Narrow Results

To understand the physiology and pathology of human skeletal system, the accurate measurement of microscopic biomechanical properties of bone is an important works. In this study, a measurement system of the Poisson's ratio with a sub-nano resolution was developed. The resulting resolution of the system was 0.3 nm, which was 0.1% of the measurement error for this system configuration. Using this measurement system, actual tests were performed to check the capability of the measurement system. Cubic bone specimens with a dimension of 300 μm were loaded up to an axial strain of 0.5%, which is within the elastic range of the specimens. The mean elastic modulus and the Poisson's ratio of bovine femoral cortical bone measured in this study were 14.42 GPa (SD ± 0.6179) and 0.265 (SD ± 0.0125) respectively. The developed system will be useful to understand the biomechanics of bones for modeling the mechanobiological bone system.

This paper studied the mechanical and chemical properties of hydroxyl apatite (HA) crystal structure in the teeth when human molars were soaked in slight acid solution. First, we soaked the ground and polished molars respectively in the liquor of 30 wt.% H₂CO₃ and the liquor of 30 wt.% H₂O₂ for 10, 20, or 60 minutes. Next, we used a nanoindenter to measure the hardness and Young's modulus. Finally, we used a scanning electron microscope (SEM) coupled with energy dispersive spectroscopy (EDS) to analyze the variation of Ca, P and Na in teeth, a high resolution transmitting electron microscope (HRTEM) to observe the arrangement of crystallization phase of HA, and X-ray diffraction (XRD) to analyze the crystallinity of the hexagonal phase of HA. The results showed that the demineralization phenomenon of the calcium–phosphorous compound in teeth made the teeth reduce sharply in hardness and Young's modulus after they were soaked in the two slight acid solutions for 10 minutes, but the re-mineralization phenomenon made the hardness and Young's modulus ascend gradually when the time lasted longer. With the same period of time, the teeth soaked in H₂CO₃ were lower in the hardness and Young's modulus than that in H₂O₂.

There exist many reviews on the biological and biochemical interactions of cancer cells and endothelial cells during the transmigration and tissue invasion of cancer cells. For the malignant progression of cancer, the ability to metastasize is a prerequisite. In particular, this means that certain cancer cells possess the property to migrate through the endothelial lining into blood or lymph vessels, and are possibly able to transmigrate through the endothelial lining into the connective tissue and follow up their invasion path in the targeted tissue. On the molecular and biochemical level the transmigration and invasion steps are well-defined, but these signal transduction pathways are not yet clear and less understood in regards to the biophysical aspects of these processes.

To functionally characterize the malignant transformation of neoplasms and subsequently reveal the underlying pathway(s) and cellular properties, which help cancer cells to facilitate cancer progression, the biomechanical properties of cancer cells and their microenvironment come into focus in the physics-of-cancer driven view on the metastasis process of cancers. Hallmarks for cancer progression have been proposed, but they still lack the inclusion of specific biomechanical properties of cancer cells and interacting surrounding endothelial cells of blood or lymph vessels. As a cancer cell is embedded in a special environment, the mechanical properties of the extracellular matrix also cannot be neglected. Therefore, in this review it is proposed that a novel hallmark of cancer that is still elusive in classical tumor biological reviews should be included, dealing with the aspect of physics in cancer disease such as the natural selection of an aggressive (highly invasive) subtype of cancer cells displaying a certain adhesion or chemokine receptor on their cell surface.

Today, the physical aspects can be analyzed by using state-of-the-art biophysical methods. Thus, this review will present current cancer research in a different light from a physical point of view with respect to cancer cell mechanics and the special and unique role of the endothelium on cancer cell invasion.

The physical view on cancer disease may lead to novel insights into cancer disease and will help to overcome the classical views on cancer. In addition, in this review it will be discussed how physics of cancer can help to reveal and propose the functional mechanism which cancer cells use to invade connective tissue and transmigrate through the endothelium to finally metastasize.

Finally, in this review it will be demonstrated how biophysical measurements can be combined with classical analysis approaches of tumor biology. The insights into physical interactions between cancer cells, the endothelium and the microenvironment may help to answer some "old," but still important questions in cancer disease progression.

In sickle cell disease (SCD), hemoglobin molecules polymerize intracellularly and lead to a cascade of events resulting in decreased deformability and increased adhesion of red blood cells (RBCs). Decreased deformability and increased adhesion of sickle RBCs lead to blood vessel occlusion (vaso-occlusion) in SCD patients. Here, we present a microfluidic approach integrated with a cell dimensioning algorithm to analyze dynamic deformability of adhered RBC at the single-cell level in controlled microphysiological flow. We measured and compared dynamic deformability and adhesion of healthy hemoglobin A (HbA) and homozygous sickle hemoglobin (HbS) containing RBCs in blood samples obtained from 24 subjects. We introduce a new parameter to assess deformability of RBCs: the dynamic deformability index (DDI), which is defined as the time-dependent change of the cell's aspect ratio in response to fluid flow shear stress. Our results show that DDI of HbS-containing RBCs were significantly lower compared to that of HbA-containing RBCs. Moreover, we observed subpopulations of HbS containing RBCs in terms of their dynamic deformability characteristics: deformable and non-deformable RBCs. Then, we tested blood samples from SCD patients and analyzed RBC adhesion and deformability at physiological and above physiological flow shear stresses. We observed significantly greater number of adhered non-deformable sickle RBCs than deformable sickle RBCs at flow shear stresses well above the physiological range, suggesting an interplay between dynamic deformability and increased adhesion of RBCs in vaso-occlusive events.

Bladder control problems affect both men and women and range from an overactive bladder, to urinary incontinence, to bladder obstruction and cancer. These disorders affect more than 200 million people worldwide. Loss of bladder function significantly affects the quality of life, both physically and psychologically, and also has a large impact on the healthcare system, i.e., the incurring costs related to diagnosis, treatment and medical/nursing care. Improvements in diagnostic capabilities and disease management are essential to improve patient care and quality of life and reduce the economic burden associated with bladder disorders. This paper summarizes some of the key contributions to understanding the mechanics of the bladder ranging from work conducted in the 1970s through the present time with a focus on material testing and theoretical modeling. Advancements have been made in these areas and a significant contribution to these changes was related to technological improvements.

This study was attempted to develop a new cell finite element model to present the cell mechanical response underlying the compression. The geometry and material properties of cytomembrane, cytoplasm, cytoskeleton, and the nucleus were obtained according the previous experimental data. 5Mpa compression loading was simulated in LS-DYNA solvers, the displacement, strain, stress contour of the cytomembrane, cytoplasm, cytoskeleton, and the nucleus were calculated in this study. According the prediction of this FE modeling, the mechanotransduction sequence of each part in cell was observed from cytomembrane to cytoskeleton and then the cytoplasm, finally to the nucleus. This phenomenon might indicate that the remodeling behavior of the cell cytoskeleton was influenced by the nucleus mechanical response.