TGF‐β1 Conjugated to Gold Nanoparticles Results in Protein Conformational Changes and Attenuates the Biological Function

Gold nanoparticles (AuNPs) are widely used as carriers or therapeutic agents due to their great biocompatibility and unique physical properties. Transforming growth factor‐beta 1 (TGF‐β1), a member of the cysteine‐knot structural superfamily, plays a pivotal role in many diseases and is known as an immunosuppressive agent that attenuates immune response resulting in tumor growth. The results reported herein reflect strong interactions between TGF‐β1 and the surface of AuNPs when incubated with serum‐containing medium, and demonstrate a time‐ and dose‐dependent pattern. Compared with other serum proteins that can also bind to the AuNP surface, AuNP–TGFβ1 conjugate is a thermodynamically favored compound. Epithelial cells undergo epithelial–mesenchymal transition (EMT) upon treatment with TGF‐β1; however, treatment with AuNPs reverses this effect, as detected by cell morphology and expression levels of EMT markers. TGF‐β1 is found to bind to AuNPs through S–Au bonds by X‐ray photoelectron spectroscopy. Fourier transform infrared spectroscopy is employed to analyze the conformational changes of TGF‐β1 on the surface of AuNPs. The results indicate that TGF‐β1 undergoes significant conformational changes at both secondary and tertiary structural levels after conjugation to the AuNP surface, which results in the deactivation of TGF‐β1 protein. An in vivo experiment also shows that addition of AuNPs attenuates the growth of TGF‐β1‐secreting murine bladder tumor 2 cells in syngeneic C3H/HeN mice, but not in immunocompromised NOD‐SCID mice, and this is associated with an increase in the number of tumor‐infiltrating CD4⁺ and CD8⁺ T lymphocytes and a decrease in the number of intrasplenic Foxp3(+) lymphocytes. The findings demonstrate that AuNPs may be a promising agent for modulating tumor immunity through inhibiting immunosuppressive TGF‐β1 signaling.     

Microstructure and Elastic Constants of Transition Metal Dichalcogenide Monolayers from Friction and Shear Force Microscopy

Optical and electrical properties of 2D transition metal dichalcogenides (TMDCs) grown by chemical vapor deposition (CVD) are strongly determined by their microstructure. Consequently, the visualization of spatial structural variations is of paramount importance for future applications. This study demonstrates how grain boundaries, crystal orientation, and strain fields can unambiguously be identified with combined lateral force microscopy and transverse shear microscopy (TSM) for CVD‐grown tungsten disulfide (WS₂) monolayers, on length scales that are relevant for optoelectronic applications. Further, angle‐dependent TSM measurements enable the fourth‐order elastic constants of monolayer WS₂ to be acquired experimentally. The results facilitate high‐throughput and nondestructive microstructure visualization of monolayer TMDCs and insights into their elastic properties, thus providing an accessible tool to support the development of advanced optoelectronic devices based on such 2D semiconductors.     

有机复合摩擦材料的成分优化及其对摩擦性能的影响

采用正交试验设计方法对有机复合摩擦材料的成分进行优化,利用MMS-2A摩擦磨损试验机对材料的摩擦系数进行测试,用比磨损率表征复合材料的磨损性能,并通过极差法对试验结果进行了分析。用Leica体式显微镜和3D激光共聚焦显微镜观察了材料摩擦磨损后的表面形貌,探索了不同成分下合成材料的摩擦磨损机理。结果表明:改性酚醛树脂对材料的平均摩擦系数和比磨损率的影响最大。摩擦系数较优的组合为A1B1C2D2,比磨损率较优的组合为A3D1C1B3。树脂含量较少时,摩擦表面的摩擦膜较少,犁沟较深,呈严重的磨粒磨损特征;随树脂含量增加,摩擦表面形成完整且连续的摩擦膜,犁沟较浅,材料的主要磨损形式为粘着磨损和磨粒磨损。     

Freezing transition of Langmuir-Gibbs alkane films on water

We show that adding CTAB (CTAB, hexadecyltrimethylammonium bromide) in sub-millimolar bulk concentrations to water reduces its surface tension (ST) to a level where spontaneous surface spreading of a monolayer of medium-sized alkane (C_nH_2n+2, 12 ≤ n ≤ 17) occurs. ST and X-ray reflectivity (XR) measurements are used to show that the quasi two-dimensional (2D) liquid monolayer can be driven through a reversible surface freezing phase transition upon cooling. Grazing incidence diffraction (GID) shows that the frozen monolayer is crystalline, hexagonally packed, with surface-normal molecules, and a crystalline coherence length of at least a few hundred Å, very similar to the structure of surface-frozen (SF) monolayers at the surface of similar-length alkane melts.     

Multiwall Carbon Nanotubes Directly Promote Fibroblast–Myofibroblast and Epithelial–Mesenchymal Transitions through the Activation of the TGF‐β/Smad Signaling Pathway

A number of studies have demonstrated that MWCNTs induce granuloma formation and fibrotic responses in vivo, and it has been recently reported that MWCNT‐induced macrophage activation and subsequent TGF‐β secretion contribute to pulmonary fibrotic responses. However, their direct effects against alveolar type‐II epithelial cells and fibroblasts and the corresponding underlying mechanisms remain largely unaddressed. Here, MWCNTs are reported to be able to directly promote fibroblast‐to‐myofibroblast conversion and the epithelial–mesenchymal transition (EMT) through the activation of the TGF‐β/Smad signaling pathway. Both of the cell transitions may play important roles in MWCNT‐induced pulmonary fibrosis. Firstly, in‐vivo and in‐vitro data show that long MWCNTs can directly interact with fibroblasts and epithelial cells, and some of them may be uptaken into fibroblasts and epithelial cells by endocytosis. Secondly, long MWCNTs can directly activate fibroblasts and increase both the basal and TGF‐β1‐induced expression of the fibroblast‐specific protein‐1, α‐smooth muscle actin, and collagen III. Finally, MWCNTs can induce the EMT through the activation of TGF‐β/Smad2 signaling in alveolar type‐II epithelial cells, from which some fibroblasts involved in pulmonary fibrosis are thought to originate. These observations suggest that the activation of the TGF‐β/Smad2 signaling plays a critical role in the process of the fibroblast‐to‐myofibroblast transition and the EMT induced by MWCNTs.     

Efficient and Layer‐Dependent Exciton Pumping across Atomically Thin Organic–Inorganic Type‐I Heterostructures

The fundamental light–matter interactions in monolayer transition metal dichalcogenides might be significantly engineered by hybridization with their organic counterparts, enabling intriguing optoelectronic applications. Here, atomically thin organic–inorganic (O–I) heterostructures, comprising monolayer MoSe₂ and mono‐/few‐layer single‐crystal pentacene samples, are fabricated. These heterostructures show type‐I band alignments, allowing efficient and layer‐dependent exciton pumping across the O–I interfaces. The interfacial exciton pumping has much higher efficiency (>86 times) than the photoexcitation process in MoSe₂, although the pentacene layer has much lower optical absorption than MoSe₂. This highly enhanced pumping efficiency is attributed to the high quantum yield in pentacene and the ultrafast energy transfer between the O–I interface. Furthermore, those organic counterparts significantly modulate the bindings of charged excitons in monolayer MoSe₂ via their precise dielectric environment engineering. The results open new avenues for exploring fundamental phenomena and novel optoelectronic applications using atomically thin O–I heterostructures.     

Goosebumps‐Inspired Microgel Patterns with Switchable Adhesion and Friction

A substrate mimicking the surface topography and temperature sensitivity of skin goosebumps is fabricated. Close‐packed arrays of thermoresponsive microgel particles undergo topographical changes in response to temperature changes between 25 and 37 °C, resembling the goosebump structure that human skin develops in response to temperature changes or other circumstances. Specifically, positively charged poly[2‐(methacryloyloxy)ethyltrimethylammonium chloride] (PMETAC) brushes serve as an anchoring substrate for negatively charged poly(NIPAm‐co‐AA) microgels. The packing density and particle morphology can be tuned by brush layer thickness and pH of the microgel suspension. For brush layer thickness below 50 nm, particle monolayers are observed, with slightly flattened particle morphology at pH 3 and highly collapsed particles at pH above 7. Polymer brush films with thickness above 50 nm lead to the formation of particle multilayers. The temperature responsiveness of the monolayer assemblies allows reversible changes in the film morphology, which in turn affects underwater adhesion and friction at 25 and 37 °C. These results are promising for the design of new functional materials and may also serve as a model for biological structures and processes.     

Evaluation of monolayers and mixed monolayers formed from mercaptobenzothiazole and decanethiol as sensing platforms

In this investigation, the characterisation of monolayer and mixed monolayers formed from mercaptobenzothiazole (MBT) and decanethiol (DT) has been carried out with cyclic voltammetry. The SAMs have been tested for their stability and electron transfer blocking properties. The redox probes used in the present study are [Fe(CN)₆]⁴⁻, [Ru(NH₃)₆]²⁺ and Cu underpotential deposition (upd). The electron transfer kinetics is investigated in acid and neutral pH range. Electron transfer kinetics is altered by the nature of charge on the redox probe and the charge on the monolayer. Electron transfer kinetics of negatively charged redox probes like ferrocyanide ions is blocked when the surface pK_a<pH_medium and at pK_a>pH_medium reversible features is observed for negatively charged probes. An exactly reverse effect is observed in the case of positively charged redox species like [Ru(NH₃)₆]^2+/3+.Cu under potential deposition studies reflects the structural integrity and compactness of the SAM layer. The utility of these monolayers and mixed monolayer for selective sensing of dopamine is discussed based on their ability to discriminate between positively and negatively charged redox species at different pH.     

Growth kinetics and thermodynamic stability of octadecyltrichlorosilane self-assembled monolayer on Si (100) substrate

We have studied the growth kinetics and thermodynamic stability of octadecyltrichlorosilane (OTS) self-assembled monolayers on Si (100) substrate in order to understand its role in controlling the adhesion and surface hydrophobicity. Time-dependent contact angle measurements, using water as a function of OTS concentration, show rapid monolayer formation in the initial stage followed by a slow attainment of full coverage and the overall kinetics approximately follows the Langmuir adsorption isotherm. The adsorption rate constant (k_a = 150 M^− 1 s^− 1) is found to be significantly greater than the desorption rate constant (k_d = 0.156 s^− 1) while the Gibbs free energy (ΔG_ads) change amounts to − 4.2 kcal/mol suggesting thermodynamic stability of OTS monolayer on a silicon surface. Partial monolayer formation by a ‘uniform’ growth mechanism, even at low coverage, is revealed by atomic force microscopy (AFM) in conjunction with grazing angle FTIR spectroscopy. Analysis of the interfacial adhesion properties using Zisman plot suggests a critical surface tension (γ_c) of 20.7 dyn/cm for OTS monolayer on Si (100) surface.     

Effects of iodine on the initial growth of MOCVD Cu on MPTMS monolayer surface at a low temperature of 110 °C

Cu was deposited by chemical vapor deposition (CVD) on self-assembled monolayers of a 3-mercapto-propyl-trimethoxy-silane (MPTMS)-coated SiO₂ substrate using (hfac)Cu(DMB) and C₂H₅I as precursors at 110 °C. The effects of iodine addition on the initial growth of Cu were investigated by scanning electron microscopy (SEM). For comparison, Cu was deposited without iodine on the MPTMS monolayer. The low temperature deposition of Cu without iodine showed that the initial growth of Cu particles is limited by the direct flux of Cu precursors on the growing Cu surface, which continues until active coalescence occurs. This results in a very low growth rate (1 Å/s) of Cu particles at the initial stage of particle growth. The addition of iodine significantly enhanced the surface-diffusion of Cu adatoms over the MPTMS surface and allowed the facile dissociation of Cu(hfac) adsorbed on the Cu surface. These two effects increased the growth rate of Cu particles to approximately 13 Å/s. However, the root square time dependence of the growth rate of Cu particles suggests that the iodine-enhanced surface diffusion of Cu adatoms is a major contributor to the increased growth of Cu particles.     

Identification of the anthelix motif in the TGF‐β superfamily by molecular 3D‐Rapid Prototyping

3D‐Rapid Prototyping (3D‐RP) is a novel technique for the construction of highly accurate three‐dimensional polyamide models of biomolecules. This method has been shown to be a valuable tool in the modeling of protein‐protein‐interactions as well as in the analysis of surface topography. Using this technique we were recently able to identify a so far unknown structure on the concave side of bone morphogenetic protein 2 (BMP‐2). Since this structure is the imprint of a left‐handed helix we have called this negative an unthelix. Obviously this novel structural feature of BMP‐2 may act as a binding side for endogenous ligands. BMP‐2 belongs to the highly conserved Transforming Growth Factor‐β (TGF‐β) superfamily, a large group of multifunctional peptides controlling differentiation, proliferation and repair in multicellular organism. The protomer structures of all members share a cystine‐knot motif as a characteristic feature. The question therefore arose whether a) the novel anthelical motif found in BMP‐2 is a common structural feature of this family and b) if there are any differences in terms of pitch and radius of the anthelix. As anthelical structures are difficult to visualize and nearly impossible to quantify using 3D molecular visualization software we constructed models of BMP‐2, BMP‐7 and TGF‐β2 from X‐ray crystallographic data by 3D‐Rapid Prototyping (3D‐RP). The anthelix motif was found in BMP‐2, BMP‐7 and TGF‐β2 with similar values for pitch (ca. 8‐10 nm) and radius (ca. 0.5‐0.7 nm). In contrast the anthelical motif was not found in a 3D‐RP model of human chorionic gonadotropin (HCG) which is also a member of the cystine‐knot family but doesn’t belong to the TGF‐β superfamily. These results were corroborated by measurements of the intersubunit angle of these dimeric proteins (141‐149°) and the distances between the center of mass (1.68‐1.96 nm) of the subunits both of which appear to be determinants of the anthelical pitch. We conclude that the anthelical groove on the concave side is a common structural motif of BMP‐2, BMP‐7 and TGF‐β2 and maybe of the whole group of the TGF‐β superfamily.     

Multiwall Carbon Nanotubes Mediate Macrophage Activation and Promote Pulmonary Fibrosis Through TGF‐β/Smad Signaling Pathway

Multiwall carbon nanotubes (MWCNTs) have been widely used in many disciplines due to their unique physical and chemical properties, but have also raised great concerns about their possible negative health impacts, especially through occupational exposure. Although recent studies have demonstrated that MWCNTs induce granuloma formation and/or fibrotic responses in the lungs of rats or mice, their cellular and molecular mechanisms remain largely unaddressed. Here, it is reported that the TGF‐β/Smad signaling pathway can be activated by MWCNTs and play a critical role in MWCNT‐induced pulmonary fibrosis. Firstly, in vivo data show that spontaneously hypertensive (SH) rats administered long MWCNTs (20–50 μm) but not short MWCNTs (0.5–2 μm) exhibit increased fibroblast proliferation, collagen deposition and granuloma formation in lung tissue. Secondly, the in vivo experiments also indicate that only long MWCNTs can significantly activate macrophages and increase the production of transforming growth factor (TGF)‐β1, which induces the phosphorylation of Smad2 and then the expression of collagen I/III and extracellular matrix (ECM) protease inhibitors in lung tissues. Finally, the present in vitro studies further demonstrate that the TGF‐β/Smad signaling pathway is indeed necessary for the expression of collagen III in fibroblast cells. Together, these data demonstrate that MWCNTs stimulate pulmonary fibrotic responses such as fibroblast proliferation and collagen deposition in a TGF‐β/Smad‐dependent manner. These observations also suggest that tube length acts as an important factor in MWCNT‐induced macrophage activation and subsequent TGF‐β1 secretion. These in vivo and in vitro studies further highlight the potential adverse health effects that may occur following MWCNT exposure and provide a better understanding of the cellular and molecular mechanisms by which MWCNTs induce pulmonary fibrotic reactions.     

Excitonic Properties of Chemically Synthesized 2D Organic–Inorganic Hybrid Perovskite Nanosheets

2D organic–inorganic hybrid perovskites (OIHPs) represent a unique class of materials with a natural quantum‐well structure and quasi‐2D electronic properties. Here, a versatile direct solution‐based synthesis of mono‐ and few‐layer OIHP nanosheets and a systematic study of their electronic structure as a function of the number of monolayers by photoluminescence and absorption spectroscopy are reported. The monolayers of various OIHPs are found to exhibit high electronic quality as evidenced by high quantum yield and negligible Stokes shift. It is shown that the ground exciton peak blueshifts by ≈40 meV when the layer thickness reduces from bulk to monolayer. It is also shown that the exciton binding energy remains effectively unchanged for (C₆H₅(CH₂)₂NH₃)₂PbI₄ with the number of layers. Similar trends are observed for (C₄H₉NH₃)₂PbI₄ in contrast to the previous report. Further, the photoluminescence lifetime is found to decrease with the number of monolayers, indicating the dominant role of surface trap states in nonradiative recombination of the electron–hole pairs.     

C60 fullerene promotes lung monolayer collapse

Airborne nanometre-sized pollutants are responsible for various respiratory diseases. Such pollutants can reach the gas-exchange surface in the alveoli, which is lined with a monolayer of lung surfactant. The relationship between physiological effects of pollutants and molecular-level interactions is largely unknown. Here, we determine the effects of carbon nanoparticles on the properties of a model of lung monolayer using molecular simulations. We simulate phase-separated lipid monolayers in the presence of a model pollutant nanoparticle, C₆₀ fullerene. In the absence of nanoparticles, the monolayers collapse only at very low surface tensions (around 0 mN m⁻¹). In the presence of nanoparticles, instead, monolayer collapse is observed at significantly higher surface tensions (up to ca 10 mN m⁻¹). Collapse at higher tensions is related to lower mechanical rigidity of the monolayer. It is possible that similar mechanisms operate on lung surfactant in vivo, which suggests that health effects of airborne carbon nanoparticles may be mediated by alterations of the mechanical properties of lung surfactant.     

Novel concept for the aggregation structure of fatty acid monolayers on the water surface and direct observation of molecular arrangements in their monolayers

The aggregation structure of fatty acid monolayers on water subphases of different pH’s was investigated by means of transmission electron microscopy. Fatty acid monolayers exhibited the phase transition from an amorphous state to a crystalline one by surface compression in the case of a highly dissociated state of hydrophilic groups, whereas they did not show the phase transition in the case of a slightly dissociated state. The aggregation structure of monolayers on the water surface was systematically classified into “the crystalline monolayer”, “the amorphous monolayer” and “the compressing crystallized monolayer” with respect to thermal and chemical (intermolecular repulsive) factors. Molecular-resolution images of fatty acid molecules in the monolayers on mica substrate were successfully observed with an atomic force microscope (AFM) for the first time. The AFM image of a lignoceric acid monolayer prepared at a surface pressure of 5mNm⁻¹ showed a two-dimensional periodic structure with locally disordered molecular arrangements. Also, the nondestructive AFM image observation was successful for a stearic acid monolayer which was prepared by a multistep creep method, indicating that a high mechanical stability of the monolayer is inevitably required for the nondestructive AFM observation.     

Significantly improved stability of n-octadecyltrichlorosilane self-assembled monolayer by plasma pretreatment on mica

It has been well known that plasma pretreatment can stabilize the hydrocarbon silane monolayer self-assembled on a mica surface. However, the extent of this improvement is not well known. To explore this issue, n-octadecyltrichlorosilane (OTS) monolayers were self-assembled on both untreated and plasma-treated mica surfaces, and their interfacial properties were investigated and compared at various physical conditions (temperature, relative humidity, contact time, high stress, and contact repetition) through the use of surface force measurements. This study revealed that in highly humid conditions (> 90% relative humidity) there is a substantial difference of stability between untreated and plasma-treated surfaces, the OTS monolayer on plasma-treated mica surface being much more stable. In particular, protrusion behavior in the monolayer was always observed in untreated samples, but never in plasma-treated samples during contact repetition experiments. This directly demonstrates that the significantly improved stability directly comes from extensive chemical bonds between OTS molecules and the plasma-treated mica surface.     

Friction and cohesion coefficients of composite concrete-to-concrete bond

Experimental study is conducted to quantitatively assess the effects of different surface textures on the friction and cohesion coefficients of concrete-to-concrete bond under different normal stresses. The top surface of concrete base specimens are treated with five different surface textures; surface “left as-cast”, deep groove, indented, and wire-brushing in longitudinal and transverse directions. The roughness profile of the treated concrete base is measured using a portable stylus roughness instrument. In addition, the “push-off” test method is conducted to determine the relationship between the roughness profile and the interface shear strength. Results show that the mean peak height, R_pm has the most significant influence on the pre-crack interface shear strength where the correlation coefficients, R² ranged from 0.9009 to 0.9209. Analytical equations are then proposed to predict the friction and cohesion coefficients by integrating R_pm into the proposed equations. The comparison shows a good concordance with the experimental results within an acceptable range.     

Use of coupling agents as a route to improvement of the compressibility of fine zirconia and alumina powders

In order to improve the compressibility of fine zirconia and alumina powders, powders were surface-treated with aluminate, silane and titanate coupling agents. The surface modification reduced both powder/powder friction and powder/die-wall friction, which increased the density of the compacts. At 2% additions, the effectiveness of the coupling agents on density increase was in the order, silane > titanate > aluminate. In zirconia systems with different titanate concentrations it was found the optimum amount of coupling agent could be approximated by the amount required for monolayer coverage on the powder surface.     

The Genetic Heterogeneity among Different Mouse Strains Impacts the Lung Injury Potential of Multiwalled Carbon Nanotubes

Genetic variation constitutes an important variable impacting the susceptibility to inhalable toxic substances and air pollutants, as reflected by epidemiological studies in humans and differences among animal strains. While multiwalled carbon nanotubes (MWCNTs) are capable of causing lung fibrosis in rodents, it is unclear to what extent the genetic variation in different mouse strains influence the outcome. Four inbred mouse strains, including C57Bl/6, Balb/c, NOD/ShiLtJ, and A/J, to test the pro‐fibrogenic effects of a library of MWCNTs in vitro and in vivo are chosen. Ex vivo analysis of IL‐1β production in bone marrow‐derived macrophages (BMDMs) as molecular initiating event (MIE) is performed. The order of cytokine production (Balb/c > A/J > C57Bl/6 > NOD/ShiLtJ) in BMDMs is also duplicated during assessment of IL‐1β production in the bronchoalveolar lavage fluid of the same mouse strains 40 h after oropharyngeal instillation of a representative MWCNT. Animal test after 21 d also confirms a similar hierarchy in TGF‐β1 production and collagen deposition in the lung. Statistical analysis confirms a correlation between IL‐1β production in BMDM and the lung fibrosis. All considered, these data demonstrate that genetic background indeed plays a major role in determining the pro‐fibrogenic response to MWCNTs in the lung.     

Molecular Beam Epitaxy Scalable Growth of Wafer‐Scale Continuous Semiconducting Monolayer MoTe2 on Inert Amorphous Dielectrics

Monolayer MoTe₂, with the narrowest direct bandgap of ≈1.1 eV among Mo‐ and W‐based transition metal dichalcogenides, has attracted increasing attention as a promising candidate for applications in novel near‐infrared electronics and optoelectronics. Realizing 2D lateral growth is an essential prerequisite for uniform thickness and property control over the large scale, while it is not successful yet. Here, layer‐by‐layer growth of 2 in. wafer‐scale continuous monolayer 2H‐MoTe₂ films on inert SiO₂ dielectrics by molecular beam epitaxy is reported. A single‐step Mo‐flux controlled nucleation and growth process is developed to suppress island growth. Atomically flat 2H‐MoTe₂ with 100% monolayer coverage is successfully grown on inert 2 in. SiO₂/Si wafer, which exhibits highly uniform in‐plane structural continuity and excellent phonon‐limited carrier transport behavior. The dynamics‐controlled growth recipe is also extended to fabricate continuous monolayer 2H‐MoTe₂ on atomic‐layer‐deposited Al₂O₃ dielectric. With the breakthrough in growth of wafer‐scale continuous 2H‐MoTe₂ monolayers on device compatible dielectrics, batch fabrication of high‐mobility monolayer 2H‐MoTe₂ field‐effect transistors and the three‐level integration of vertically stacked monolayer 2H‐MoTe₂ transistor arrays for 3D circuitry are successfully demonstrated. This work provides novel insights into the scalable synthesis of monolayer 2H‐MoTe₂ films on universal substrates and paves the way for the ultimate miniaturization of electronics.