Although mesenchymal stem cells (MSCs) are the natural source for bone regeneration, the exact mechanisms governing MSC crosstalk with collagen I have not yet been uncovered. Cell adhesion to ...collagen I is mostly mediated by three integrin receptors - α1β1, α2β1 and α11β1. Using human MSC (hMSC), we show that α11 subunit exhibited the highest basal expression levels but on osteogenic stimulation, both α2 and α11 integrins were significantly upregulated. To elucidate the possible roles of collagen-binding integrins, we applied short hairpin RNA (shRNA)-mediated knockdown in hMSC and found that α2 or α11 deficiency, but not α1, results in a tremendous reduction of hMSC numbers owing to mitochondrial leakage accompanied by Bcl-2-associated X protein upregulation. In order to clarify the signaling conveyed by the collagen-binding integrins in hMSC, we analyzed the activation of focal adhesion kinase, extracellular signal-regulated protein kinase and serine/threonine protein kinase B (PKB/Akt) kinases and detected significantly reduced Akt phosphorylation only in α2- and α11-shRNA hMSC. Finally, experiments with hMSC from osteoporotic patients revealed a significant downregulation of α2 integrin concomitant with an augmented mitochondrial permeability. In conclusion, our study describes for the first time that disturbance of α2β1- or α11β1-mediated interactions to collagen I results in the cell death of MSCs and urges for further investigations examining the impact of MSCs in bone conditions with abnormal collagen I.
•UNCD and DLC films were modified by UV/O3 treatments, O2 or NH3-containing plasmas.•Surface composition, wettability and surface energy change upon modifications.•Higher efficiency of UNCD ...modifications was observed.•Cell attachment and growth were influenced by the surface termination and roughness.
Diamond and diamond-like carbon (DLC) films possess a set of excellent physical and chemical properties which together with a high biocompatibility make them attractive candidates for a number of medical and biotechnological applications. In the current work thin ultrananocrystalline diamond (UNCD) and DLC films were comparatively investigated with respect to cell attachment and proliferation after different surface modifications. The UNCD films were prepared by microwave plasma enhanced chemical vapor deposition, the DLC films by pulsed laser deposition (PLD). The films were comprehensively characterized with respect to their basic properties, e.g. crystallinity, morphology, chemical bonding nature, etc. Afterwards the UNCD and DLC films were modified applying O2 or NH3/N2 plasmas and UV/O3 treatments to alter their surface termination. The surface composition of as-grown and modified samples was studied by X-ray photoelectron spectroscopy (XPS). Furthermore the films were characterized by contact angle measurements with water, formamide, 1-decanol and diiodomethane; from the results obtained the surface energy with its dispersive and polar components was calculated. The adhesion and proliferation of MG63 osteosarcoma cells on the different UNCD and DLC samples were assessed by measurement of the cell attachment efficiency and MTT assays. The determined cell densities were compared and correlated with the surface properties of as-deposited and modified UNCD and DLC films.
Although mesenchymal stem cells (MSCs) are the natural source for bone regeneration, the exact mechanisms governing MSC crosstalk with collagen I have not yet been uncovered. Cell adhesion to ...collagen I is mostly mediated by three integrin receptors - alpha 1 beta 1, alpha 2 beta 1 and alpha 11 beta 1. Using human MSC (hMSC), we show that alpha 11 subunit exhibited the highest basal expression levels but on osteogenic stimulation, both alpha 2 and alpha 11 integrins were significantly upregulated. To elucidate the possible roles of collagen-binding integrins, we applied short hairpin RNA (shRNA)-mediated knockdown in hMSC and found that alpha 2 or alpha 11 deficiency, but not alpha 1, results in a tremendous reduction of hMSC numbers owing to mitochondrial leakage accompanied by Bcl-2-associated X protein upregulation. In order to clarify the signaling conveyed by the collagen-binding integrins in hMSC, we analyzed the activation of focal adhesion kinase, extracellular signal-regulated protein kinase and serine/threonine protein kinase B (PKB/Akt) kinases and detected significantly reduced Akt phosphorylation only in alpha 2- and alpha 11-shRNA hMSC. Finally, experiments with hMSC from osteoporotic patients revealed a significant downregulation of alpha 2 integrin concomitant with an augmented mitochondrial permeability. In conclusion, our study describes for the first time that disturbance of alpha 2 beta 1- or alpha 11 beta 1-mediated interactions to collagen I results in the cell death of MSCs and urges for further investigations examining the impact of MSCs in bone conditions with abnormal collagen I.
COVID-19 has proven to be a disease that affects not only the respiratory tract but also leads to a state of generalized systemic hyperinflammation and overall immune dysregulation. An important role ...in its pathogenesis is the disturbance of many cytokines – a condition which, in its most pronounced form, is also called a „cytokine storm“.
Transformation from higher to ultra low friction coefficient was observed in ultrananocrystalline diamond film (UNCD) while changing the test atmospheric conditions. High friction coefficients were ...observed in dry argon and nitrogen atmosphere, however, low and ultra low friction coefficients were obtained in dry oxygen and in ambient atmospheric conditions, respectively. Wear rates follow the same trends as the friction coefficients. This fascinating behavior of friction and wear of UNCD film is explained by the chemical changes of sliding surfaces and extent of passivation of dangling covalent bonds.
Friction coefficients for the various samples under the various test conditions.
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► High to ultra low friction coefficient of UNCD film depends on atmospheric conditions. ► High friction coefficient was obtained in dry argon and nitrogen atmosphere. ► Ultra low friction coefficient was measured in ambient atmospheric condition. ► Chemical changes in wear track influence tribological properties of UNCD film.
Nanocrystalline diamond/amorphous carbon (NCD/a-C) composite films have been prepared by microwave plasma chemical vapor deposition (MWCVD) from methane/nitrogen mixtures. The complex nature of the ...coatings required the application of a variety of complementary analytical techniques in order to elucidate their structure. The crystallinity of the samples was studied by selected-area electron diffraction (SAED). The diffraction patterns revealed the presence of diamond crystallites within the films. From the images taken by transmission electron microscopy (TEM) the crystallite size was determined to be on the order of 3–5 nm. The results were confirmed by X-ray diffraction (XRD) measurements exhibiting broad (111) and (220) peaks of diamond from which the average size of the crystallites was calculated. The grain boundary width is 1–1.5 nm as observed by TEM images which corresponds to a matrix volume fraction of about 40–50%. This correlates very well with the crystalline phase content of about 50% in the films estimated from their density (2.75 g/cm
3 as determined by X-ray reflectivity). The bonding structure of the composite films was studied by electron energy loss spectroscopy (EELS) in the region of carbon core level. The spectra were dominated by a peak at 292 eV indicating the diamond nature of the investigated films. In addition, the spectra of NCD/a-C films possessed a shoulder at 284 eV due to the presence of a small sp
2 bonded fraction. This phase was identified also by X-ray photoelectron spectroscopy (XPS). The sp
2/sp
3 ratio was on the order of 10% as determined by deconvolution of the C1s XPS peak.
Diamond nanopillars with diameters of 1 μm down to 50 nm have been fabricated from two types of diamond thin films, namely nanocrystalline diamond (NCD) and ultrananocrystalline diamond (UNCD) using ...electron beam lithography (EBL) and reactive ion etching (RIE) in an inductively coupled oxygen plasma (ICP). Aim of the study was to investigate the suitability of these pillars to incorporate nitrogen‐vacancy (NV) color centers for applications in quantum information technology (QIT). The first part of the investigation is devoted to a characterization of the pillars, their shape, size, and properties. The second part of this investigation concerns the optical properties of NCD and UNCD nanopillars and the incorporation of NV centers within them. Among others, fluorescence mapping and photoluminescence measurements have been employed for this purpose. It turned out that NCD pillars are quite promising for the applications in QIT envisioned. At the present time, the opposite is the case for UNCD pillars. The reasons for these differences will be discussed on the basis of the differences of the two materials NCD and UNCD.
Nanocrystalline diamond films in an amorphous matrix have been deposited by microwave plasma chemical vapour deposition from CH
4/N
2 mixtures and characterized with respect to their morphology and ...structure, composition, crystallinity and bonding structure. The films turned out to be nanocrystalline with crystallite sizes on the order of 3–5 nm and a density of 2.75 g/cm
3. They contain approximately 0.5–1% nitrogen and 10% hydrogen. The nitrogen content of the gas phase has a strong influence on the growth rates and the morphology of the films, whereas the bonding structure is almost unaffected. Raman spectra prove the existence of sp
2 bonded carbon in the matrix; however, according to electron energy loss spectroscopy and X-ray photoelectron spectroscopy investigations the sp
2 content is rather small. Infrared spectra show that the hydrogen is bonded primarily in the form of sp
3 CH
x
groups.
Nanocrystalline diamond/amorphous carbon (NCD/a-C) composite thin films have been deposited by microwave plasma chemical vapour deposition from methane-rich CH
4/N
2 mixtures. The films have been ...thoroughly characterized with respect to basic properties such as growth rates, morphology and structure, composition, crystallinity, and bonding environment. They consist of diamond nanocrystals with diameters of 3–5 nm, which are embedded in an amorphous carbon matrix. Further studies are aimed at application relevant properties.
I/
V and Hall measurements showed that the films are p-type conductive with a resistitivity of 0.14 Ω cm, a carrier concentration of 1.9
×
10
17 cm
−
3, and a carrier mobility of 250 cm
2/Vs. Reflection, scattering and ellipsometric measurements revealed a refractive index of 1.95–2.1 in the visible region and an rather high extinction coefficient of about 0.14 at 400 nm. The films possess a hardness of ca. 40 GPa and a Young's modulus of ca. 390 GPa. Nano tribo test and nano scratch tests proved a low friction coefficient, and a strong protective effect and good adhesion on silicon substrates. First biomedical tests showed that the films are not cytotoxic but bioinert. Finally, the deposition of multilayers nano/polycrystalline diamond with improved properties is demonstrated.
The initial growth phase of ultrananocrystalline diamond/amorphous carbon nanocomposite films (UNCD/a-C) has been investigated by scanning electron microscopy, atomic force microscopy and especially ...Raman spectroscopy. As due to resonance effects Raman spectra of carbon materials strongly depend on the excitation wavelength, a multiwavelength analysis has been performed with
λ
exc ranging from the UV region (325
nm) over the visible range (488 and 514
nm) to the IR region (785
nm). In addition, a set of measurements has been performed with a confocal Raman microscope, i.e. depth resolved, with a wavelength of 532
nm. The samples investigated were deposited with constant parameters, the deposition time being the only parameter varied, resulting in film thicknesses from 100 to 500
nm. It turned out that the diamond fraction and also the grain boundary material do not vary during that stage whereas there are slight but distinct changes of the nature of the amorphous matrix which reflect, among others, in a shift of the graphite-related G band to higher wavenumbers and in an increase of the ratio of D and G bands with increasing film thickness. These changes are discussed in terms of the above mentioned resonance effects; the major changes are a transition of hydrogen containing sp
2 chains to hydrogen-free condensed sp
2 rings when the material is no longer in the surface region of the films but becomes incorporated within the film bulk.
► Investigation of the first stages of UNCD growth. ► Multiwavelength Raman spectroscopy. ► Confocal Raman spectroscopy.
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