxygen plasma treatment on titanium oxide layer formation via a hydrothermal technique. Our results indicate that alterations in the titanium oxide layer and surface nanotopography significantly influence cell interactions. This work offers promising insights into designing multifunctional biomaterial surfaces that selectively promote specific cell types' proliferationâwhich is a crucial advancement in next-generation vascular implants.
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Materiales Biocompatibles , Trombosis , Humanos , Adhesión Celular , Propiedades de SuperficieRESUMEN
Aiming at speeding up the discovery and understanding of promising electrocatalysts, a novel experimental platform, i.e., the Nano Lab, is introduced. It is based on state-of-the-art physicochemical characterization and atomic-scale tracking of individual synthesis steps as well as subsequent electrochemical treatments targeting nanostructured composites. This is provided by having the entire experimental setup on a transmission electron microscopy (TEM) grid. Herein, the oxygen evolution reaction nanocomposite electrocatalyst, i.e., iridium nanoparticles dispersed on a high-surface-area TiOxNy support prepared on the Ti TEM grid, is investigated. By combining electrochemical concepts such as anodic oxidation of TEM grids, floating electrode-based electrochemical characterization, and identical location TEM analysis, relevant information from the entire composite's cycle, i.e., from the initial synthesis step to electrochemical operation, can be studied. We reveal that Ir nanoparticles as well as the TiOxNy support undergo dynamic changes during all steps. The most interesting findings made possible by the Nano Lab concept are the formation of Ir single atoms and only a small decrease in the N/O ratio of the TiOxNy-Ir catalyst during the electrochemical treatment. In this way, we show that the precise influence of the nanoscale structure, composition, morphology, and electrocatalyst's locally resolved surface sites can be deciphered on the atomic level. Furthermore, the Nano Lab's experimental setup is compatible with ex situ characterization and other analytical methods, such as Raman spectroscopy, X-ray photoelectron spectroscopy, and identical location scanning electron microscopy, hence providing a comprehensive understanding of structural changes and their effects. Overall, an experimental toolbox for the systematic development of supported electrocatalysts is now at hand.
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A versatile approach to the production of cluster- and single atom-based thin-film electrode composites is presented. The developed TiO x N y -Ir catalyst was prepared from sputtered Ti-Ir alloy constituted of 0.8 ± 0.2 at % Ir in α-Ti solid solution. The Ti-Ir solid solution on the Ti metal foil substrate was anodically oxidized to form amorphous TiO2-Ir and later subjected to heat treatment in air and in ammonia to prepare the final catalyst. Detailed morphological, structural, compositional, and electrochemical characterization revealed a nanoporous film with Ir single atoms and clusters that are present throughout the entire film thickness and concentrated at the Ti/TiO x N y -Ir interface as a result of the anodic oxidation mechanism. The developed TiO x N y -Ir catalyst exhibits very high oxygen evolution reaction activity in 0.1 M HClO4, reaching 1460 A g-1 Ir at 1.6 V vs reference hydrogen electrode. The new preparation concept of single atom- and cluster-based thin-film catalysts has wide potential applications in electrocatalysis and beyond. In the present paper, a detailed description of the new and unique method and a high-performance thin film catalyst are provided along with directions for the future development of high-performance cluster and single-atom catalysts prepared from solid solutions.
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Nowadays, it is a great challenge to develop new medicines for treating various infectious diseases. The treatment of these diseases is of utmost interest to further prevent the development of multi-drug resistance in different pathogens. Carbon quantum dots, as a new member of the carbon nanomaterials family, can potentially be used as a highly promising visible-light-triggered antibacterial agent. In this work, the results of antibacterial and cytotoxic activities of gamma-ray-irradiated carbon quantum dots are presented. Carbon quantum dots (CQDs) were synthesized from citric acid by a pyrolysis procedure and irradiated by gamma rays at different doses (25, 50, 100 and 200 kGy). Structure, chemical composition and optical properties were investigated by atomic force microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, Raman spectroscopy, UV-Vis spectrometry and photoluminescence. Structural analysis showed that CQDs have a spherical-like shape and dose-dependent average diameters and heights. Antibacterial tests showed that all irradiated dots had antibacterial activity but CQDs irradiated with dose of 100 kGy had antibacterial activity against all seven pathogen-reference bacterial strains. Gamma-ray-modified CQDs did not show any cytotoxicity toward human fetal-originated MRC-5 cells. Moreover, fluorescence microscopy showed excellent cellular uptake of CQDs irradiated with doses of 25 and 200 kGy into MRC-5 cells.
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The influence of the flooding gas during ToF-SIMS depth profiling was studied to reduce the matrix effect and improve the quality of the depth profiles. The profiles were measured on three multilayered samples prepared by PVD. They were composed of metal, metal oxide, and alloy layers. Dual-beam depth profiling was performed with 1 keV Cs+ and 1 keV O2+ sputter beams and analyzed with a Bi+ primary beam. The novelty of this work was the application of H2, C2H2, CO, and O2 atmospheres during SIMS depth profiling. Negative cluster secondary ions, formed from sputtered metals/metal oxides and the flooding gases, were analyzed. A systematic comparison and evaluation of the ToF-SIMS depth profiles were performed regarding the matrix effect, ionization probability, chemical sensitivity, sputtering rate, and depth resolution. We found that depth profiling in the C2H2, CO, and O2 atmospheres has some advantages over UHV depth profiling, but it still lacks some of the information needed for an unambiguous determination of multilayered structures. The ToF-SIMS depth profiles were significantly improved during H2 flooding in terms of matrix-effect reduction. The structures of all the samples were clearly resolved while measuring the intensity of the MnHm-, MnOm-, MnOmH-, and Mn- cluster secondary ions. A further decrease in the matrix effect was obtained by normalization of the measured signals. The use of H2 is proposed for the depth profiling of metal/metal oxide multilayers and alloys.
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In our study, plasma surface modification was employed to tailor the surface properties of magnesium in terms of surface chemistry, topography, and wettability. For two sets of samples, the plasma treatment involved two steps using two different gases (hydrogen and oxygen), while one set of samples was treated with one step only using oxygen. X-ray photoelectron spectroscopy (XPS) was applied to determine the surface composition, oxidation state of the elements, and the thickness of the surface oxide layer on the Mg samples after different plasma treatments. The surface morphology was characterised using atomic force microscopy (AFM) and scanning electron microscopy (SEM). The wettability was analysed by measuring the static water-contact angles and the corrosion was evaluated using potentiodynamic measurements. The interaction of the live cells with the differently modified Mg surfaces was evaluated in terms of biocompatibility using MG-63 cells (human bone osteosarcoma cells). We have shown that a plasma surface treatment significantly decreased the carbon content and the formation of a 15-20-nm-thick MgO layer was observed. This improves the corrosion resistance, while the biocompatibility was retained, compared to the untreated Mg. A plasma surface treatment is therefore an important step in the development of novel surfaces with improved corrosion resistance for magnesium in biomedical applications.