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Soares JS, Ramos JCM, Sorgato JC, Ribeiro LM, Reis LC. Brassavola tuberculata Hook.: in vitro growth and ex vitro establishment as a function of the micropropagation system and sucrose. BRAZ J BIOL 2023; 83:e270892. [PMID: 37466510 DOI: 10.1590/1519-6984.270892] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2023] [Accepted: 05/31/2023] [Indexed: 07/20/2023] Open
Abstract
This study examines the in vitro growth and ex vitro establishment of Brassavola tuberculata in relation to the micropropagation system and sucrose concentration employed in the in vitro culture. A completely randomized experimental design was utilized, employing a 2 x 5 factorial arrangement. The experimental period began with seedlings cultivated in vitro for 180 days, which were subsequently transferred to Murashige and Skoog culture media containing sucrose concentrations of 0, 15, 30, 45, or 60 g L-1. The cultures were subjected to two micropropagation systems: conventional and gas exchange. After 90 days of in vitro cultivation, the plants were evaluated, transplanted into a substrate, and placed in a screened nursery for ex vitro cultivation. After 300 days of ex vitro cultivation, the survival and initial characteristics of the plants were assessed. The micropropagation system allowing gas exchange and sucrose concentrations up to 30 g L-1 enhanced the shoot and root growth of in vitro propagated plants. No noticeable anatomical differences were observed after 90 days of in vitro culture among the different sucrose concentrations and micropropagation systems used. In the ex vitro establishment, irrespective of sucrose concentration, the micropropagation system facilitating gas exchange positively influenced all evaluated characteristics.
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Affiliation(s)
- J S Soares
- Universidade Federal da Grande Dourados - UFGD, Faculdade de Ciências Agrárias, Dourados, MS, Brasil
| | - J C M Ramos
- Universidade Federal da Grande Dourados - UFGD, Faculdade de Ciências Agrárias, Dourados, MS, Brasil
| | - J C Sorgato
- Universidade Federal da Grande Dourados - UFGD, Faculdade de Ciências Agrárias, Dourados, MS, Brasil
| | - L M Ribeiro
- Universidade Federal da Grande Dourados - UFGD, Faculdade de Ciências Agrárias, Dourados, MS, Brasil
| | - L C Reis
- Universidade Federal da Grande Dourados - UFGD, Faculdade de Ciências Agrárias, Dourados, MS, Brasil
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Liu H, Soares JS, Walmsley J, Li DS, Raut S, Avazmohammadi R, Iaizzo P, Palmer M, Gorman JH, Gorman RC, Sacks MS. The impact of myocardial compressibility on organ-level simulations of the normal and infarcted heart. Sci Rep 2021; 11:13466. [PMID: 34188138 PMCID: PMC8242073 DOI: 10.1038/s41598-021-92810-y] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2020] [Accepted: 05/25/2021] [Indexed: 11/09/2022] Open
Abstract
Myocardial infarction (MI) rapidly impairs cardiac contractile function and instigates maladaptive remodeling leading to heart failure. Patient-specific models are a maturing technology for developing and determining therapeutic modalities for MI that require accurate descriptions of myocardial mechanics. While substantial tissue volume reductions of 15-20% during systole have been reported, myocardium is commonly modeled as incompressible. We developed a myocardial model to simulate experimentally-observed systolic volume reductions in an ovine model of MI. Sheep-specific simulations of the cardiac cycle were performed using both incompressible and compressible tissue material models, and with synchronous or measurement-guided contraction. The compressible tissue model with measurement-guided contraction gave best agreement with experimentally measured reductions in tissue volume at peak systole, ventricular kinematics, and wall thickness changes. The incompressible model predicted myofiber peak contractile stresses approximately double the compressible model (182.8 kPa, 107.4 kPa respectively). Compensatory changes in remaining normal myocardium with MI present required less increase of contractile stress in the compressible model than the incompressible model (32.1%, 53.5%, respectively). The compressible model therefore provided more accurate representation of ventricular kinematics and potentially more realistic computed active contraction levels in the simulated infarcted heart. Our findings suggest that myocardial compressibility should be incorporated into future cardiac models for improved accuracy.
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Affiliation(s)
- Hao Liu
- James T. Willerson Center for Cardiovascular Modeling and Simulation, The University of Texas at Austin, Austin, TX, USA
| | - João S Soares
- Engineered Tissue Multiscale Mechanics and Modeling Laboratory, Virginia Commonwealth University, Richmond, VA, USA
| | - John Walmsley
- James T. Willerson Center for Cardiovascular Modeling and Simulation, The University of Texas at Austin, Austin, TX, USA
| | - David S Li
- James T. Willerson Center for Cardiovascular Modeling and Simulation, The University of Texas at Austin, Austin, TX, USA
| | - Samarth Raut
- James T. Willerson Center for Cardiovascular Modeling and Simulation, The University of Texas at Austin, Austin, TX, USA
| | - Reza Avazmohammadi
- Computational Cardiovascular Bioengineering Lab, Texas A&M University, College Station, TX, USA
| | - Paul Iaizzo
- Visible Heart Lab, University of Minnesota Twin Cities, Minneapolis, MN, USA
| | - Mark Palmer
- Corporate Core Technologies, Medtronic, Inc., Minneapolis, USA
| | - Joseph H Gorman
- Gorman Cardiovascular Research Group, University of Pennsylvania, Philadelphia, PA, USA
| | - Robert C Gorman
- Gorman Cardiovascular Research Group, University of Pennsylvania, Philadelphia, PA, USA
| | - Michael S Sacks
- James T. Willerson Center for Cardiovascular Modeling and Simulation, The University of Texas at Austin, Austin, TX, USA.
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Abstract
Understanding and predicting the mechanical behavior of myocardium under healthy and pathophysiological conditions are vital to developing novel cardiac therapies and promoting personalized interventions. Within the past 30 years, various constitutive models have been proposed for the passive mechanical behavior of myocardium. These models cover a broad range of mathematical forms, microstructural observations, and specific test conditions to which they are fitted. We present a critical review of these models, covering both phenomenological and structural approaches, and their relations to the underlying structure and function of myocardium. We further explore the experimental and numerical techniques used to identify the model parameters. Next, we provide a brief overview of continuum-level electromechanical models of myocardium, with a focus on the methods used to integrate the active and passive components of myocardial behavior. We conclude by pointing to future directions in the areas of optimal form as well as new approaches for constitutive modeling of myocardium.
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Affiliation(s)
- Reza Avazmohammadi
- James T. Willerson Center for Cardiovascular Modeling and Simulation, Oden Institute for Computational Engineering and Sciences, and Department of Biomedical Engineering, University of Texas, Austin, Texas 78712, USA;
| | - João S Soares
- James T. Willerson Center for Cardiovascular Modeling and Simulation, Oden Institute for Computational Engineering and Sciences, and Department of Biomedical Engineering, University of Texas, Austin, Texas 78712, USA;
- Department of Mechanical and Nuclear Engineering, Virginia Commonwealth University, Richmond, Virginia 23284, USA
| | - David S Li
- James T. Willerson Center for Cardiovascular Modeling and Simulation, Oden Institute for Computational Engineering and Sciences, and Department of Biomedical Engineering, University of Texas, Austin, Texas 78712, USA;
| | - Samarth S Raut
- James T. Willerson Center for Cardiovascular Modeling and Simulation, Oden Institute for Computational Engineering and Sciences, and Department of Biomedical Engineering, University of Texas, Austin, Texas 78712, USA;
| | - Robert C Gorman
- Gorman Cardiovascular Research Group, Smilow Center for Translational Research, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
| | - Michael S Sacks
- James T. Willerson Center for Cardiovascular Modeling and Simulation, Oden Institute for Computational Engineering and Sciences, and Department of Biomedical Engineering, University of Texas, Austin, Texas 78712, USA;
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Avazmohammadi R, Mendiola EA, Soares JS, Li DS, Chen Z, Merchant S, Hsu EW, Vanderslice P, Dixon RAF, Sacks MS. A Computational Cardiac Model for the Adaptation to Pulmonary Arterial Hypertension in the Rat. Ann Biomed Eng 2018; 47:138-153. [PMID: 30264263 DOI: 10.1007/s10439-018-02130-y] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2018] [Accepted: 09/11/2018] [Indexed: 01/01/2023]
Abstract
Pulmonary arterial hypertension (PAH) imposes pressure overload on the right ventricle (RV), leading to RV enlargement via the growth of cardiac myocytes and remodeling of the collagen fiber architecture. The effects of these alterations on the functional behavior of the right ventricular free wall (RVFW) and organ-level cardiac function remain largely unexplored. Computational heart models in the rat (RHMs) of the normal and hypertensive states can be quite valuable in simulating the effects of PAH on cardiac function to gain insights into the pathophysiology of underlying myocardium remodeling. We thus developed high-fidelity biventricular finite element RHMs for the normal and post-PAH hypertensive states using extensive experimental data collected from rat hearts. We then applied the RHM to investigate the transmural nature of RVFW remodeling and its connection to wall stress elevation under PAH. We found a strong correlation between the longitudinally-dominated fiber-level adaptation of the RVFW and the transmural alterations of relevant wall stress components. We further conducted several numerical experiments to gain new insights on how the RV responds both normally and in the post-PAH state. We found that the effect of pressure overload alone on the increased contractility of the RV is comparable to the effects of changes in the RV geometry and stiffness. Furthermore, our RHMs provided fresh perspectives on long-standing questions of the functional role of the interventricular septum in RV function. Specifically, we demonstrated that an inaccurate identification of the mechanical adaptation of the septum can lead to a significant underestimation of RVFW contractility in the post-PAH state. These findings show how integrated experimental-computational models can facilitate a more comprehensive understanding of the cardiac remodeling events during PAH.
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Affiliation(s)
- Reza Avazmohammadi
- Willerson Center for Cardiovascular Modeling and Simulation, Institute for Computational Engineering and Sciences and the Department of Biomedical Engineering, The University of Texas at Austin, Austin, TX, USA
| | - Emilio A Mendiola
- Willerson Center for Cardiovascular Modeling and Simulation, Institute for Computational Engineering and Sciences and the Department of Biomedical Engineering, The University of Texas at Austin, Austin, TX, USA
| | - João S Soares
- Department of Mechanical & Nuclear Engineering, Virginia Commonwealth University, Richmond, VA, USA
| | - David S Li
- Willerson Center for Cardiovascular Modeling and Simulation, Institute for Computational Engineering and Sciences and the Department of Biomedical Engineering, The University of Texas at Austin, Austin, TX, USA
| | - Zhiqiang Chen
- Department of Molecular Cardiology, Texas Heart Institute, Houston, TX, USA
| | - Samer Merchant
- Department of Biomedical Engineering, University of Utah, Salt Lake City, UT, USA
| | - Edward W Hsu
- Department of Biomedical Engineering, University of Utah, Salt Lake City, UT, USA
| | - Peter Vanderslice
- Department of Molecular Cardiology, Texas Heart Institute, Houston, TX, USA
| | - Richard A F Dixon
- Department of Molecular Cardiology, Texas Heart Institute, Houston, TX, USA
| | - Michael S Sacks
- Willerson Center for Cardiovascular Modeling and Simulation, Institute for Computational Engineering and Sciences and the Department of Biomedical Engineering, The University of Texas at Austin, Austin, TX, USA.
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Avazmohammadi R, Li DS, Leahy T, Shih E, Soares JS, Gorman JH, Gorman RC, Sacks MS. An integrated inverse model-experimental approach to determine soft tissue three-dimensional constitutive parameters: application to post-infarcted myocardium. Biomech Model Mechanobiol 2018; 17:31-53. [PMID: 28861630 PMCID: PMC5809201 DOI: 10.1007/s10237-017-0943-1] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2017] [Accepted: 07/17/2017] [Indexed: 10/19/2022]
Abstract
Knowledge of the complete three-dimensional (3D) mechanical behavior of soft tissues is essential in understanding their pathophysiology and in developing novel therapies. Despite significant progress made in experimentation and modeling, a complete approach for the full characterization of soft tissue 3D behavior remains elusive. A major challenge is the complex architecture of soft tissues, such as myocardium, which endows them with strongly anisotropic and heterogeneous mechanical properties. Available experimental approaches for quantifying the 3D mechanical behavior of myocardium are limited to preselected planar biaxial and 3D cuboidal shear tests. These approaches fall short in pursuing a model-driven approach that operates over the full kinematic space. To address these limitations, we took the following approach. First, based on a kinematical analysis and using a given strain energy density function (SEDF), we obtained an optimal set of displacement paths based on the full 3D deformation gradient tensor. We then applied this optimal set to obtain novel experimental data from a 1-cm cube of post-infarcted left ventricular myocardium. Next, we developed an inverse finite element (FE) simulation of the experimental configuration embedded in a parameter optimization scheme for estimation of the SEDF parameters. Notable features of this approach include: (i) enhanced determinability and predictive capability of the estimated parameters following an optimal design of experiments, (ii) accurate simulation of the experimental setup and transmural variation of local fiber directions in the FE environment, and (iii) application of all displacement paths to a single specimen to minimize testing time so that tissue viability could be maintained. Our results indicated that, in contrast to the common approach of conducting preselected tests and choosing an SEDF a posteriori, the optimal design of experiments, integrated with a chosen SEDF and full 3D kinematics, leads to a more robust characterization of the mechanical behavior of myocardium and higher predictive capabilities of the SEDF. The methodology proposed and demonstrated herein will ultimately provide a means to reliably predict tissue-level behaviors, thus facilitating organ-level simulations for efficient diagnosis and evaluation of potential treatments. While applied to myocardium, such developments are also applicable to characterization of other types of soft tissues.
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Affiliation(s)
- Reza Avazmohammadi
- Center for Cardiovascular Simulation, Institute for Computational Engineering and Sciences, Department of Biomedical Engineering, The University of Texas at Austin, 201 East 24th St, Stop C0200, Austin, Texas, 78712-1229, USA
| | - David S Li
- Center for Cardiovascular Simulation, Institute for Computational Engineering and Sciences, Department of Biomedical Engineering, The University of Texas at Austin, 201 East 24th St, Stop C0200, Austin, Texas, 78712-1229, USA
| | - Thomas Leahy
- Center for Cardiovascular Simulation, Institute for Computational Engineering and Sciences, Department of Biomedical Engineering, The University of Texas at Austin, 201 East 24th St, Stop C0200, Austin, Texas, 78712-1229, USA
| | - Elizabeth Shih
- Center for Cardiovascular Simulation, Institute for Computational Engineering and Sciences, Department of Biomedical Engineering, The University of Texas at Austin, 201 East 24th St, Stop C0200, Austin, Texas, 78712-1229, USA
| | - João S Soares
- Center for Cardiovascular Simulation, Institute for Computational Engineering and Sciences, Department of Biomedical Engineering, The University of Texas at Austin, 201 East 24th St, Stop C0200, Austin, Texas, 78712-1229, USA
| | - Joseph H Gorman
- Gorman Cardiovascular Research Group, Smilow Center for Translational Research, 3400 Civic Center Blvd - Building 421 11th Floor, Room 112, Philadelphia, PA, 19104-5156, USA
| | - Robert C Gorman
- Gorman Cardiovascular Research Group, Smilow Center for Translational Research, 3400 Civic Center Blvd - Building 421 11th Floor, Room 112, Philadelphia, PA, 19104-5156, USA
| | - Michael S Sacks
- Center for Cardiovascular Simulation, Institute for Computational Engineering and Sciences, Department of Biomedical Engineering, The University of Texas at Austin, 201 East 24th St, Stop C0200, Austin, Texas, 78712-1229, USA.
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Soares JS, Zhang W, Sacks MS. A mathematical model for the determination of forming tissue moduli in needled-nonwoven scaffolds. Acta Biomater 2017; 51:220-236. [PMID: 28063987 DOI: 10.1016/j.actbio.2016.12.038] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2016] [Revised: 12/14/2016] [Accepted: 12/20/2016] [Indexed: 11/17/2022]
Abstract
Formation of engineering tissues (ET) remains an important scientific area of investigation for both clinical translational and mechanobiological studies. Needled-nonwoven (NNW) scaffolds represent one of the most ubiquitous biomaterials based on their well-documented capacity to sustain tissue formation and the unique property of substantial construct stiffness amplification, the latter allowing for very sensitive determination of forming tissue modulus. Yet, their use in more fundamental studies is hampered by the lack of: (1) substantial understanding of the mechanics of the NNW scaffold itself under finite deformations and means to model the complex mechanical interactions between scaffold fibers, cells, and de novo tissue; and (2) rational models with reliable predictive capabilities describing their evolving mechanical properties and their response to mechanical stimulation. Our objective is to quantify the mechanical properties of the forming ET phase in constructs that utilize NNW scaffolds. We present herein a novel mathematical model to quantify their stiffness based on explicit considerations of the modulation of NNW scaffold fiber-fiber interactions and effective fiber stiffness by surrounding de novo ECM. Specifically, fibers in NNW scaffolds are effectively stiffer than if acting alone due to extensive fiber-fiber cross-over points that impart changes in fiber geometry, particularly crimp wavelength and amplitude. Fiber-fiber interactions in NNW scaffolds also play significant role in the bulk anisotropy of the material, mainly due to fiber buckling and large translational out-of-plane displacements occurring to fibers undergoing contraction. To calibrate the model parameters, we mechanically tested impregnated NNW scaffolds with polyacrylamide (PAM) gels with a wide range of moduli with values chosen to mimic the effects of surrounding tissues on the scaffold fiber network. Results indicated a high degree of model fidelity over a wide range of planar strains. Lastly, we illustrated the impact of our modeling approach quantifying the stiffness of engineered ECM after in vitro incubation and early stages of in vivo implantation obtained in a concurrent study of engineered tissue pulmonary valves in an ovine model. STATEMENT OF SIGNIFICANCE Regenerative medicine has the potential to fully restore diseased tissues or entire organs with engineered tissues. Needled-nonwoven scaffolds can be employed to serve as the support for their growth. However, there is a lack of understanding of the mechanics of these materials and their interactions with the forming tissues. We developed a mathematical model for these scaffold-tissue composites to quantify the mechanical properties of the forming tissues. Firstly, these measurements are pivotal to achieve functional requirements for tissue engineering implants; however, the theoretical development yielded critical insight into particular mechanisms and behaviors of these scaffolds that were not possible to conjecture without the insight given by modeling, let alone describe or foresee a priori.
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Affiliation(s)
- João S Soares
- Institute for Computational Engineering and Sciences, Department of Biomedical Engineering, Center for Cardiovascular Simulation, The University of Texas at Austin, 201 East 24th Street, Stop C0200, Austin, TX 78712-1229, United States
| | - Will Zhang
- Institute for Computational Engineering and Sciences, Department of Biomedical Engineering, Center for Cardiovascular Simulation, The University of Texas at Austin, 201 East 24th Street, Stop C0200, Austin, TX 78712-1229, United States
| | - Michael S Sacks
- Institute for Computational Engineering and Sciences, Department of Biomedical Engineering, Center for Cardiovascular Simulation, The University of Texas at Austin, 201 East 24th Street, Stop C0200, Austin, TX 78712-1229, United States.
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Bluestein D, Soares JS, Zhang P, Gao C, Pothapragada S, Zhang N, Slepian MJ, Deng Y. Multiscale Modeling of Flow Induced Thrombogenicity With Dissipative Particle Dynamics and Molecular Dynamics. J Med Device 2014; 8:0209541-209542. [PMID: 25053978 DOI: 10.1115/1.4027347] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2013] [Revised: 10/17/2013] [Indexed: 11/08/2022] Open
Affiliation(s)
- Danny Bluestein
- Department of Biomedical Engineering , Stony Brook University, Stony Brook, NY 11794
| | - João S Soares
- Department of Biomedical Engineering , Stony Brook University, Stony Brook, NY 11794
| | - Peng Zhang
- Department of Biomedical Engineering , Stony Brook University, Stony Brook, NY 11794
| | - Chao Gao
- Department of Biomedical Engineering , Stony Brook University, Stony Brook, NY 11794
| | - Seetha Pothapragada
- Department of Applied Mathematics and Statistics , Stony Brook University, Stony Brook, NY 11794
| | - Na Zhang
- Department of Applied Mathematics and Statistics , Stony Brook University, Stony Brook, NY 11794
| | | | - Yuefan Deng
- Department of Applied Mathematics and Statistics , Stony Brook University, Stony Brook, NY 11794
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Soares JS, B Le T, Sotiropoulos F, S Sacks M. Modeling the Role of Oscillator Flow and Dynamic Mechanical Conditioning on Dense Connective Tissue Formation in Mesenchymal Stem Cell-Derived Heart Valve Tissue Engineering. J Med Device 2013; 7:0409271-409272. [PMID: 24895524 DOI: 10.1115/1.4025984] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2013] [Revised: 11/05/2013] [Indexed: 11/08/2022] Open
Affiliation(s)
- João S Soares
- Institute for Computational Engineering and Sciences, University of Texas at Austin , Austin, TX 78712
| | | | - Fotis Sotiropoulos
- Saint Anthony Falls Laboratory, Department of Civil Engineering, University of Minnesota , Minneapolis, MN 55414
| | - Michael S Sacks
- Institute for Computational Engineering and Sciences, Department of Biomedical Engineering, University of Texas at Austin , Austin, TX 78712
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Machado LD, Legoas SB, Soares JS, Shadmi N, Jorio A, Joselevich E, Galvão DS. Dynamics of the formation of carbon nanotube serpentines. Phys Rev Lett 2013; 110:105502. [PMID: 23521270 DOI: 10.1103/physrevlett.110.105502] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/05/2012] [Indexed: 06/01/2023]
Abstract
Recently, Geblinger et al. [Nat. Nanotechnol. 3, 195 (2008)] reported the experimental realization of carbon nanotube S-like shaped nanostructures, the so-called carbon nanotube serpentines. We report here results from multimillion fully atomistic molecular dynamics simulations of their formation. We consider one-μm-long carbon nanotubes placed on stepped substrates with and without a catalyst nanoparticle on the top free end of the tube. A force is applied to the upper part of the tube during a short period of time and turned off; then the system is set free to evolve in time. Our results show that these conditions are sufficient to form robust serpentines and validates the general features of the "falling spaghetti model" proposed to explain their formation.
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Affiliation(s)
- L D Machado
- Instituto de Física Gleb Wataghin, Universidade Estadual de Campinas, CP 6165, 13083-970 Campinas, Sao Paulo, Brazil
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Araujo PT, Barbosa Neto NM, Chacham H, Carara SS, Soares JS, Souza AD, Cançado LG, de Oliveira AB, Batista RJC, Joselevich E, Dresselhaus MS, Jorio A. In situ atomic force microscopy tip-induced deformations and Raman spectroscopy characterization of single-wall carbon nanotubes. Nano Lett 2012; 12:4110-4116. [PMID: 22731916 DOI: 10.1021/nl3016347] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
In this work, an atomic force microscope (AFM) is combined with a confocal Raman spectroscopy setup to follow in situ the evolution of the G-band feature of isolated single-wall carbon nanotubes (SWNTs) under transverse deformation. The SWNTs are pressed by a gold AFM tip against the substrate where they are sitting. From eight deformed SWNTs, five exhibit an overall decrease in the Raman signal intensity, while three exhibit vibrational changes related to the circumferential symmetry breaking. Our results reveal chirality dependent effects, which are averaged out in SWNT bundle measurements, including a previously elusive mode symmetry breaking that is here explored using molecular dynamics calculations.
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Affiliation(s)
- P T Araujo
- Departamento de Física, Universidade Federal de Minas Gerais, Belo Horizonte, MG, 30123-970 Brazil
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Abstract
The use of biodegradable polymers in biomedical applications has been successful in nonload bearing applications, such as biodegradable implants for local drug delivery, and in simple load bearing situations such as surgical sutures and orthopedic fixation screws. The desire to incorporate these materials in more complex load bearing situations, such as tissue engineering scaffolds and endovascular or urethral stents, is strong, but the lack of constitutive models describing the evolution of biodegradable polymers over the course of degradation has severely hampered the rational design process for these more complex biodegradable medical applications. With the objective of predicting biodegradable stent behavior, we incorporated constitutive models of biodegradable polymeric materials in a computational setting and the mechanical response of three different stent designs were analyzed as degradation progressed. A thermodynamically consistent constitutive model for materials undergoing deformation-induced degradation was applied to a commonly employed biodegradable polymer system, poly(L-lactic acid), and its specific form was determined by corroboration against experimental data. Depreciation of mechanical properties due to degradation confers time-dependent characteristics to the response of the biodegradable material: the deformation imparted by a constant load increases over time, i.e. the body creeps, and the stress necessary to keep a fixed deformation decreases, i.e. the body relaxes. Biodegradable stents, when subjected to constant pressure in its exterior, deflect inwards and ultimately fail as the structure loses its mechanical integrity. The complex geometry of endovascular stents and their physiological loading conditions lead to inhomogeneous deformations, and consequently, inhomogeneous degradation ensues. Degradation is mostly confined to the bends of the stent rings and junction points, which are the locations that carry most of the deformation, whereas mostly undeformed connector bars remain less degraded. If failure occurs, it will occur most likely at those sensitive locations and large, nondegraded pieces can provoke severe embolic problems. Highly nonuniform degradation indicates that some stent designs are at higher risk for complications. Deformation patterns of stents made of a material that loses its integrity are different than those of permanent stents. Blind adaptation of permanent stent design concepts is ill-suited for biodegradable stent design. The time-dependent aspect of the implant not only must be taken into account but should also be used to interact with the body’s reaction and to enhance healing.
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Affiliation(s)
- João S. Soares
- Department of Mathematics, Center for Mathematics and Its Applications (CEMAT), Instituto Superior Tecnico, Avenida Rovisto Pais 1, Lisboa 1049-001, Portugal
| | - James E. Moore
- Department of Biomedical Engineering, Texas A&M University, 337 Zachry Engineering Center, 3120 TAMU, College Station, TX 77843
| | - Kumbakonam R. Rajagopal
- Department of Biomedical Engineering, Department of Mechanical Engineering, Texas A&M University, College Station, TX 77843
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Ladeira MS, Andrade VA, Gomes ERM, Aguiar CJ, Moraes ER, Soares JS, Silva EE, Lacerda RG, Ladeira LO, Jorio A, Lima P, Leite MF, Resende RR, Guatimosim S. Highly efficient siRNA delivery system into human and murine cells using single-wall carbon nanotubes. Nanotechnology 2010; 21:385101. [PMID: 20798464 DOI: 10.1088/0957-4484/21/38/385101] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
Development of RNA interference (RNAi) technology utilizing short interfering RNA sequences (siRNA) has focused on creating methods for delivering siRNAs to cells and for enhancing siRNA stability in vitro and in vivo. Here, we describe a novel approach for siRNA cellular delivery using siRNA coiling into carboxyl-functionalized single-wall carbon nanotubes (SWCNTs). The CNT-siRNA delivery system successfully demonstrates nonspecific toxicity and transfection efficiency greater than 95%. This approach offers the potential for siRNA delivery into different types of cells, including hard-to-transfect cells, such as neuronal cells and cardiomyocytes. We also tested the CNT-siRNA system in a non-metastatic human hepatocellular carcinoma cell line (SKHep1). In all types of cells used in this work the CNT-siRNA delivery system showed high efficiency and apparent no side effects for various in vitro applications.
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Affiliation(s)
- M S Ladeira
- Department of Physiology and Biophysics, Federal University of Minas Gerais, Belo Horizonte, MG, Brazil
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Soares JS, Zunino P. A mixture model for water uptake, degradation, erosion and drug release from polydisperse polymeric networks. Biomaterials 2010; 31:3032-42. [DOI: 10.1016/j.biomaterials.2010.01.008] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2009] [Accepted: 01/03/2010] [Indexed: 10/19/2022]
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Sousa JE, Manrigue R, Freire RJ, Loures JB, Pimentel WA, Gizzi JC, Büchler J, Furtado RJ, Souza JA, Soares JS. [Myocardial function and cardiac metabolism in patients with lesions of 1, 2, and 3 coronary vessels subjected to atrial stimulation]. Arq Bras Cardiol 1978; 31:305-11. [PMID: 747534] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
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