Atomic Force Microscopy Images Research Articles

Peptide Self-Assembly Facilitating DNA Transfection and the Application in Inhibiting Cancer Cells.

Non-viral vectors have been developing in gene delivery due to their safety and low immunogenicity. But their transfection effect is usually very low, thus limiting the application. Hence, we designed eight peptides (compounds 1-8). We compared their performances; compound 8 had the best transfection efficacy and biocompatibility. The transfection effect was similar with that of PEI, a most-widely-employed commercial transfection reagent. Atomic force microscope (AFM) images showed that the compound could self-assemble and the self-assembled peptide might encapsulate DNA. Based on these results, we further analyzed the inhibitory result in cancer cells and found that compound 8 could partially fight against Hela cells. Therefore, the compound is promising to pave the way for the development of more effective and less toxic transfection vectors.

Insight into the mechanisms of acid treatment on alkali-soluble polysaccharides from crispy and mealy lotus rhizomes

The present study investigated the structural disparities in cell wall polysaccharides between lotus rhizomes with mealy and crispy textures through a combination of acid and enzyme treatments. The results from size exclusion chromatography equipped with multi-angle light scattering detectors, viscometer detector and differential refractive index (SEC-MALS-DRI-VD) indicated that, before and after acid treatment, the CASP (alkali-soluble polysaccharides from crisp lotus rhizomes) were all semi-flexible chains using, while MASP (alkali-soluble polysaccharides from mealy lotus rhizomes) changed from flexible chains to semi-flexible. The atomic force microscope (AFM) images revealed a reduction in pectin chain length and decreased chain height of CASP following acid hydrolysis. However, MASP exhibited adhesion of pectin chains and formation of cluster structure. Through the analysis of monosaccharide composition result, the structural disparities between pectin are closely linked to the acid hydrolysis discrepancies observed in CASP and MASP. This study offers a molecular-level rationale for enhancing the thermal texture of fruits and vegetables through acid treatment.

Zirconium oxide thin films deposited via DC magnetron sputtering: corrosion and morphological investigation

Purpose The purpose of this study is to investigate the structural, surface roughness and corrosion properties of the zirconium oxide thin films deposited onto SS304 substrates using the direct current (DC) magnetron sputtering technique. Design/methodology/approach DC sputtering at different powers – 80, 100 and 120 W – was used to deposit ZrO2 thin films onto different substrates (Si/SS304) without annealing of the substrate. Atomic force microscope (AFM), energy-dispersive X-ray spectroscopy (EDS), Tafel extrapolation and contact angle techniques were applied to investigate the surface roughness, chemical compositions, corrosion behavior and hydrophobicity of these films. Findings Results showed that the thickness of the deposited film increased with power increase, while the corrosion current decreased with power increase. AFM images indicated that the surface roughness decreased with an increase in DC power. EDS analysis showed that the thin film has a stoichiometric ZrO2 (Zr:O 1:2) composition with basic uniformity. Water contact angle measurements indicated that the hydrophobicity of the synthesized films decreased with an increase in surface roughness. Originality/value DC magnetron sputtering technique is infrequently used to deposition thin films. The obtained thin films showed good hydrophobic and anticorrosion properties. Finally, results are compared with other deposition techniques.

Tailoring optical response in nanostructured bilayers: Effects of surface roughness and layer thickness on NbN/Nb and TiN/Ti

Numerical calculations were performed on NbN/Nb and TiN/Ti nanostructured bilayers. Discrete dipole approximationimplemented in the DDSCAT code was utilized. In order to design a TUC (Target Unit Cell) with realistic surfaceroughnesspattern, Atomic Force Microscope images of 100 ±10 nm Nb thin films were used. The optical properties of nanostructured bilayers (60-100 nm thickness with a ±10 nm surface roughness) were calculated, keeping the interfacebetween the layers as smooth flat surfaces. For the NbN/Nb nanostructure with a thickness between 100 ±10 nm, and 70 ±10 nm, in a wavelength range between 200 and 350 nm, the reflectance and absorptance show a nearly flat spectrumwith an intensity of 20% and 80%, respectively. For larger wavelengths, absorptance decays smoothly. In contrast, for the 60 ±10 nm bilayer, the absorptance decays faster. For the TiN/Ti nanostructure, at 415 nm, a relative maximum in the reflectance, and a minimum in absorptance, are observed. The critical value of the absorbed light spectra begins to shift to higher wavelengths as the thickness of the TiN layer increases. We demonstrate that adding a rough nitride layer on top of its metallized layer drastically modifies the optical response of the nanostructured bilayer, an interesting result forplasmonics and nanoelectronics applications.

Wavelet-based information theory in quantitative assessment of AFM images’ quality

The quantitative assessment of the image quality produced by atomic force microscopy (AFM) is an ongoing and challenging task. In our study, we demonstrate Shannon’s application of information theory for measuring image quality. Specifically, we propose quantifying the loss of image information due to the various distortion processes by exploring the relationship between image information based on the information channel capacity (ICC), spectral image representation, and visual quality. Since the ideal image is unavailable, the power and noise spectrum, the critical input information for the image quality evaluation, must be robustly estimated in the proposed method. The classical, most popular Welch method for spectral estimation uses an average of several windowed periodograms and can produce biased spectrum estimates. Therefore, in our work, we discuss an alternative technique based on the wavelet transform that can be applied to solve this challenging problem, specifically in the case of noisy, uncertain AFM measurements. Finally, we validate the performance of the enhanced ICC-wavelet-based algorithm with noisy measurement AFM data.

Nanoscale Dots, Grids, Ripples, and Hierarchical Structures on PET by UV Laser Processing

Nanostructures can be produced on poly(ethylene terephthalate) (PET) foils by using a krypton fluoride (KrF) excimer laser with a wavelength of 248 nm and a pulse duration of about 20 ns. We show that surface nanoripples, nanodots, nanogrids, and hybrid patterns of ripples with dots or finer ripples on top can be fabricated. The effects of a water layer in front of the PET foil and of cooling during laser processing were investigated. For pattern formation, several irradiation parameters (pulse number, pulse energy, and polarization) were varied systematically. The spatial periods of the ripples were changed by adjusting the angle of incidence of the laser beam. All nanostructures were characterized by scanning electron microscopy, and relevant morphological parameters, such as peak-to-peak distances and spatial periods, were assessed. Shapes and heights of some structures were characterized by using focused ion beam cuts to avoid the tip-sample convolution effects typical of atomic force microscopy images. We further demonstrate nanoripple formation on PET foils as thin as 12 µm, 6 µm, and 1.4 µm. The remarkable variety of nanostructures on PET we present here enables customized fabrication for a wide range of applications.

Effects of UV irradiation of TEMPO-oxidized cellulose nanofibril/water dispersions on chemical structure, molar mass, and morphology

A commercial TEMPO-oxidized cellulose (TOC) and three laboratory-made TOC samples prepared under different conditions were converted to aqueous 0.4% dispersions of TEMPO-oxidized cellulose nanofibrils (TEMPO-CNFs) by high-pressure homogenization in water under the same conditions. The obtained TEMPO-CNF/water dispersions were irradiated with ultraviolet (UV) light for 0–48 h using a high-pressure mercury lamp at a main wavelength of 365 nm. The changes in the light transmittance, viscosity, pH, zeta-potential, and average particle size of the dispersions, and mass recovery ratio, molar mass, and carboxylate content of the acid-insoluble and freeze-dried fractions separated and isolated from the UV-irradiated dispersions were investigated. The results were analyzed in terms of the UV-irradiation time. The dispersion pH, and the mass recovery ratio, carboxylate content, and mass-average degree of polymerization (DPw) of the acid-soluble fraction decreased with increasing UV-irradiation time. This shows that some acid-soluble acidic compounds were formed from the TEMPO-CNFs via UV-induced depolymerization, degradation, and removal of carboxylate groups from the TEMPO-CNFs in water, depending on the UV-irradiation time. The average CNF length, which was determined from atomic force microscopy images, decreased with increasing UV-irradiation time. After UV irradiation of dispersions of the laboratory-made TEMPO-CNFs for 12 h, the average CNF lengths were 130–150 nm and their length distributions were narrower. UV irradiation of TEMPO-CNF/water dispersions is therefore a promising method for efficiently decreasing the dispersion viscosity, DPw, and average CNF length, depending on the TEMPO-CNF properties and UV-irradiation conditions.Graphical abstract

Melt adsorption of poly(tert-butyl methacrylate) and poly(ethyl methacrylate) on silica studied with chip nanocalorimetry

Irreversible adsorption of polymer chains from a melt on a substrate surface can be strongly affected by interfacial interactions. In this study, we examined the adsorption of two polymers, poly(tert-butyl methacrylate) (PtBMA) and poly(ethyl methacrylate) (PEMA), on a silica surface at temperatures above their glass transition temperatures. The degree of adsorption γ(t) over time was evaluated with variations of storage heat capacity determined with alternating current chip nanocalorimetry (in-situ measurement of a buried interface). γ(t) revealed two-step profiles for both polymers. At the second stage of adsorption (regime II), the slope of a plot of γ(t) vs. log t increased as adsorption proceeded; this trend has not been reported for other polymers and may be characteristic of the present polymers. The trend observed in regime II suggested that the unadsorbed free chains near the interface became less mobile and were incorporated into the adsorbed layer via interactions with the tails of the chains directly attached to the substrate surface. The increasing slope in regime II was more prominent for PtBMA than for PEMA. In addition, a difference was observed for PtBMA and PEMA in the atomic force microscopy images of the exposed adsorption layer surfaces.

ВЛИЯНИЕ ИСКУССТВЕННОГО СТАРЕНИЯ НА ИЗМЕНЕНИЕ ШЕРОХОВАТОСТИ ГЛАЗУРОВАННОЙ И ПОЛИРОВАННОЙ ПОВЕРХНОСТИ ДИОКСИДА ЦИРКОНИЯ: ИССЛЕДОВАНИЕ IN VITRO

Aim: to evaluate the characteristics of glazed and polished surface during hydrothermal aging using different types of zirconium dioxide. 
 Materials and Methods. The same standardized samples from different types of zirconium dioxide with a diameter of 10 mm and a height of 1 mm were used for all experiments. These types included Katana (Kuraray Noritake Dental, Tokyo, Japan) HTML (control) UTML, STML, and ZirCAD Prime (Ivoclar Vivadent). Atomic force microscopy (AFM) was used to measure the roughness and to visualize the surface morphology of the samples. The Bruker Innova instrument was used as an atomic force microscope. Image acquisition was carried out in semi-contact mode. The probe sensor was TESP-V2 with a triangular-shaped probe and a tip radius of 7 nm. The scanning area was 50 x 50 μm. Frequency 0.5 Hz. The study of roughness was reduced to the processing of AFM image data. For this purpose, three arbitrary sections were made in the height map channel and the necessary roughness parameters Ra, Rz were calculated using software.
 Results. There was an increase in roughness during artificial aging of the control group of glazed surface, Prime group of polished surface, and Prime group of glazed surface. There is a decrease of roughness in the process of artificial aging of the control group of glazed surface, for STML and UTML groups of both glazed and polished surface. In the case of samples of group "polishing" it is possible to observe that roughness is formed by traces of abrasive material. From the results of the study of roughness it can be noted that for the samples of the group "Glaze" roughness is formed mainly by traces of brush or other tools used in the process of glaze application
 Conclusion. Artificial aging affects the roughness of the glazed and polished surface of zirconium dioxide with cubic phase predominance depending on the amount of yttrium content.

Structure of Amyloid Peptide Ribbons Characterized by Electron Microscopy, Atomic Force Microscopy, and Solid-State Nuclear Magnetic Resonance.

Polypeptides often self-assemble to form amyloid fibrils, which contain cross-β structural motifs and are typically 5-15 nm in width and micrometers in length. In many cases, short segments of longer amyloid-forming protein or peptide sequences also form cross-β assemblies but with distinctive ribbon-like morphologies that are characterized by a well-defined thickness (on the order of 5 nm) in one lateral dimension and a variable width (typically 10-100 nm) in the other. Here, we use a novel combination of data from solid-state nuclear magnetic resonance (ssNMR), dark-field transmission electron microscopy (TEM), atomic force microscopy (AFM), and cryogenic electron microscopy (cryoEM) to investigate the structures within amyloid ribbons formed by residues 14-23 and residues 11-25 of the Alzheimer's disease-associated amyloid-β peptide (Aβ14-23 and Aβ11-25). The ssNMR data indicate antiparallel β-sheets with specific registries of intermolecular hydrogen bonds. Mass-per-area values are derived from dark-field TEM data. The ribbon thickness is determined from AFM images. For Aβ14-23 ribbons, averaged cryoEM images show a periodic spacing of β-sheets. The combined data support structures in which the amyloid ribbon growth direction is the direction of intermolecular hydrogen bonds between β-strands, the ribbon thickness corresponds to the width of one β-sheet (i.e., approximately the length of one molecule), and the variable ribbon width is a variable multiple of the thickness of one β-sheet (i.e., a multiple of the repeat distance in a stack of β-sheets). This architecture for a cross-β assembly may generally exist within amyloid ribbons.

The enhanced sulfidation mechanism of surface activation in hemimorphite through ammonium complexation: An experimental and density functional theory study

This study investigated the impact of ammonia (NH3) solution on the flotation behavior of hemimorphite sulfidation, employing a comprehensive analysis that encompasses micro-flotation experiments, X-ray photoelectron spectroscopy (XPS) analysis, contact angle testing, atomic force microscopy (AFM) imaging, and density functional theory (DFT) calculations. The introduction of ammonia water (NH3·H2O) resulted in a significant 22.64 % increase in hemimorphite recovery rate, as demonstrated in flotation tests. In this study, both XPS and AFM analyses provided compelling evidence supporting the assertion that NH3·H2O facilitated the sulfidation of the mineral surface, resulting in an increased formation of sulfide products. Contact angle testing indicated that surface modification with NH3·H2O enhanced the hydrophobic properties of the hemimorphite. DFT calculations offered valuable insights into the effect of NH3 on the hydration layer, indicating that NH3 substituted H2O molecules and increased the distance between Zinc (Zn) and O5 (H2O) to 5.6 Å. Furthermore, the adsorption energy of HS− on the hemimorphite (110) surface significantly increased with NH3 enhancement (−18.05 eV) as opposed to without NH3 enhancement (−12.79 eV). These results indicated that the adsorption configuration of NH3 in conjunction with HS− was more stable than that of HS− alone on the hemimorphite (110) surface. Thus, the collective results provided valuable insights into the enhanced sulfidation mechanism activated by ammonium complexation on the hemimorphite surface.

Evaluation of Surface Structure and Morphological Phenomena of Caucasian Virgin Hair with Atomic Force Microscopy.

Background and Objectives: Atomic force microscopy (AFM) as a type of scanning microscopy (SPM), which has a resolution of fractions of a nanometer on the atomic scale, is widely used in materials science. To date, research using AFM in medicine has focused on neurodegenerative diseases, osteoporosis, cancer tumors, cell receptors, proteins and the DNA mismatch repair (MMR) system. Only a few small studies of hair imaging have been conducted, mostly in biotechnology or cosmetology. Thanks to the possibilities offered by AFM imaging, dermatologists can non-invasively assess the condition of hair and its possible disorders. Our goal was to capture images and microscopically analyze morphological changes in the surface of healthy hair. Materials and Methods: In this study, three to five hairs were collected from each person. Each hair was examined at nine locations (0.5; 1.0; 1.5; 2.0; 3.5; 4.5; 5.5; 6.5 and 7.0 cm from the root). At least 4 images (4-10 images) were taken at each of the 9 locations. A total of 496 photos were taken and analyzed. Metric measurements of hair scales, such as apparent length, width and scale step height, were taken. Results: This publication presents the changes occurring in hair during the natural delamination process. In addition, morphoological changes visualized on the surface of healthy hair (pitting, oval indentations, rod-shaped macro-fibrillar elements, globules, scratches, wavy edge) are presented. A quantitative analysis of the structures found was carried out. Conclusions: The findings of this study can be used in further research and work related to the subject of human hair. They can serve as a reference for research on scalp and hair diseases, as well as hair care.

Water Vapor Permeation in Alumina Films on Polymer Substrates

Herein, the water vapor transmission rate (WVTR) of aluminum oxide (Al2O3) films on polyethylene terephthalate (PET) substrates is investigated and is focused on the impact of the film defects on the transmission rate. The aluminum oxide films are prepared on PET substrates by magnetron sputtering, and the effects of the film thickness, sputtering power, temperature, and bias voltage on the WVTR are studied. The surface morphologies of the films are examined using atomic force microscopy (AFM), and a method for obtaining the defect ratio of the film from AFM images is proposed. Subsequently, the influences of the defect ratio on the WVTR are quantitatively evaluated based on a 3D diffusion model. The simulated WVTR values are well in agreement with the experimental ones.

Cell Surface Parameters for Accessing Neutrophil Activation Level with Atomic Force Microscopy.

In this study, we examine the topography and adhesion images of the cell surface of neutrophils during the activation process. Our analysis of cell surface parameters indicates that the most significant changes in neutrophils occur within the first 30 min of activation, suggesting that reactive oxygen species may require approximately this amount of time to activate the cells. Interestingly, we observed surface granular structure as early as 10 min after neutrophil activation when examining atomic force microscopy images. This finding aligns with the reorganization observed within the cells under confocal laser scanning microscopy. By analyzing the cell surface images of adhesion, we identified three spatial surface parameters that correlate with the activation time. This finding enables us to estimate the degree of activation by using atomic force microscopy maps of the cell surface.

Structure Discovery in Atomic Force Microscopy Imaging of Ice.

The interaction of water with surfaces is crucially important in a wide range of natural and technological settings. In particular, at low temperatures, unveiling the atomistic structure of adsorbed water clusters would provide valuable data for understanding the ice nucleation process. Using high-resolution atomic force microscopy (AFM) and scanning tunneling microscopy, several studies have demonstrated the presence of water pentamers, hexamers, and heptamers (and of their combinations) on a variety of metallic surfaces, as well as the initial stages of 2D ice growth on an insulating surface. However, in all of these cases, the observed structures were completely flat, providing a relatively straightforward path to interpretation. Here, we present high-resolution AFM measurements of several water clusters on Au(111) and Cu(111), whose understanding presents significant challenges due to both their highly 3D configuration and their large size. For each of them, we use a combination of machine learning, atomistic modeling with neural network potentials, and statistical sampling to propose an underlying atomic structure, finally comparing its AFM simulated images to the experimental ones. These results provide insights into the early phases of ice formation, which is a ubiquitous phenomenon ranging from biology to astrophysics.

The Morphology and Ultrastructure of Dermal Telocytes Characterized by TEM and AFM.

This investigation delves into the structural foundation of human dermal telocytes (TCs) with the aim of elucidating their role in signal transmission. Dermal TCs were isolated from human foreskins via enzymatic digestion and flow cytometric sorting, and identified by immunohistochemical staining with an antibody against CD34. The ultrastructure of TCs was examined using transmission electron microscopy (TEM). The proliferation rates of sorted TCs and CD34-negative fibroblasts were compared using the MTS assay (Cell Proliferation Assay). Images of viable cultured TCs were analyzed using atomic force microscopy (AFM) under normal atmospheric pressure and temperature. Results demonstrated that dermal TCs were positive for CD34 and vimentin, predominantly distributed in the reticular dermis and subcutaneous tissue, forming interwoven networks. Each TC had a small body with a high nuclear-plasma ratio and two or three extremely long and thin telopodes (TPs), exhibiting a typical 'moniliform' appearance. Compared with CD34-negative fibroblasts, dermal TCs exhibited significantly lower proliferation rates. Cultured TCs displayed typical moniliform projections (namely, TPs) in the AFM images. The distal ends of TPs were enlarged, shaped like a broom, and extended multiple pseudopods to contact other cell bodies. Slender filamentary pseudopodia and thick, short cone-like structures were observed on the surfaces of the dilated segments and terminals of TPs. These structures are assumed to be evidence of the secretion and release of endosomes, such as exosomes, and the communication between cells. TCs form interstitial networks in the reticular dermis and subcutaneous tissue, providing a structural basis for contacts between cells and the secretion of signal-carrying substances, involving intercellular connections and communication.

Characterizing the early stages of fibrin fiber assembly via atomic force microscopy imaging

Characterizing the early stages of fibrin fiber assembly via atomic force microscopy imaging

Determination of in-plane surface directions in scanning probe microscopy images.

We describe an approach to determine the in-plane crystallographic surface directions in scanning probe microscopy (SPM) images. This method is based on a one-time characterization of the SPM instrument with an appropriate test sample and is exemplified by the analysis of non-contact atomic force microscopy (NC-AFM) images on surfaces whose natural cleavage occurs along {111} planes. We introduce a two-dimensional rotation matrix relating the crystallographic surface directions known from an analysis of the macroscopic crystal to the directions in the NC-AFM images. The procedure takes into account rotations and mirror axes resulting from sample mounting, the SPM scanner rotation, the choice of scan direction, as well as data processing, storage, and display. We demonstrate the practicability of the approach by determining the [112̄] direction in topographic images of a CeO2(111) film grown on a Si(111) wafer and atomic resolution images of CaF2(111) with an instrument based on the beetle-type scanner.

Preparation of 2D Tungsten Diselenide (WSe2) thin films by selenization of DC-sputtered W precursors

Two-dimensional layered transition metal dichalcogenides based on WSe2 films demonstrated promising properties for nano-electronics and photovoltaic applications. In this work, WSe2 films were prepared by selenization of DC-sputtered W precursors. The influence of the selenization temperature on the structural, morphology, and optical properties of the WSe2 films was investigated. The selenization temperature was varied from 350 °C to 450 °C at the interval of 50 °C. Structural, morphology and optical properties of the WSe2 were investigated using X-ray diffractometry (XRD), Atomic Force Microscope (AFM), and UV-VIS-NIR spectrophotometer, respectively. XRD analysis revealed that all WSe2 were polycrystalline and exhibited the co-existence of c-axis perpendicular and parallel substrate texture. Samples selenized at 400 °C demonstrated strong - types of crystal orientations – perpendicular c-axis substrate texture – dominated crystal growth. The AFM images further revealed the co-existence of parallel and perpendicular crystal orientations for samples selenized at 350 °C and 450 °C. Optical measurement showed that all WSe2 samples were transparent and consisted of an excitonic peak at the wavelength of around 620 nm. The estimated bandgap values were in the range of 1.22 eV to 1.37 eV which is somchat lower than expected – the presence of W5O14 phases is suggested to be the main cause.

In situ creation of aramid fiber surface coating with polymerizable deep eutectic solvents and their interfacial bonding properties with rubber

AbstractThe coating was created on the surface of aramid fibers (AFs) by solution dip‐coating and in situ UV curable method, using a polymerizable deep eutectic solvent (PDES), dissolved poly(ethylene imine), and poly(ethylene glycol) diacrylate (PEGDA). Fourier transform infrared spectroscopy and thermogravimetry confirmed the successful construction of the coating on the AF surface, which accounted for 12%–17% of the total fiber mass. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) images revealed a 2 μm increase in fiber diameter and a maximum fiber surface average roughness (Ra) of 263.7 nm when the polyethyleneimine content was 0.5% (AF‐PDES‐0.5). Based on these results, H pull‐out samples of fiber/rubber composites were fabricated. The results indicated that the H pull‐out force of AF‐PDES‐0.5 samples increased by 109.74% than that of untreated fiber, and reached 12.92 N of the maximum strength. In summary, the method is simple, rapid, non‐polluting, capable of continuous, and intelligent construction of coatings on the surface of AF. Thus, making it highly promising for application in the field of aviation tires.Highlights Using PDES, green, and low‐carbon preparation processes. Solution dip‐coating and UV reaction for improved reaction speed and workability. Quantitative of interface thickness and modulus using EDS and AFM.