scholarly journals Decellularization Following Fixation of Explanted Aortic Valves as a Strategy for Preserving Native Mechanical Properties and Function

2022 ◽  
Vol 9 ◽  
Author(s):  
Manisha Singh ◽  
Clara Park ◽  
Ellen T. Roche
Keyword(s):  
Mechanical Properties ◽  
Learning Experience ◽  
Fixation Method ◽  
Valvular Regurgitation ◽  
Aortic Valves ◽  
Hands On Learning ◽  
Human Cadavers ◽  
Primary Focus ◽  
Hemodynamic Performance ◽  
And Function

Mechanical or biological aortic valves are incorporated in physical cardiac simulators for surgical training, educational purposes, and device testing. They suffer from limitations including either a lack of anatomical and biomechanical accuracy or a short lifespan, hence limiting the authentic hands-on learning experience. Medical schools utilize hearts from human cadavers for teaching and research, but these formaldehyde-fixed aortic valves contort and stiffen relative to native valves. Here, we compare a panel of different chemical treatment methods on explanted porcine aortic valves and evaluate the microscopic and macroscopic features of each treatment with a primary focus on mechanical function. A surfactant-based decellularization method after formaldehyde fixation is shown to have mechanical properties close to those of the native aortic valve. Valves treated in this method were integrated into a custom-built left heart cardiac simulator to test their hemodynamic performance. This decellularization, post-fixation technique produced aortic valves which have ultimate stress and elastic modulus in the range of the native leaflets. Decellularization of fixed valves reduced the valvular regurgitation by 60% compared to formaldehyde-fixed valves. This fixation method has implications for scenarios where the dynamic function of preserved valves is required, such as in surgical trainers or device test rigs.

scholarly journals Do differences in early hemodynamic performance of current generation biologic aortic valves predict outcomes 1 year following surgery?

2015 ◽  
Vol 149 (1) ◽  
pp. 163-173.e2 ◽  
Author(s):  
Nassir M. Thalji ◽  
Rakesh M. Suri ◽  
Hector I. Michelena ◽  
Kevin L. Greason ◽  
Joseph A. Dearani ◽  
...  
Keyword(s):  
Aortic Valves ◽  
Current Generation ◽  
Hemodynamic Performance

scholarly journals Mechanical Properties of Bovine Rhodopsin and Bacteriorhodopsin:  Possible Roles in Folding and Function†

Langmuir ◽  
2008 ◽  
Vol 24 (4) ◽  
pp. 1330-1337 ◽  
Author(s):  
K. Tanuj Sapra ◽  
Paul S.-H. Park ◽  
Krzysztof Palczewski ◽  
Daniel J. Muller
Keyword(s):  
Mechanical Properties ◽  
Bovine Rhodopsin ◽  
And Function

Stress Dependent Collagen Fibril Diameter Distribution in Human Aortic Valves

2007 ◽  
Author(s):  
Angelique Balguid ◽  
Anita Mol ◽  
Niels Driessen ◽  
Carlijn Bouten ◽  
Frank Baaijens
Keyword(s):  
Mechanical Properties ◽  
Collagen Fibril ◽  
Diameter Distribution ◽  
Connective Tissues ◽  
Aortic Valves ◽  
Cross Links ◽  
Fibril Morphology ◽  
Stress Dependent ◽  
Collagenous Tissues ◽  
Fibril Diameter

The mechanical properties of collagenous tissues are known to depend on a wide variety of factors, such as the type of tissue and the composition of its extracellular matrix. Relating mechanical roles to individual matrix components in such a complex system is difficult, if not impossible. However, as collagen is the main load bearing component in connective tissues, the relation between collagen and tissue biomechanics has been studied extensively in various types of tissues. The type of collagen, the amount and type of inter- and intramolecular covalent cross-links and collagen fibril morphology are involved in the tissues mechanical behavior (Beekman et al., 1997; Parry et al., 1978; Avery and Bailey, 2005). From literature it is known that the the collagen fibril diameter distribution can be directly related to the mechanical properties of the tissue. In particular, the diameter distribution of collagen fibrils is largely determined by the tissues requirement for tensile strength and elasticity (Parry et al., 1978).

scholarly journals An integrative method for testing form–function linkages and reconstructed evolutionary pathways of masticatory specialization

2015 ◽  
Vol 12 (107) ◽  
pp. 20150184 ◽  
Author(s):  
Z. Jack Tseng ◽  
John J. Flynn
Keyword(s):  
Mechanical Properties ◽  
Morphological Evolution ◽  
Integrative Approach ◽  
Deep Time ◽  
Integrate Form ◽  
Functional Changes ◽  
Form And Function ◽  
Form Function ◽  
Evolutionary Pathways ◽  
And Function

Morphology serves as a ubiquitous proxy in macroevolutionary studies to identify potential adaptive processes and patterns. Inferences of functional significance of phenotypes or their evolution are overwhelmingly based on data from living taxa. Yet, correspondence between form and function has been tested in only a few model species, and those linkages are highly complex. The lack of explicit methodologies to integrate form and function analyses within a deep-time and phylogenetic context weakens inferences of adaptive morphological evolution, by invoking but not testing form–function linkages. Here, we provide a novel approach to test mechanical properties at reconstructed ancestral nodes/taxa and the strength and direction of evolutionary pathways in feeding biomechanics, in a case study of carnivorous mammals. Using biomechanical profile comparisons that provide functional signals for the separation of feeding morphologies, we demonstrate, using experimental optimization criteria on estimation of strength and direction of functional changes on a phylogeny, that convergence in mechanical properties and degree of evolutionary optimization can be decoupled. This integrative approach is broadly applicable to other clades, by using quantitative data and model-based tests to evaluate interpretations of function from morphology and functional explanations for observed macroevolutionary pathways.

Cell and Tissue Mechanics

2004 ◽  
Author(s):  
W. Mark Saltzman
Keyword(s):  
Mechanical Properties ◽  
Tissue Mechanics ◽  
Elastic Materials ◽  
Robert Hooke ◽  
Hooke’S Law ◽  
Original Shape ◽  
Hooke's Law ◽  
Natural Counterpart ◽  
Tensile Elastic Modulus ◽  
And Function

Mechanics is the branch of physics that is concerned with the action of forces on matter. Tissue engineers can encounter mechanics in various settings. Often, the mechanical properties of replacement biological materials must replicate the normal tissue: for example, there is limited use for a tissue-engineered bone that cannot support the load encountered by its natural counterpart. In addition, the mechanical properties of cells and cell–cell adhesions can determine the architecture of a tissue during development. This phenomenon can sometimes be exploited, since the final form of engineered tissues depends on the forces encountered during assembly and maturation. Finally, the mechanics of individual cells—and the molecular interactions that restrain cells—are important determinants of cell growth, movement, and function within an organism. This chapter introduces the basic elements of mechanics applied to biological systems. Some examples of biomechanical principles that appear to be important for tissue engineering are also provided. For further reading, comprehensive treatments of various aspects of biomechanics are also available. Consider an elongated object—for example, a segment of a biological tissue or a synthetic biomaterial—that is fixed at one end and suddenly exposed to a constant applied load. The material will change or deform in response to the load. For some materials, the deformation is instantaneous and, under conditions of low loading, deformation varies linearly with the magnitude of the applied force: . . . σ[≡F/A]= Eε (5-1) . . . where σ is the applied stress and ε is the resulting strain. This relationship is called Hooke’s law, after the British physicist Robert Hooke, and it describes the behavior of many elastic materials, such as springs, which deform linearly upon loading and recover their original shape upon removal of the load. The Young’s modulus or tensile elastic modulus, E, is a property of the material; some typical values are provided in Table 5.1. Not all elastic materials obey Hooke’s law (for example, rubber does not); some materials will recover their original shape, but strain is not linearly related to stress. Fortunately, many interesting materials do follow Equation 5-1, particularly if the deformations are small.

scholarly journals Extraction of mechanical properties of materials through deep learning from instrumented indentation

2020 ◽  
Vol 117 (13) ◽  
pp. 7052-7062 ◽  
Author(s):  
Lu Lu ◽  
Ming Dao ◽  
Punit Kumar ◽  
Upadrasta Ramamurty ◽  
George Em Karniadakis ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Deep Learning ◽  
Scaling Laws ◽  
Three Dimensional ◽  
Instrumented Indentation ◽  
Multilayered Structures ◽  
Mechanical Properties Of Materials ◽  
Properties Of Materials ◽  
Indentation Problem ◽  
And Function

Instrumented indentation has been developed and widely utilized as one of the most versatile and practical means of extracting mechanical properties of materials. This method is particularly desirable for those applications where it is difficult to experimentally determine the mechanical properties using stress–strain data obtained from coupon specimens. Such applications include material processing and manufacturing of small and large engineering components and structures involving the following: three-dimensional (3D) printing, thin-film and multilayered structures, and integrated manufacturing of materials for coupled mechanical and functional properties. Here, we utilize the latest developments in neural networks, including a multifidelity approach whereby deep-learning algorithms are trained to extract elastoplastic properties of metals and alloys from instrumented indentation results using multiple datasets for desired levels of improved accuracy. We have established algorithms for solving inverse problems by recourse to single, dual, and multiple indentation and demonstrate that these algorithms significantly outperform traditional brute force computations and function-fitting methods. Moreover, we present several multifidelity approaches specifically for solving the inverse indentation problem which 1) significantly reduce the number of high-fidelity datasets required to achieve a given level of accuracy, 2) utilize known physical and scaling laws to improve training efficiency and accuracy, and 3) integrate simulation and experimental data for training disparate datasets to learn and minimize systematic errors. The predictive capabilities and advantages of these multifidelity methods have been assessed by direct comparisons with experimental results for indentation for different commercial alloys, including two wrought aluminum alloys and several 3D printed titanium alloys.

scholarly journals Selection of helical braided flow diverter stents based on hemodynamic performance and mechanical properties

2016 ◽  
Vol 9 (10) ◽  
pp. 999-1005 ◽  
Author(s):  
Takashi Suzuki ◽  
Hiroyuki Takao ◽  
Soichiro Fujimura ◽  
Chihebeddine Dahmani ◽  
Toshihiro Ishibashi ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Reduction Rate ◽  
Flow Diverter ◽  
Outer Diameter ◽  
Cfd Simulations ◽  
Flow Reduction ◽  
Radial Stiffness ◽  
Flow Diverter Stent ◽  
Hemodynamic Performance ◽  
Longitudinal Flexibility

BackgroundAlthough flow diversion is a promising procedure for the treatment of aneurysms, complications have been reported and it remains poorly understood. The occurrence of adverse outcomes is known to depend on both the mechanical properties and flow reduction effects of the flow diverter stent.ObjectiveTo clarify the possibility of designing a flow diverter stent considering both hemodynamic performance and mechanical properties.Materials and methodsComputational fluid dynamics (CFD) simulations were conducted based on an ideal aneurysm model with flow diverters. Structural analyses of two flow diverter models exhibiting similar flow reduction effects were performed, and the radial stiffness and longitudinal flexibility were compared.ResultsIn CFD simulations, two stents–Pore2-d35 (26.77° weave angle when fully expanded, 35 μm wire thickness) and Pore3-d50 (36.65°, 50 μm respectively)–demonstrated similar flow reduction rates (68.5% spatial-averaged velocity reduction rate, 85.0% area-averaged wall shear stress reduction rate for Pore2-d35, and 68.6%, 85.4%, respectively, for Pore3-d50). However, Pore3-d50 exhibited greater radial stiffness than Pore2-d35 (40.0 vs 21.0 mN/m at a 3.5 mm outer diameter) and less longitudinal flexibility (0.903 vs 0.104 N·mm bending moments at 90°). These measurements indicate that changing the wire thickness and weave angle allows adjustment of the mechanical properties while maintaining the same degree of flow reduction effects.ConclusionsThe combination of CFD and structural analysis can provide promising solutions for an optimized stent. Stents exhibiting different mechanical properties but the same flow reduction effects could be designed by varying both the weave angle and wire thickness.

scholarly journals Design principles of hair-like structures as biological machines

2018 ◽  
Vol 15 (142) ◽  
pp. 20180206 ◽  
Author(s):  
Madeleine Seale ◽  
Cathal Cummins ◽  
Ignazio Maria Viola ◽  
Enrico Mastropaolo ◽  
Naomi Nakayama
Keyword(s):  
Mechanical Properties ◽  
Surface Area ◽  
Large Surface Area ◽  
Structural Basis ◽  
Basic Design ◽  
Form And Function ◽  
Mechanical Unit ◽  
Wide Range ◽  
Range Of Functions ◽  
And Function

Hair-like structures are prevalent throughout biology and frequently act to sense or alter interactions with an organism's environment. The overall shape of a hair is simple: a long, filamentous object that protrudes from the surface of an organism. This basic design, however, can confer a wide range of functions, owing largely to the flexibility and large surface area that it usually possesses. From this simple structural basis, small changes in geometry, such as diameter, curvature and inter-hair spacing, can have considerable effects on mechanical properties, allowing functions such as mechanosensing, attachment, movement and protection. Here, we explore how passive features of hair-like structures, both individually and within arrays, enable diverse functions across biology. Understanding the relationships between form and function can provide biologists with an appreciation for the constraints and possibilities on hair-like structures. Additionally, such structures have already been used in biomimetic engineering with applications in sensing, water capture and adhesion. By examining hairs as a functional mechanical unit, geometry and arrangement can be rationally designed to generate new engineering devices and ideas.

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