Thermal stress-assisted formation of submicron pillars from a thin film of CoCrCuFeNi high entropy alloy: experiments and simulations.

In this work, for the first time, the thermal stress-assisted formation of submicron pillars (SPs) from a high entropy alloy (HEA) thin film is made possible, and novel molecular dynamics (MD) simulations are proposed to assess the underlying mechanisms. In a series of experiments, the growth of quasi-equiatomic HEA SPs from CoCrCuFeNi HEA thin films was demonstrated under different heating and cooling conditions. Atomistic simulations are performed to probe possible formation mechanisms in two ways. One is to first obtain surface elastic constants and then conduct surface stability analysis with the consideration of size-dependent surface stress. The other is to effectively apply large compressive stress while simplifying the molecular dynamics (MD) model by using the Stoney equation to perform long-term MD simulations. From the former, it is suggested that surface diffusion is likely not the dominant cause for the observed pillar formation. From the latter, it is revealed that the level of compressive stress plays a much greater role than the crystalline structure of the film sample. Light has been shed on the stress-assisted formation of submicron pillars from CoCrCuFeNi HEA films by both experimental and simulation approaches.

Metabolic dependency of non-small cell lung cancer cells affected by three-dimensional scaffold and its stiffness

Three-dimensional (3D) extracellular matrix (ECM) microenvironment is an important regulator of the stiffness of the tumors. Cancer cells require heterogeneous metabolic phenotypes to cope with resistance in the malignant process. However, how the stiffness of the matrix affects the metabolic phenotypes of cancer cells, is lacking. In this study, the young’s modulus of the synthesized collagen-chitosan scaffolds was adjusted according to the percentage ratio of collagen to chitosan. We cultured non-small cell lung cancer (NSCLC) cells in four different microenvironments (two-dimensional (2D) plates, stiffest 0.5–0.5 porous collagen-chitosan scaffolds, middle stiff 0.5–1 porous collagen-chitosan scaffolds, and softest 0.5–2 porous collagen-chitosan scaffolds) to investigate the influence of the difference of 2D and 3D cultures as well as the 3D scaffolds with different stiffnesses on the metabolic dependency of NSCLC cells. The results revealed that NSCLC cells cultured in 3D collagen-chitosan scaffolds displayed higher capacity of mitochondrial metabolism and fatty acid metabolism than that cultured in 2D culture. The metabolic response of NSCLC cells is differential for 3D scaffolds with different stiffnesses. The cells cultured in middle stiff 0.5–1 scaffolds displayed a higher potential of mitochondrial metabolism than that of stiffer 0.5–0.5 scaffolds and softer 0.5–2 scaffolds. Furthermore, NSCLC cells culture in 3D scaffolds displayed drug resistance compared with that in 2D culture which maybe via the hyperactivation of the mTOR pathway. Moreover, the cells cultured in 0.5–1 scaffolds showed higher ROS levels, which were counterbalanced by an equally high expression of antioxidant enzymes when compared to the cells grown in 2D culture, which may be regulated by the increased expression of PGC-1α. Together, these results demonstrate that differences in the microenvironments of cancer cells profoundly impact their metabolic dependencies. (AU)

Metabolic dependency of non-small cell lung cancer cells affected by three-dimensional scaffold and its stiffness.

Three-dimensional (3D) extracellular matrix (ECM) microenvironment is an important regulator of the stiffness of the tumors. Cancer cells require heterogeneous metabolic phenotypes to cope with resistance in the malignant process. However, how the stiffness of the matrix affects the metabolic phenotypes of cancer cells, is lacking. In this study, the young's modulus of the synthesized collagen-chitosan scaffolds was adjusted according to the percentage ratio of collagen to chitosan. We cultured non-small cell lung cancer (NSCLC) cells in four different microenvironments (two-dimensional (2D) plates, stiffest 0.5-0.5 porous collagen-chitosan scaffolds, middle stiff 0.5-1 porous collagen-chitosan scaffolds, and softest 0.5-2 porous collagen-chitosan scaffolds) to investigate the influence of the difference of 2D and 3D cultures as well as the 3D scaffolds with different stiffnesses on the metabolic dependency of NSCLC cells. The results revealed that NSCLC cells cultured in 3D collagen-chitosan scaffolds displayed higher capacity of mitochondrial metabolism and fatty acid metabolism than that cultured in 2D culture. The metabolic response of NSCLC cells is differential for 3D scaffolds with different stiffnesses. The cells cultured in middle stiff 0.5-1 scaffolds displayed a higher potential of mitochondrial metabolism than that of stiffer 0.5-0.5 scaffolds and softer 0.5-2 scaffolds. Furthermore, NSCLC cells culture in 3D scaffolds displayed drug resistance compared with that in 2D culture which maybe via the hyperactivation of the mTOR pathway. Moreover, the cells cultured in 0.5-1 scaffolds showed higher ROS levels, which were counterbalanced by an equally high expression of antioxidant enzymes when compared to the cells grown in 2D culture, which may be regulated by the increased expression of PGC-1α. Together, these results demonstrate that differences in the microenvironments of cancer cells profoundly impact their metabolic dependencies.

Stiffer-Matrix-Induced PGC-1α Upregulation Enhanced Mitochondrial Biogenesis and Oxidative Stress Resistance in Non-small Cell Lung Cancer.

Introduction: Metabolic strategies in different microenvironments can affect cancer metabolic adaptation, ultimately influencing the therapeutic response. Understanding the metabolic alterations of cancer cells in different microenvironments is critical for therapeutic success. Methods: In this study, we cultured non-small cell lung cancer cells in three different microenvironments (two-dimensional (2D) plates, soft elastic three-dimensional (3D) porous 2 wt% scaffolds, and stiff elastic 3D porous 4 wt% scaffolds) to investigate the effects of different matrix elasticity as well as 2D and 3D culture settings on the metabolic adaptation of cancer cells. Results: The results revealed that PGC-1α expression is sensitive to the elasticity of the 3D scaffold. PGC-1α expression was markedly increased in cancer cells cultured in stiff elastic 3D porous 4 wt% scaffolds compared with cells cultured in soft elastic 3D porous 2 wt% scaffolds or 2D plates, enhancing mitochondrial biogenesis and oxidative stress resistance of non-small cell lung cancer through increased reactive oxygen species (ROS) detoxification capacity. However, phosphofructokinase-1 (PFK-1) expression, a key rate-limiting enzyme in glycolysis, did not change significantly in the three microenvironments, indicating that microenvironments may not affect the early stage of glycolysis. Conversely, monocarboxylate transporter 1 (MCT1) expression in 3D culture was significantly reduced compared to 2D culture but without significant difference between soft and stiff scaffolds, indicating that MCT1 expression is more sensitive to the shape of the different cultures of 2D and 3D microenvironment surrounding cells but is unaffected by the scaffold elasticity. Conclusions: Together, these results demonstrate that differences in the microenvironment of cancer cells profoundly impact their metabolic response.

Nanocarriers for drug-delivery systems using a ureido-derivatized polymer gatekeeper for temperature-controlled spatiotemporal on-off drug release.

Accidental chemotherapy extravasation exacerbates the side effects of anticancer drugs. Therefore, drug-delivery nanocarriers should be designed to avoid persistent drug release at off-target sites and promote burst drug release at on-target. Considering these requirements, poly(allylamine)-co-poly(allylurea) (PAU), a ureido-derivatized temperature responsive polymer with upper critical solution temperature (UCSTs), is an ideal material. This report describes the fabrication, characterization, and in vitro cellular toxicity of PAU polymer-grafted magnetic mesoporous silica nanoparticles as drug-delivery nanocarriers. A UCST of 43 °C and an ultranarrow transition temperature range of 39-43 °C was realized, ensuring that the nanocarriers suppressed undesirable leakage to below 10 % of the drug loading for 8 h in the absence of a thermal stimulus. A drug release burst of up to 75 % of the drug loading was achieved within 30 min after the stimulus, reducing the viability of the in vitro cancer cells to 12 %. Therefore, the ureido-derivatized polymer is one of the most suitable gatekeepers for drug-delivery nanocarriers.

Bioengineered PLEKHA7 nanodelivery regularly induces behavior alteration and growth retardation of acute myeloid leukemia.

Acute myeloid leukemia (AML) is the most lethal leukemia with an extremely poor prognosis and high relapse rates. In leukemogenesis, adhesion abnormalities can readily guide an imbalance between hematopoietic progenitor cells and bone marrow stromal cells, altering the normal hematopoietic bone marrow microenvironment into leukemic transformation that enhances leukemic proliferation. Here, we have firstly studied the PLEKHA7 expression in leukemic cells to assess their growth capability affected by the restoration of PLEKHA7 in the cells. The efficacy of PLEKHA7-loaded cRGD-mediated PEGylated cationic lipid nanoparticles for efficient PLEKHA7 delivery in leukemic cells as well as the effect of PLEKHA7 on the regulated induction of AML behavior and growth alterations were investigated. PLEKHA7 re-expression diminished colony-forming ability and reinforced the incidence of growth retardation without apoptosis in AML cell lines. PLEKHA7 regulated the restoration of cell surface adhesion and integrity during normal homeostasis. Our findings revealed that PLEKHA7 functions as a behavior and growth modulator in AML. To our knowledge, the role of PLEKHA7 in AML had not been studied previously and our data could be exploited for further mechanistic studies and insights into altering human AML behavior and growth.

Nanotwinning and tensile behavior in cold-welded high-entropy-alloy nanowires.

Since the fabrication technique for high-entropy alloy (HEA) nanowires/nanopillars is still in its infancy, neither experimental nor modeling analyses of their cold-welding performance have been reported. Based on insights accumulated in our previous experiments and simulations regarding cold-welded metallic nanowires, in this study, the cold-welding performance of HEA nanowires is probed by atomistic simulations. Among different materials, our simulations reveal that extensively twinned structures are formed in CoCrMnFeNi samples, but not in CoCrCuFeNi or Ni samples. The larger fracture strain in certain HEAs is due to the improved ductility around the fracturing area as well as multiple twinning. Unlike in Ni samples, the fracture strains in HEA samples, regardless of being cuboid or cylindrical, are improved by shrinking the sample size. Among different orientations, the [010]-direction monocrystalline nanowires fail at a strain over 0.6, which is almost double that of the [111] direction. The fracture strains in polycrystalline HEA samples are, on average, larger than those in polycrystalline Ni samples. Furthermore, fracture strains in randomly generated polycrystalline HEA samples are more predictable than those in polycrystalline Ni samples with identical grain configurations. As previously reported, dislocation emission is still a prerequisite to fracture in all cold-welded samples.

Fabrication of γ-Fe2O3 Nanowires from Abundant and Low-cost Fe Plate for Highly Effective Electrocatalytic Water Splitting.

Water splitting is thermodynamically uphill reaction, hence it cannot occur easily, and also highly complicated and challenging reaction in chemistry. In electrocatalytic water splitting, the combination of oxygen and hydrogen evolution reactions produces highly clean and sustainable hydrogen energy and which attracts research communities. Also, fabrication of highly active and low cost materials for water splitting is a major challenge. Therefore, in the present study, γ-Fe2O3 nanowires were fabricated from highly available and cost-effective iron plate without any chemical modifications/doping onto the surface of the working electrode with high current density. The fabricated nanowires achieved the current density of 10 mA/cm2 at 1.88 V vs. RHE with the scan rate of 50 mV/sec. Stability measurements of the fabricated Fe2O3 nanowires were monitored up to 3275 sec with the current density of 9.6 mA/cm2 at a constant potential of 1.7 V vs. RHE and scan rate of 50 mV/sec.

The optimal mechanical condition in stem cell-to-tenocyte differentiation determined with the homogeneous strain distributions and the cellular orientation control.

In tendon tissue engineering, mechanical stimulus-induced differentiation is one of the most attractive techniques for stem cell-to-tenocyte differentiation in terms of cost, safety and simplicity. However, the most effective strain amplitude for differentiation using cyclic stretching remains unknown. Existing studies have not constrained cell reorientation behavior during cyclic stretching, resulting in uncertainty regarding the loads experienced by cells. In addition, strain distribution homogeneity of the culture membrane is important. Here, we improved the strain distribution uniformity of the membrane and employed a microgrooved membrane to suppress cell reorientation. Then we evaluated the most effective strain amplitude (0, 2, 4, 5, 6, or 8%) for the differentiation of mesenchymal stem cells into tenocytes by measuring mRNA expression levels. The maximum expression of all tenogenic markers was observed at a 5% strain. These results contribute to tendon tissue engineering by clarifying the most effective strain amplitude during tenogenic differentiation induction using cyclic stretching.

Local permittivity measurement of dielectric materials based on the non-contact force curve of microwave atomic force microscopy.

We report a non-contact and quantitative method to measure the local permittivity of dielectric materials with a nanometer-scale spatial resolution. A theoretical model based on near-field approximation was developed to describe the effect of a microwave on the interaction between a probe and a sample. Under the non-contact mode, we successfully measured the force curves of Si, Al2O3, Ge, and ZrO2 using microwave atomic force microscopy and observed the variation in the force caused by the microwave. According to the established theoretical model, a quantitative non-contact evaluation of the local permittivity of dielectric materials was performed.

A 64-pin Nanowire Surface Fastener Like a Ball Grid Array Applied for Room-temperature Electrical Bonding.

Surface-mount techniques primarily depend on soldering. However, soldering techniques have encountered some challenges in recent years. These challenges include rare metal recycling, thermal problems, and Pb toxicity. We recently developed a metallic nanowire surface fastener (NSF) to resolve the abovementioned problems. This fastener can be used to connect electronic components on a substrate at room temperature using the van der Waals force between each nanowire. This study demonstrates a 64-pin NSF that behaves like a ball grid array (BGA) for application to actual electronic devices. The adhesion strength and electrical properties of the NSF were investigated by adjusting the nanowire parameters, such as diameter, length, density (number per area), preload, and shape. The shape control of the nanowires greatly contributed to the improvement of the properties. A maximum adhesion strength of 16.4 N/cm2 was achieved using a bent, hook-like NSF. This strength was 4-5 times the value of the straight NSF. The contact resistivity was 2.98 × 10-2 Ω∙cm2. The NSF fabricated through the simple template method showed the room temperature bonding ability and adaptability to a highly ordered electrode like the BGA.

Effect of Electropulsing Treatment on the Fatigue Crack Growth Behavior of Copper.

Crack propagation was quantitatively evaluated to investigate the effect of electropulsing treatment (EPT) on fatigue crack growth of copper specimens. Varying fatigue cycles were obtained under six different load levels. The crack lengths were measured under two load levels to examine the effect of cyclic stress. The microhardness was measured around the vicinity of the crack tip. Furthermore, the fracture surface was observed by scanning electron microscopy. Results show that EPT with electric current density of 150 A/mm² enhances the high-cycle fatigue life, and the effect tends to increase with the decrease in cyclic stress. Vickers microhardness (HV) near the crack tip decreases to normal levels after treatment, and the approaching cracks on two sides can be observed. Local annealing and recrystallization occur around the fatigue crack tip. Accordingly, crack propagation can be delayed, and fatigue life can be prolonged by EPT.

Fabrication of multiwall carbon nanotube sheet based hydrogen sensor on a stacking multi-layer structure.

In this research, we propose a new simple method to fabricate hydrogen gas sensors by stacking multiwall carbon nanotube (MWCNT) sheets. MWCNT sheets offer a larger surface area and more CNT contact, which are key factors for gas sensing, because of their super-high alignment and end-to-end structure compared to traditional CNT film. Besides, MWCNT sheets can be directly drawn from spinnable CNT arrays on large scales. Therefore, this method is a potential answer for the mass production and commercialization of CNT-based sensors with high responsivity. By stacking layers of sheets in various arrangements, the microstructure and CNT interactions in the layers were changed and their influence on gas sensing investigated. It was observed that the sample with three layers of sheet and functionalized with 3 nm thick Pd showed the best gas sensing performance, with a response of 12.31% at 4% H2 and response time below 200 s.

Nanowire surface fastener fabrication on flexible substrate.

The market for wearable devices has increased considerably in recent years. In response to this demand, flexible electronic circuit technology has become more important. The conventional bonding technology in electronic assembly depends on high-temperature processes such as reflow soldering, which result in undesired thermal damages and residual stress at a bonding interface. In addition, it exhibits poor compatibility with bendable or stretchable device applications. Therefore, there is an urgent requirement to attach electronic parts on printed circuit boards with good mechanical and electrical properties at room temperature. Nanowire surface fasteners (NSFs) are candidates for resolving these problems. This paper describes the fabrication of an NSF on a flexible substrate, which can be used for room temperature conductive bonding. The template method is used for preparing high-density nanowire arrays. A Cu thin film is layered on the template as the flexible substrate. After etching the template, a Cu NSF is obtained on the Cu film substrate. In addition, the electrical and mechanical properties of the Cu NSF are studied under various fabrication conditions. The Cu NSF exhibits high shear adhesion strength (∼234 N cm-2) and low contact resistivity (2.2 × 10-4 Ω cm2).

Synthesis of a single-crystal Fe2O3 nanowire array based on stress-induced atomic diffusion used for solar water splitting.

In this study, we successfully fabricated a single-crystal Fe2O3 nanowire array based on stress-induced atomic diffusion and used this array as the photoelectrode for solar water splitting. With the surface polishing treatment on the sample surface, the density of the Fe2O3 nanowire array reached up to 28.75 wire µm-2 when heated for 90 min at 600°C. The photocurrent density of the optimized sample was 0.9 mA cm-2 at 1.23 V versus a reversible hydrogen electrode in a three-electrode system under AM 1.5 G illumination. The incident photon-to-electron conversion efficiency was 6.8% at 400 nm.