Surface Nanomechanical Properties Research Articles

New Generation of Orthodontic Elastomeric Ligature to Prevent Enamel Demineralization In Vivo.

This study aimed to synthesize a novel elastomeric ligature with dimethylaminohexadecyl methacrylate (DMAHDM) grafted, providing a new strategy for improving the issue of enamel demineralization during fixed orthodontics. DMAHDM was incorporated into elastomeric ligatures at different mass fractions using ultraviolet photochemical grafting. The antibacterial properties were evaluated and the optimal DMAHDM amount was determined based on cytotoxicity assays. Moreover, tests were conducted to evaluate the in vivo changes in the mechanical properties of the elastomeric ligatures. To assess the actual in vivo effectiveness in preventing enamel demineralization, a rat demineralization model was established, with analyses focusing on changes in surface microstructure, elemental composition, and nanomechanical properties. Elastomeric ligatures with 2% DMAHDM showed excellent biocompatibility and the best antibacterial properties, reducing lactic acid production by 65.3% and biofilm bacteria by 50.0% within 24 h, without significant mechanical property differences from the control group (p > 0.05). Most importantly, they effectively prevented enamel demineralization in vivo, enhancing elastic modulus by 73.2% and hardness by 204.8%. Elastomeric ligatures incorporating DMAHDM have shown great potential for application in preventing enamel demineralization, providing a new strategy to solve this issue during fixed orthodontics.

A Comparative Evaluation of Surface Hardness and Nanomechanical Properties of Nickel-Titanium Orthodontic Wires: An In Vitro Study.

The study aimed to evaluate the influence of various surface coatings (epoxy, Teflon, and rhodium) on the surface roughness (SR) and nanomechanical characteristics of nickel-titanium (NiTi) archwires. The study compared these coated archwires to uncoated ones from a single manufacturer, which served as a control. There were 15 rectangular samples of four distinct archwires measuring 0.17 × 0.25. These were ultrasonically treated with an alkaline solution at 60°C for 15 minutes before being rinsed with distilled water to remove precipitates. With an orthodontic soft wire cutter, the straight buccal sections of coated and uncoated archwires were cut into 20 mm lengths. A three-dimensional optical noncontact surface profilometer evaluated the surface. Profilometers use contact scanning white light interferometry. Using the Vision64 software (Bruker Corporation, San Jose, CA), the profilometer's nanolens atomic force microscopy module has a completely automated turret with programmed X, Y, and Z motions. Images were taken in five random locations. Five average measurements matched specimen SR. A nanoindenter with a Berkovich diamond indenter measured nanohardness (NH) and elastic modulus (EM). The experimental results were analyzed using the Statistical Package for the Social Sciences software version 26.0 (SPSS Inc., Chicago, IL). To examine mean differences at 5% significance, analysis of variance and Tukey's post hoc test were applied for SR, NH, and EM. Wires coated with epoxy had the highest SR (1.499 ± 0.082), followed by Teflon (0.811 ± 0.023) and rhodium (0.308 ± 0.024). The SR of the control group was 0.289 ± 0.027. Significant differences in SR were found (p < 0.0001). Except for the comparison between rhodium and the control group (p = 0.684), all intergroup comparisons of SR showed significant differences (p < 0.0001). The rhodium-coated wires exhibited the highest NH (0.185 ± 0.014), and the epoxy group had the lowest (0.147 ± 0.017). Variations in NH were significant between the study groups (p < 0.0001). The epoxy, Teflon, and rhodium groups showed significant differences against the control group (p < 0.0001) in intergroup comparisons for NH. The Teflon group had the highest EM (5.367 ± 0.379), and the epoxy group had the lowest (5.012 ± 0.498). The EM of the control group was 56.946 ± 0.737. Results indicate considerable EM changes between the groups (p < 0.05). Comparisons between experimental and control groups showed significant differences (p < 0.0001). The study's findings indicate that the SR of rhodium-coated archwires is substantially comparable to that of uncoated archwires. However, Teflon-, rhodium-, and epoxy-coated archwires had significantly different NH and EM compared to uncoated ones. Further, uncoated archwires have higher NH and EM.

Atomic force microscopy correlates mechanical and electrical properties of HepG2 cells with curcumin concentration

Hepatocellular carcinoma (HCC) is a highly prevalent cancer with a significant impact on human health. Curcumin, a natural compound, induces cytoskeletal changes in liver cancer cells and modifies the distribution of lipids, proteins, and polysaccharides on plasma membranes, affecting their mechanical and electrical properties. In this study, we used nanomechanical indentation techniques and Kelvin probe force microscopy (KPFM) based on atomic force microscopy (AFM) to investigate the changes in surface nanomechanical and electrical properties of nuclear and cytoplasmic regions of HepG2 cells in response to increasing curcumin concentrations. CCK-8 assays and flow cytometry results demonstrated time- and concentration-dependent inhibition of HepG2 cell proliferation by curcumin. Increasing curcumin concentration led to an initial increase and then decrease in the mechanical properties of nuclear and cytoplasmic regions of HepG2 cells, represented by the Young's modulus (E), as observed through nanoindentation. KPFM measurements indicated decreasing trends in both cell surface potential and height. Fluorescence microscopy results indicated a positive correlation between curcumin concentration and phosphatidylserine translocation from the inner to the outer membrane, which influenced the electrical properties of HepG2 cells. This study provides valuable insights into curcumin's mechanisms against cancer cells and aids nanoscale evaluation of therapeutic efficacy and drug screening.

Chemical and mechanochemical degradations of ultrafast laser surface structured Ti6Al4V in simulated body fluid environment

In the present study, the effect of ultrafast laser surface structuring of Ti6Al4V (using a Ti: Sapphire laser with a pulse duration of 100 fs and 3000 fs) on its surface topography, nanomechanical properties, tribocorrosion property, and bioactivity has been undertaken. Surface structuring leads to defect-free periodic surface structures with shockwave-induced compressive residual stresses and grain refinement (subgrain size of 5.2 µm) as compared to as received Ti6Al4V (26 µm). There is a significant enhancement in nano hardness (5600–5800 MPa) and Young's modulus (139 – 148 GPa) as compared to as received Ti6Al4V ((nano hardness of 3800 MPa), (Young's modulus of 117 GPa)) due to laser surface structuring. The tribocorrosion kinetics were significantly reduced in laser surface structured Ti6Al4V as compared to as received one. The individual influence of tribocorrosion property was established. A detailed microstructural study and immersion studies showed the presence of a higher fraction of calcium phosphate deposition in surface-structured samples (0.0432–0.0461 mg/cm2 after 7 days) as compared to as received Ti6Al4V (0.018 mg/cm2 after 7 days). The presence of hydroxyapatite has been confirmed by X-ray photoelectron spectroscopic analysis.

Nanomechanical surface properties of co-sputtered thin film polymorphic metallic glasses based on Ti-Fe-Cu, Zr-Fe-Al, and Zr-W-Cu

Metallic glasses are amorphous materials that have shown prospects in several applications including biomedical due to their superior and unique mechanical, tribological, and bioactive properties. New functional coatings of thin film polymorphic metallic glasses (Ti-Fe-Cu, Zr-Fe-Al, and Zr-W-Cu) were deposited by co-sputtering of constituents from high purity (99.9%) targets. The thin film metallic glasses were deposited on stainless steel 316 L (SS316L) and titanium alloy (Ti) substrates. Co-sputtering offers tuneable parameters (pressure, power, and time), which fosters high-quality polymorphic films of desired thickness and composition. Surface and nanomechanical properties of the films, including surface morphology, structure, mechanical, and tribological properties were investigated using SEM, AFM, XRD, XPS, nanoindentation, and scratch test. The coated substrates exhibit uniform nanostructured films with surface roughness in the range of 1.5 to 7 nm. The XRD spectra show a dominant amorphous glassy polymorphic feature on both substrates with crystallites size in the range of 65–108 nm. Nanomechanical characteristics of the films suggest high wear resistance with film adhesion strength ranging between 624 - 2159 µN and 2273 - 2978 µN on SS316L and Ti substrates, respectively. Overall, these polymorphic Ti-Fe-Cu, Zr-Fe-Al, and Zr-W-Cu nanostructured uniform films with low surface roughness and high adhesion on SS316L and Ti substrates are potential functional surfaces for biomedical applications.

Cannabidiol-Loaded Extracellular Vesicles from Human Umbilical Cord Mesenchymal Stem Cells Alleviate Paclitaxel-Induced Peripheral Neuropathy.

In cancer patients, chronic paclitaxel (PTX) treatment causes excruciating pain, limiting its use in cancer chemotherapy. The neuroprotective potential of synthetic cannabidiol (CBD) and CBD formulated in extracellular vesicles (CBD-EVs) isolated from human umbilical cord derived mesenchymal stem cells was investigated in C57BL/6J mice with PTX-induced neuropathic pain (PIPN). The particle size of EVs and CBD-EVs, surface roughness, nanomechanical properties, stability, and release studies were all investigated. To develop neuropathy in mice, PTX (8 mg/kg, i.p.) was administered every other day (four doses). In terms of decreasing mechanical and thermal hypersensitivity, CBD-EVs treatment was superior to EVs treatment or CBD treatment alone (p < 0.001). CBD and CBD-EVs significantly reduced mitochondrial dysfunction in dorsal root ganglions and spinal homogenates of PTX-treated animals by modulating the AMPK pathway (p < 0.001). Studies inhibiting the AMPK and 5HT1A receptors found that CBD did not influence the neurobehavioral or mitochondrial function of PIPN. Based on these results, we hypothesize that CBD and CBD-EVs mitigated PIPN by modulating AMPK and mitochondrial function.

In situ nanomechanical characterization of hydrogen effects on nickel-based alloy 725 under different metallurgical conditions

• In-situ nanoindentation test was used to study the H effect on alloy 725 • Both solution-annealed and precipitation-hardened alloy 725 were tested • H effect on surface integrity and nanomechanical properties were studied in detail • Different H behaviors were compared based on H content and microstructure The effect of hydrogen on the surface morphology and nanomechanical properties of Ni-based Alloy 725 under solution-annealed (SA) and precipitation-hardened (API) conditions was thoroughly studied. The investigation involved in situ nanoindentation testing, microscopy characterization, statistical analysis, and numerical simulation approaches. The results showed the distinctive effects of hydrogen on the pop-in and hardness in the SA and API samples. For the SA sample, hydrogen mainly dissolved as solid solute in the matrix, causing enhanced lattice friction on the dislocation motion and increasing the internal stress via lattice expansion. Thus, an enhanced hardness, a reduced pop-in width/load ratio, and numerous surface steps were detected in the presence of hydrogen. For the API sample, the strengthening γ’’ phases were the stress concentrators, and the dislocations nucleated heterogeneously, demonstrating indistinctive pop-in phenomena. Furthermore, the precipitates in the API sample affected the trapping behavior of hydrogen, thereby resulting in the hardness change, which reflected the competition between solution hardening in the matrix and vacancy softening mechanism in precipitates.

Experimental investigation into the evolution of microstructure and nanomechanical characterization of electric discharge deposited surface layers on Ti64

In the current study, Ti64′s surface has been transformed by electric discharge machining, and its microstructure, surface crack density, layer composition, and nanomechanical properties are examined, as well as the effects of peak current and pulse on time. The studies were carried out using a two-factor, three-level full factorial design. On the deposited layer, OM, XRD, EDS, SEM, and nanoindentation tests were performed. According to the variation in the process parameters, it was discovered that the deposited layer is not uniform and has a thickness range of 45–182 μm. Additionally, it has a dual microstructure that is both equiaxed and dendritic. Carbon deposition (up to 70% by weight), andcarbide formationwere all found to increase with parameter values. It is discovered that the layer's hardness is twice (718HV) as compared tothe basematerial. Additionally, a minor modification in reduced modulus has been noted. SCD and crack width were discovered to be rising as parameter level rose.

A 3D surface nanomechanical property mapping method with a magnetic-drive orthogonal cantilever probe.

Traditional force-distance curve based atomic force microscopy (FD-AFM) is limited to two-dimensional (2D) surface characterization, making the in situ mapping of three-dimensional (3D) surface nanomechanical properties (SNMP) challenging. This paper presents a multimode 3D FD-AFM based on a magnetic-drive orthogonal cantilever probe (MD-OCP) that can achieve SNMP imaging of 3D micro-nano structures with surface contour fluctuations reaching or exceeding several microns. Bending, torsion and vector tracking modes are integrated into this method for a 2D horizontal surface, 2D sidewall, and 3D surface mapping, respectively. The MD-OCP consists of a horizontal cantilever, a vertical cantilever with a protruding tip, and a magnetized bead. It can be utilized in the detection of deep trench and dense microarray units. The force analysis during 3D SNMP measurement is performed through mathematical derivation, which shows a clear relationship between effective indentation force, friction, and total tip-sample interactions. Single-point SNMP evaluation, discrete 2D SNMP imaging, and continuous omnidirectional 3D SNMP mapping of a 3D microarray unit verify the accurate and comprehensive measurement abilities of the reported method in its bending, torsion, and vector tracking modes. The experimental results demonstrate that this method can achieve excellent 3D quantitative characterization of topography and SNMP, including critical dimensions, adhesion, Young's modulus, stiffness, and energy dissipation, along a 3D device surface. This novel 3D FD-AFM technique has many potential applications in the further exploration of 3D micro-nano devices.

Probing maltodextrins surface properties by atomic force microscopy: Interplay of glass transition and reconstitution properties

Reconstitution kinetics of three maltodextrins powders with different dextrose-equivalent (DE) values (low, intermediate, high DE) were evaluated under the glassy and rubbery states. Reconstitution times were found mostly shear rate of agitation in water and DE dependent in the glassy state, with shorter reconstitution times for high shear rates and DE. For powders under the rubbery state, reconstitution times were less shear rate dependent, especially for high DE values. To have a better understanding of powder surface features that can impact reconstitution properties, single particles surface topographies and nanomechanical properties were probed by Atomic Force Microscopy (AFM). It was shown that surface roughness was higher for high DE maltodextrins under the glassy state, whereas a surface smoothing and slight hollows formation was observed for all powders under the rubbery state. Also, a significant reduction and uniformity of Young modulus at the particle surface were observed under the rubbery state. Finally, surface modification at microscale (smoothing and softening) was linked to powder behavior evolution at macroscale (relative shear rate independence during reconstitution) when the powder crosses the glass transition. • Glass transition significantly impacted maltodextrin reconstitution properties. • Surface topographies revealed surface smoothing above glass transition. • Surface nanoscale hollow formation was observed at the rubbery state. • Young modulus decreased significantly at the rubbery state.

Thickness-dependent physical and nanomechanical properties of [formula omitted] thin films

A set of undoped AlxGa1−xN epilayers with different thicknesses were grown on (0001) sapphire substrates using metal-organic chemical vapor deposition (MOCVD) technique, using the same gas-phase composition of trimethylaluminum (TMAl) and trimethylgallium (TMGa). Giving that the first growth stage is crucial for the successful fabrication of AlxGa1-xN epilayers; thus, SiN nano-mask, as an alternative method to nanoimprint lithography (NIL) which is used for patterning substrates, was deposited on sapphire substrate. Indeed, SiN treatment initiates the three-dimensional (3D) growth mode to efficiently decrease the threading dislocation density. It was found that depending on the film surface coalescence degree, the physical and nanomechanical properties are thoroughly dependent. As the non-coalescent surface is present, the porosity effects are dominant. As soon as the film thickness attains the surface coalescence, the Al incorporation is enhanced and convoyed with it point defects. Despite the decrease of the threading dislocations along with the film thickness evolution, it was observed that the physical properties are slightly decreased and the nanomechanical properties are improved. This is likely related to point defect interaction with nucleated dislocations. Moreover, the defects did not severally affect the plastic deformation capacity (ductility) of AlxGa1-xN films, where high indentation force was applied and no failure was revealed. Therefore, the balance between AlxGa1−xN physical and nanomechanical performances devotes to manufacture a wider range of efficient UV devices.

Quantitative effect of seawater on the hydration kinetics and microstructure development of Ultra High Performance Concrete (UHPC)

This paper aims at quantitatively investigating the effect of seawater on the hydration kinetics and microstructure development of Ultra-High Performance Concrete (UHPC). Specifically, the macroscopic properties of UHPC mixed with seawater are tested, including fresh behaviors, mechanical properties and autogenous shrinkage. In addition, hydration products, hydration heat and hydration degree of UHPC made with seawater are quantitatively evaluated. Finally, the influences of seawater on the surface morphology, nano-mechanical properties and pore structure of UHPC are analyzed. The obtained results uncover that the incorporation of seawater can dramatically decrease the flowability, enhance the flexural and compressive strengths, as well as deteriorate the autogenous shrinkage of UHPC. Moreover, with the addition of seawater, the hydration degree can be increased by 4.67%, not only by consuming more cementitious materials to generate more hydration products (about 12.25%), but also by enhancing the mean chain length of C-S-H gels from 3.5068 to 4.1595 and increasing Q2/Q1 from 0.7533 to 1.0796 to improve the polymerization of hydration products. Additionally, the incorporation of seawater can contribute to a dense microstructure of UHPC by enhancing indentation modulus and hardness of paste by approximately 25.25% and 29.10%, optimizing the ITZ by about 15 mm, as well as refining pore size and reducing the porosity by more than 8%.

Surface-Modified and Unmodified Calcite: Effects of Water and Saturated Aqueous Octanoic Acid Droplets on Stability and Saturated Fatty Acid Layer Organization.

A profound understanding of the properties of unmodified and saturated fatty acid-modified calcite surfaces is essential for elucidating their resistance and stability in the presence of water droplets. Additional insights can be obtained by also studying the effects of carboxylic acid-saturated aqueous solutions. We elucidate surface wettability, structure, and nanomechanical properties beneath and at the edge of a deposited droplet after its evaporation. When calcite was coated by a highly packed monolayer of stearic acid, a hydrophilic region was found at the three-phase contact line. In atomic force microscopy mapping, this region is characterized by low adhesion and a topographical hillock. The surface that previously was covered by the droplet demonstrated a patchy structure of about 6 nm height, implying stearic acid reorganization into a patchy bilayer-like structure. Our data suggest that during droplet reverse dispensing and droplet evaporation, pinning of the three-phase contact line leads to the transport of dissolved fatty carboxylic acid and possibly calcium bicarbonate Ca(HCO3)2 molecules to the contact line boundary. Compared to the surface of intrinsically hydrophobic materials, such as polystyrene, the changes in contact angle and base diameter during droplet evaporation on stearic acid-modified calcite are strikingly different. This difference is due to stearic acid reorganization on the surface and transport to the water–air interface of the droplet. An effect of the evaporating droplet is also observed on unmodified calcite due to dissolution and recrystallization of the calcite surface in the presence of water. In the case where a water droplet saturated with octanoic acid is used instead of water, the stearic acid-coated calcite remains considerably more stable. Our findings are discussed in terms of the coffee-ring effect.

Heads or tails: Nanostructure and molecular orientations in organised erucamide surface layers

HypothesisDespite the widespread industrial usage of erucamide as a slip additive to modify polymer surface properties, a controversy appears to have persisted regarding the nanostructure of erucamide surface layers, particularly the molecular orientation at the outermost layer. The erucamide nanostructure and molecular orientation, along with its surface coverage, hydrophobicity, and adhesive response, can be tuned by simply varying the erucamide concentration in the solution from which the spin coated layer is prepared. ExperimentsSynchrotron X-ray reflectivity (XRR) allowed a comprehensive characterisation of the out-of-plane structural parameters (e.g. molecular packing and thickness) of the erucamide layers prepared via spin coating from nonaqueous solution on silica. Complementary Atomic Force Microscopy (AFM) imaging with high lateral resolution revealed localised in-plane structures. Contact angle measurements provided information on the wettability of erucamide-coated surfaces. Peak Force Quantitative Nanomechanical Mapping (QNM) allowed a correlation between the erucamide nanostructure with the surface nanomechanical properties (i.e. adhesive response). FindingsOur results reveal erucamide surface nanostructures on silica as patchy monolayers, isolated circular bilayers/rounded rectangle-like aggregates and overlapping plate-like multilayers as the erucamide concentration in the spin coating solution was varied. In all the cases, XRR and AFM results were consistent with the picture that the erucamide tails were oriented outwards. The QNM adhesion force mapping of all the observed morphologies also supported this molecular orientation at the outermost erucamide monolayer. The wettability study further confirmed this conclusion with the observed increase in the surface hydrophobicity and coverage upon increasing erucamide concentration, with the macroscopic water contact angle θ = 92.9° ± 2.9° at the highest erucamide concentration of 2 wt%.

Sustainable eco-friendly bricks from slate tailings through geopolymerization: synthesis and characterization analysis

With the objective of decreasing the adverse impact on the environment and recycling the waste of tailings, the possibility of producing eco-friendly building materials by utilizing the slate tailings (ST) was investigated. Besides ST, the fly ash (FA) and metakaolin (MK) mixtures were added to the raw materials through geopolymerization to improve the brick quality. The mechanical performance of the geopolymer brick was characterized by unconfined compression tests, and the physical properties, microstructure and geopolymerization processes were evaluated using X-ray diffraction (XRD), Scanning electron microscope (SEM) and Fourier transform infrared spectroscopy (FTIR). The results show that at different ST contents, the variations of the compressive strength are attributed to the coupling effects of pore filling and geopolymer gelation. Higher alkaline activator/solid ratio and extended curing time generally lead to higher strength and bulk density while reduce the water absorption rate. Atomic force microscopy (AFM) was utilized to offer detailed information of geopolymer gels at higher resolutions for obtaining both surface morphology and nano-mechanical properties. The optimum conditions are found to be that the ST is 50%, alkali content and forming days are respectively 14% and 28 days. Under these conditions, the compressive strength and water absorption of the brick samples are 20.47 MPa and 13.4%, respectively, and the other physical properties meet the Chinese Non-sintered Waste Tailing Brick Standard (JC/T 422-2007).

In-Situ Investigation on Nanoscopic Biomechanics of Streptococcus mutans at Low pH Citric Acid Environments Using an AFM Fluid Cell.

Streptococcus mutans (S. mutans) is widely regarded as the main cause of human dental caries via three main virulence factors: adhesion, acidogenicity, and aciduricity. Citric acid is one of the antibiotic agents that can inhibit the virulence capabilities of S. mutans. A full understanding of the acidic resistance mechanisms (ARMs) causing bacteria to thrive in citrate transport is still elusive. We propose atomic force microscopy (AFM) equipped with a fluid cell to study the S. mutans ARMs via surface nanomechanical properties at citric acid pH 3.3, 2.3, and 1.8. Among these treatments, at pH 1.8, the effect of the citric acid shock in cells is demonstrated through a significantly low number of high adhesion zones, and a noticeable reduction in adhesion forces. Consequently, this study paves the way to understand that S. mutans ARMs are associated with the variation of the number of adhesion zones on the cell surface, which is influenced by citrate and proton transport. The results are expected to be useful in developing antibiotics or drugs involving citric acid for dental plaque treatment.

Choline Supplementation Sensitizes Legionella dumoffii to Galleria mellonella Apolipophorin III.

The growth of Legionella dumoffii can be inhibited by Galleria mellonella apolipophorin III (apoLp-III) which is an insect homologue of human apolipoprotein E., and choline-cultured L. dumoffii cells are considerably more susceptible to apoLp-III than bacteria grown without choline supplementation. In the present study, the interactions of apoLp-III with intact L. dumoffii cells cultured without and with exogenous choline were analyzed to explain the basis of this difference. Fluorescently labeled apoLp-III (FITC-apoLp-III) bound more efficiently to choline-grown L. dumoffii, as revealed by laser scanning confocal microscopy. The cell envelope of these bacteria was penetrated more deeply by FITC-apoLp-III, as demonstrated by fluorescence lifetime imaging microscopy analyses. The increased susceptibility of the choline-cultured L. dumoffii to apoLp-III was also accompanied by alterations in the cell surface topography and nanomechanical properties. A detailed analysis of the interaction of apoLp-III with components of the L. dumoffii cells was carried out using both purified lipopolysaccharide (LPS) and liposomes composed of L. dumoffii phospholipids and LPS. A single micelle of L. dumoffii LPS was formed from 12 to 29 monomeric LPS molecules and one L. dumoffii LPS micelle bound two molecules of apoLp-III. ApoLp-III exhibited the strongest interactions with liposomes with incorporated LPS formed of phospholipids isolated from bacteria cultured on exogenous choline. These results indicated that the differences in the phospholipid content in the cell membrane, especially PC, and LPS affected the interactions of apoLp-III with bacterial cells and suggested that these differences contributed to the increased susceptibility of the choline-cultured L. dumoffii to G. mellonella apoLp-III.

Effects of Micro-Arc Oxidation Process Parameters on Characteristics of Calcium-Phosphate Containing Oxide Layers on the Selective Laser Melted Ti13Zr13Nb Alloy

Titania-based films on selective laser melted Ti13Zr13Nb have been formed by micro-arc oxidation (MAO) at different process parameters (voltage, current, processing time) in order to evaluate the impact of MAO process parameters in calcium and phosphate (Ca + P) containing electrolyte on surface characteristic, early-stage bioactivity, nanomechanical properties, and adhesion between the oxide coatings and substrate. The surface topography, surface roughness, pore diameter, elemental composition, crystal structure, surface wettability, and the early stage-bioactivity in Hank’s solution were evaluated for all coatings. Hardness, maximum indent depth, Young’s modulus, and Ecoating/Esubstrate, H/E, H3/E2 ratios were determined in the case of nanomechanical evaluation while the MAO coating adhesion properties were estimated by the scratch test. The study indicated that the most important parameter of MAO process influencing the coating characteristic is voltage. Due to the good ratio of structural and nanomechanical properties of the coatings, the optimal conditions of MAO process were found at 300 V during 15 min, at 32 mA or 50 mA of current, which resulted in the predictable structure, high Ca/P ratio, high hydrophilicity, the highest demonstrated early-stage bioactivity, better nanomechanical properties, the elastic modulus and hardness well close to the values characteristic for bones, as compared to specimens treated at a lower voltage (200 V) and uncoated substrate, as well as a higher critical load of adhesion and total delamination.

Influence of several biodegradable components added to pure and nanosilver-doped PMMA bone cements on its biological and mechanical properties.

Acrylic bone cements (BC) are wildly used in medicine. Despite favorable mechanical properties, processability and inject capability, BC lack bioactivity. To overcome this, we investigated the effects of selected biodegradable additives to create a partially-degradable BC and also we evaluated its combination with nanosilver (AgNp). We hypothesized that using above strategies it would be possible to obtain bioactive BC. The Cemex was used as the base material, modified at 2.5, 5 or 10wt% with either cellulose, chitosan, magnesium, polydioxanone or tricalcium-phosphate. The resulted modified BC was examined for surface morphology, wettability, porosity, mechanical and nanomechanical properties and cytocompatibility. The composite BC doped with AgNp was also examined for its release and antibacterial properties. The results showed that it is possible to create modified cement and all studied modifiers increased its porosity. Applying the additives slightly decreased BC wettability and mechanical properties, but the positive effect of the additives was observed in nanomechanical research. The relatively poor cytocompatibility of modified BC was attributed to the unreacted monomer release, except for polydioxanone modification which increased cells viability. Furthermore, all additives facilitated AgNp release and increased BC antibacterial effectiveness. Our present studies suggest the optimal content of biodegradable component for BC is 5wt%. At this content, an improvement in BC porosity is achieved without significant deterioration of BC physical and mechanical properties. Polydioxanone and cellulose seem to be the most promising additives that improve porosity and antibacterial properties of antibiotic or nanosilver-loaded BC. Partially-degradable BC may be a good strategy to improve their antibacterial effectiveness, but some caution is still required regarding their cytocompatibility. STATEMENT OF SIGNIFICANCE: The lack of bone cement bioactivity is the main limitation of its effectiveness in medicine. To overcome this, we have created composite cements with partially-degradable properties. We also modified these cements with nanosilver to provide antibacterial properties. We examined five various additives at three different contents to modify a selected bone cement. Our results broaden the knowledge about potential modifiers and properties of composite cements. We selected the optimal content and the most promising additives, and showed that the combination of these additives with nanosilver would increase cements` antibacterial effectiveness. Such modified cements may be a new solution for medical applications.

Evaluating the Effect of Azole Antifungal Agents on the Stress Response and Nanomechanical Surface Properties of Ochrobactrum anthropi Aspcl2.2.

Azole antifungal molecules are broadly used as active ingredients in various products, such as pharmaceuticals and pesticides. This promotes their release into the natural environment. The detailed mechanism of their influence on the biotic components of natural ecosystems remains unexplored. Our research aimed to examine the response of Ochrobactrum anthropi AspCl2.2 to the presence of four azole antifungal agents (clotrimazole, fluconazole, climbazole, epoxiconazole). The experiments performed include analysis of the cell metabolic activity, cell membrane permeability, total glutathione level and activity of glutathione S-transferases. These studies allowed for the evaluation of the cells’ oxidative stress response to the presence of azole antifungals. Moreover, changes in the nanomechanical surface properties, including adhesive and elastic features of the cells, were investigated using atomic force microscopy (AFM) and spectrophotometric methods. The results indicate that the azoles promote bacterial oxidative stress. The strongest differences were noted for the cells cultivated with fluconazole. The least toxic effect has been attributed to climbazole. AFM observations unraveled molecular details of bacterial cell texture, structure and surface nanomechanical properties. Antifungals promote the nanoscale modification of the bacterial cell wall. The results presented provided a significant insight into the strategies used by environmental bacterial cells to survive exposures to toxic azole antifungal agents.