Biomechanical characterization
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Atomic force microscopy (AFM) is not only a high-resolution imaging technique but also a sensitive tool able to study biomechanical properties of bio-samples (biomolecules, cells) in native conditions-i.e., in buffered solutions (culturing media) and stable temperature (mostly 37 °C). Micromechanical transducers (cantilevers) are often used to map surface stiffness distribution, adhesion forces, and viscoelastic parameters of living cells; however, they can also be used to monitor time course of cardiomyocytes contraction dynamics (e.g. beating rate, relaxation time), together with other biomechanical properties. Here we describe the construction of an AFM-based biosensor setup designed to study the biomechanical properties of cardiomyocyte clusters, through the use of standard uncoated silicon nitride cantilevers. Force-time curves (mechanocardiograms, MCG) are recorded continuously in real time and in the presence of cardiomyocyte-contraction affecting drugs (e.g., isoproterenol, metoprolol) in the medium, under physiological conditions. The average value of contraction force and the beat rate, as basic biomechanical parameters, represent pharmacological indicators of different phenotype features. Robustness, low computational requirements, and optimal spatial sensitivity (detection limit 200 pN, respectively 20 nm displacement) are the main advantages of the presented method.
- MeSH
- biomechanika * MeSH
- biosenzitivní techniky MeSH
- kardiomyocyty cytologie MeSH
- lidé MeSH
- mikroskopie atomárních sil * přístrojové vybavení metody MeSH
- pluripotentní kmenové buňky cytologie MeSH
- preklinické hodnocení léčiv MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
The present article introduces a novel method of characterizing the macromechanical cartilage properties based on dynamic testing. The proposed approach of instrumented impact testing shows the possibility of more detailed investigation of the acting dynamic forces and corresponding deformations within the wide range of strain rates and loads, including the unloading part of stress-strain curves and hysteresis loops. The presented results of the unconfined compression testing of both the native joint cartilage tissues and potential substitute materials outlined the opportunity to measure the dissipation energy and thus to identify the initial mechanical deterioration symptoms and to introduce a better definition of material damage. Based on the analysis of measured specimen deformation, the intact and pathologically changed cartilage tissue can be distinguished and the differences revealed.
- MeSH
- biologické modely MeSH
- časové faktory MeSH
- chondrocyty fyziologie MeSH
- kloubní chrupavka fyziologie MeSH
- kultivované buňky MeSH
- lidé MeSH
- mechanický stres MeSH
- pevnost v tlaku MeSH
- pružnost MeSH
- selhání protézy MeSH
- testování materiálů * MeSH
- tkáňové inženýrství * MeSH
- tkáňové podpůrné struktury * MeSH
- zvířata MeSH
- Check Tag
- lidé MeSH
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
The rapidly growing field of mechanobiology demands for robust and reproducible characterization of cell mechanical properties. Recent achievements in understanding the mechanical regulation of cell fate largely rely on technological platforms capable of probing the mechanical response of living cells and their physico-chemical interaction with the microenvironment. Besides the established family of atomic force microscopy (AFM) based methods, other approaches include optical, magnetic, and acoustic tweezers, as well as sensing substrates that take advantage of biomaterials chemistry and microfabrication techniques. In this review, we introduce the available methods with an emphasis on the most recent advances, and we discuss the challenges associated with their implementation.
- Publikační typ
- časopisecké články MeSH
- přehledy MeSH
A pathological disorder of human penile function, known as Peyronie's disease, is characterized by the formation of plaque particles within the tunica albuginea. The plagues in the shape of rigid plate form in the scars as a result of the imperfect healing process. Due to high stiffness, plagues are the source of pain and anomalous deformations during erectile penis function. The authors simulate the biomechanical behavior of the penile structure by a 3D finite element model. The numerical model is based on the real geometrical shape and the tissue structure with consideration of large nonlinear deformations. The penile erection is modeled by the initial strains imposed on the corpus cavernosa. The stress analysis is performed in a case study of various plague locations. The Peyronie's syndrome manifested by the penis angular deviation simulated by the analysis is compared with the clinical data. The computational simulations provide a rational explanation for the clinical observations on patients. The objective is to apply the proposed modeling approach for the development and validation of treatment methods based on the application of shock waves.
- Publikační typ
- časopisecké články MeSH
Human cryopreserved allografts of pulmonary and aortic heart valves, aortas and pulmonary trunks are used for valve replacement. However, it is unknown how the composition of these allografts relate to their mechanical properties. Our aims were to correlate the histological compositions and passive mechanical properties of aortic and pulmonary valves and to observe the microcracks of aortas and pulmonary trunks. The following parameters were quantified: ultimate stress; ultimate strain; Young's modulus of elasticity; valve cusp wall thickness; pulmonary and aortic intima-media thickness; area fraction of elastin, collagen and calcification; and length density of elastic fibres. The propagation of experimentally induced microcracks avoided elastic fibres. Ultimate strain was negatively correlated with the area fraction of calcification (r=-0.4) in aortas. Ultimate stress (r=0.27) and Young's modulus in small deformation (r=0.29) and in large deformation (r=0.32) correlated with wall thickness in valve cusps. Young's modulus (r=0.34) and ultimate strain (r=0.31) correlated with intima-media thickness. Ultimate strain correlated with the area fraction of elastin (r=-0.40) and collagen in the arteries (r=0.31). As conventional histology does not fully explain the mechanical properties of cryopreserved grafts, both morphological and biomechanical tests should be used complementarily when characterizing the ageing of the grafts.
- MeSH
- alografty MeSH
- aorta anatomie a histologie fyziologie MeSH
- aortální chlopeň anatomie a histologie fyziologie transplantace MeSH
- arteria pulmonalis anatomie a histologie fyziologie MeSH
- biomechanika fyziologie MeSH
- kryoprezervace MeSH
- lidé MeSH
- mechanický stres MeSH
- pevnost v tahu MeSH
- plicní chlopeň anatomie a histologie fyziologie transplantace MeSH
- pružnost MeSH
- tkáňové banky MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
- Geografické názvy
- Česká republika MeSH
The aim of this study was to simulate different types of cervical vertebra loading and to find out whether mechanical stress would concentrate in regions known in clinical practice as predilection sites for osteophyte formation. The objective was to develop a theoretical model that would elucidate clinical observations concerning the predilection site of bone remodelling in view of the physiological changes inside the cervical vertebral body. MATERIAL AND METHODS A real 3D-geometry of the fourth cervical vertebra had been made by the commercially available system ATOS II. This is a high-resolution measuring system using principles of optical triangulation. This flexible optical measuring machine projects fringe patterns on the surface of a selected object and the pattern is observed with two cameras. 3D coordinates for each camera pixel were calculated with high precision and a polygon mesh of the object's surface was further generated. In the next step an ANSYS programme was used to calculate strains and stresses in each finite element of the virtual vertebra. The applied forces used in the experiment corresponded in both magnitude and direction to physiological stress. Mechanical loading in neutral position was characterized by a distribution of 80% mechanical stress to the vertebral body and 10% to each of the zygoapophyseal joints. Hyperlordotic loading was simulated by 60% force transfer to the vertebral body end-plate and 20% to each of the small joint while kyphotic loading involved a 90% load on the vertebral body end-plate and 5% on each facet. RESULTS Mechanical stress distribution calculated in a neutral position of the model correlated well with bone mineral distribution of a healthy vertebra, and verified the model itself. The virtual mechanical loading of a vertebra in kyphotic position concentrated deformation stress into the uncinate processes and the dorsal apophyseal rim of the vertebral body. The simulation of mechanical loading in hyperlordosis, on the other hand, shifted the region of maximum deformation into the articulation process of the Z-joint. All locations are known as areas of osteophyte formation in degenerated cervical vertebrae. DISCUSSION AND CONCLUSIONS The theoretical model developed during this study corresponded well with human spine behaviour in terms of predilection sites for osteodegenerative changes, as observed in clinical practice. A mathematical simulation of mechanical stress distribution in pre-operative planning may lead to the optimisation of post-operative anatomical relationship between adjacent vertebrae. Such improvement in our surgical practice may further reduce the incidence of degenerative changes in adjacent motion segments of the cervical spine and possibly also lead to better subjective and clinical results after cervical spine reconstruction.
Cortical bone plays a vital role in determining overall bone strength. We investigate the structural, compositional, and nanomechanical properties of cortical bone following ovariectomy (OVX) of 12-week-old Sprague Dawley rats, since this animal model is frequently employed to evaluate the performance of implantable biomaterials in compromised bone healing conditions. Morphological parameters and material properties of bone in the geometrical center of the femoral cortex were investigated four and eight weeks post-OVX and in unoperated controls (Ctrl), using X-ray micro-computed tomography, backscattered electron scanning electron microscopy, Raman spectroscopy, and nanoindentation. The OVX animals showed increase in body weight, diminished bone mineral density, increased intracortical porosity, but increased bone mass through periosteal apposition (e.g., increases in periosteal perimeter, cortical cross-sectional thickness, and cross-sectional area). However, osteocyte densities, osteocyte lacunar dimensions, and the nanomechanical behavior on the single mineralized collagen fibril level remained unaffected. Our correlative multiscale investigation provides structural, chemical, and nanomechanical evidence substantiating earlier reports suggesting that rats ovariectomized at 12 weeks undergo simultaneous bone loss and growth, resulting in the effects of OVX being less obvious. Periosteal apposition contradicts the conventional view of bone loss in osteoporosis but appears advantageous for the greater functional demand imposed on the skeleton by increased body weight and fragility induced by increased intracortical porosity. Through a variety of morphological changes, it is likely that 12-week-old rats are able to adapt to OVX-related microstructural and compositional alterations. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 106A: 997-1007, 2018.
- MeSH
- biomechanika MeSH
- extracelulární matrix metabolismus MeSH
- femur patologie patofyziologie MeSH
- kortikální kost diagnostické zobrazování patologie patofyziologie MeSH
- lineární modely MeSH
- minerály metabolismus MeSH
- nanočástice chemie MeSH
- osteocyty metabolismus MeSH
- osteoporóza diagnostické zobrazování patologie patofyziologie MeSH
- počet buněk MeSH
- poréznost MeSH
- potkani Sprague-Dawley MeSH
- rentgenová mikrotomografie MeSH
- tělesná hmotnost MeSH
- zvířata MeSH
- Check Tag
- ženské pohlaví MeSH
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
Kombinace pohybů v ramenním pletenci se vyznačuje velkou složitostí a variabilitou řešení, kterými lze dosáhnout finální polohu vybraného segmentu. V důsledku toho je možné realizovat pohyb velkého rozsahu, zároveň však narůstají požadavky na udržení stability v daném kloubu. Biomechanika je jednou ze skupiny vědních disciplín, které umožňují popsat příčiny těchto jevů, průběh vlastních dějů i možné následky. V tomto článku jsme se pokusili o shromáždění základních biomechanických údajů, které se vztahují k pohybům v jednotlivých kloubech ramenního pletence a k působení sil, které jsou pro tyto pohyby určující.
The combination of motions in shoulder girdle is characterized by great complexity and variability of solutions, which may reach final position of a selected segment. That is why locomotion of in great range is possible, but there are simultaneously requirements for maintaining stability in the given joint. Biomechanics is one of the groups of scientific disciplines, which enable description of these events, their course and possible consequences.The authors present an attempt to summarize basic biomechanic events, which are related to the motions in individual joints of shoulder girdle and to the action of forces, which are decisive for these movements.
An assessment of vocal impairment is presented for separating healthy people from persons with early untreated Parkinson's disease (PD). This study's main purpose was to (a) determine whether voice and speech disorder are present from early stages of PD before starting dopaminergic pharmacotherapy, (b) ascertain the specific characteristics of the PD-related vocal impairment, (c) identify PD-related acoustic signatures for the major part of traditional clinically used measurement methods with respect to their automatic assessment, and (d) design new automatic measurement methods of articulation. The varied speech data were collected from 46 Czech native speakers, 23 with PD. Subsequently, 19 representative measurements were pre-selected, and Wald sequential analysis was then applied to assess the efficiency of each measure and the extent of vocal impairment of each subject. It was found that measurement of the fundamental frequency variations applied to two selected tasks was the best method for separating healthy from PD subjects. On the basis of objective acoustic measures, statistical decision-making theory, and validation from practicing speech therapists, it has been demonstrated that 78% of early untreated PD subjects indicate some form of vocal impairment. The speech defects thus uncovered differ individually in various characteristics including phonation, articulation, and prosody.
- MeSH
- biomechanika MeSH
- dospělí MeSH
- fonace MeSH
- kvalita hlasu MeSH
- lidé středního věku MeSH
- lidé MeSH
- měření tvorby řeči MeSH
- Parkinsonova nemoc komplikace diagnóza patofyziologie MeSH
- periodicita MeSH
- poruchy artikulace diagnóza etiologie patofyziologie MeSH
- poruchy hlasu diagnóza etiologie patofyziologie MeSH
- poruchy řeči diagnóza etiologie patofyziologie MeSH
- posuzování pracovní neschopnosti MeSH
- senioři nad 80 let MeSH
- senioři MeSH
- statistické modely MeSH
- studie případů a kontrol MeSH
- stupeň závažnosti nemoci MeSH
- vibrace MeSH
- zvuková spektrografie MeSH
- Check Tag
- dospělí MeSH
- lidé středního věku MeSH
- lidé MeSH
- mužské pohlaví MeSH
- senioři nad 80 let MeSH
- senioři MeSH
- ženské pohlaví MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- Geografické názvy
- Česká republika MeSH
Textile-based implant (mesh) treatment is considered as a standard of care for abdominal wall hernia repair. Computational models and simulations have appeared as one of the most promising approach to investigate biomechanics related to hernia repair and to improve clinical outcomes. This paper presents a novel anisotropic hypo-elastoplastic constitutive model specifically established for surgical knitted textile implants. The major mechanical characteristics of these materials such as anisotropy and permanent set have been reproduced. For the first time ever, we report an extensive mechanical characterization of one of these meshes, including cyclic uniaxial tension, planar equibiaxial tension and plunger type testing. These tests highlight the complex mechanical behavior with strong nonlinearity, anisotropy and permanent set. The novel anisotropic hypo-elasto-plastic constitutive model has been identified based on the tensile experiments and validated successfully against the data of the plunger experiment. In the future, implementation of this characterization and modeling approach to additional surgical knitted textiles should be the direction to follow in order to develop clinical decision support software for abdominal wall repair.
- MeSH
- chirurgické síťky * MeSH
- lidé MeSH
- operace kýly MeSH
- protézy a implantáty MeSH
- testování materiálů MeSH
- textilie MeSH
- ventrální hernie * MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
