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A complex study of the adhesion of multi-walled carbon nanotubes to a titanium surface, depending on the modes of irradiation with He+ ions of the "MWCNT/Ti" system, was conducted using atomic force microscopy and X-ray photoelectron spectroscopy. A quantitative assessment of the adhesion force at the interface, performed using atomic force microscopy, demonstrated its significant increase as a result of treatment of the "MWCNT/Ti" system with a beam of helium ions. The nature of the chemical bonding between multi-walled carbon nanotubes and the surface of the titanium substrate, which causes this increase in the adhesion of nanotubes to titanium as a result of ion irradiation, was investigated by X-ray photoelectron spectroscopy. It was established that this bonding is the result of the formation of chemical C–O–Ti bonds between titanium and carbon atoms with the participation of oxygen atoms of oxygen-containing functional groups, which are localized on defects in the nanotube walls formed during ion irradiation. It is significant that there are no signs of direct bonding between titanium and carbon atoms. [ABSTRACT FROM AUTHOR]

We have investigated the morphology of two-dimensional monolayers of gramicidin-D (GD) and alamethicin (Al) formed on the water surface by the dropping method (DM) using surface tension measurement (STm), Brewster angle microscopy (BAM), and atomic force microscopy (AFM). Dynamic light scattering (DLS) revealed that GD in alcoholic solutions formed a dimeric helical structure. According to the CD and NMR spectroscopies, GD molecules existed in dimer form in methanol and lipid membrane environments. The STm results and BAM images revealed that the GD dimer monolayer was in a liquid expanded (LE) state, whereas the Al monolayer was in a liquid condensed (LC) state. The limiting molecular area (A0) was 6.2 ± 0.5 nm2 for the GD-dimer and 3.6 ± 0.5 nm2 for the Al molecule. The AFM images also showed that the molecular long axes of both the GD-dimer and Al were horizontal to the water surface. The stability of each monolayer was confirmed by the time dependence of the surface pressure (π) observed using the STm method. The DM monolayer preparation method for GD-dimer and Al peptide molecules is a useful technique for revealing how the model biological membrane's components assemble in two dimensions on the water surface. [ABSTRACT FROM AUTHOR]

Alzheimer's disease (AD) is the fifth leading cause of death among adults aged 65 and older, yet the onset and progression of the disease is poorly understood. What is known is that the presence of amyloid, particularly polymerized Aβ42, defines when people are on the AD continuum. Interestingly, as AD progresses, less Aβ42 is detectable in the plasma, a phenomenon thought to result from Aβ becoming more aggregated in the brain and less Aβ42 and Aβ40 being transported from the brain to the plasma via the CSF. We propose that extracellular vesicles (EVs) play a role in this transport. EVs are found in bodily fluids such as blood, urine, and cerebrospinal fluid and carry diverse "cargos" of bioactive molecules (e.g., proteins, nucleic acids, lipids, metabolites) that dynamically reflect changes in the cells from which they are secreted. While Aβ42 and Aβ40 have been reported to be present in EVs, it is not known whether this interaction is specific for these peptides and thus whether amyloid-carrying EVs play a role in AD and/or serve as brain-specific biomarkers of the AD process. To determine if there is a specific interaction between Aβ and EVs, we used isothermal titration calorimetry (ITC) and discovered that Aβ42 and Aβ40 bind to EVs in a manner that is sequence specific, saturable, and endothermic. In addition, Aβ incubation with EVs overnight yielded larger amounts of bound Aβ peptide that was fibrillar in structure. These findings point to a specific amyloid–EV interaction, a potential role for EVs in the transport of amyloid from the brain to the blood, and a role for this amyloid pool in the AD process. [ABSTRACT FROM AUTHOR]

In tropical regions, lack of moisture-damage-resistant fillers in flexible pavements poses significant challenges for infrastructure development and maintenance. Hence, this study examined sawdust ash (SDA) for such purposes. SDA is abundant as agricultural waste in rice-producing countries like India and China. Durability assessment of SDA-enriched bituminous concrete (BC) against moisture damage is considered as state-of-art in this investigation. To implement this study, numerous laboratory tests were carried out. First, the Marshall test was carried out to estimate the optimal bitumen content (OBC) and several Marshall properties, including Marshall volumetric properties. After that, a modified Marshall immersion test, energy loss ratio test, ultrasonic pulse velocity (UPV) test, indirect tensile strength test (ITS), resilient modulus ratio test, and rutting resistance test were done to execute this investigation. Furthermore, the morphological characteristics of the studied filler were investigated by atomic force microscopy (AFM). The experimental result shows that the 8% SDA-enriched BC mix may be applied in low-volume roads in tropical regions like India with 86.94% structural integrity for the presence of ample amounts of calcium oxide (CaO), silicon oxide (SiO2), ferric oxide (Fe2O3), and higher loss on ignition value in that ash. Moreover, the results have shown that the mixes containing 8% SDA perform exceptionally well against moisture damage with the highest energy loss ratio (63.27%) and dynamic modulus (12.1 MPa) after 14 days of immersion. Similarly, this type of mix delivers the highest tensile strength ratio (96.27%) and resilient modulus ratio (89.21%), with minimum rutting depth (9.55 mm), and performs not only in terms of moisture resistance but also in its ability to withstand rutting deformation significantly. These results make it a promising choice for asphalt pavements, to mitigate the detrimental effects of both rutting and moisture on the overall durability and longevity of the road. [ABSTRACT FROM AUTHOR]

[Display omitted] Humic acids (HA) are ubiquitous in surface waters, leading to significant fouling challenges. While zwitterion-like and zwitterionic surfaces have emerged as promising candidates for antifouling, a quantitative understanding of molecular interaction mechanism, particularly at the nanoscale, still remains elusive. In this work, the intermolecular forces between HA and charged, zwitterion-like or zwitterionic monolayers in aqueous environments were quantified using atomic force microscope. Compared to cationic MTAC ([2-(methacryloyloxy)ethyl]trimethylammonium chloride), which exhibited an adhesion energy of ∼1.342 mJ/m2 with HA due to the synergistic effect of electrostatic attraction and possible cation-π interaction, anionic SPMA (3-sulfopropyl methacrylate) showed a weaker adhesion energy (∼0.258 mJ/m2) attributed to the electrostatic repulsion. Zwitterion-like MTAC/SPMA mixture, driven by electrostatic attraction between opposite charges, formed a hydration layer that prevented the interaction with HA, thereby considerably reducing adhesion energy to ∼0.123 mJ/m2. In contrast, zwitterionic MPC (2-methacryloyloxyethyl phosphorylcholine) and DMAPS ([2-(methacryloyloxy)ethyl]dimethyl-(3-sulfopropyl) ammonium hydroxide) displayed ultralow adhesion energy (0.06–0.07 mJ/m2) with HA, arising from their strong dipole moments which could induce a tight hydration layer that effectively inhibited HA fouling. The pH-mediated electrostatic interaction resulted in the increased adhesion energy for MTAC but decreased adhesion energy for SPMA with elevated pH, while the adhesion energy for zwitterion-like and zwitterionic surfaces was independent of environmental pH. Density functional theory (DFT) simulation confirmed the strong binding capability of MPC and DMAPS with water molecules (∼–12 kcal mol−1). This work provides valuable insights into the molecular interaction mechanisms underlying humic-substance-fouling resistance of charged, zwitterion-like and zwitterionic materials at the nanoscale, shedding light on developing more effective strategy for HA antifouling in water treatment. [ABSTRACT FROM AUTHOR]

Here is described the influence of deposition parameters of ZnO thin films doped with Ga and co-doped with (Ga + Nd) upon the structural, morphological, optical and electrical properties. The transparent conductive thin films were fabricated by radiofrequency (RF) magnetron sputtering using a power of 100 W and a deposition distance of 6 cm. The deposition was performed on glass substrates heated at 150 °C with a time deposition of 90 min. The influence of doping upon the structure of thin films was analyzed by x-ray diffraction (XRD). Optical transmission measurements showed an 85% transparency in the visible range for the undoped ZnO films and the transparency of these films decreased when the dopants were added. Micro-structural analysis obtained by atomic force microscopy (AFM) evidenced that the type of doping modify the microstructure of thin films. Raman and resistivity measurements emphasize the successful incorporation of dopants into the ZnO host material. [ABSTRACT FROM AUTHOR]

We calculate a universal shift in work function of 59.4 meV per decade of dopant concentration change that applies to all doped semiconductors and from this use Monte Carlo simulations to simulate the resulting change in secondary electron yield for doped GaAs. We then compare experimental images of doped GaAs layers from scanning electron microscopy and conductive atomic force microscopy. Kelvin probe force microscopy allows to directly measure and map local work function changes, but values measured are often smaller, typically only around half, of what theory predicts for perfectly clean surfaces. LAY DESCRIPTION: Doping means the intentional contamination of a semiconductor by foreign atoms that are integrated as ions into the crystal lattice after either donating (as donors) additional electrons or (as acceptors) electronic holes and thereby change the local electric properties. The resulting material is called n‐ or p‐doped, and pn‐junctions are used in all diodes and transistors that form the basic units of more complicated electronic devices such as computers or solar cells. We calculate how doping changes the energy needed to extract an electron from the semiconductor (called its work function) and how this influences the secondary electron yield in scanning electron microscopy and resistive or Kelvin probe measurements in conductive atomic force microscopy. Both microscopy methods can be used to directly map the spatial distribution of dopants in doped nanostructures but quantitative measurements are difficult due to the influence of surface effects. [ABSTRACT FROM AUTHOR]

This study focuses on achieving mechanical enhancements in biocompatible organic coatings. A solvent‐based method is employed to produce biocompatible nanocomposites using polyvinylpyrrolidone (PVP) and bentonite nanoclays (BNT) as constituents to achieve this objective. Subsequently, the nanocomposites are spin‐coated onto a glass substrate, resulting in smooth and defect‐free films with a thickness of 5 μm. Through instrumented‐indentation testing, it is observed that BNT reinforcement leads to significant improvements in mechanical properties. Specifically, the addition of 0.5, 1, and 5 wt% of BNT in PVP results in enhancements of 105%, 77%, and 430% in elastic modulus, respectively, while hardness is improved by 166%, 211%, and 448%, respectively. The considerable improvements in the composite modulus cannot be adequately explained by assuming perfect adhesion between the constituents of the composite (as suggested by the Halpin–Tsai model) or by considering the contributions from the interface/network of silicate layers (as proposed by the Modified Halpin–Tsai model). Instead, the significant enhancements in hardness and modulus values are primarily attributed to a notable increase in the BNT volume fraction, ranging from 4 to 9 times, occurring under the Berkovich tip due to the aggregated silicate layers. The findings highlight the role of aggregated silicate layers in enhancing both hardness and modulus and contribute to the development of advanced biocompatible coatings with improved mechanical properties. Highlights: Enhanced mechanical properties in biocompatible coatings.Biocompatible nanocomposites of polyvinylpyrrolidone (PVP) and bentonite nanoclays (BNT).Spin‐coated nanocomposite films on glass: smooth, defect‐free, 5 μm thick.BNT reinforcement boosts elastic modulus and hardness of PVP.Aggregated silicate layers under compression drive substantial mechanical improvements. [ABSTRACT FROM AUTHOR]

This study investigates the interaction of polyacrylamide (PAM) of different functional groups (sulfonate vs. carboxylate) and charge density (30% hydrolysed vs. 10% hydrolysed) with calcium carbonate (CaCO3) via atomic force microscopy (AFM) and partly via molecular dynamic (MD) simulations. The PAM used were F3330 (30% hydrolysed), AN125 (25% sulfonated), and AN910 (% hydrolysed). A total of 100 ppm of PAMs was prepared in 0.1% NaCl, 3% NaCl, and 4.36% NaNO3 to be employed in AFM experiments, while oligomeric models (30 repeating units) of hydrolysed polyacrylamide (HPAM), sulfonated polyacrylamide (SPAM), and neutral PAM (NPAM) were studied on a model calcite surface on MD simulations. AFM analysis indicated that F3330 has a higher average adhesion and interaction energy with CaCO3 than AN125 due to the bulky sulfonate side group of AN125 interfering with SPAM adsorption. Steric repulsion of both PAMs was similar due to their comparable molecular weights and densities of the charged group. In contrast, AN910 showed lower average adhesion and interaction energy, along with slightly longer steric repulsion with calcite than F3330, suggesting AN910 adopts more loops and tails than the slightly flatter F3330 configuration. An increase in salt concentration from 0.1% to 3% NaCl saw a reduction in adhesion and interaction energy for F3330 and AN125 due to charge screening, while AN910 saw an increase, and these values increased further at 4.36% NaNO3. MD simulations revealed that the salt ions in the system formed salt bridges between PAM and calcite, indicating that the adhesion and interaction energy observed from AFM are likely to be the net balance between PAM charged group screening and salt bridging by the salt ions present. Salt ions with larger bare radii and smaller hydrated radii were shown to form stronger salt bridges. [ABSTRACT FROM AUTHOR]

The plasticity and growth of plant cell walls (CWs) remain poorly understood at the molecular level. In this work, we used atomic force microscopy (AFM) to observe elastic responses of the root transition zone of 4‐day‐old Arabidopsis thaliana wild‐type and almt1‐mutant seedlings grown under Fe or Al stresses. Elastic parameters were deduced from force‐distance curve measurements using the trimechanic‐3PCS framework. The presence of single metal species Fe2+ or Al3+ at 10 µM exerts no noticeable effect on the root growth compared with the control conditions. On the contrary, a mix of both the metal ions produced a strong root‐extension arrest concomitant with significant increase of CW stiffness. Raising the concentration of either Fe2+ or Al3+ to 20 µM, no root‐extension arrest was observed; nevertheless, an increase in root stiffness occurred. In the presence of both the metal ions at 10 µM, root‐extension arrest was not observed in the almt1 mutant, which substantially abolishes the ability to exude malate. Our results indicate that the combination of Fe2+ and Al3+ with exuded malate is crucial for both CW stiffening and root‐extension arrest. However, stiffness increase induced by single Fe2+ or Al3+ is not sufficient for arresting root growth in our experimental conditions. Summary statement: We investigate the change in stiffness of the external primary cell wall of living Arabidopsis thaliana seedlings in the presence of metallic stress using atomic force microscopy. Results reveal for the first time the uncoupling between mechanical response (CW stiffening) and root extension arrest. [ABSTRACT FROM AUTHOR]

In this paper we present the results of atomic force microscopy (AFM), which is applied to characterize the surface morphology of graphite samples with glassy carbon coatings is developed, stored for 28 months under different conditions. One sample was stored on Earth at room temperature and second one was mounted on the outer side of the International Space Station. [ABSTRACT FROM AUTHOR]

Simulation of atomic force microscopy (AFM) computationally emulates experimental scanning of a biomolecular structure to produce topographic images that can be correlated with measured images. Its application to the enormous amount of available high-resolution structures, as well as to molecular dynamics modelling data, facilitates the quantitative interpretation of experimental observations by inferring atomistic information from resolution-limited measured topographies. The computation required to generate a simulated AFM image generally includes the calculation of contacts between the scanning tip and all atoms from the biomolecular structure. However, since only contacts with surface atoms are relevant, a filtering method shall highly improve the efficiency of simulated AFM computations. In this report, we address this issue and present an elegant solution based on graphics processing unit (GPU) computations that significantly accelerates the computation of simulated AFM images. This method not only allows for the visualization of biomolecular structures combined with ultra-fast synchronized calculation and graphical representation of corresponding simulated AFM images (live simulation AFM), but, as we demonstrate, it can also reduce the computational effort during the automatized fitting of atomistic structures into measured AFM topographies by orders of magnitude. Hence, the developed method will play an important role in post-experimental computational analysis involving simulated AFM, including expected applications in machine learning approaches. The implementation is realized in our BioAFMviewer software (ver. 3) package for simulated AFM of biomolecular structures and dynamics. [ABSTRACT FROM AUTHOR]

One route to the improvement of thermoelectric material performance is nanostructuring. Herein, BiSb thin films are grown by molecular‐beam epitaxy on two types of InP(001) substrate: flat epiready wafer, and nano‐patterned by ion bombardment and annealing (IBA). The effects of IBA on InP substrate are presented, and the structural and electrical properties of the BiSb films are measured. BiSb films on flat substrates are highly textured with (003) orientation, while films on IBA‐patterned substrates are less well ordered with mainly (012) orientation. A simple calculation method for nonplanar Hall measurements is proposed to explain the electrical conduction in rough films. The effects of BiSb film texture, roughness, and thickness on carrier density and mobility are provided. Sheet carrier density is independent of thickness at 77 K, which suggests conduction via surface states. Topological protection of such states may support nano‐patterning as a route to reducing thermal conductivity while maintaining electrical conductivity. [ABSTRACT FROM AUTHOR]

Composite modification of an asphalt binder forms an interesting approach to enhance the properties over diverse performance regimes. Aging of asphalt binders during the production, construction, and service life of the asphalt mixtures in pavement increases its stiffness and may have a negative impact on their resistance toward fatigue and low-temperature cracking, thus generating the need to evaluate the aging behavior of a composite-modified asphalt binder. This study analyzed the aging characteristics of individual and composite asphalt binders produced with waste ethylene-propylene-diene-monomer (EPDM) rubber, derived from manufacturing units dealing with nontire automotive rubber products, and the tire pyrolysis oil (TPO) derived from the pyrolysis of scrap tires. Three different pathways were used to formulate composite-modified binders, namely, without pretreatment and with pretreatment through heat and microwave irradiation. The study focused on the evaluation of physical, rheological, chemical, and microstructural characteristics of the composite-modified binders produced in different manners after being subjected to both short-term and long-term aging. Results showed that the effect of aging was adverse on the base binder and the binder prepared with TPO alone. In contrast, the addition of EPDM rubber alone improved the binder's aging resistance. The composite-modified binder through the pretreatment yielded significantly improved performance against aging; thus, composite modification with pretreatment can be a useful approach to yield aging-resistant binders prepared by EPDM and TPO. [ABSTRACT FROM AUTHOR]

Light can effectively interrogate biological systems in a reversible and physiologically compatible manner with high spatiotemporal precision. Understanding the biophysics of photo‐induced processes in bio‐systems is crucial for achieving relevant clinical applications. Employing membranes doped with the photolipid azobenzene‐phosphatidylcholine (azo‐PC), a holistic picture of light‐triggered changes in membrane kinetics, morphology, and material properties obtained from correlative studies on cell‐sized vesicles, Langmuir monolayers, supported lipid bilayers, and molecular dynamics simulations is provided. Light‐induced membrane area increases as high as ≈25% and a ten‐fold decrease in the membrane bending rigidity is observed upon trans‐to‐cis azo‐PC isomerization associated with membrane leaflet coupling and molecular curvature changes. Vesicle electrodeformation measurements and atomic force microscopy reveal that trans azo‐PC bilayers are thicker than palmitoyl‐oleoyl phosphatidylcholine (POPC) bilayers but have higher specific membrane capacitance and dielectric constant suggesting an increased ability to store electric charges across the membrane. Lastly, incubating POPC vesicles with azo‐PC solutions results in the insertion of azo‐PC in the membrane enabling them to become photoresponsive. All these results demonstrate that light can be used to finely manipulate the shape, mechanical and electric properties of photolipid‐doped minimal cell models, and liposomal drug carriers, thus, presenting a promising therapeutic alternative for the repair of cellular disorders. [ABSTRACT FROM AUTHOR]

This study investigates the mechanical properties, degradation behavior, and biocompatibility of poly[(α-amino acid ester) phosphazene] electrospun fibers based on the ethyl ester of L-methionine (PαAPz-M), a material with potential applications in tissue engineering. We utilized atomic force microscopy (AFM) to evaluate the fiber mechanical characteristics and calculate its Young's modulus, revealing it to closely mimic the stiffness of a natural extracellular matrix (ECM). We also studied the degradation behavior of PαAPz-M scaffolds over 21 days, showing that they maintain the highly porous structure required for tissue engineering. Further evaluation of mesenchymal multipotent 10T1/2 cell and mesenchymal stem cell (MSC) behavior on the scaffolds demonstrated significant cell viability, proliferation, and successful MSC differentiation into smooth muscle cells. Expression of collagen and elastin by MSCs on the fiber mats highlighted potential ECM formation during scaffold degradation, confirming PαAPz-M as a promising material for vascular tissue engineering. [ABSTRACT FROM AUTHOR]

The biophysical properties of cells described at the level of whole cells or their membranes have many consequences for their biological behavior. However, our understanding of the relationships between mechanical parameters at the level of cell (stiffness, viscoelasticity) and at the level of the plasma membrane (fluidity) remains quite limited, especially in the context of pathologies, such as cancer. Here, we investigated the correlations between cells' stiffness and viscoelastic parameters, mainly determined via the actin cortex, and plasma membrane microviscosity, mainly determined via its lipid profile, in cancer cells, as these are the keys to their migratory capacity. The mechanical properties of cells were assessed using atomic force microscopy (AFM). The microviscosity of membranes was visualized using fluorescence-lifetime imaging microscopy (FLIM) with the viscosity-sensitive probe BODIPY 2. Measurements were performed for five human colorectal cancer cell lines that have different migratory activity (HT29, Caco-2, HCT116, SW 837, and SW 480) and their chemoresistant counterparts. The actin cytoskeleton and the membrane lipid composition were also analyzed to verify the results. The cell stiffness (Young's modulus), measured via AFM, correlated well (Pearson r = 0.93) with membrane microviscosity, measured via FLIM, and both metrics were elevated in more motile cells. The associations between stiffness and microviscosity were preserved upon acquisition of chemoresistance to one of two chemotherapeutic drugs. These data clearly indicate that mechanical parameters, determined by two different cellular structures, are interconnected in cells and play a role in their intrinsic migratory potential. [ABSTRACT FROM AUTHOR]

Previously, the analysis of atomic force microscopy (AFM) images allowed us to distinguish normal from cancerous/precancerous human epithelial cervical cells using only the fractal dimension parameter. High-resolution maps of adhesion between the AFM probe and the cell surface were used in that study. However, the separation of cancerous and precancerous cells was rather poor (the area under the curve (AUC) was only 0.79, whereas the accuracy, sensitivity, and specificity were 74%, 58%, and 84%, respectively). At the same time, the separation between premalignant and malignant cells is the most significant from a clinical point of view. Here, we show that the introduction of machine learning methods for the analysis of adhesion maps allows us to distinguish precancerous and cancerous cervical cells with rather good precision (AUC, accuracy, sensitivity, and specificity are 0.93, 83%, 92%, and 78%, respectively). Substantial improvement in sensitivity is significant because of the unmet need in clinical practice to improve the screening of cervical cancer (a relatively low specificity can be compensated by combining this approach with other currently existing screening methods). The random forest decision tree algorithm was utilized in this study. The analysis was carried out using the data of six precancerous primary cell lines and six cancerous primary cell lines, each derived from different humans. The robustness of the classification was verified using K-fold cross-validation (K = 500). The results are statistically significant at p < 0.0001. Statistical significance was determined using the random shuffle method as a control. [ABSTRACT FROM AUTHOR]

The salt erosion environment will lead to the deterioration of asphalt pavement performance and seriously restrict the service life and sustainability of asphalt pavement. In this research, the evolution mechanism of asphalt performance induced by chloride salt erosion was explored by atomic force microscopy (AFM) and molecular dynamics (MD) simulation from the nanoscale. The AFM test results demonstrated that with increasing chloride salt concentration and erosion time, the adhesion force, adhesion energy, surface free energy, and dissipated energy of asphalt binder decreased significantly. The fitted modulus of the four contact mechanics models all decrease with increasing chloride erosion time. It is recommended to use the Cone Sphere or Johnson-Kendall-Roberts (JKR) model to fit the Young's modulus of asphalt binder. The MD simulation results show that the tensile strength and shear strength of asphalt binder in the three directions decreased after chloride salt erosion, and there are differences in the magnitude of reduction in different directions. Chloride salt erosion not only inhibits the translational migration behavior of SARA fractions [saturates (S), aromatics (A), resin (R), and asphaltenes (A)] but also limits the rotational migration behavior. Although chloride salt erosion has little effect on the aggregation behavior of asphaltene, it still affects the degree of molecular entanglement of SARA fractions. The distribution of asphalt molecules becomes heterogeneous after chloride salt erosion. This research not only presents the erosion damage mechanisms of the asphalt binder but also helps to promote the sustainability of the asphalt pavements exposed to a chloride salt environment. [ABSTRACT FROM AUTHOR]

In this work, the interaction of hydrolysed polyacrylamide (HPAM) of two molecular weights (F3330, 11–13 MDa; F3530, 15–17 MDa) with calcium carbonate (CaCO3) was studied via atomic force microscopy (AFM). In the absence of polymers at 1.7 mM and 1 M NaCl, good agreement with DLVO theory was observed. At 1.7 mM NaCl, repulsive interaction during approach at approximately 20 nm and attractive adhesion of approximately 400 pN during retraction was measured, whilst, at 1 M NaCl, no repulsion during approach was found. Still, a significantly larger adhesion of approximately 1400 pN during retraction was observed. In the presence of polymers, results indicated that F3330 displayed higher average adhesion (450–625 pN) and interaction energy (43–145 aJ) with CaCO3 than F3530's average adhesion (85–88 pN) and interaction energy (8.4–11 aJ). On the other hand, F3530 exerted a longer steric repulsion distance (70–100 nm) than F3330 (30–70 nm). This was likely due to the lower molecular weight. F3330 adopted a flatter configuration on the calcite surface, creating more anchor points with the surface in the form of train segments. The adhesion and interaction energy of both HPAM with CaCO3 can be decreased by increasing the salt concentration. At 3% NaCl, the average adhesion and interaction energy of F3330 was 72–120 pN and 5.6–17 aJ, respectively, while the average adhesion and interaction energy of F3530 was 11.4–48 pN and 0.3–2.98 aJ, respectively. The reduction of adhesion and interaction energy was likely due to the screening of the COO− charged group of HPAM by salt cations, leading to a reduction of electrostatic attraction between the negatively charged HPAM and the positively charged CaCO3. [ABSTRACT FROM AUTHOR]

Astrocyte cells play a critical role in the mechanical behaviour of the brain tissue; hence understanding the properties of Astrocytes is a big step toward understanding brain diseases and abnormalities. Conventionally, atomic force microscopy (AFM) has been used as one of the most powerful tools to characterize the mechanical properties of cells. However, due to the complexities of experimental work and the complex behaviour of living cells, the finite element method (FEM) is commonly used to estimate the cells' response to mechanical stimulations. In this study, we developed a finite element model of the Astrocyte cells to investigate the effect of two key parameters that could affect the response of the cell to mechanical loading; the properties of the underlying substrate and the nucleus. In this regard, the cells were placed on two different substrates in terms of thickness and stiffness (gel and glass) with varying properties of the nucleus. The main achievement of this study was to develop an insight to investigate the response of the Astrocytes to mechanical loading for future studies, both experimentally and computationally. [ABSTRACT FROM AUTHOR]

Rhodopsin is a G protein‐coupled receptor (GPCR) present in the rod outer segment (ROS) of photoreceptor cells that initiates the phototransduction cascade required for scotopic vision. Due to the remarkable advancements in technological tools, the chemistry of rhodopsin has begun to unravel especially over the past few decades, but mostly at the ensemble scale. Atomic force microscopy (AFM) is a tool capable of providing critical information from a single‐molecule point of view. In this regard, to bolster our understanding of rhodopsin at the nanoscale level, AFM‐based imaging, force spectroscopy, and nano‐indentation techniques were employed on ROS disc membranes containing rhodopsin, isolated from vertebrate species both in normal and diseased states. These AFM studies on samples from native retinal tissue have provided fundamental insights into the structure and function of rhodopsin under normal and dysfunctional states. We review here the findings from these AFM studies that provide important insights on the supramolecular organization of rhodopsin within the membrane and factors that contribute to this organization, the molecular interactions stabilizing the structure of the receptor and factors that can modify those interactions, and the mechanism underlying constitutive activity in the receptor that can cause disease. [ABSTRACT FROM AUTHOR]

Cowpea chlorotic mottle virus (CCMV) and brome mosaic virus (BMV) are naked plant viruses with similar characteristics; both form a T = 3 icosahedral protein capsid and are members of the bromoviridae family. It is well known that these viruses completely disassemble and liberate their genome at a pH around 7.2 and 1 M ionic strength. However, the 1 M ionic strength condition is not present inside cells, so an important question is how these viruses deliver their genome inside cells for their viral replication. There are some studies reporting the swelling of the CCMV virus using different techniques. For example, it is reported that at a pH~7.2 and low ionic strength, the swelling observed is about 10% of the initial diameter of the virus. Furthermore, different regions within the cell are known to have different pH levels and ionic strengths. In this work, we performed several experiments at low ionic strengths of 0.1, 0.2, and 0.3 and systematically increased the pH in 0.2 increments from 4.6 to 7.4. To determine the change in virus size at the different pHs and ionic strengths, we first used dynamic light scattering (DLS). Most of the experiments agree with a 10% capsid swelling under the conditions reported in previous works, but surprisingly, we found that at some particular conditions, the virus capsid swelling could be as big as 20 to 35% of the original size. These measurements were corroborated by atomic force microscopy (AFM) and transmission electron microscopy (TEM) around the conditions where the big swelling was determined by DLS. Therefore, this big swelling could be an easier mechanism that viruses use inside the cell to deliver their genome to the cell machinery for viral replication. [ABSTRACT FROM AUTHOR]

Nanofiber mats can be electrospun by different techniques, usually subdivided into needle-based and needleless. The latter allow for producing large-area nanofiber mats, e.g., with a width of 50 cm and lengths of several meters, if electrospinning proceeds for several hours, depending on the required thickness. Even spinning smaller samples, however, raises the question of homogeneity, especially if defined mechanical properties or a defined thickness is required, e.g., for filtration purposes. Very often, only the inner parts of such electrospun nanofiber mats are used to avoid too high variation of the nanofiber mat thickness. For this study, we used wire-based electrospinning to prepare nanofiber mats with slightly varying spinning parameters. We report investigations of the thickness and mass per unit area, measured on different positions of needleless electrospun nanofiber mats. Martindale abrasion tests on different positions are added as a measure of the mechanical properties. All nanofiber mats show unexpectedly strong variations of thickness, mass per unit area, and porosity, as calculated from the apparent density of the membranes. The thickness especially varied by nearly one order of magnitude within one sample, while the apparent density, as the most uniform parameter, still showed variations by more than a factor of two within one sample. This shows that even for apparently highly homogeneous areas of such nanofiber mats, variations cannot be neglected for all potential applications. [ABSTRACT FROM AUTHOR]

Induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs) hold enormous potential in cardiac disease modeling, drug screening, and regenerative medicine. Furthermore, patient-specific iPSC-CMS can be tested for personalized medicine. To provide a deeper understanding of the contractile force dynamics of iPSC-CMs, we employed Atomic Force Microscopy (AFM) as an advanced detection tool to distinguish the characteristics of force dynamics at a single cell level. We measured normal (vertical) and lateral (axial) force at different pacing frequencies. We found a significant correlation between normal and lateral force. We also observed a significant force–frequency relationship for both types of forces. This work represents the first demonstration of the correlation of normal and lateral force from individual iPSC-CMs. The identification of this correlation is relevant because it validates the comparison across systems and models that can only account for either normal or lateral force. These findings enhance our understanding of iPSC-CM properties, thereby paving the way for the development of therapeutic strategies in cardiovascular medicine. [ABSTRACT FROM AUTHOR]

This study analyzed the influence of asphalt binder nanostructures and inherent variability on their mechanical responses. This was achieved by reconstructing asphalt binder nanostructures using generative adversarial networks (GANs). GANs are able to detect hidden patterns in a given data set automatically, and they generate distribution-free data because they are not bound to specific probability functions. The mechanical responses of GANs-generated nanostructures were analyzed using finite-element (FE) analysis. The asphalt nanostructures were captured using atomic force microscopy (AFM). To overcome the limited number of AFM nanostructures, image augmentation techniques and stochastic random fields (RF) modeling were used to generate virtual images of asphalts' nanostructures, which were utilized as the expanded training data set for the GANs. This approach helped to enhance the GANs' generalization abilities and avoid training problems such as mode collapse. Modeling parameters were optimized to expedite the training process and reduce the computational time. The results demonstrated that GANs are capable of generating probable arrangements of nanostructures, thus expanding the body of knowledge regarding probabilistic analysis of asphalt mechanical behavior. The ability of GANs to reconstruct nanostructures indicates that the complex and variable nature of asphalt nanostructures can be identified and replicated by GANs, offering the opportunity to generate many replicates of nanostructures without the need to conduct many laboratory tests. The results successfully related the properties and distribution of the asphalt nanostructures to the variation in the mechanical response. This study proposes a methodology that combines aspects of AFM testing, GANs modeling, and FE modeling for the analysis of the mechanical response of asphalt binder nanostructures. The outcomes of this work link nanoscale properties to bulk properties. Consequently, practitioners and researchers can use the developed methodology to study uncertainty in mechanical response of asphalt binders and design blends with tailored properties and enhanced performance. Researchers also can benefit from this methodology to incorporate sustainable modifiers that enhance fundamental nanoscale properties of asphalt binders. Moreover, this work enables computational evaluation of various material designs that would be impractical to conduct in a laboratory environment, thus conserving resources. Finally, the methodology can be generalized to study nanostructures of other engineering materials to optimize their performance. [ABSTRACT FROM AUTHOR]

An in‐depth understanding of the mechanical properties of the dermis is indispensable to improve wound healing or slow‐down skin ageing. Despite crucial research issues for dermatological and cosmetic industries, very little is known about the mechanical behaviour of the dermis at nanoscale level. This knowledge is relevant not only to human skin but also to mouse skin since this animal model is widely used in basic and preclinical studies for skin biology and health. Here, we describe an original protocol that we developed to specifically measure the mechanical properties of mouse dermis using atomic force microscopy‐based nano‐indentation approach. Using horizontal cryosections (i.e. parallel to the skin surface) performed at different depths through the dermis of dorsal skin, our protocol allowed us to detect nanoscale mechanical changes between female and male dermis samples. We found that the dermis was softer (i) in females than in males and (ii) with depth within the dermis of male mice. We also quantified compositional differences between female and male skin dermis and found that increased extracellular matrix gene expression and type V collagen staining were associated with increased dermal stiffness in male mice, compared with females. Our results demonstrating a sexual dimorphism in the nanomechanical properties and molecular composition of mouse dermis, open the way to better consider sex‐related cutaneous differences to understand skin disease and to stimulate the development of female versus male‐specific products with more appropriate dermatological treatments and cosmetic interventions. [ABSTRACT FROM AUTHOR]

[Display omitted] Bacteria adapt the mechanical properties of their cell envelope, including cell wall stiffness, turgor, and cell wall tension and deformation, to grow and survive in harsh environments. However, it remains a technical challenge to simultaneously determine these mechanical properties at a single cell level. Here we combined theoretical modelling with an experimental approach to quantify the mechanical properties and turgor of Staphylococcus epidermidis. It was found that high osmolarity leads to a decrease in both cell wall stiffness and turgor. We also demonstrated that the turgor change is associated with a change in the viscosity of the bacterial cell. We predicted that the cell wall tension is much higher in deionized (DI) water and it decreases with an increase in osmolality. We also found that an external force increases the cell wall deformation to reinforce its adherence to a surface and this effect can be more significant in lower osmolarity. Overall, our work highlights how bacterial mechanics supports survival in harsh environments and uncovers the adaption of bacterial cell wall mechanical integrity and turgor to osmotic and mechanical challenges. [ABSTRACT FROM AUTHOR]

Automobile/industrial waste ethylene-propylene-diene monomer (EPDM) rubber has attracted considerable interest as a potential asphalt binder modifier. A rubberized asphalt binder must have adequate storage stability to assure homogeneity during storage and hauling and attain the desired performance after construction. This study focused on the application of tire pyrolytic oil (TPO) derived from the pyrolysis of scrap tires as an additive for composite modification to enhance the storage stability of the EPDM rubberized binder. Sequential and pretreatment were the two different approaches employed to produce the TPO-EPDM rubberized asphalt binders in this work. Furthermore, the effect of a crosslinking agent (sulfur) on the compatibility of the TPO-EPDM rubberized binder was investigated for both sequential and pretreatment approaches. In all total, 18 different combinations of rubberized binders with EPDM, TPO, and sulfur were fabricated for storage stability characterization. Various empirical, rheological, chemical, and microstructural analyses based separation parameters indicated that TPO usage enhanced the storage stability of rubberized asphalt binder. Both sequential and pretreatment approaches increased the storage stability of EPDM rubberized binders with an increase in TPO dosages; however, the pretreatment approach outperformed the sequential approach. The addition of sulfur further improved the compatibility of rubberized binders. The results of Fourier transform infrared spectroscopy (FTIR) and atomic force microscopy (AFM)–based separation parameters were similar to those found using empirical and rheological tests. Grey relational analysis (GRA) was used to rank the binders according to their separation parameters. GRA showed the best results in both sequential and pretreatment approaches with and without sulfur for an optimal TPO dosage of 6%. The enhanced storage stability performance of rubberized binders with the incorporation of TPO in the pretreatment approach of binder preparation was attributed to the achieved preswelling of rubber particles during premixing and conditioning processes. [ABSTRACT FROM AUTHOR]

Daunomycin (DM), an anthracycline antibiotic, is frequently used to treat various cancers, but the direct effects of DM on gene expression and DNA structure are unclear. We used an in vitro cell-free system, optimized with spermine (SP), to study the effect of DM on gene expression. A bimodal effect of DM on gene expression, weak promotion followed by inhibition, was observed with increasing concentration of DM. We also performed atomic force microscopy observation to measure how DM affects the higher-order structure of DNA induced with SP. DM destroyed SP-induced flower-like conformations of DNA by generating double-strand breaks, and this destructive conformational change of DNA corresponded to the inhibitory effect on gene expression. Interestingly, the weakly enhanced cell-free gene expression occurred as DNA conformations were elongated or relaxed at lower DM concentrations. We expect these newly unveiled DM effects on gene expression and the higher-order structure of DNA will contribute further to the development and refinement of useful anticancer therapy chemicals. [ABSTRACT FROM AUTHOR]

The human papillomavirus (HPV) E2 protein is essential for regulating the initiation of viral DNA replication as well as the regulation of transcription of certain HPV-encoded genes. Its ability to recognize and bind to its four recognition sequences in the viral origin is a key step in the initiation of HPV DNA replication. Thus, understanding the mechanism of DNA binding by E2 protein and the unique roles played by individual DNA sequence elements of the replication origin is essential. We have purified the recombinant full-length HPV type 11 E2 protein. Quantitative DNA binding analysis indicated E2 protein bound all four DNA binding sites with reasonably high affinities but with distinct preferences. It bound its cognate binding sites 1, 2, and 4 with higher affinities, but bound binding site 3 with lower affinity. Analysis of binding to these sites unraveled multiple sequence elements that appeared to influence E2 binding affinity and target discrimination, including the sequence of spacer region, flanking sequences, and proximity of E2 binding sites. Thermodynamic analysis indicated hydrophobic interaction in the protein-DNA complex formation. Our studies indicate a large multi-protein complex formation on the HPV-origin DNA, likely due to reasonably high binding affinities as well as intrinsic oligomerization propensity of E2 dimers. [ABSTRACT FROM AUTHOR]

The extracellular microenvironment regulates many of the mechanical and biochemical cues that direct musculoskeletal development and are involved in musculoskeletal disease. The extracellular matrix (ECM) is a main component of this microenvironment. Tissue engineered approaches towards regenerating muscle, cartilage, tendon, and bone target the ECM because it supplies critical signals for regenerating musculoskeletal tissues. Engineered ECM–material scaffolds that mimic key mechanical and biochemical components of the ECM are of particular interest in musculoskeletal tissue engineering. Such materials are biocompatible, can be fabricated to have desirable mechanical and biochemical properties, and can be further chemically or genetically modified to support cell differentiation or halt degenerative disease progression. In this review, we survey how engineered approaches using natural and ECM-derived materials and scaffold systems can harness the unique characteristics of the ECM to support musculoskeletal tissue regeneration, with a focus on skeletal muscle, cartilage, tendon, and bone. We summarize the strengths of current approaches and look towards a future of materials and culture systems with engineered and highly tailored cell–ECM–material interactions to drive musculoskeletal tissue restoration. The works highlighted in this review strongly support the continued exploration of ECM and other engineered materials as tools to control cell fate and make large-scale musculoskeletal regeneration a reality. [ABSTRACT FROM AUTHOR]

Self-assembling of organic molecules is of considerable interest seeing the development of functional biocompatible materials, micro- and nanoparticles, as well as the study of biomolecules structure and functioning. Here, we report on self-assembling of L-N-stearoyl glutamic acid and its dimethyl ester revealed by atomic force microscopy (AFM). The difference in size, shape, and behavior of the objects, detected on the surface, depending on their chemical nature, solvent, and AFM substrate, as well as deposition technique, is shown. Unwinding and re-assembling of the objects under the impact of the microscope probe were observed, indicating their quasi-stable chemical structure. [ABSTRACT FROM AUTHOR]

The precise observation of a solid–liquid interface by means of frequency modulation atomic force microscopy (FM-AFM) was performed, demonstrating its applicability to a study on lead acid batteries using an electrochemical test cell for in-liquid FM-AFM embedded with a specialized cantilever holder. The consistency and reproducibility of each surface profile observed via amplitude modulation AFM and FM-AFM were verified properly in a strong acidic electrolyte. In terms of FM-AFM, the ability to observe remarkable changes in the force mapping is the most beneficial, especially near the negative electrode surface. The localization of lignosulfonate (LS) added into the electrolyte as an expander could be visualized since this characteristic force mapping was captured when LS was added to electrolyte. [ABSTRACT FROM AUTHOR]

Background: Intracellular hemoglobin polymerization has been supposed to be the major determinant for the elevated rigidity/stiffness of sickle erythrocytes from sickle cell anemia (SCA) patients. However, the contribution of the cell envelope remains unclear. Results: In this study, using atomic force microscopy (AFM), we compared the normal and sickled erythrocyte surfaces for stiffness and topography. AFM detected that sickle cells had a rougher surface and were stiffer than normal erythrocytes and that sickle cell ghosts had a rougher surface (for both outer and inner surfaces) and were thicker than normal ghosts, the latter implying a higher membrane-associated hemoglobin content/layer in the sickle cell envelope. Compared to healthy subjects, the SCA patients had lower plasma lipoprotein levels. AFM further revealed that a mild concentration of methyl-β-cyclodextrin (MβCD, a putative cholesterol-depleting reagent) could induce an increase in roughness of erythrocytes/ghosts and a decrease in thickness of ghosts for both normal and sickle cells, implying that MβCD can alter the cell envelope from outside (cholesterol in the plasma membrane) to inside (membrane-associated hemoglobin). More importantly, MβCD also caused a more significant decrease in stiffness of sickle cells than that of normal erythrocytes. Conclusions: The data reveal that besides the cytosolic hemoglobin fibers, the cell envelope containing the membrane-associated hemoglobin also is involved in the biomechanical properties (e.g., stiffness and shape maintenance) of sickle erythrocytes. [ABSTRACT FROM AUTHOR]

As the requirements of micro-/nano printing technologies are continuously increasing, direct writing technologies on a submicron scale are drawing attention. One of the promising methods is a nozzle-based precision patterning with atomic force microscopy (AFM), which has the advantages of high position controllability including nozzle-to-substrate distance feedback under a nanometer scale. It uses a fluidic channel and a dispensing nozzle integrated with a cantilever structure for deflection monitoring. In this paper, we introduce micro/nanofluidics integrated cantilevers for nozzle-based precision patterning in several considerations: 1) numerous fabrication strategies for nozzle-integrated fluidic cantilevers; 2) methods for liquid transport; 3) methods for pattern formation; and 4) applications with various printing materials. [ABSTRACT FROM AUTHOR]

Neodymium titanate ( Nd 2 Ti 2 O 7 ) is a ferroelectric as well as a pyroelectric material with a transition temperature of 1480 °C. Hence, Nd 2 Ti 2 O 7 offers potential to be utilized as high temperature pyroelectric sensor in both bulk and thin film form. In this work, bulk Nd 2 Ti 2 O 7 powders were synthesized using solid state reaction method, which were later pressed into the pellets. Later, thin films of Nd 2 Ti 2 O 7 were deposited on commercially available platinized(111) silicon and Si(100) substrates via pulsed laser deposition technique. The huge c/a ratio (∼1.695) and the thermal expansion mismatch with most of the commonly used substrates like silicon and platinized silicon, results into crack formation in Nd 2 Ti 2 O 7 thin films. Crack formation on Nd 2 Ti 2 O 7 thin film, which deteriorates pyroelectric property of Nd 2 Ti 2 O 7 film, was suppressed by the introduction of La 0.7 Sr 0.3 M n O 3 ± δ buffer layer between the film and substrate. The calculated value of thermal expansion coefficient of Nd 2 Ti 2 O 7 is 2.86 × 10−5 °C−1. Moreover, thermally generated strain between Nd 2 Ti 2 O 7 film and platinum substrate was found to be around 2%. The piezoresponse force microscopy experiment confirms the existence of ferroelectric domains in the film. Pyroelectric coefficient (p) calculated from the pyrocurrent studies was estimated around 3.52 and 13.6 μC/m2K in the bulk and thin film, respectively. [ABSTRACT FROM AUTHOR]

Modeling ionizing radiation interaction with biological matter is a major scientific challenge, especially for protons that are nowadays widely used in cancer treatment. That presupposes a sound understanding of the mechanisms that take place from the early events of the induction of DNA damage. Herein, we present results of irradiation-induced complex DNA damage measurements using plasmid pBR322 along a typical Proton Treatment Plan at the MedAustron proton and carbon beam therapy facility (energy 137–198 MeV and Linear Energy Transfer (LET) range 1–9 keV/μm), by means of Agarose Gel Electrophoresis and DNA fragmentation using Atomic Force Microscopy (AFM). The induction rate Mbp−1 Gy−1 for each type of damage, single strand breaks (SSBs), double-strand breaks (DSBs), base lesions and non-DSB clusters was measured after irradiations in solutions with varying scavenging capacity containing 2-amino-2-(hydroxymethyl)propane-1,3-diol (Tris) and coumarin-3-carboxylic acid (C3CA) as scavengers. Our combined results reveal the determining role of LET and Reactive Oxygen Species (ROS) in DNA fragmentation. Furthermore, AFM used to measure apparent DNA lengths provided us with insights into the role of increasing LET in the induction of highly complex DNA damage. [ABSTRACT FROM AUTHOR]

Bone consists of organic (mostly collagen) and inorganic (mostly bioapatite mineral) components that are organized into hierarchical structures from nano-to macro-scales that provide load-bearing functions. The structures and properties of bone are affected by bone remodeling activities, which are affected by mechanotransduction, a process through which mechanical signals are converted to biochemical signals in cellular signaling. Atomic Force Microscopy (AFM) technique can be used to characterize the surface morphology and mechanical properties of the specimens and can achieve atomic resolution in the resulting images. Therefore, the AFM technique has been applied in bone research and has provided new understandings of the structures and properties of hierarchical structures in bone across multiple length scales. This review begins by introducing the tip-surface interactions and the operation modes of AFM, including the recently developed sub-resonance modes, including PeakForce Tapping mode. Then the contact adhesion theories used in analyzing AFM data are reviewed, followed by a systematic review of the applications of the AFM technique to bone and bone-related tissues and cells, including surface morphology imaging, contact indentation testing, and other mechanical tests. The applications of sub-resonance tapping mode to bone and other biological molecules, cells, and tissues are also reviewed. • Development and operation modes of Atomic Force Microscope (AFM). • Contact, adhesion, indentation theories and models related to AFM. • Application of AFM to research on bone and related tissues and cells. • Recent advances with PeakForce mapping AFM on bone research. [ABSTRACT FROM AUTHOR]

3D-printed materials are present in numerous applications, from medicine to engineering. The aim of this study is to assess their suitability for an application of interest today, that of testing of 3D-printed polylactic acid (PLA)-based reactors for biogas production using anaerobic digestion. The impact of temperature, pH, and aqueous phase on the tested bioreactor is investigated, together with the effect of the gaseous phase (i.e., produced biogas). Two batches of materials used separately, one after another inside the bioreactor were considered, in a realistic situation. Two essential parameters inside the reactor (i.e., pH and temperature) were continuously monitored during a time interval of 25 to 30 days for each of the two biogas-generating processes. To understand the impact of these processes on the walls of the bioreactor, samples of 3D-printed material were placed at three levels: at the top (i.e., outside the substrate), in the middle, and at the bottom of the bioreactor. The samples were analyzed using a non-destructive imaging method, Optical Coherence Tomography (OCT). An in-house developed swept-source (SS) OCT system, master–slave (MS) enhanced, operating at a central wavelength of 1310 nm was utilized. The 3D OCT images related to the degradation level of the material of the PLA samples were validated using Scanning Electron Microscopy (SEM). The differences between the impact of the substrate on samples situated at the three considered levels inside the reactor were determined and analyzed using their OCT B-scans (optical cross-section images). Thus, the impact of the biogas-generating process on the interior of the bioreactor was demonstrated and quantified, as well as the capability of OCT to perform such assessments. Therefore, future work may target OCT for in situ investigations of such bioreactors. [ABSTRACT FROM AUTHOR]

Microorganisms interplay with their neighbors according their intrinsic cellular adhesion and membrane rigidity. The protein receptors located at the cellular membrane mediate specific recognition processes with biomolecules and others cells. This topic has generated great interest based on the huge variability displayed at different environmental conditions. Aquatic ecosystems present notably versatility of microorganisms and dissolved molecules that mutually influence in their viability, proliferation and biological performance. Biodiversity preservation of the current water reservoirs strongly depends on the gathering of these properties and their accurate interpretation. Bulk measurements from meso-scale techniques provide average information of aquatic microorganisms hidden relevant details. For this reason, it is opportune to devote high-throughput single molecule tools as atomic force microscopy (AFM) to determine the physico-chemical properties exhibited by individual aquatic microorganisms and thus, establish a full comprehension of all parameters that influence the state of aquatic ecosystems. The present work aims to highlight the potential applications and future perspectives of AFM for the study of all living entities involved in aquatic ecosystems to better understand their inherent characteristics at the single molecule level. [ABSTRACT FROM AUTHOR]

The interplay between the mechanical properties of double-stranded and single-stranded DNA is a phenomenon that contributes to various genetic processes in which both types of DNA structures coexist. Highly stiff DNA duplexes can stretch single-stranded DNA (ssDNA) segments between the duplexes in a topologically constrained domain. To evaluate such an effect, we designed short DNA nanorings in which a DNA duplex with 160 bp is connected by a 30 nt single-stranded DNA segment. The stretching effect of the duplex in such a DNA construct can lead to the elongation of ssDNA, and this effect can be measured directly using atomic force microscopy (AFM) imaging. In AFM images of the nanorings, the ssDNA regions were identified, and the end-to-end distance of ssDNA was measured. The data revealed a stretching of the ssDNA segment with a median end-to-end distance which was 16% higher compared with the control. These data are in line with theoretical estimates of the stretching of ssDNA by the rigid DNA duplex holding the ssDNA segment within the nanoring construct. Time-lapse AFM data revealed substantial dynamics of the DNA rings, allowing for the formation of transient crossed nanoring formations with end-to-end distances as much as 30% larger than those of the longer-lived morphologies. The generated nanorings are an attractive model system for investigation of the effects of mechanical stretching of ssDNA on its biochemical properties, including interaction with proteins. [ABSTRACT FROM AUTHOR]

The most common neurological disorders, i.e., Parkinson's disease (PD) and Alzheimer's disease (AD), are characterized by degeneration of cognitive functions due to the loss of neurons in the central nervous system. The aggregation of amyloid proteins is an important pathological feature of neurological disorders.The aggregation process involves a series of complex structural transitions from monomeric to the formation of fibrils. Despite its potential importance in understanding the pathobiology of PD and AD diseases, the details of the aggregation process are still unclear. Nanoparticles (NPs) absorbed by the human circulatory system can interact with amyloid proteins in the human brain and cause PD. In this work, we report the study of the interaction between TiO2 nanoparticles (TiO2-NPs) and ZnO nanoparticles (ZnO-NPs) on the aggregation kinetics of β-amyloid fragment 1-40 (βA) and α-synuclein protein using surface-enhanced Raman spectroscopy (SERS) and tip-enhanced Raman spectroscopy (TERS). The characterizations of ZnO-NPs and TiO2-NPs were evaluated by X-ray diffraction (XRD) spectrum, atomic force microscopy (AFM), and UV-Vis spectroscopy. The interaction of nanoparticles with amyloid proteins was investigated by SERS. Our study showed that exposure of amyloid protein molecules to TiO2-NPs and ZnO-NPs after incubation at 37 °C caused morphological changes and stimulated aggregation and fibrillation. In addition, significant differences in the intensity and location of active Raman frequencies in the amide I domain were found. The principal component analysis (PCA) results show that the effect of NPs after incubation at 4 °C does not cause changes in βA structure. [ABSTRACT FROM AUTHOR]

Simple Summary: Colorectal cancer (CRC) is presently the third-most abundant and the second-most lethal cancer worldwide. Thus, there is a real and urgent need to investigate the processes behind the appearance, development, and proliferation of CRC cells. Several biochemical pathways have been investigated to understand their role in oncogene activation and tumor-suppressor gene inhibition. Despite the research increase in biochemistry, there is still a need to better understand the biophysical cues that drive the activation of signaling pathways relevant to mechanotransduction and cell transformation. The elucidation of these biological processes may help to hinder oncogenic mechanisms and to find biomarkers that could be used to design more personalized therapeutic strategies. Colorectal cancer (CRC) has been addressed in the framework of molecular, cellular biology, and biochemical traits. A new approach to studying CRC is focused on the relationship between biochemical pathways and biophysical cues, which may contribute to disease understanding and therapy development. Herein, we investigated the mechanical properties of CRC cells, namely, HCT116, HCT15, and SW620, using static and dynamic methodologies by atomic force microscopy (AFM). The static method quantifies Young's modulus; the dynamic method allows the determination of elasticity, viscosity, and fluidity. AFM results were correlated with confocal laser scanning microscopy and cell migration assay data. The SW620 metastatic cells presented the highest Young's and storage moduli, with a defined cortical actin ring with distributed F-actin filaments, scarce vinculin expression, abundant total focal adhesions (FAK), and no filopodia formation, which could explain the lessened migratory behavior. In contrast, HCT15 cells presented lower Young's and storage moduli, high cortical tubulin, less cortical F-actin and less FAK, and more filopodia formation, probably explaining the higher migratory behavior. HCT116 cells presented Young's and storage moduli values in between the other cell lines, high cortical F-actin expression, intermediate levels of total FAK, and abundant filopodia formation, possibly explaining the highest migratory behavior. [ABSTRACT FROM AUTHOR]

Atomic Force Microscopy (AFM) is widely used for topographic imaging of DNA and protein-DNA complexes in ambient conditions with nanometer resolution. In AFM studies of protein-DNA complexes, identifying the protein's location on the DNA substrate is one of the major goals. Such studies require distinguishing between the DNA ends, which can be accomplished by end-specific labeling of the DNA substrate. We selected as labels three-way DNA junctions (3WJ) assembled from synthetic DNA oligonucleotides with two arms of 39–40 bp each. The third arm has a three-nucleotide overhang, GCT, which is paired with the sticky end of the DNA substrate generated by the SapI enzyme. Ligation of the 3WJ results in the formation of a Y-type structure at the end of the linear DNA mole cule, which is routinely identified in the AFM images. The yield of labeling is 69%. The relative orientation of arms in the Y-end varies, such dynamics were directly visualized with time-lapse AFM studies using high-speed AFM (HS-AFM). This labeling approach was applied to the characterization of the nucleosome arrays assembled on different DNA templates. HS-AFM experiments revealed a high dynamic of nucleosomes resulting in a spontaneous unraveling followed by disassembly of nucleosomes. [ABSTRACT FROM AUTHOR]

T7 phages are E. coli-infecting viruses that find and invade their target with high specificity and efficiency. The exact molecular mechanisms of the T7 infection cycle are yet unclear. As the infection involves mechanical events, single-particle methods are to be employed to alleviate the problems of ensemble averaging. Here we used TIRF microscopy to uncover the spatial dynamics of the target recognition and binding by individual T7 phage particles. In the initial phase, T7 virions bound reversibly to the bacterial membrane via two-dimensional diffusive exploration. Stable bacteriophage anchoring was achieved by tail-fiber complex to receptor binding which could be observed in detail by atomic force microscopy (AFM) under aqueous buffer conditions. The six anchored fibers of a given T7 phage-displayed isotropic spatial orientation. The viral infection led to the onset of an irreversible structural program in the host which occurred in three distinct steps. First, bacterial cell surface roughness, as monitored by AFM, increased progressively. Second, membrane blebs formed on the minute time scale (average ~5 min) as observed by phase-contrast microscopy. Finally, the host cell was lysed in a violent and explosive process that was followed by the quick release and dispersion of the phage progeny. DNA ejection from T7 could be evoked in vitro by photothermal excitation, which revealed that genome release is mechanically controlled to prevent premature delivery of host-lysis genes. The single-particle approach employed here thus provided an unprecedented insight into the details of the complete viral cycle. [ABSTRACT FROM AUTHOR]

To explore the influence of water on the multiscale adhesive behavior between asphalt binder and aggregate, the nanosurface morphology and microsurface energy of asphalt binder and the macrobonding force between the asphalt binder and aggregate over different soaking times were examined using atomic force microscopy (AFM) and the pull-off test. Relationships between the macrobonding and the nanosurface roughness as well as the microsurface energy were analyzed. The results demonstrated that the effect of water on the surface morphology of asphalt binder was important. After immersion in water, water-induced bulges occurred on the asphalt binder surface, which further changed the nanosurface roughness and the surface energy of asphalt. As per the sensitivity results, it can be concluded that the surface energy of asphalt and the effective contact area between asphalt and aggregate were reduced because of moisture, thus resulting in the failure of adhesion. [ABSTRACT FROM AUTHOR]

This study evaluated tire pyrolytic oil (TPO) derived from waste tire pyrolysis as a rejuvenating agent for three types of aged asphalt binders (unmodified, polymer-modified, and crumb rubber–modified). Gas chromatography–mass spectrometry (GC–MS) was performed to identify chemical compounds present in TPO. The rheological characteristics of all binders were examined through the complex viscosity–frequency profile, zero-shear viscosity, failure temperature, Black space diagrams, Cole–Cole plots, Superpave fatigue parameter, Glover–Rowe parameter, and linear amplitude sweep (LAS) tests. Mass loss was also determined for the rejuvenated binders. All binders were subjected to Fourier transform infrared (FTIR) analysis, and sulfoxide and carbonyl indices were computed. Atomic force microscopy (AFM) was conducted to study the effect of TPO on the micromorphology of the binders. The normalized Euclidean distance approach was used to rank the rejuvenated binders with respect to the proximity of their rheological and FTIR characteristics to that of the unaged binder. The use of TPO as a rejuvenating agent enabled the aged binders to achieve properties comparable to those of the unaged asphalt binder. The AFM-based rejuvenation index (RI) indicated a good potential of TPO as a rejuvenator. The results of the binder rheological parameters and the FTIR indicators investigated in the study indicated that a 9% dosage of TPO as a rejuvenating agent was the most effective. [ABSTRACT FROM AUTHOR]

Amphiphilic copolymers with a main chain containing polyethylene glycol (PEG) and side chains of different molecular weight and hydrophobicity form spherical aggregates (micelles) in aqueous solution. The suitability of these for incorporation and delivery of small hydrophobic molecules depends strongly on their stability in solution and on their structural changes in contact with surfaces. Atomic force microscopy (AFM) in tapping mode in liquid was used to characterize adsorbed aggregates of a series of copolymers on a model hydrophilic surface (mica). Adsorbed aggregates did not retain the core-shell character they had in solution, but opened up completely to form a layer only 0.5−1 nm thick which corresponds to one or two cross-sectional diameters of individual PEG chains. A good correlation was found between the number of polymer chains in individual adsorbed aggregates as determined with AFM and that known from light scattering studies on the corresponding structures in solution, indicating that each aggregate on the surface originated from one aggregate in solution. Adsorption could be reduced with a more stable hydrophobic core and some copolymers did not adsorb on mica within the time studied. [ABSTRACT FROM AUTHOR]

Extracellular vesicles are evaluated by nanoparticle tracking analysis (NTA), providing information on their hydrodynamic diameters, and by atomic force microscopy (AFM) to calculate their geometric diameters. The aim of this study is to explore the influence of Brownian movements in a sample drop and preparation time on imaging-based measurements and to determine the relationship between the geometric and hydrodynamic sizes of the extracellular vesicles measured by the AFM and the NTA, respectively. Exosomes derived from the human prostate cancer cell line PC3 were evaluated by NTA and AFM, and those results were compared with Monte Carlo simulations. The mean size, evaluated by AFM shortly after application on the mica substrate, is less than its real value. It obtains the correct value faster for a thinner sample drop. Fitting the log-normal distribution to the geometric and hydrodynamic diameters leads to the conclusion that the latter could arise from the former by linear scaling by a factor that could be used to characterize the analyzed extracellular vesicles. The size of the vesicles attached to the mica substrate depends on time. The effect of Brownian motion and stretch of the lipid bilayer should be considered in the context of exosome AFM studies. [ABSTRACT FROM AUTHOR]