Potential Of Atomic Force Microscopy Research Articles

Size-effect on the intracellular antioxidative activity of Prussian blue nanoparticles investigated by atomic force microscopy

Nanoparticles-based antioxidative therapy has been highlighted in a series of diseases triggered by excessive reactive oxygen species (ROS). Prussian blue nanoparticles (PBNPs), as a representative artificial nanozyme, have been proved as highly effective ROS scavengers. However, its detailed intracellular antioxidant mechanism is not clear yet. Herein, a series of PBNPs with different particle sizes were synthesized and their intracellular antioxidant activities were studied by atomic force microscopy (AFM) from a biomechanical perspective. We first validated the ROS scavenging ability of PBNPs in vitro. It indicated that PBNPs had great scavenging effect on multiple ROS, such as hydroxyl radicals (•OH), superoxide radicals (O2•−) and hydrogen peroxide (H2O2). By observing the changes in morphology and mechanical properties of human umbilical vascular endothelium cells (HUVECs), it was further found that PBNPs could apparently alleviate the decrease of Young's modulus caused by oxidative stress damage and kept cells in their normal morphology. In addition, the distribution of F-actin revealed that the enhancement of cytoskeleton stability by PBNPs might be a key way to protect HUVECs from oxidative damage. Importantly, the antioxidant activities of PBNPs were found to be size-dependent, which indicated the smaller particle size had better antioxidant activities compared with the larger particle size. This study serves as a novel medium to reveal the mechanism of nanoparticles on cells at the single-cell level and demonstrates the great potential of atomic force microscopy in studying the application of nanoparticles in cell biology.

Methods for Studying Endometrial Pathology and the Potential of Atomic Force Microscopy in the Research of Endometrium.

The endometrium lines the uterine cavity, enables implantation of the embryo, and provides an environment for its development and growth. Numerous methods, including microscopic and immunoenzymatic techniques, have been used to study the properties of the cells and tissue of the endometrium to understand changes during, e.g., the menstrual cycle or implantation. Taking into account the existing state of knowledge on the endometrium and the research carried out using other tissues, it can be concluded that the mechanical properties of the tissue and its cells are crucial for their proper functioning. This review intends to emphasize the potential of atomic force microscopy (AFM) in the research of endometrium properties. AFM enables imaging of tissues or single cells, roughness analysis, and determination of the mechanical properties (Young’s modulus) of single cells or tissues, or their adhesion. AFM has been previously shown to be useful to derive force maps. Combining the information regarding cell mechanics with the alternations of cell morphology or gene/protein expression provides deeper insight into the uterine pathology. The determination of the elastic modulus of cells in pathological states, such as cancer, has been proved to be useful in diagnostics.

Atоmiс Force Microscopy of Graphene-Like Films Deposited onto Preirradiated SiO2/Si

The electron-beam exposure of dielectrics is actively explored in various fields of science. Recently, we have shown the possibility of the selective growth of graphene-like films on oxidized silicon due to an increase in the growth rate of a carbon film on exposed areas. Since the mechanism of the detected phenomenon is unclear, its study is a difficult scientific challenge. In this paper, the potential of atomic-force microscopy as a key instrument for characterization of these films is demonstrated. In particular, the point contact method provides grounds for interpreting processes occurring on the surface in the case of alternating synthesis and exposure to different irradiation doses. This method allows surface topography data and other characteristics (“adhesion” and “gradient” modes) to be obtained in one scan pass. The surface of the graphene-like films is scanned before and after exposure by means of atomic-force microscopy. Analysis of the data obtained shows that the “adhesion” mode enables special features of the samples that are either difficult or impossible to identify in a topographic image to be revealed. The study demonstrates the possibility of obtaining valuable information using cantilever-needle interaction with the surface to measure additional parameters.

AFM of tissue sections is a useful complementary tool as a biomedical marker

The aim of the study was to demonstrate a good diagnostic potential of atomic force microscopy (AFM) in tracking morphological changes in the extracellular matrix (ECM) of connective tissue due to pathological processes. Here we summarize our experience in AFM application in a number of biomedical studies on the connective tissue disease, both for research and clinical purposes. AFM has been shown to reveal visible deviations from the normal morphology of the extracellular matrix in diseased tissues. We found that AFM and related techniques are capable of tracking disease-related changes at different levels of collagen organization in the ECM. AFM may also monitor a ratio between collagen and non-fibrous material of the ECM, for example, in inflammatory and neoplastic processes. The FNS parameters provide quantification of the morphological changes visualized by AFM. The PeakForce QNM and nanoindentation studies give a further insight into the state of ECM via tracking changes in the local mechanical and adhesive properties. All our AFM studies appeared in a good agreement with the histological findings and generally had a superior sensitivity to the ECM pathological changes. AFM may serve as a valuable complementary diagnostic tool for tracking pathological changes in the connective tissue.

Force‐Controlled Fluidic Injection into Single Cell Nuclei

Surpassing the physical barriers of the cytoplasmic and nuclear membranes to deliver biomolecules directly into cell nuclei offers opportunities to investigate dynamic processes in living cells. The potential of atomic force microscopy coupled to microfluidics (FluidFM) for volume-controlled intranuclear delivery is demonstrated, whereby minimally invasive microchanneled probes are remotely driven with high spatiotemporal resolution.

Atomic force microscopic study of variations in the surface morphology of porous silica upon thermal treatment

A combination of atomic force microscopy and adsorption methods is used to investigate variations caused by thermal treatment at 200–1100°C in the structure of ShSKG silica gel and its surface morphology. It is shown that silica gel is characterized by two hierarchic levels of structural organization. The structural characteristics of silica gel begin to vary at a temperature above 800°C. The analytical potential of atomic force microscopy is illustrated as applied to studying the initial stages of physicochemical transformations of the surface of the coarse-pore silica carrier.

The use of atomic force microscopy for estimating morphometric characteristics of blood cell

The potential of atomic force microscopy for estimating geometric characteristics of blood cells is demonstrated. Comparison of hemocyte morphometric characteristics recorded using different scanning modes has demonstrated that noncontact and semicontact imaging are adequate for studying the size and geometry of biological objects. A contact scanning of cells leads to their irreversible deformation.

Nanophysiology: fact or fiction?

When in 1982 the scanning tunneling microscope was invented [1], its possibilities excited those scientists working in the material sciences. Electrically conductive material could be investigated with such precision that physics moved into a new nanoscale era. When in 1986 the principle of the atomic force microscope was described [2] and Binnig and Rohrer, the inventors of the tunneling microscope were awarded the Nobel prize for physics, life scientists paid little attention. At that time, molecular biology and molecular genetics were starting their logarithmic phase of development but, in addition, there was a small and heterogenous community of scientists with a major interest in biology who dared to take the first steps in applying these new technological advances to biology. Although there were a number of exciting breakthroughs in the 1990s, most life scientists at that time followed the rapid developments of cell biology, but there appeared to be little intellectual curiosity for other lines of enquiry. Toward the end of the 1990s, however, the life science community started to realize the potential of atomic force microscopy (AFM). Researchers slowly came to the conclusion that AFM is not simply another microscope that, at best, can compete with the well-established electron microscope but that it is a versatile instrument—an invasive tool, a scanning microscope, a force measuring device— that allows novel approaches in the study of live cells. Fortunately, physicists and, in particular, biophysicists helped to pave the way for making the AFM a tool suitable for biologists, physiologists, and medical scientists. At the same time, some industrial companies realized the potential of the AFM as a new research tool and produced AFMs easy to use for studying biological samples, from living cells to single molecules. Now, at the beginning of 2008, the ice is broken and the wide field of cellular and molecular physiology is ready for AFM. This was what drove us to collect 21 papers from laboratories around the world that use AFM as their major research tool. The selection of contributors to this special issue named “Nanophysiology” was made on the basis of AFM expertise and a clear commitment to approach open questions of physiology. The common denominator was ‘AFM,’ but the physiological window was wide open. In this special issue, there are about the same number of reviews and original papers. The reviews focus on different topics. They should help to understand why AFM is useful for life science research, how different AFM modes are applied, and what is novel about such approaches. It is hoped that the reviews will also help to calm down prejudices that AFM is a technique that is too complex and difficult to handle and expensive to run, whereas today none of these is true. Intermingled between the reviews, there are original papers that demonstrate that important questions in physiology, biology, and medicine can be addressed in this unique way. In addition to high-resolution imaging at the nanoscale level, a major emphasis is put on cellular and molecular mechanics by using native live material that has not been treated with fixatives. This has enabled the stiffness of living cells to be quantitatively measured—a new parameter in cell physiology. Eventually, mechanical cell membrane stiffness may be recognized to be as important as the electrical cell membrane potential, one of the major trademarks in physiology. I would suggest that in a few years membrane, stiffness may be another. Pflugers Arch Eur J Physiol (2008) 456:1–2 DOI 10.1007/s00424-008-0464-y

How steroid hormones act on the endothelium—insights by atomic force microscopy

Vascular actions of steroid hormones have gained increasing importance. Indeed, some steroid hormones favorably influence vascular structure and function, whereas others are detrimental. This review will focus on the endothelial effects of steroid hormones. In the first part, we summarize data from in vivo studies elucidating the regulation of endothelial function by steroid hormones. Accumulating data argue for an improvement of endothelium-derived relaxation and impaired vascular contraction by estradiol, whereas testosterone, progesterone, and aldosterone have contrary effects. In the second part, we present data from novel atomic force microscopy studies performed in living endothelial cells under the influence of steroid hormones. These studies provide insight into structural and functional alterations of endothelial cells characterized by changes in volume, apical surface, and stiffness. We summarize the available evidence that changes in shape of endothelial cells translate into changes of endothelial cell stiffness. Under the influence of estradiol, endothelial cells become spherical with consecutive improvement of elasticity, whereas aldosterone flattens endothelial cell-shape leading to increased stiffness. Both, endothelial cell shape and stiffness are major determinants of endothelial nitric oxide production. These studies emphasize the great potential of atomic force microscopy to investigate the function of living endothelial cells.

Analysis of photopolymerized acrylic films by AFM in pulsed force mode

This paper highlights the potential of atomic force microscopy in the pulsed force mode to investigate the photopatterning of acrylic-based films. The pulsed force mode is a nonresonant mode designed to allow approach curves to be recorded along the scanning path. It thereby provides the topography of the sample and a direct and simple local characterization of adhesion and stiffness. This mode can be used either for imaging or for locally probing the mechanical properties of a surface. In particular, a correlation between stiffness and conversion of the monomer was established. The close examination of the pulsed force mode signal brought accurate information on the photoinduced modification of the film. Polymer films with submicron photopatterning generated by interferometric illumination were analyzed by pulsed force mode. It was established that the gradient of mechanical properties throughout the films was strongly dependant on the irradiation conditions.

Real‐time atomic force microscopy of root dentine during demineralization when subjected to chelating agents

To explore the potential of atomic force microscopy (AFM) for the examination of changes to dentine surfaces during demineralization and evaluate qualitatively the effect of EDTA, EDTAC and citric acid. Nine canine teeth were sectioned transversely at the cemento-enamel junction, and the crowns discarded. Subsequently, each root was embedded in an epoxy cylinder and discs approximately 5 mm thick were cut. A standard metallographic procedure was then used to prepare the surfaces for observation. From the central portion of these samples, two specimens were symmetrically prepared per tooth so that a total number of 18 samples was produced. To allow the use of a liquid cell during AFM, the samples were embedded in silicone rubber and were then randomly divided into three groups, as follows: group 1: 17% EDTA (pH 7.7), group 2: 17% EDTAC (pH 7.7) and group 3: 10% citric acid (pH 1.4). Topographical images were acquired during the demineralization process, allowing real-time observation of the dentine surface. Two operators assigned scores to the AFM images using a double-blind method. anova analysis with random effects (P < 0.05) was used to compare the results. The average scores were 6.13 +/- 0.35 for EDTAC, 7.36 +/- 0.23 for EDTA and 14.55 +/- 1.21 for citric acid. Citric acid was statistically different from EDTA and EDTAC while EDTA and EDTAC were not statistically different. The most effective demineralizing substance was citric acid. The methodology developed for real-time observation of dentine surfaces is a valuable method to evaluate demineralization.

Specific Detection of Glycans on a Plasma Membrane of Living Cells with Atomic Force Microscopy

Among the many alterations of cancer cells is the expression of different surface oligosaccharides. In this work, oligosaccharide expression in living cells (cancer and reference ones) was studied with atomic force microscopy by using lectins as probes. The unbinding force obtained for the same lectin type (concanavalin A or Sambucus nigra) suggested slightly dissimilar structures of binding sites of the same ligand type. For the lectin from Phaseolus vulgaris, a much larger unbinding force indicated a distinct structure of the binding site in cancer cells. The unbinding probability confirmed a higher content of both sialic acid and mannose-containing ligands in cancer and reference cells, respectively. These results demonstrate the potential of atomic force microscopy to directly probe the presence of molecules on a living cell surface, together with the quantitative description of their expression.

The determining role of clay particles on mechanically induced surface damage and associated stress whitening in polybutene–clay nanocomposites

The potential of atomic force microscopy to quantify the surface topography is combined with the surface features obtained by electron microscopy to examine susceptibility to mechanically induced surface damage in neat polybutene and polybutene–clay nanocomposites. The scratch tracks in polybutene are characterized by ‘fish-scale psiloma’ morphology indicative of compressive plastic deformation and quasi-periodic cracking. While in polybutene–clay nanocomposites, ‘ironing’, which is a less severe surface damage mechanism was dominant. Also, polybutene–clay nanocomposites experience significantly reduced stress whitening, and is characterized by lower gray level in the plastically deformed surface damage region. This behavior is attributed to the effective reinforcement by clay particles that act in concert increasing the tensile modulus of the composite and restricts plastic deformation of the polymer matrix.

Jerky motion of grain boundaries in NiAl: an atomic force microscopy study

It is known that moving grain boundaries (GBs) interact with the thermal grooves developing along the line where the GB intersects the surface. The questions of the GB migration character (continuous or jerky) is of principal importance for the theory of GB migration and grain growth. Recent computer simulation studies of GB migration in pure materials have shown that the calculated GB mobilities are many orders of magnitude higher than those usually observed in the experiment even in very pure materials. If the jerky GB motion is a common phenomenon then the GB mobility measured in the macroscopic experiments can differ considerably from the true microscopic mobility, since in the former case the time which the GB spent in the locked position is taken into account. In this paper, the authors will demonstrate the potential of atomic force microscopy (AFM) in deducing the real dynamic behavior of the GBs at high temperature from the post-mortem studies of the surface topography in the region of ghost lines.

Atomic force microscopy of liquid-covered surfaces: Atomic resolution images

Images of graphite surfaces that are covered with oil reveal the hexagonal rings of carbon atoms. Images of a sodium chloride surface, protected from moisture by oil, exhibit a monoatomic step. Together, these images demonstrate the potential of atomic force microscopy (AFM) for studying both conducting and nonconducting surfaces, even surfaces covered with liquids. Our AFM uses a cross of double wires with an attached diamond stylus as a force sensor. The force constant is ≊40 N/m. The resonant frequency is ≊3 kHz. The lateral and vertical resolutions are 0.15 nm and 5 pm.