The technique of AFM bending test of a suspended nanoobject has been improved.An analytical method has been created for calculating Young's and shear moduli of object's material based on data of such tests.In Timoshenko approximation, we consider problems of bending a beam one or both ends of which lie on elastic Winkler foundations.The obtained solutions are used to eliminate uncertainties in the calculation of elastic moduli that arise when the conditions of fixing an object (console or bridge) on the edges of a recess in the substrate are unknown.

Here, we investigate an influence of Fe3+ content on the mechanical behavior of Mg3Si2O5(OH)4 synthetic phyllosilicate nanoscrolls with chrysotile structure during the bending tests carried out by atomic force microscopy. The developed approach to the microscopy data treatment allowed us to consider fixing conditions, elasticity of the foundation, and shear strain contributions to the observed Young’s modulus value. Doping by 6 at.% of Fe3+ decreased the Young’s modulus from 238 down to 150 GPa. The applied density-functional theory calculations confirmed the same trend for the most energy preferable types of Mg2+ and Si4+ substitutons by Fe3+. Despite major part of the experimental data has been satisfactory explained within the shear strain contribution assumption, doping by Fe3+ gives rise to nanoscrolls with anomalous Young’s modulus value (600±200 GPa). Potential reasons of the effect are considered.

Consoles and bridges of MgNi2Si2O5(OH)4 nanoscrolls were tested for bending in atomic force microscope. Using test data, we analyze how the consoles or bridges were fixed, and took this information into account when calculating the Young’s modulus of the nanoscrolls. The results on the consoles are in good agreement with the results on the bridges when modeling the latter as three-span beams, and the former as beams on an elastic foundation with a suspended console.

In hydrosilicates with the structure of chrysotile, pecoraite, and halloysite, elastic strains in the composite hydrosilicate layer are compensated by folding into nanoscrolls. A wide range of such particles with different compositions can be produced by hydrothermal synthesis, which, together with the structural and morphological characteristics, makes them promising adsorbents, capsules, catalysts, and reinforcing components of composite materials. For such potential applications as magnetically controlled adsorbents and catalysts, ferromagnetic chemical elements are included in the composition of the nanoscrolls. Studies of the individual nanoscrolls require special approaches. This article discusses the use of atomic force microscopy for such studies.

The technique of atomic force microscopy (AFM) bending tests of a suspended nano-object (scroll, tube, rod) makes it possible to calculate the Young's modulus of the material it is made of based on experimental data. However, the calculation results involve a large error due to uncertain conditions (console or bridge) of fixing the test object. One of the ways to reduce this error is based on the theoretical consideration of consoles or bridges as beams with one or two ends resting on Winkler elastic foundations. The beam bending problems have been solved in both cases using Krylov's functions. This has allowed for developing an approach to the analytical identification of fixing conditions and including them in the calculations. The application of the approach is illustrated by AFM measurements of the Young's modulus of MgNi_{2}Si_{2}O_{5}(OH)_{4} nanoscrolls.

A group of phyllosilicate nanoscrolls conjoins several hydrosilicate layered compounds with a size mismatch between octahedral and tetrahedral sheets. Among them, synthetic Mg3Si2O5(OH)4 chrysotile nanoscrolls (obtained via the hydrothermal method) possess high thermal stability and mechanical properties, making them prospective composite materials fillers. However, accurate determination of these nano-objects with Young's modulus remains challenging. Here, we report on a study of the mechanical properties evolution of individual synthetic phyllosilicate nanoscrolls after a series of heat treatments, observed with an atomic force microscopy and calculated using the density functional theory. It appears that the Young's modulus, as well as shear deformation's contribution to the nanoscrolls mechanical behavior, can be controlled by heat treatment. The main reason for this is the heat-induced formation of covalent bonding between the adjacent layers, which complicate the shear deformation.

Consoles and bridges of MgNi2Si2O5(OH)4 nanoscrolls were tested for bending in atomic force microscope. Using test data, we analyze how the consoles or bridges were fixed, and took this information into account when calculating the Young's modulus of the nanoscrolls. The results on the consoles are in good agreement with the results on the bridges when modeling the latter as three-span beams, and the former as beams on an elastic foundation with a suspended console.

Opiate use to treat chronic pain is known to be associated with negative side effects. Therefore, the development of new safe and effective non-opioid analgesics is both important and urgent goal of modern science. Previously, we showed that tetrapeptide Ac-RERR-NH2 has potential as an analgesic drug substance, since it can reduce the excitability of nociceptive neurons responsible for encoding nociceptive signals. The effect of sub-nanomolar concentration of Ac-RERR-NH2 tetrapeptide on embryonic sensory neurons was investigated with the use of atomic force microscopy (AFM) and organotypic tissue culture method. The quasi-static PeakForce QNM AFM mode was used, which allows mapping of local mechanical cell properties. Following administration of the substance, sensory neurons tended to decrease their stiffness. This result is based on the analysis of the values of the apparent Young’s modulus of sensory neurons and their deformation, controlled for the slipping of the tip of the probe over the surface under study. The area index (AI) criterion showed that the studied tetrapeptide has pronounced neurite-stimulating properties. The data obtained suggest that Ac-RERR-NH2, acting at very low concentrations, is able to trigger an as yet unidentified intracellular cascade regulating the growth of neurites of sensory neurons.

The effects of ouabain on the mechanical characteristics of primary sensory neurons and fibroblasts of 10- to 12-day-old chicken embryos were investigated by atomic force microscopy under physiologically relevant conditions. Fibroblasts express only the α1 isoform of Na,K-ATPase, while sensory neurons express the α1 and α3 isoforms. It was found that exposure to ouabain in the concentration corresponding to its endogenous level led to an increase in membrane rigidity of sensory neurons, which was apparently due to activation of the transducer rather than the pumping function of Na,K-ATPase. The mechanical parameters of fibroblasts were not affected by exposure to endogenous concentrations of ouabain. These results suggest that endogenous ouabain specifically modulates the transducer function of the α3 Na,K-ATPase isoform in the sensory neuron membrane. Thus, atomic force microscopy was efficiently applied to perform a comparative study of intracellular signaling cascades in living cells.

The responses of primary sensory neurons to subnanomolar and nanomolar ouabain concentrations, corresponding to the endogenous ouabain (EO) concentration, were studied. Atomic force microscopy (AFM) studies showed that exposure to EO led to an increase in neuron stiffness. Studies using local voltage clamping showed that ligand-receptor binding of EO with the Na,K-ATPase/Src complex decreased the effective charge of the activatory gate system of Na V 1.8 channels. Furthermore, the EO-activated intracellular cascade in which the Na,K-ATPase/Src complex operates as a signal transducer was found to lead to a decrease in the fluorescence intensity of antibodies to Na V 1.8 channels, as demonstrated by confocal laser scanning microscopy. These results suggest that EO, triggering the transduction function of the Na,K-ATPase/Src complex and the corresponding intracellular signal cascade, is able to modulate the expression of the SCN10A gene, which produces Na V 1.8 channels, which are responsible for encoding nociceptive signals.

Atomic force microscopy was used to study under physiologically adequate conditions the effect of ouabain on the mechanical characteristics of sensory neurons and fibroblasts of 10–12-day old chick embryos. Fibroblasts express only the α1-isoform of Na,K-ATPase, and sensory neurons the α1- and α3-isoforms. It was found that the action of ouabain at a concentration corresponding to the endogenous value leads to an increase in the membrane rigidity of sensory neurons, which is apparently due to the activation of the transducer function of Na,K-ATPase, rather than the pumping function. The endogenous concentration of ouabain did not change the mechanical characteristics of fibroblasts. The results obtained suggest that endogenous ouabain modulates the transducer function of the α3-isoform of Na,K-ATPase of the sensory neuron membrane. Thus, the method of atomic force microscopy allows a comparative study of intracellular signaling cascades in living cells.

Some phyllosilicate compounds have the ability of spontaneous scrolling because of the size mismatch between the covalently bounded metal oxide and silica sheets. Their unique structure and high theoretically predicted Young's modulus (around 210–230 GPa) induce phyllosilicates’ application as reinforcing fillers. However, previous nanomechanical experiments with individual phyllosilicate nanoscrolls are in poor agreement with theory. The main reason for this is the low accuracy of experiments, which leads to large measurement errors compared to measured average values. Here, the study of the mechanical properties of synthetic (Mg1–xNix)3Si2O5(OH)4 phyllosilicates is reported by testing a suspended nanoobject (a nanobridge) with an atomic force microscope (AFM). The Young's modulus of corresponding phyllosilicate model layers is also calculated by means of the density functional theory (DFT). The original AFM approach makes it possible to account for the probe slipping off the nanobridge and determine its boundary conditions. The measured Young's modulus values are considered within the models of surface tension and shear strain contributions. The shear strain appears to have a decisive impact on the measured Young's modulus (from 150 ± 70 GPa to 200 ± 210 GPa) and its spread.

Ni3Si2O5(OH)(4) phyllosilicate nanoscrolls were investigated by two techniques: the bending-based test method of AFM and the indentation method with visual control in STEM. In the first case, the average measured Young's modulus, about 200 GPa, turned out to be significantly higher than in the second one, 40 GPa. The reasons for this discrepancy are analyzed.

The responses of the primary sensory neuron to the effect of subnanomolar and nanomolar concentrations of ouabain, which correspond to its endogenous concentrations (EO), were investigated. By the method of atomic force microscopy (AFM) it was found that the effect of EO led to an increase in the stiffness of the neuron. It was found using the patch-clamp method that due to the ligand-receptor binding of EO to the Na, K-ATPase/Src complex, the effective charge of the activation gating system of NaV1.8 channels decreases. It was also found that EO-activated triggering of the intracellular cascade, in which the Na, K-ATPase/Src complex acts as a signal transducer, leads to a decrease in the fluorescence intensity of antibodies to NaV1.8 channels, which was revealed using confocal laser scanning microscopy. The results obtained allowed us to suggest that EO, triggering the transducer function of the Na, K-ATPase/Src complex and the corresponding intracellular signaling cascade, is able to modulate the expression of the SCN10A gene, which produces the NaV1.8 channels responsible for encoding nociceptive signals.

A method is proposed for increasing the accuracy of nanomechanical measurements in an atomic force microscope. To describe the contact interaction of the cantilever with the sample, an analytical model was used that takes into account the following factors: the cantilever probe sticks to the sample surface or slides along it, the geometric and mechanical characteristics of the sample and cantilever, and their relative position. Under the assumption of sliding, a filter was developed to correct the signals of contact stiffness and deformation measured on a sample with a developed relief. The use of the filter is illustrated in images obtained in an atomic force microscope with an imaging mode based on point-by-point registration of the force quasistatic interaction of the cantilever probe with the sample.

We propose a method for improving accuracy of nanomechanical measurements by an atomic force microscope. We describe the contact interaction of the cantilever with the sample using an analytic model taking into account different mechanisms of the cantilever probe operation (it can be clamped or can slide over the sample surface), the geometrical and mechanical characteristics of the sample and the cantilever, and their mutual arrangement. For the case of sliding, a filter is developed for correcting signals of contact stiffness and deformation measured on a sample with a developed relief. The application of the filter is illustrated by images obtained with an atomic force microscope in the visualization regime based on point-by-point recording of the forced quasi-static interaction of the cantilever probe with the sample.

Using atomic force and confocal laser scanning microscopy, we studied the effect of colchicine, 1 µg/ml, which is known to cause the depolymerization of tubulin microtubules, on the primary rat fibroblast culture. When analyzing atomic force microscopy data, the sliding type of probe–cell contact was revealed by observing a clear increase of deformation signal at the sample inclined areas. For an unambiguous interpretation of the observed variations in the mechanical characteristics of fibroblasts, it is necessary to prove the sliding of the probe over the cell surface. It was found that some fibroblasts are soft and are characterized by a quite uniform distribution of the apparent Young's modulus over their surface, while others, much harder cells have rigid fibrous structures on the Young's modulus map. Colchicine has been shown to cause significant cell hardening in both groups. Confocal microscopy data show that the observed effect is associated with an increase in the intracellular content of F-actin in fibroblasts.

In the primary sensory neuron, ouabain activates the dual mechanism that modulates the functional activity of Na V 1.8 channels. Ouabain at endogenous concentrations (EO) triggers two different signaling cascades, in which the Na,K-ATPase/Src complex is the EO target and the signal transducer. The fast EO effect is based on modulation of the Na V 1.8 channel activation gating device. EO triggers the tangential signaling cascade along the neuron membrane from Na,K-ATPase to the Na V 1.8 channel. It evokes a decrease in effective charge transfer of the Na V 1.8 channel activation gating device. Intracellular application of PP2, an inhibitor of Src kinase, completely eliminated the effect of EO, thus indicating the absence of direct EO binding to the Na V 1.8 channel. The delayed EO effect probably controls the density of Na V 1.8 channels in the neuron membrane. EO triggers the downstream signaling cascade to the neuron genome, which should result in a delayed decrease in the Na V 1.8 channels’ density. PKC and p38 MAPK are involved in this pathway. Identification of the dual mechanism of the strong EO effect on Na V 1.8 channels makes it possible to suggest that application of EO to the primary sensory neuron membrane should result in a potent antinociceptive effect at the organismal level.

Atomic force microscopy (AFM) measurements have revealed hardening of intact fibroblasts after treatment with colchicine. The reliability of AFM measurements was confirmed by the identification of cells the lateral response of which to indentation did not disturb the normal force contribution. AFM data on the mechanical characteristics of such cells admit an unambiguous interpretation.

It was found that living fibroblasts become more rigid after exposure to colchicine. For reliable measurements, we identified the cells, that during indentation interact with weak lateral forces that do not distort the normal force contribution. The atomic force microscopy data of the mechanical characteristics of such cells are interpreted unambiguously.