Effects of High-Fat Diet on Rat Aortic Endothelial Cell Morphology and Stiffness / 医用生物力学

Objective To investigate the high-fat diet effect on morphology and stiffness of endothelial cells. Methods SD rats were randomly divided into high-fat diet group (AS group, n=3) and control group (CON group, n=3). Rat aortic endothelial cells were obtained from rat thoracic aorta by explant method. Cell morphology was observed under inverted microscopy. The mean fluorescent intensity of F-actin in two groups was calculated by immunofluorescence staining. Cell stiffness was measured by atomic force microscopy (AFM). Results The endothelial cells migrated from tissue plant on the 7th day and formed confluence after cultivation for 14 days. Endothelial cells were identified by factor Ⅷ immunofluorescence staining. Cells in AS group showed enhanced perimeter (P＜0.01), aspect ratio (P＜0.01), and area (P＞0.05), while less circularity (P＜0.01) compared with the cells in control group. The mean fluorescence intensity of F-actin in AS group was significantly higher than that in control group (P＜0.01). AFM showed that the cell stiffness of AS group was significantly higher than that of control group (P＜0.01). Conclusions High-fat diet would change the morphology and stiffness of endothelial cells, which might subsequently affect their normal function and become an important incentive to AS.

Application of atomic force microscopy (AFM) to study bacterial biofilms / 生物工程学报

Because of the nanometre resolution, piconewton force sensitivity, label-free technique and the ability to operate in liquid environments, atomic force microscopy (AFM) has emerged as a powerful tool to explore the biofilm development processes. AFM provides three-dimensional topography and structural details of biofilm surfaces under in-situ conditions. It also helps to generate key information on the mechanical properties of biofilm surfaces, such as elasticity and stickiness. Additionally, single-molecule and single-cell force spectroscopies can be applied to measure the strength of adhesion, attraction, and repulsion forces between cell-solid and cell-cell surfaces. This paper outlined the basic principle of AFM technique and introduced recent advances in the application of AFM for the investigation of ultra-morphological, mechanical and interactive properties of biofilms. Furthermore, the existing problems and future prospects were discussed.

Physicochemical and Biological Investigation of Different Structures of Carbon Coatings Deposited onto Polyurethane

The aim of this study was to examine the thrombogenic properties of polyurethane that was surface modified with carbon coatings. Physicochemical properties of manufactured coatings were investigated using transmission electron microscopy (TEM), atomic force microscopy (AFM), X-ray Photoelectron Spectroscopy (XPS), Raman spectroscopy and contact angle measurement methods. Samples were examined by the Impact-R method evaluating the level of platelets activation and adhesion of particular blood cell elements. The analysis of antimicrobial resistance against E. coli colonization and viability of endothelial cells showed that polyurethane modified with use of carbon layers constituted an interesting solution for biomedical application.

s size with AFM

Atomic Force Microscopy (AFM) can be used to obtain high-resolution topographical images of bacteria revealing surface details and cell integrity. During scanning however, the interactions between the AFM probe and the membrane results in distortion of the images. Such distortions or artifacts are the result of geometrical effects related to bacterial cell height, specimen curvature and the AFM probe geometry. The most common artifact in imaging is surface broadening, what can lead to errors in bacterial sizing. Several methods of correction have been proposed to compensate for these artifacts and in this study we describe a simple geometric model for the interaction between the tip (a pyramidal shaped AFM probe) and the bacterium (Escherichia coli JM-109 strain) to minimize the enlarging effect. Approaches to bacteria immobilization and examples of AFM images analysis are also described.

Measuring bacterial cells size with AFM

Atomic Force Microscopy (AFM) can be used to obtain high-resolution topographical images of bacteria revealing surface details and cell integrity. During scanning however, the interactions between the AFM probe and the membrane results in distortion of the images. Such distortions or artifacts are the result of geometrical effects related to bacterial cell height, specimen curvature and the AFM probe geometry. The most common artifact in imaging is surface broadening, what can lead to errors in bacterial sizing. Several methods of correction have been proposed to compensate for these artifacts and in this study we describe a simple geometric model for the interaction between the tip (a pyramidal shaped AFM probe) and the bacterium (Escherichia coli JM-109 strain) to minimize the enlarging effect. Approaches to bacteria immobilization and examples of AFM images analysis are also described.

Ultrastructure and compression elasticity of sarcomere in different activated states using atomic force microscopy / 医用生物力学

Objective To construct a system for studying the ultrastructure and mechanical properties of insect flight muscle fiber in different activated states so as to carry out cardiac biomechanics study in physiological environment, and further promote understanding of the relationship between cardiac structure, mechanical properties and physiological function, and provide more clues for the basic and clinical research on cardiac diseases. Methods The ultrastructure of insect flight muscle fibrils in rigor, relaxed and activated state was investigated using the tapping mode of atomic force microscopy (AFM), and the elasticity of muscle fibers in different physiological states was studied using the nanoindentation. Results Sarcomere lengths of insect flight muscle fiber in rigor, relaxed and activated state were (2.10±0.05), (3.10±0.10), (2.50±0.15) μm (2 mmol/L Ca2+), (2.60±0.25) μm (5 mmol/L Ca2+) and (2.55±0.15) μm (10 mmol/L Ca2+), respectively, while the A-band length maintained at 1.50 μm and I-band changed from 0.7~1.6 μm. Mechanical test found that the elasticity of different bands or lines in the same physiological state varied in the order of Z-line>M-line>overlap>I-band. Conclusions Critical Ca2+ concentration for muscle fiber activation was 5 mmol/L, and sarcomere length distributions were in line with the relative slip theory and structure model, and AFM was the potential tool for the high resolution study on ultrastructure and mechanical properties of the muscle fibers.

Application of atomic force microscopy in ultrastructure and biomechanics of cells and biomacromolecules / 医用生物力学

To be the representative fruition resulted from the rapid development in micro-nano theory and technology, atomic force microscopy (AFM) has greatly promoted the expansion of biological research in micro-nano scale, and facilitated the birth and development of micro-nano biology as an important technique in its 25-year evolutional progress. Based on the fundamental principles and detection modes of AFM, as well as the author’s research findings and work experience in this field, the paper reviews the application of AFM in the study on ultrastructure and biomechanical properties of cells and biomacromolecules in the aspects of biological structure and morphology, surface physicochemical characterization and mechanical manipulation of biological macromolecules, and focus on some important scientific and technical problems on AFM in micro-nano biomedical research needed to be improved and solved urgently, with exploratory insights and recommendations for potential users in ultrastructure and biomechanics of cells and biomacromolecules.

Scope of atomic force microscopy in the advancement of nanomedicine.

One of the most exciting fields of current research is nanomedicine, but its definition and landscape remains elusive due to its continuous expansion in all directions and thus constantly eroding its boundaries and defying definitions. This lack of conceptual framework and confusing definitions was a hurdle for policy makers to enunciate credible goals and allocate resources for the advancement of the field. In this mini review, we have provided a broad framework of nanomedicine which defines its elusive landscape, and we hope this framework will accommodate its explosive growth in the future. Also, we have highlighted the role and scope of atomic force microscopy techniques in the advancement of nanomedicine. For improving health care of all that eventually would require successful intervention at fundamental biological processes, the importance of understanding the structure-function relationship of biomolecules cannot be over emphasized. In this context, AFM and its variants play a pivotal role in contributing towards the nanomedicine knowledge-base that is required for fruitful developments in nano-diagnostics and nano-therapeutics.

Imaging study of interaction between Yersinia pestis and its surface antibody by atomic force microscopy / 中华微生物学和免疫学杂志

Objective To observe and compare the atomic force microscopy (AFM) images of Yersinia pestis EV76 and the changes in the morphology of the bacteria treated with normal serum and F1 antibody from rabbit,and to explore the immunoassay method to detect Yersinia pestis by AFM. Methods The Yersinia pestis were treated with normal serum and F1 antibody from rabbit and control buffer. All the prepared samples were observed and analyzed by AFM. The changes in the cell surface structures were probed and characterized through sectional analysis,especially the changes of Ra and Rq value. Results The normal morphology of Yersinia pestis was oval in shape with a relatively smooth surface, the size dimension of which was about 1.1-1.3 μm in length with a section profile of 0.8-1.0 μm in width and 0.04-0.06 μm in step height. The step height of the bacteria treated with the normal serum and F1 antibody was obviously enlarged. The shape of the bacteria treated with F1 antibody changed irregularly. Furthermore, the surface of the bacteria was more roughened. Conclusion The morphological characters of Yersinia pestis has been acquired through its AFM images. The morphology of Yersinia pestis treated with F1 antibody has changed greatly, and the index of roughness can be regarded as the distinguished index to detect Yersinia pestis by AFM.