Multiscale approach to the characterization of the interfacial properties of micellar casein and whey protein blends and their effects on recombined dairy creams.

In this study, whipped cream with blends of micellar casein (MCN) and whey protein (WPI) in different ratios were prepared to investigate the role of protein interfacial behavior in determining foam properties at multiple scales, using theoretical modeling, and microscopic and macroscopic analysis. Fluid force microscopy has been used for the first time as a more realistic and direct means of analyzing interfaces properties in multiphase systems. The adsorption kinetics showed that the interfacial permeability constant of WPI (4.24 × 10-4 s-1) was significantly higher than that of the MCN (2.97 × 10-4 s-1), and the WPI interfacial layer had a higher modulus of elasticity (71.38 mN/m) than that of the MCN (47.89 mN/m). This model was validated via the mechanical analysis of the fat globules in real emulsions. The WPI-stabilized fat globule was found to have a higher Young's modulus (219.67 Pa), which contributes to the integrity of its fat globule morphology. As the ratio of MCN was increased in the sample, however, both the interfacial modulus and Young's modulus decreased. Moreover, the rate of partial coalescence was found to increase, a phenomenon that decreased the stability of the emulsion and increased the rate of aeration. The mechanical analysis also revealed a higher level of adhesion between MCN-stabilized fat globule (25.16 nN), which increased fat globule aggregation and emulsion viscosity, while improving thixotropic recovery. The synergistic effect of the blended MCN and WPI provided the highest overrun, at 194.53 %. These studies elucidate the role of the interfacial behavior of proteins in determining the quality of whipped cream and provide ideas for the application of proteins in multiphase systems.

Morphological and functional analyses for investigation of sexually selected legs in the frog legged beetle Sagra femorata (Coleoptera: Chrysomelidae).

Mate choice and male-male combat over successful mating often cause disproportionate exaggeration of male trait relative to body size. However, the exaggeration is often not the only trait involved with male-male combat and mate choice: suites of co-expressed traits may function together as a coordinated unit. When this occurs, dimorphism may be expected for these additional, non-exaggerated, structures. S. femorata males have disproportionately large hind-legs used in male-male combat over females. During the fights, fore- and mid-legs are used to keep males in positions where advantageous for leverage. Because use of the exaggerated hind-legs is coordinated with the other legs, they will coevolve as a functional unit. Here, we show that 1) S. femorata has sexual size differences in all three legs; 2) males show positive allometry in the relative sizes of all three legs; and 3) microstructures of tarsi on the fore- and mid-legs are also sexually dimorphic. Despite these differences in the tarsal microstructure, 4) adhesion forces of the tarsi had no sexual difference in flat surface. The microstructure would be specialized on attaching elytra surface. These results suggest that the three pairs of legs function together during fighting behavior, with hind-legs employed primarily for fighting, and the fore- and mid-legs functioning to grip females, keeping males positioned on the back of the female during combat.

A 3D in vitro model for assessing the influence of intraocular lens: Posterior lens capsule interactions on lens epithelial cell responses.

Posterior Capsule Opacification (PCO), the most frequent complication of cataract surgery, is caused by the infiltration and proliferation of lens epithelial cells (LECs) at the interface between the intraocular lens (IOL) and posterior lens capsule (PLC). According to the "no space, no cells, no PCO" theory, high affinity (or adhesion force) between the IOL and PLC would decrease the IOL: PLC interface space, hinder LEC migration, and thus reduce PCO formation. To test this hypothesis, an in vitro hemisphere-shaped simulated PLC (sPLC) was made to mimic the human IOL: PLC physical interactions and to assess their influence on LEC responses. Three commercially available IOLs with different affinities/adhesion forces toward the sPLC, including Acrylic foldable IOL, Silicone IOL, and PMMA IOL, were used in this investigation. Using the system, the physical interactions between IOLs and sPLC were quantified by measuring the adhesion force and interface space using an adhesion force apparatus and Optical Coherence Tomography, respectively. Our data shows that high adhesion force and tight binding between IOL and sPLC contribute to a small interface space (or "no space"). By introducing LECs into the in vitro system, we found that, with small interface space, among all IOLs, acrylic foldable IOLs permitted the least extent of LEC infiltration, proliferation, and differentiation (or "no cells"). Further statistical analyses using clinical data revealed that weak LEC responses are associated with low clinical PCO incidence rates (or "no PCO"). The findings support that the in vitro system could simulate IOL: PLC interplays and predict IOLs' PCO potential in support of the "no space, no cells, no PCO" hypothesis.

Controlled Preparation of High Quality Bubble-Free and Uniform Conducting Interfaces of Vertical van der Waals Heterostructures of Arrays.

Sharp and clean interfaces of van der Waals (vdW) heterostructures are highly demanded in two-dimensional (2D) materials-based devices. However, current assembly methods usually cause interfacial bubbles and wrinkles, hindering carrier interlayer transport. The preparation of a large-scale vdW heterostructure with a bubble-free interface is still a challenge. Although many efforts have been made to eliminate bubbles, the evolution processes of the interfacial bubbles are rarely studied. Here, the interface bubble formation and evolution of the transferred 2D materials and their vdW heterostructure are systemically studied by the atomic force microscopy (AFM) technique and high-resolution surface current mapping. A thermal annealing procedure is developed to reduce the number of bubbles and to improve the quality of interfaces. In addition, influences of the interface residues and nanosteps on bubble evolution are also discussed. Further, we develop the polystyrene (PS)-mediated polydimethylsiloxane (PDMS) transfer technique to realize the high-quality transfer of heterostructure arrays. Finally, high-resolution surface current mapping results confirm that we can now produce highly uniform electrical conduction interfaces of heterojunctions. This study provides guidance for assembling high quality interfaces and paves the way for production of bubble-free heterostructure-based electronic devices with high performance and good uniformity.

Influence of Preparation Methods and Nanomaterials on Hydrophobicity and Anti-Icing Performance of Nanoparticle/Epoxy Coatings.

Despite their effectiveness in preventing icing, hydrophobic coatings possess drawbacks such as susceptibility to detachment and limited wear resistance, leading to inadequate longevity in melting ice/snow. To enhance the surface stability and durability of superhydrophobic coatings, nanoparticle/epoxy formulations were developed using three types of nanoparticles, two dispersion techniques, three application methods, and two epoxy resin introduction approaches. Testing encompassed water contact angle measurements, assessment of ice adhesion force, and determination of icing rates on asphalt concrete coated with these hydrophobic formulations. Fourier-transform infrared spectroscopy was employed to analyze the molecular structures of the coatings, while scanning electron microscopy facilitated observation of the surface morphology of the hydrophobic coatings. The findings indicated that nano-ZnO, TiO2, and SiO2 particles could be modified into hydrophobic forms using stearic acid. Application of the hydrophobic coating improved the concrete's hydrophobicity, reduced ice adhesion strength on both concrete and asphalt, and delayed the onset of icing. Furthermore, optimal dosages of stearic acid, nanoparticles, and epoxy resin were identified as crucial parameters within specific ranges to ensure the optimal hydrophobicity and durability of the coatings.

Optothermal Needle-Free Injection of Vaterite Nanocapsules.

The propulsion and acceleration of nanoparticles with light have both fundamental and applied significance across many disciplines. Needle-free injection of biomedical nano cargoes into living tissues is among the examples. Here a new physical mechanism of laser-induced particle acceleration is explored, based on abnormal optothermal expansion of mesoporous vaterite cargoes. Vaterite nanoparticles, a metastable form of calcium carbonate, are placed on a substrate, underneath a target phantom, and accelerated toward it with the aid of a short femtosecond laser pulse. Light absorption followed by picosecond-scale thermal expansion is shown to elevate the particle's center of mass thus causing acceleration. It is shown that a 2 µm size vaterite particle, being illuminated with 0.5 W average power 100 fsec IR laser, is capable to overcome van der Waals attraction and acquire 15m sec-1 velocity. The demonstrated optothermal laser-driven needle-free injection into a phantom layer and Xenopus oocyte in vitro promotes the further development of light-responsive nanocapsules, which can be equipped with additional optical and biomedical functions for delivery, monitoring, and controllable biomedical dosage to name a few.

Use of biosilica to improve loading and delivery of bone morphogenic protein 2.

The clinical utility of bone morphogenetic protein 2 (BMP2) is limited because of the poor attraction between BMP2 and carriers, resulting in low loading efficiency and initial burst release. Here, the high binding affinity of BMP2 to the biosilica surface was utilized to overcome this limitation. Atomic force microscopy revealed that BMP2 bound nearly 8- and 2-fold more strongly to biosilica-coated hydroxyapatite than to uncoated and plain silica-coated hydroxyapatite, respectively. To achieve controlled release, collagen was introduced between the silica layers on hydroxyapatite, which was optimized by adjusting the collagen concentration and number of layers. The optimal biosilica/collagen formulation induced sustained BMP2 release without compromising loading efficiency. BMP2 combined with the mentioned formulation led to an increase in osteogenesis, as compared to the combination of BMP2 with either biosilica-coated or non-coated hydroxyapatite in vitro. In rat calvarial defect models, the biosilica/collagen-coated hydroxyapatite with 1 µg BMP2 showed 26 % more bone regeneration than the same dose of BMP2-loaded hydroxyapatite and 10.6 % more than hydroxyapatite with 2.5-fold dose of BMP2. Using BMP2 affinity carriers coated with biosilica/collagen allows for more efficacious in situ loading and delivery of BMP2, making them suitable for the clinical application of growth factors through a soaking method.

Host Cell Geometry and Cytoskeletal Organization Governs Candida-Host Cell Interactions at the Nanoscale.

Candida is one of the most common opportunistic fungal pathogens in humans. Its adhesion to the host cell is required in parasitic states and is important for pathogenesis. Many studies have shown that there is an increased risk of developing candidiasis when normal tissue barriers are weakened or when immune defenses are compromised, for example, during cancer treatment that induces immunosuppression. The mechanical properties of malignant cells, such as adhesiveness and viscoelasticity, which contribute to cellular invasion and migration are different from those of noncancerous cells. To understand host invasion and its relationship with host cell health, we probed the interaction of Candida spp. with cancerous and noncancerous human cell lines using atomic force microscopy in the single-cell force spectroscopy mode. There was significant adhesion between Candida and human cells, with more adhesion to cancerous versus noncancerous cell lines. This increase in adhesion is related to the mechanobiological properties of cancer cells, which have a disorganized cytoskeleton and lower rigidity. Altered geometry and cytoskeletal disruption of the human cells impacted adhesion parameters, underscoring the role of cytoskeletal organization in Candida-human cell adhesion and implicating the manipulation of cell properties as a potential future therapeutic strategy.

Accelerating Gas Escape in Anion Exchange Membrane Water Electrolysis by Gas Diffusion Layers with Hierarchical Grid Gradients.

At high current densities, gas bubble escape is the critical factor affecting the mass transport and performance of the electrolyzer. For tight assembly water electrolysis technologies, the gas diffusion layer (GDL) between the catalyst layer (CL) and the flow field plate plays a critical role in gas bubble removal. Herein, we demonstrate that the electrolyzer's mass transport and performance can be significantly improved by simply manipulating the structure of the GDL. Combined with 3D printing technology, ordered nickel GDLs with straight-through pores and adjustable grid sizes are systematically studied. Using an in situ high-speed camera, the gas bubble releasing size and resident time have been observed and analyzed upon the change of the GDL architecture. The results show that a suitable grid size of the GDL can significantly accelerate mass transport by reducing the gas bubble size and the bubble resident time. An adhesive force measurement has further revealed the underlying mechanism. We then proposed and fabricated a novel hierarchical GDL, reaching a current density of 2 A/cm2 at a cell voltage of 1.95 V and 80 °C, one of the highest single-cell performances in pure-water-fed anion exchange membrane water electrolysis (AEMWE).

Exploring carbonate rock wettability across scales: Role of (bio)minerals.

HYPOTHESIS: The wettability of carbonate rocks is expected to be affected by the organic components of biominerals which are complex, nanostructured organo-mineral assemblages. Elucidating the nanoscale mechanisms driving the wettability of solid surfaces will enable a better understanding of the role of biominerals in the wetting properties of carbonate rocks to control various geological, environmental and industrial processes. EXPERIMENTS: Using Atomic Force Microscopy and Spectroscopy (AFM/AFS) we probed the wettability properties of carbonate rocks with different amounts of organic material. The adhesion properties of two types of limestones were determined in liquid environments at different length scales (nm to mm) using functionalized tips with different chemical groups to determine the extent of surface hydrophobic and hydrophilic organo-mineral interactions. FINDINGS: We observed homogeneous hydrophobic areas at length scales below < 5 µm. The origin of this hydrophobicity is linked to the presence of organics, whose amount and spatial distribution depend on the rock composition. Specifically, our results reveal that the biogenic vs non-biogenic origin of the mineral grains is the main rock property controlling the wettability of the solid surface. Overall, our methodology offers a multi-scale approach to unravel the role that organic moieties and biominerals play in controlling the wettability of rock-water interfaces.

CD109-regulated mechanical properties of endothelial cells.

CD109 antigen on the endothelial cell surface plays an important role in vascular pathology. The aim of the work was to investigate the effect of the immobilization of CD109 antigen with specific antibodies on nanomechanical properties of human umbilical endothelial cells (HUVECs) using atomic force microscopy in quantitative nanomechanical property mapping mode (PeakForce QNM). Anti-CD109 antibodies induced significant stiffening of the cell surface Me(LQ; UQ): in 1.45(1.07;2.29) times with respect to control cells for fixed cells and in 4.9(3.6;5.9) times with respect to control cells for living cells, and changes in the spatial distribution of cell surface mechanical properties. The changes in the HUVEC's mechanical properties were accompanied by the activation of the TGF-/Smad2/3 signaling pathway and reorganization of the vimentin and actin cytoskeletal elements. Our findings show that blocking CD109 antigen using anti-CD109 antibodies leads in HUVECs to the processes similar to that occur after cell TGF-ß-signaling activation. Therefore, we suggest that CD109 antigen may be involved in regulating the mechanical behavior of endothelial cells.

Adhesion-Induced Demolding Forces of Hard Coated Microstructures Measured with a Novel Injection Molding Tool.

The demolding of plastic parts remains a challenging aspect of injection molding. Despite various experimental studies and known solutions to reduce demolding forces, there is still not a complete understanding of the effects that occur. For this reason, laboratory devices and in-process measurement injection molding tools have been developed to measure demolding forces. However, these tools are mostly used to measure either frictional forces or demolding forces for a specific part geometry. Tools that can be used to measure the adhesion components are still the exception. In this study, a novel injection molding tool based on the principle of measuring adhesion-induced tensile forces is presented. With this tool, the measurement of the demolding force is separated from the actual ejection step of the molded part. The functionality of the tool was verified by molding PET specimens at different mold temperatures, mold insert conditions and geometries. It was demonstrated that once a stable thermal state of the molding tool was achieved, the demolding force could be accurately measured with a comparatively low force variance. A built-in camera was found to be an efficient tool for monitoring the contact surface between the specimen and the mold insert. By comparing the adhesion forces of PET molded on polished uncoated, diamond-like carbon and chromium nitride (CrN) coated mold inserts, it was found that a CrN coating reduced the demolding force by 98.5% and could therefore be an efficient solution to significantly improve demolding by reducing adhesive bond strength under tensile loading.

Temperature dependence of adhesion properties at liquid-aluminum/solid interfaces.

The adhesion problem of the liquid aluminum (Al) and solid surfaces in the production process has not been completely solved. In this paper, by performing the molecular dynamic simulations, we first establish models composed of liquid-Al/Al and liquid-Al/silicon (Si) systems, in which the region of solid temperature is from 100 K to 800 K. Then, the dependence between the adhesion force and the solid temperature is qualitatively investigated. The adhesion mechanism of liquid atoms is explored in terms of their diffusion behavior. The results show that there is an opposite effect of the temperature on adhesion properties between the liquid-Al/Al interface and the liquid-Al/Si interface. The thermal excitation effect induces enlargement of the probability of atomic collisions, which accounts for the increase of the adhesion force at the liquid-Al/Al interface. Conversely, the thermal excitation effect leads to the detachment of the atoms in contact with each other, which reduces the adhesion force at the liquid-Al/Si interface. Our findings reveal that the solid Al surface is aluminophilic but the solid Si surface is aluminophobic. In addition, the adhesion between liquid-Al and solid surfaces can be explained by the variation of the interfacial potential.

Analysis of phellinus igniarius effects on gastric cancer cells by atomic force microscopy.

Gastric cancer is one of the common malignant tumors in the world, which originates from the gene mutation of human cells. In this work, an atomic force microscope was used to quantitatively detect the changes of multiple physical parameters such as the cell morphology, surface roughness, elasticity modulus and adhesion force before and after Phellinus linteus stimulation. The experimental results show that Phellinus linteus can change the shape of gastric cancer cells (SGC-7901) from flat to spherical, and increase their height and surface roughness values. The adhesion force of cells is reduced and the elasticity modulus is increased. But there are no significant differences in the morphology and mechanical properties of gastric epithelial cells (GES-1). The results indicate that Phellinus linteus has a high anticancer effect on the gastric cancer cells, but has less toxic side effects on the gastric epithelial cells. This work proves that Phellinus linteus can be used as a preferred anticancer drug for the treatment of gastric cancer cells.

How droplets move on laser-structured surfaces: Determination of droplet adhesion forces on nano- and microstructured surfaces.

HYPOTHESIS: Lateral adhesion forces are a fundamental property of liquid-solid interactions and a key aspect of dynamic droplet mobility. But, commonly applied conventional wetting analysis is limited to static and quasi-static methods and cannot resolve dynamic and spatial liquid-solid interactions. However, droplet mobility is assumed to be affected by chemical and topographic surface inhomogeneities introduced by femtosecond laser treatment. EXPERIMENTS: In this study, we used a customized droplet adhesion force instrument to determine lateral adhesion forces on various femtosecond laser-structured surface designs to obtain a deeper understanding of the dynamic droplet motion with regard to chemical and topographic surface features. FINDINGS: We show that the droplet motion was highly affected by the chemical and topographical surface design and local inhomogeneities. The droplet mobility on femtosecond laser-structured surfaces could be classified into a static, a transfer, and a kinetic regime, which is essential for designing surfaces with extreme wetting characteristics and a wide range of scientific and industrial processes. Furthermore, with proper tailoring of surface structures and chemical modification, we were able to provoke adhesion forces on self-organized laser microstructures similar to those found on the natural lotus leaves.

Impact of sodium nitroprusside concentration added to batch cultures of Escherichia coli biofilms on the c-di-GMP levels, morphologies and adhesion of biofilm-dispersed cells.

Biofilm dispersion can be triggered by the application of dispersing agents such as nitric oxide (NO)-donors, resulting in the release of biofilm-dispersed cells into the environment. In this work, biofilm-dispersed cells were obtained by adding different concentrations of NO-donor sodium nitroprusside (0.5, 5, 50 µM, and 2.5 mM of SNP) to batch cultures of pre-formed Escherichia coli biofilms. Except for those dispersed by 5 µM of SNP, biofilm-dispersed cells were found to be wider and longer than the planktonic cells and to have higher c-di-GMP levels and greater adhesion forces to silicon nitride surfaces in water as measured by atomic force microscope. Consequently, the optimum concentration of SNP to disperse E. coli biofilms was found to be 5 µM of SNP, whose addition to batch cultures resulted in a significant biofilm dispersion and the dispersed cells having c-di-GMP levels, morphologies and adhesion strengths similar to their planktonic counterparts.

The glycocalyx affects the mechanotransductive perception of the topographical microenvironment.

The cell/microenvironment interface is the starting point of integrin-mediated mechanotransduction, but many details of mechanotransductive signal integration remain elusive due to the complexity of the involved (extra)cellular structures, such as the glycocalyx. We used nano-bio-interfaces reproducing the complex nanotopographical features of the extracellular matrix to analyse the glycocalyx impact on PC12 cell mechanosensing at the nanoscale (e.g., by force spectroscopy with functionalised probes). Our data demonstrates that the glycocalyx configuration affects spatio-temporal nanotopography-sensitive mechanotransductive events at the cell/microenvironment interface. Opposing effects of major glycocalyx removal were observed, when comparing flat and specific nanotopographical conditions. The excessive retrograde actin flow speed and force loading are strongly reduced on certain nanotopographies upon strong reduction of the native glycocalyx, while on the flat substrate we observe the opposite trend. Our results highlight the importance of the glycocalyx configuration in a molecular clutch force loading-dependent cellular mechanism for mechanosensing of microenvironmental nanotopographical features.

Measurement of Interfacial Adhesion Force with a 3D-Printed Fiber-Tip Microforce Sensor.

With the current trend of device miniaturization, the measurement and control of interfacial adhesion forces are increasingly important in fields such as biomechanics and cell biology. However, conventional fiber optic force sensors with high Young's modulus (>70 GPa) are usually unable to measure adhesion forces on the micro- or nano-Newton level on the surface of micro/nanoscale structures. Here, we demonstrate a method for interfacial adhesion force measurement in micro/nanoscale structures using a fiber-tip microforce sensor (FTMS). The FTMS, with microforce sensitivity of 1.05 nm/µN and force resolution of up to 19 nN, is fabricated using femtosecond laser two-photon polymerization nanolithography to program a clamped-beam probe on the end face of a single-mode fiber. As a typical verification test, the micronewton-level contact and noncontact adhesion forces on the surfaces of hydrogels were measured by FTMS. In addition, the noncontact adhesion of human hair was successfully measured with the sensor.

Role of Interfacial Water in the Tribological Behavior of Graphene in an Electric Field.

Friction properties in the electric field are important for the application of graphene as a solid lubricant in graphene-based micro/nanoelectromechanical systems. The studies based on conductive atomic force microscopy show that interfacial water between graphene and the SiO2/Si substrate affects the friction of graphene in the electric field. Friction without applying voltage remains low because the interfacial water retains a stable ice-like network. However, friction after applying voltage increases because the polar water molecules are attracted by the electric field and gather around the tip. The gathered interfacial water not only increases the deformation of graphene but is also pushed by the tip during frictional sliding, which results in the increased friction. These studies provide beneficial guidelines for the applications of graphene as a solid lubricant in the electric field.

Role of fibronectin and IOL surface modification in IOL: Lens capsule interactions.

Posterior Capsule Opacification (PCO) is one of the most common complications of cataract surgery. While studies have shown that IOL material properties and fibronectin adsorption may affect IOL-induced PCO in the clinical setting, the mechanism governing such interactions is not totally understood. Since strong adhesion forces between IOLs and posterior capsules (PCs) have been shown to impede cell infiltration and thus reduce PCO formation, this study was designed to assess whether fibronectin adsorption and IOL material properties would impact the IOL:PC adhesion force and cell infiltration using a PCO predictive in vitro model and a macromolecular dye imaging model, respectively. Our results showed that fibronectin adsorption significantly increased the adhesion forces and reduced simulated cell infiltration between acrylic foldable IOLs and the PC at physiological temperature in comparison to fibronectin-free controls. This fibronectin-mediated strong IOL: PC bond may be contributing to low PCO rates in the clinic for acrylic foldable IOLs. In addition, acrylic foldable IOLs coated with Di(ethylene glycol) (Diglyme), a hydrophilic coating known to reduce protein adsorption, was tested for its ability to alter adhesion force and cell infiltration. We observed that IOLs coated with Diglyme coating greatly reduced surface hydrophobicity and fibronectin adsorption of acrylic foldable IOLs. Furthermore, Diglyme coated IOLs showed significantly reduced adhesion force and increased simulated cell infiltration at the IOL:PC interface. The overall results support the hypothesis that IOL surface properties and their ability to adsorb fibronectin may have great impact on the IOL:PC adhesion force. A tight binding between IOLs and PC may contribute to the reduction of cell infiltration and thus the PCO incidence rate in the clinic.