Hasil untuk "Microscopy"

D. Faria, S. Silva, M. D. Oliveira

J. M. Kemp, T. Powell

Miki Kajihara, Hiroto Suzuki, Tatsuya Amamiya et al.

Molybdenum disulfide (MoS2) is widely used as a solid lubricant, owing to its layered crystalline structure. However, for tribological performance, the stable bonding of solid lubricants to metallic substrates remains a critical issue. In conventional methods, solid lubricants dispersed in grease are sprayed and deposited onto the substrate surface. However, the lubricant layer may delaminate and disappear during frictional contact. Here, we employ laser-induced particle impact testing (LIPIT), which ejects micro-sized particles at high velocities via laser ablation. Particle impact with high velocity induces severe plastic deformation, forming deep micro-dimples that can retain lubricants and improve tribological performance. We propose a two-step LIPIT: the first step deposits and bonds MoS2 particles and the second step generates micro-dimple structures through the impact of hard particles. The treated surface is characterized using energy-dispersive X-ray spectroscopy, focused ion-beam analysis, and transmission electron microscopy, revealing that the MoS2 is strongly bonded at the crater center (lowest depth). Frictional tests with ball-on-disk contact sliding indicate that micro-dimples with adhered MoS2 created by LIPIT function as lubricant reservoirs and significantly improve tribological performance. The results show that our proposed LIPIT-treated surfaces exhibit both a reduced friction coefficient and enhanced resistance to seizure.

Martyna Zemlik, Beata Białobrzeska, Mateusz Stachowicz et al.

As a result of welding processes in boron-alloyed martensitic armor steels, unfavorable microstructural changes occur, leading to a significant reduction in the mechanical properties of both the weld metal and the base material. The dendritic structure of the weld metal and the partial tempering in the heat-affected zone contribute to the decreased durability of structural components, thereby deteriorating their performance. This issue is particularly important since such steels are widely used not only in the defense industry but also in the mining, construction, transportation, and metallurgical sectors, where they operate under conditions of intensive abrasive wear. For this reason, the authors attempted to improve the mechanical properties of welded joints of boron-alloyed martensitic armor steel (with a nominal hardness of 500 HBW) through post-weld heat treatment. The welded joint was evaluated based on metallographic examinations using light microscopy and scanning electron microscopy, as well as abrasive wear tests carried out on a T-07 tribotester. The conducted investigations demonstrated that, under loose abrasive conditions (using electrofused alumina), heat treatment increased the wear resistance of the joints by 55% compared to the as-welded condition. The obtained results were compared with selected grades of Hardox steel commonly used in industrial applications.

Yongtao Su, Yongtao Su, Xianwei Zhu et al.

Titanium dioxide nanoparticles (TiO2NPs) are widely synthesized chemically for industrial applications. However, these methods often have negative environmental impacts, rendering them unsuitable for biomedical applications. Green synthesis approaches offer a promising alternative due to their simplicity, environmental friendliness, and cost-effectiveness. In this study, we report the biosynthesis of TiO2NPs using Morus alba leaf extract and their subsequent incorporation into a gellan gum (GG) biopolymer to create a hydrogel. The physicochemical properties of the biosynthesized TiO2NPs and the TiO2NP@GG hydrogel were characterized using Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and X-ray photoelectron spectroscopy (XPS). Furthermore, the bioactivity of the materials was investigated through antibacterial assays against Staphylococcus aureus and Escherichia coli, as well as in vitro wound healing studies using a 3T3 fibroblast scratch assay. XRD analysis confirmed the successful formation of anatase phase TiO2. SEM images revealed the presence of irregular and rod-shaped TiO2 nanoparticles, with EDS analysis confirming their composition of oxygen and titanium. The particle size was determined to be 80–90 nm, and the nanoparticles exhibited homogeneous distribution throughout the gellan gum biopolymer network. The TiO2NP@GG hydrogel displayed significant antibacterial activity against both S. aureus and E. coli. In vitro wound healing studies using a scratch assay on 3T3 fibroblast cells seeded onto the hydrogel demonstrated a high cell survival rate and enhanced cell migration, suggesting potential for biomedical applications as a wound dressing material.

Takehiro Ohkami, Ichika Kitashin, Riko Kawashima et al.

Coronavirus non-structural protein 1 (nsp1) is a pathogenic determinant of <i>Betacoronaviruses</i>. Previous studies demonstrated that the nsp1 of various coronaviruses induces host shutoff through a variety of mechanisms; however, there is little information on the function of bovine coronavirus (BCoV) nsp1. We aimed to characterize the host gene expression suppression function of BCoV nsp1. We first confirmed that the expression of BCoV nsp1 in MAC-T cells, a bovine mammary epithelial cell line, suppressed host and reporter gene expression. Subsequently, lysine and phenylalanine at amino acid positions 232 and 233, respectively, were identified as key residues required for this suppressive effect. Expression levels of housekeeping genes are comparable in cells expressing wild-type BCoV nsp1 and a mutant with alanine substitutions at positions 232 and 233 (BCoV nsp1-KF). Wild-type BCoV nsp1 localized to both the cytoplasm and nucleus; however, BCoV nsp1-KF exhibited prominent nuclear accumulation with dot-like structures. Using confocal microscopy and co-sedimentation analysis, we identified an association between wild-type BCoV nsp1, but not BCoV nsp1-KF, and ribosomes, suggesting that ribosome binding is required for BCoV nsp1-mediated suppression of host gene expression. This is the first study of the characterization of host gene expression suppression by BCoV nsp1.

Chanhee Park, Joonho Lee, Woo-Sang Jung

This study investigated the microstructural evolution of the γ′′, γ′, and δ phases during creep for alloy 718. Creep tests on two-step aged samples were conducted under different stresses and temperatures ranging from 600 to 700 °C. Analysis of precipitates was performed on two-step aged and crept samples using scanning electron microscopy and transmission electron microscopy. The creep rupture lives were decreased with increasing stresses and temperatures and showed a linear correlation between experimental data and Larson-Miller parameter curve predictions. The γ′′ phase was formed as a disc shape in the grain interior and had an orientation relationship of (001)γ′′//{001}γ and [100]γ′′//<100>γ with γ matrix. The length of the γ′′ phases increased with increasing temperatures and creep exposure time. The activation energy for γ′′ lengthening was 323 kJ/mol, similar to that for lattice diffusion of Nb in Ni. It was found that the formation mechanisms of δ phase were different from temperatures. The δ phase was formed in grain interiors and grain boundaries and had a blocky shape during a sub-δ solvus annealing process. On the other hand, the δ phase was formed as a plate shape and had an orientation relationship of (010)δ//(111¯)γ and [102]δ//[011]γ with γ matrix at creep temperatures. The growth rates of plate δ phase were faster than blocky δ phase at all creep temperatures.

CHEN Yunhua, LI Di, ZHAO Xiaoyan, CHEN Ming, LI Hongling, ZHAO Chunhua

Objective To investigate the role of a novel human-specific long noncoding RNA (lncRNA), MEK6-AS1, and its potential molecular mechanism in improving the osteogenic differentiation of senescent mesenchymal stem cells (MSCs). Methods An in vitro human MSCs replicative senescence model was established by sequential passaging, and then senescence was identified by β staining and senescence-related gene expression. RT-qPCR was used to detect the expression of MEK6-AS1 during senescence and osteogenic differentiation of human MSCs (hMSCs); Lentiviral knockdown technology was used to regulate the expression of MEK6-AS1 in the MSCs replicative senescence model. Transcriptome sequencing technology was utilized to analyze the effects of MEK6-AS1 on the transcriptome of hMSCs especially on genes and pathways related to osteogenic differentiation. The effect of MEK6-AS1 as an intervention target at osteogenic differentiation of human senescent hMSCs was evaluated with alkaline phosphatase staining microscopy. PCR technology was used to detect osteogenic gene expression levels in cells. Results With aging process, the osteogenic differentiation ability of hMSCs decreased significantly while the expression level of MEK6-AS1 was enhanced(P＜0.000 1). Knockdown of MEK6-AS1 significantly enhanced the osteogenic differentiation of MSCs by the up-regulating expression of osteogenic markers and increasing mineralization capacity(P＜0.001). Conclusions Knockdown of human-specific lncRNA MEK6-AS1 improves osteogenic differentiation of senescent MSCs, providing a new target and theoretical basis for the treatment of senescence-associated osteoporosis.

Fien De Witte, Ivana A. Penagos, Davy Van de Walle et al.

Palm oil (PO), a semi-solid fat at room temperature, is a popular food ingredient. To steer the fat functionality, sucrose esters (SEs) are often used as food additives. Many SEs exist, varying in their hydrophilic-to-lipophilic balance (HLB), making them suitable for various food and non-food applications. In this study, a stearic–palmitic sucrose ester with a moderate HLB (6) was studied. It was found that the SE exhibited a complex thermal behavior consistent with smectic liquid crystals (type A). Small-angle X-ray scattering revealed that the mono- and poly-esters of the SE have different packings, more specifically, double and single chain-length packing. The polymorphism encountered upon crystallization was repeatable during successive heating and cooling cycles. After studying the pure SE, it was added to palm oil, and the crystallization behavior of the mixture was compared to that of pure palm oil. The crystallization conditions were varied by applying cooling at 20 °C/min (fast) and 1 °C/min (slow) to 0 °C, 20 °C or 25 °C. The samples were followed for one hour of isothermal time. Differential scanning calorimetry (DSC) showed that nucleation and polymorphic transitions were accelerated. Wide-angle X-ray scattering (WAXS) unraveled that the α-to-β′ polymorphic transition remained present upon the addition of the SE. SAXS showed that the addition of the SE at 0.5 wt% did not significantly change the double chain-length packing of palm oil, but it decreased the domain size when cooling in a fast manner. Ultra-small-angle X-ray scattering (USAXS) revealed that the addition of the SE created smaller crystal nanoplatelets (CNPs). The microstructure of the fat crystal network was visualized by means of polarized light microscopy (PLM) and cryo-scanning electron microscopy (cryo-SEM). The addition of the SE created a finer and space-filling network without the visibility of separate floc structures.

Hazirah Pengiran, Jahangir Kamaldin, Leo Bey Fen et al.

The study investigates nonmodified kenaf cellulose nanofiber (CNF) physicochemical properties, loading capability, and its acute toxicity against Daphnia magna and Dania rerio concerning the dispersion stability behavior of the kenaf CNF as a potential larvicide nanocarrier. The physicochemical properties of kenaf CNF were characterized using field emission scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, specific surface area and porosity, and zeta potential. The loading capability was assessed using various water volumes, and the acute ecotoxicity was determined following the Organisation for Economic Cooperation and Development test guidelines Test no. 202 and Test no. 203, respectively. Kenaf CNF is a fibrous high aspect ratio nanomaterial comprising a negatively charged hydroxyl group with moderate particle stability and high loading capability. With high dispersion stability in the freshwater environment’s aquatic conditions, kenaf CNF did not cause abnormalities and mortality to the D. rerio and no acute immobilization against D. magna. The kenaf CNF could be a candidate to function as a larvicide nanocarrier with insignificant acute ecotoxicity. The EC50 and LC50 for D. magna and D. rerio were above 100 mg/L and classified as nonhazardous to the aquatic environment according to the Globally Harmonized System (GHS).

Bhaskar Jyoti Borah, Chi-Kuang Sun

Summary: A resonant-scanning multiphoton optical microscope (MPM) with a millimeter-scale field-of-view (FOV) often encounters a poor Nyquist figure-of-merit (NFOM), leading to an aliasing effect owing to limited effective voxel-sampling rate. In this protocol, we provide a design guideline to enable high-NFOM MPM imaging while simultaneously securing a large FOV/digital-resolution ratio and a fast resonant raster-scanning speed. We further provide a free version of our custom acquisition software to assist with a smooth and easy construction process.For complete details on the use and execution of this protocol, please refer to Borah et al. (2021).

Cut Rahmawati, Sri Aprilia, Taufiq Saidi et al.

In this study, Typha latifolia (Typha sp.) was investigated as a new raw material for the isolation of cellulose nanocrystals (CNCs) for future application in geopolymer cement. Cellulose was extracted from the stem fibers by carrying out alkali and bleaching treatments. CNCs were then isolated from the extracted cellulose using the acid hydrolysis method. The chemical composition of cellulose, hemicellulose, and lignin was 60.9%, 7.0%, and 5.7%, respectively. Transmission electron microscopy showed a reduction in particle size due to the loss of the amorphous portion of the Typha sp. fiber. Thermogravimetric analysis showed that CNCs in the acid hydrolysis treatment have good thermal stability at 240 °C which is higher than raw ones. Based on the characteristics of a Typha sp. CNCs, it can be concluded that CNCs have the potential to be used as a reinforcement in geopolymer cement.

Pradip Kumar Sukul, Puspendu Das, Gopal Lal Dhakar et al.

Herein, aggregation behaviors of melem or melamine in the presence of three symmetric carboxylic acids (1,3,5-tris(4-carboxyphenyl)benzene (TPCA), 1,3,5-benzene-tri-carboxylic acid (BTA) and 1,3,5-cyclohexane-tri-carboxylic acid (CHTA)) have been performed to check the influence of acid on the formation of aggregated structures which have been investigated by optical microscopy, FESEM, FTIR, XRD and viscoelastic properties have been explored with rheological studies. Interestingly, melem, that has limited solubility in aqueous medium, forms aggregation that leads to the formation of hydrogels with TPCA. More significantly, hydrogel is formed here by matching the size selectivity. Melem forms hydrogel with only large tricarboxylic acid, whereas melamine produces hydrogel with any kind of its counterpart from small to large tricarboxylic acid derivatives. Present investigations and results provide the strategy of design of organic self-assembled materials having two component systems.

Robert J. Hamers, R. Tromp, J. Demuth

Ștefania Adelina Milea, Oana Crăciunescu, Gabriela Râpeanu et al.

Significant quantities of onion are cultivated annually, such that industrial processing leads to an appreciable amount of by-products, estimated at around 500,000 tons. Onion skins are considered an important source of naturally occurring antioxidant compounds, particularly flavonoid compounds. Our study follows the development of a sustainable solution in order to manage the by-products of yellow onion skins by designing ingredients with multifunctional activities. A green solvent aqueous extraction of flavonoids was applied to obtain a safe, flavonoid-enriched extract, yielding a total flavonoid content of 50.21 ± 0.09 mg quercetin equivalent (QE)/g dry weight (DW), and an antioxidant activity of 250.81 ± 6.76 mM Trolox/g DW. Complex biopolymeric matrices consisting of whey protein isolates, whey protein hydrolysates, maltodextrin, and pectin were further dissolved in the flavonoid-enriched aqueous extract, followed by freeze-drying. Two powders were obtained, both showing satisfactory phytochemical content and good stability during storage. The application of confocal microscopy revealed that the microscopic structure of the powders have a distribution of the bioactive compounds within the biopolymeric matrices. The in vitro digestion suggested remarkable stability in the gastric tract and a flavonoid-controlled release in the intestinal phase. A significant compatibility range of up to 1 mg/mL for both powders was found, whereas concentrations between 10 and 250 µg/mL stimulated cell proliferation after 24 h of cultivation. The powders showed satisfactory thermal and pH stability, which favors their addition to different food matrices.

S. Nie, D. Chiu, R. Zare

L. Reimer

Jerica Sabotič, Jože Brzin, Jana Erjavec et al.

Ralstonia solanaceraum is the quarantine plant pathogenic bacterium that causes bacterial wilt in over 200 host plants, which include economically important crops such as potato, tomato, tobacco, banana, and ginger. Alternative biological methods of disease control that can be used in integrated pest management are extensively studied. In search of new proteins with antibacterial activity against R. solanacearum, we identified L-amino acid oxidases (LAOs) from fruiting bodies of Amanita phalloides (ApLAO) and Infundibulicybe geotropa (CgLAO). We describe an optimized isolation procedure for their biochemical characterization, and show that they are dimeric proteins with estimated monomer molecular masses of 72 and 66 kDa, respectively, with isoelectric point of pH 6.5. They have broad substrate specificities for hydrophobic and charged amino acids, with highest Km for L-Leu, and broad pH optima at pH 5 and pH 6, respectively. An enzyme with similar properties is also characterized from the mycelia of I. geotropa (CgmycLAO). Fractionated aqueous extracts of 15 species of mushrooms show that LAO activity against L-Leu correlates with antibacterial activity. We confirm that the LAO activities mediate the antibacterial actions of ApLAO, CgLAO, and CgmycLAO. Their antibacterial activities are greater against Gram-negative versus Gram-positive bacteria, with inhibition of growth rate, prolongation of lag-phase, and decreased endpoint biomass. In Gram-positive bacteria, they mainly prolong the lag phase. These in vitro antibacterial activities of CgLAO and CgmycLAO are confirmed in vivo in tomato plants, while ApLAO has no effect on disease progression in planta. Transmission electron microscopy shows morphological changes of R. solanacearum upon LAO treatments. Finally, broad specificity of the antibacterial activities of these purified LAOs were seen for in vitro screening against 14 phytopathogenic bacteria. Therefore, these fungal LAOs show great potential as new biological phytoprotective agents and show the fruiting bodies of higher fungi to be a valuable source of antimicrobials with unique features.

Casey M. Gries, Zuivanna Rivas, Justin Chen et al.

Bacterial infections associated with implanted medical devices represents a healthcare crisis due to their persistence, antibiotic tolerance, and immune avoidance. Indwelling devices are rapidly coated with host plasma and extracellular matrix proteins which can then be exploited by bacterial pathogens for adherence and subsequent biofilm development. Our understanding of the host-pathogen interface that determines the fate of biofilm-mediated infections is limited to the experimental models employed by laboratories studying these organisms. Current in vivo models of biofilm-mediated infection, while certainly useful, are typically limited to end-point analyses of bacterial burden enumeration, immune cell profiling, and cytokine/chemokine analysis. Thus, with these models, the complex, real-time assessment of biofilm development and innate immune cell activity remains imperceptible. Here, we describe a novel murine biofilm infection model employing time-lapse intravital multiphoton microscopy which permits concurrent and real-time visualization of Staphylococcus aureus biofilm formation and immune cell activity. Using cell tracking, we found that S. aureus biofilms impede neutrophil chemotaxis, redirecting their migration patterns to prevent biofilm invasion. This approach is the first to directly examine device-associated biofilm development and host-pathogen interactions and will serve to both further our understanding of infection development and help reveal the effects of future antibiofilm treatment strategies.

M. Gustafsson, D. Agard, J. Sedat