Sputtering and surface modification of thermoplastic polymers with low energy ion beams

Low energy ion beam irradiation proved itself to be suitable technique to alter chemical and physical properties of polymer surfaces. Spin coated thin films and commercial sheets of polymers were irradiated with argon, nitrogen and oxygen ions at energies of 0.5 – 5 keV in the fluence range from 10E12 to 10E16 cm-2. When ion interacts with polymer surface, chain bonds are broken resulting in the formation of smaller molecules, many of which may be volatile that are desorbed. At the same time, formed free radicals participate in different reactions during which the chemistry of polymer surfaces is easily and irreversibly changed resulting in alteration of polymer surface properties. Polymer sputter rates were found to depend on polymer chemistry and ion beam parameters. The sputter rates of polymers decreased strongly with the ion fluence, followed by constant removal rate in the steady-state region. The decrease of typically one order of magnitude was attributed to the chemical changes in polymer structure that occurred in the ion fluence range 10E13 – 10E15 cm-2 depending on polymer chemistry, ion energy and type. Induced changes in the polymer surface layer showed large influence on metal/polymer adhesion properties. Three types of practical adhesion strength, measured using 90° peel test, were observed: (i) adhesion increased with the ion fluence until saturation was reached; (ii) peel strength increased at low ion fluencies, reached maximum and at prolonged treatment decreased; (iii) no improvement in the peel strength on treated polymer surfaces was recorded. XPS analysis of peeled-off surfaces showed that in most cases the failure location changed from interfacial for untreated polymers to cohesive failure in the polymer for treated surfaces. An improvement in the metal polymer adhesion in the ion fluence range 10E13 – 10E16 cm-2 is attributed to the creation of a large density of new adsorption sites resulting in larger contact area and incorporation of chemically active groups that lead to the increased interaction between metal and polymer through metal-oxygen/nitrogen-polymer species formation

Friction force microscopy analysis of self-adaptive W-S-C coatings:nanoscale friction and wear

Transition metal dichalcogenides (TMD) are increasingly popular due to unique structural and mechanical properties. They belong, together with graphene and similar 2D materials, to a small family of solid lubricants with potential to produce ultralow friction state. At the macroscale, low friction stems from the ability to form well-oriented films on the sliding surface (typically up to 10 nm thick), with the TMD basal planes aligned parallel to the surface. In this study, we quantitatively evaluate tribological properties of three sputtered tungsten–sulfur–carbon (W–S–C) coatings at a nanoscale using friction force microscopy. In particular, we investigate possible formation of well-ordered tungsten disulfide (WS2) layers on the coating surface. The coefficient of friction decreased with increasing load independently of coating composition or mechanical properties. In contrast, hard coatings with high tungsten carbide content were more resistant to wear. We successfully identified a WS2 tribolayer at the sliding interface, which peeled off as ultrathin flakes and attached to AFM tip. Nanoscale tribological behavior of WSC coatings replicates deviation of Amonton’s law observed in macroscale testing and strongly suggests that the tribolayer is formed almost immediately after the start of sliding

Structural and elemental analysis of the freshwater, low-Mg calcite coralline alga <i>pneophyllum cetinaensis</i>

Coralline algae are one of the most diversified groups of red algae and represent a major component of marine benthic habitats from the poles to the tropics. This group was believed to be exclusively marine until 2016, when the first freshwater coralline algae Pneophyllum cetinaensis was discovered in the Cetina River, southern Croatia. While several studies investigated the element compositions of marine coralline algal thalli, no information is yet available for the freshwater species. Using XRD, LA-ICP-MS and nano indentation, this study presents the first living low-Mg calcite coralline algae with Mg concentrations ten times lower than is common for the average marine species. Despite the lower Mg concentrations, hardness and elastic modulus (1.71 ± 1.58 GPa and 29.7 ± 18.0 GPa, respectively) are in the same range as other marine coralline algae, possibly due to other biogenic impurities. When compared to marine species, Ba/Ca values were unusually low, even though Ba concentrations are generally higher in rivers than in seawater. These low values might be linked to different physical and chemical characteristics of the Cetina River

Effect of radiation-induced damage of trabecular bone tissue evaluated using indentation and digital volume correlation

Exposure to X-ray radiation for an extended amount of time can cause damage to the bone tissue and therefore affect its mechanical properties. Specifically, high-resolution X-ray Computed Tomography (XCT), in both synchrotron and lab-based systems, has been employed extensively for evaluating bone micro-to-nano architecture. However, to date, it is still unclear how long exposures to X-ray radiation affect the mechanical properties of trabecular bone, particularly in relation to lab-XCT systems. Indentation has been widely used to identify local mechanical properties such as hardness and elastic modulus of bone and other biological tissues. The purpose of this study is therefore, to use indentation and XCT-based investigative tools such as digital volume correlation (DVC) to assess the microdamage induced by long exposure of trabecular bone tissue to X-ray radiation and how this affects its local mechanical properties. Trabecular bone specimens were indented before and after X-ray exposures of 33 and 66 h, where variation of elastic modulus was evaluated at every stage. The resulting elastic modulus was decreased, and micro-cracks appeared in the specimens after the first long X-ray exposure and crack formation increased after the second exposure. High strain concentration around the damaged tissue exceeding 1% was also observed from DVC analysis. The outcomes of this study show the importance of designing appropriate XCT-based experiments in lab systems to avoid degradation of the bone tissue mechanical properties due to radiation and these results will help to inform future studies that require long X-ray exposure for in situ experiments or generation of reliable subject-specific computational models

Quantification of molecular interactions between apoE, Amyloid-beta (Aβ) and laminin:relevance to accumulation of Aβ in Alzheimer’s disease

Accumulation of amyloid-? (A?) in plaques in the brain and in artery walls as cerebral amyloid angiopathy indicates a failure of elimination of A? from the brain with age and Alzheimer's disease. A major pathway for elimination of A? and other soluble metabolites from the brain is along basement membranes within the walls of cerebral arteries that represent the lymphatic drainage pathways for the brain. The motive force for the elimination of A? along this perivascular pathway appears to be the contrary (reflection) wave that follows the arterial pulse wave. Following injection into brain parenchyma, A? rapidly drains out of the brain along basement membranes in the walls of cerebral arteries; such drainage is impaired in apolipoprotein E ?4 (ApoE4) mice. For drainage of A? to occur in a direction contrary to the pulse wave, some form of attachment to basement membrane would be required to prevent reflux of A? back into the brain during the passage of the subsequent pulse wave. In this study, we show first that apolipoprotein E co-localizes with A? in basement membrane drainage pathways in the walls of arteries. Secondly, we show by Atomic Force Microscopy that attachment of ApoE4/A? complexes to basement membrane laminin is significantly weaker than ApoE3/A? complexes. These results suggest that perivascular elimination of ApoE4/A? complexes would be less efficient than with other isoforms of apolipoprotein E, thus endowing a higher risk for Alzheimer's disease. Therapeutic correction for ApoE4/A?/laminin interactions may increase the efficiency of elimination of A? in the prevention of Alzheimer's disease

Quantification of molecular interactions between ApoE, amyloid-beta (Aβ) and laminin: Relevance to accumulation of Aβ in Alzheimer\u27s disease

Accumulation of amyloid-β (Aβ) in plaques in the brain and in artery walls as cerebral amyloid angiopathy indicates a failure of elimination of Aβ from the brain with age and Alzheimer\u27s disease. A major pathway for elimination of Aβ and other soluble metabolites from the brain is along basement membranes within the walls of cerebral arteries that represent the lymphatic drainage pathways for the brain. The motive force for the elimination of Aβ along this perivascular pathway appears to be the contrary (reflection) wave that follows the arterial pulse wave. Following injection into brain parenchyma, Aβ rapidly drains out of the brain along basement membranes in the walls of cerebral arteries; such drainage is impaired in apolipoprotein E ε4 (ApoE4) mice. For drainage of Aβ to occur in a direction contrary to the pulse wave, some form of attachment to basement membrane would be required to prevent reflux of Aβ back into the brain during the passage of the subsequent pulse wave. In this study, we show first that apolipoprotein E co-localizes with Aβ in basement membrane drainage pathways in the walls of arteries. Secondly, we show by Atomic Force Microscopy that attachment of ApoE4/Aβ complexes to basement membrane laminin is significantly weaker than ApoE3/Aβ complexes. These results suggest that perivascular elimination of ApoE4/Aβ complexes would be less efficient than with other isoforms of apolipoprotein E, thus endowing a higher risk for Alzheimer\u27s disease. Therapeutic correction for ApoE4/Aβ/laminin interactions may increase the efficiency of elimination of Aβ in the prevention of Alzheimer\u27s disease. © 2015 Elsevier B.V.Embargo Period 12 month

Transcutaneous anaesthetic nano-enabled hydrogels for eyelid surgery

Local anaesthetics are administered as a diffuse superficial slow injection in blepharoplasty. Current transcutaneous local anaesthetic formulations are not licensed for use on the face due to safety concerns. Here we report for the first time the permeation of local anaesthetics (lidocaine, bupivacaine loaded SNEDDS and their hydrogels) across human eyelid and mouse skin as a novel and ocular safe formulation for eyelid surgery. SNEDDS were loaded with high levels of anaesthetics and incorporated within carbomer hydrogels to yield nano-enabled gels. Lidocaine hydrogels have a significantly reduced lag time compared to EMLA, while they enhance lidocaine flux across human eyelid skin by 5.2 fold. Ex vivo tape stripping experiments indicated localisation of anaesthetics within the stratum corneum and dermis. Initial histopathological studies have shown no apparent signs of skin irritation. These results highlight the potential clinical capability of nano-enabled anaesthetic hydrogels as a non-invasive anaesthetic procedure for eyelid surgery

Intertidal Mediterranean coralline algae habitat is expecting a shift towards a reduced growth and a simplified associated fauna under climate change

Coralline algae represent the most important bioconstructors in the Mediterranean Sea and are currently impaired by the effects of climate change (CC), particularly by global warming and ocean acidification (OA). We studied the effects of these two drivers on Ellisolandia elongate, an intertidal coralline algae that is known to host a rich biodiversity of associated fauna. We cultured turfs of E. elongate in experimental conditions of increased temperature and OA (using the values of the IPCC scenario RCP- 8.5 expected for 2100: actual mean temperature +3 degrees C and pH = 7.78), and estimated alteration of algal linear growth and community structure, focusing especially on peracarid crustaceans and annelids. Our findings revealed a decrease in linear growth, yet with no significant changes on structural integrity, and a simplification of associated community, in particular for peracarids. Our study contributes to understand community-level response to CC drivers, highlighting the vulnerability of the fauna associated to an important Mediterranean marine habitat