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Atomic force microscopy techniques of rapid indentation make it possible to obtain physical and mechanical properties simultaneously with the topography of the surface. In the general case, the obtained relief depends on the load with which the probe indents the surface. The paper presents a method of treatment of the force curves that highlights the changes in the relief at each individual step of the applied load: the surface topography (the moment of the probe touching the material), the transition region, and the sub-surface structures are separated (standard software only provides the topography corresponding to the maximum of the applied load). The proposed approach is illustrated by studying both soft and relatively stiff materials. In the first case, a two-phase polymer (polyurethane) was considered – the fibrillar structure of the polymer hidden by the soft nanolayer was shown; a study of the protein layer deposited on the surface of this polymer revealed a dendritic nanostructure of the protein film under the homogeneous surface layer. In the second case, a polymer modified by plasma implantation of carbon ions was investigated – subsurface inhomogeneities of the implanted carbon layer were shown; deformation-induced nanocracks were found to be first formed under the surface in the stiffest part of the modified layer. The paper proposes a method for estimating the thickness of the soft surface layer. It is also shown that the most complete picture of the subsurface structure does not correspond to the maximum of the applied load. The paper raises the problem of investigating adhesion interactions and the validity of using adhesion in calculating the elastic modulus in cases where the surface of an inhomogeneous material is covered by some nanolayer. The considered methods not only allow one to determine the surface relief and the features of the subsurface structures but also give the knowledge of what the researcher sees when using standard software of the device.

Abstract. Recently, there have been increasing an interest to study a role of polyamines in intercellular interactions, especially in the focus of inflammation, where accumulation of such polycations is observed. In this regard, products of microbial origin - cadaverine and putrescine – are of particular attention. The role of polyamines as "scavengers" of free radicals has been described, but no data of their effect on the leukocyte radical-producing activity have been obtained so far.The aim of the investigation was to study features of hydroxyl radical generation by human leukocytes exposed to microbe-derived polyamines.Materials and methods. Peripheral venous blood samples were obtained from 20 healthy donors. To assess radical production, a luminol-dependent chemiluminescence reaction was carried out with blood leukocytes pre-incubated with cadaverine (0.01 M) and putrescine (0.01 M), measured on a Luminoskan Ascent® Thermo Labsystems luminometer (USA) for 180 min. For statistical analysis, an integral chemiluminescence index was used for the entire measurement period (RLU).Results and discussion. It was shown that cadaverine has a stimulating effect on the leukocyte potential  to produce radicals (averaged area under the curve is 6.7±0.7 r.u, p0.05). Putrescine had little effect on the radical-producing activity of human cells (2.8±0.4 r.u., p0.05). This might be due to the direct influence of polycations on the mechanisms of radical generation, as well as increased activity of leukocyte diamine oxidase catalyzing the conversion of diamines into aminoaldehyde, which is accompanied by the release of hydrogen peroxide reacting with luminol. In addition, the enzyme inactivates other compounds, such as histamine leading to formation of a less pronounced clinical picture. Polyamines, particularly cadaverine and putrescine, can be referred to the factors remodeling the metabolic activity of the host leukocytes, which is aimed at maintaining the viability and increasing the number of microorganisms.Conclusion. Thus, cadaverine and putrescine produced by microorganisms, depending on the conditions of the microenvironment, might be evidently considered as mediators of the mild or asymptomatic course of inflammatory diseases, which contributes to underlying persistent potential of bacteria.

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