scholarly journals Fabrication and Modeling of Dynamic Multipolymer Nanofibrous Scaffolds

2009 ◽  
Vol 131 (10) ◽  
Author(s):  
Brendon M. Baker ◽  
Nandan L. Nerurkar ◽  
Jason A. Burdick ◽  
Dawn M. Elliott ◽  
Robert L. Mauck
Keyword(s):  
Mechanical Properties ◽  
Rational Design ◽  
Cell Infiltration ◽  
Tissue Properties ◽  
Matrix Deposition ◽  
Native Tissue ◽  
Nanofibrous Scaffolds ◽  
Wide Range ◽  
Anisotropic Mechanical Properties

Aligned nanofibrous scaffolds hold tremendous potential for the engineering of dense connective tissues. These biomimetic micropatterns direct organized cell-mediated matrix deposition and can be tuned to possess nonlinear and anisotropic mechanical properties. For these scaffolds to function in vivo, however, they must either recapitulate the full dynamic mechanical range of the native tissue upon implantation or must foster cell infiltration and matrix deposition so as to enable construct maturation to meet these criteria. In our recent studies, we noted that cell infiltration into dense aligned structures is limited but could be expedited via the inclusion of a distinct rapidly eroding sacrificial component. In the present study, we sought to further the fabrication of dynamic nanofibrous constructs by combining multiple-fiber populations, each with distinct mechanical characteristics, into a single composite nanofibrous scaffold. Toward this goal, we developed a novel method for the generation of aligned electrospun composites containing rapidly eroding (PEO), moderately degradable (PLGA and PCL/PLGA), and slowly degrading (PCL) fiber populations. We evaluated the mechanical properties of these composites upon formation and with degradation in a physiologic environment. Furthermore, we employed a hyperelastic constrained-mixture model to capture the nonlinear and time-dependent properties of these scaffolds when formed as single-fiber populations or in multipolymer composites. After validating this model, we demonstrated that by carefully selecting fiber populations with differing mechanical properties and altering the relative fraction of each, a wide range of mechanical properties (and degradation characteristics) can be achieved. This advance allows for the rational design of nanofibrous scaffolds to match native tissue properties and will significantly enhance our ability to fabricate replacements for load-bearing tissues of the musculoskeletal system.

Bioprinted Nanoparticles for Tissue Engineering Applications

2009 ◽  
Author(s):  
Kivilcim Buyukhatipoglu ◽  
Robert Chang ◽  
Wei Sun ◽  
Alisa Morss Clyne
Keyword(s):  
Tissue Engineering ◽  
Tissue Growth ◽  
Bioactive Components ◽  
Engineering Applications ◽  
Tissue Properties ◽  
Native Tissue ◽  
3D Architecture

Tissue engineering may require precise patterning of cells and bioactive components to recreate the complex, 3D architecture of native tissue. However, it is difficult to image and track cells and bioactive factors once they are incorporated into the tissue engineered construct. These bioactive factors and cells may also need to be moved during tissue growth in vitro or after implantation in vivo to achieve the desired tissue properties, or they may need to be removed entirely prior to implantation for biosafety concerns.

Reliability Investigation of Tissue Resonator Indenter Device

2010 ◽  
Author(s):  
Ming Jia ◽  
Jean W. Zu ◽  
Alireza Hariri
Keyword(s):  
Mechanical Properties ◽  
Soft Tissue ◽  
Soft Tissues ◽  
Tissue Properties ◽  
University Of Toronto ◽  
In Vivo Measurements ◽  
Disease Diagnostics ◽  
Working Principle ◽  
The University

Knowledge of tissue mechanical properties is widely required by medical applications, such as disease diagnostics, surgery operation, simulation, planning, and training. A new portable device, called Tissue Resonator Indenter Device (TRID), has been developed for measurement of regional viscoelastic properties of soft tissues at the Bio-instrument and Biomechanics Lab of the University of Toronto. As a device for soft tissue properties in-vivo measurements, the reliability of TRID is crucial. This paper presents TRID’s working principle and the experimental study of TRID’s reliability with respect to inter-reliability, intra-reliability, and the indenter misalignment effect as well. The experimental results show that TRID is a reliable device for in-vivo measurements of soft tissue mechanical properties.

Design of Tissue-Engineered Leaflet Shape for the Ovine Pulmonary Valve Single Leaflet Replacement Surgery

2011 ◽  
Author(s):  
Rong Fan ◽  
Christopher M. Hobson ◽  
Ahmed Bayoumi ◽  
John E. Mayer ◽  
William R. Wagner ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Pulmonary Valve ◽  
Fe Simulation ◽  
Somatic Growth ◽  
Initial Shape ◽  
Replacement Surgery ◽  
Anisotropic Mechanical Properties ◽  
The One ◽  
Leaflet Shape

Pulmonary valve (PV) replacement surgery is a treatment option for patients with a congenitally defective pulmonary outflow track. A tissue engineered pulmonary valve (TEPV) is a potential approach to serve as a replacement pediatric heart valve that has the potential for somatic growth. The single leaflet replacement surgical model can assist in assessing candidate biomaterials responses to in-vivo function. However, an empirically determined unloaded leaflet shape may result in abnormal valve function due to incomplete coaptation of leaflets and asymmetric stress distributions. Thus, to determine the final deformed shape of an engineered scaffold replacement PV leaflet under transvalvular pressure the following key factors must be determined: the scaffold anisotropic mechanical properties, optimal thickness, and the exact initial leaflet shape. We have used electrospun poly (ester urethane) ureas (ES-PEUU) scaffolds since they exhibit mechanical properties very similar to the native PV [1]. In this work we present a design framework of the optimal leaflet shape determination utilizing a single sheet of ES-PEUU for single leaflet replacement surgery via finite element (FE) simulation. The mechanical properties of ES-PEUU scaffold for leaflet replacement were obtained from biaxial in-plane tension and three-point bending flexural deformation experiments. Generalized Fung-type hyperelastic constitutive model [2] was implemented into a commercial FE software package to simulate the mechanical behavior of ES-PEUU scaffolds. By perturbing the initial shape of leaflet and simulating its quasi-static deformation under PV diastolic loading, the optimal shape of unloaded leaflet can be determined by comparing the deformed shape of leaflet obtained from FE simulation of TEPV with the one from microCT scan of a native ovine PV.

A Brief Review of the Modelling of the Time Dependent Mechanical Properties of Tissue Engineering Scaffolds

2010 ◽  
Vol 6 ◽  
pp. 19-33 ◽  
Author(s):  
N.K. Bawolin ◽  
W.J. Zhang ◽  
Xiong Biao Chen
Keyword(s):  
Mechanical Properties ◽  
Tissue Engineering ◽  
Treatment Process ◽  
Effective Properties ◽  
Critical Role ◽  
Time Dependent ◽  
Tissue Engineering Scaffolds ◽  
Wide Range ◽  
Scaffold Degradation

The functionality of tissue scaffolds in vivo plays a critical role in the treatment process. Due to the time dependent nature of the mechanical properties of the constituent phases of the scaffold, a wide range of mechanical property histories may be observed during the treatment process, possibly influencing outcomes. The critical nature of the mechanical properties in load bearing applications indicates a need for the simultaneous modelling of both scaffold degradation and tissue regeneration with time, and the resulting effective properties of the tissue engineering construct. To this end, a review of the literature is conducted to identify the various existing approaches to modelling scaffold degradation, tissue behavior, and the dependency of the two processes on one another.

scholarly journals Tyrosine-Derived Polycarbonate Nerve Guidance Tubes Elicit Pro-Regenerative Extracellular Matrix Deposition When Used to Bridge Segmental Nerve Defects in Swine

2020 ◽  
Author(s):  
JC Burrell ◽  
D Bhatnagar ◽  
DP Brown ◽  
NS Murthy ◽  
J Dutton ◽  
...  
Keyword(s):  
Extracellular Matrix ◽  
Schwann Cell ◽  
Cell Infiltration ◽  
Large Animal ◽  
Matrix Deposition ◽  
Regenerative Response ◽  
Large Animal Models ◽  
Segmental Nerve ◽  
Collagen Iii ◽  
Wide Range

AbstractPromising biomaterials should be tested in appropriate large animal models that recapitulate human inflammatory and regenerative responses. Previous studies have shown tyrosine-derived polycarbonates (TyrPC) are versatile biomaterials with a wide range of applications across multiple disciplines. The library of TyrPC has been well studied and consists of thousands of polymer compositions with tunable mechanical characteristics and degradation and resorption rates that are useful for nerve guidance tubes (NGTs). NGTs made of different TyrPCs have been used in segmental nerve defect models in small animals. The current study is an extension of this work and evaluates NGTs made using two different TyrPC compositions in a 1 cm porcine peripheral nerve repair model. We first evaluated a nondegradable TyrPC formulation, demonstrating proof-of-concept chronic regenerative efficacy up to 6 months with similar nerve/muscle electrophysiology and morphometry to the autograft repair control. Next, we characterized the acute regenerative response using a degradable TyrPC formulation. After 2 weeks in vivo, TyrPC NGT promoted greater deposition of pro-regenerative extracellular matrix (ECM) constituents (in particular collagen I, collagen III, collagen IV, laminin and fibronectin) compared to commercially available collagen-based NGTs. This corresponded with dense Schwann cell infiltration and axon extension across the lumen. These findings confirmed results reported previously in a mouse model and reveal that TyrPC NGTs were well tolerated in swine and facilitated host axon regeneration and Schwann cell infiltration in the acute phase across segmental defects - likely by eliciting a favorable neurotrophic ECM milieu. This regenerative response ultimately can contribute to functional recovery.

scholarly journals Toughening mechanisms for the attachment of architectured materials: The mechanics of the tendon enthesis

2021 ◽  
Author(s):  
Mikhail Golman ◽  
Adam C Abraham ◽  
Iden Kurtaliaj ◽  
Brittany P Marshall ◽  
Yizhong Jenny Hu ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Mouse Model ◽  
Energy Absorption ◽  
Protein Denaturation ◽  
Simultaneous Observation ◽  
In Vivo Models ◽  
Trade Offs ◽  
Wide Range ◽  
Architectured Materials

Architectured materials offer tailored mechanical properties but are limited in engineering applications due to challenges in maintaining toughness across their attachments. The enthesis connects tendon and bone, two vastly different architectured materials, and exhibits toughness across a wide range of loadings. Understanding the mechanisms by which this is achieved could inform the development of engineered attachments. Integrating experiments, simulations, and novel imaging that enabled simultaneous observation of mineralized and unmineralized tissues, we identified putative mechanisms of enthesis toughening in a mouse model and then manipulated these mechanisms via in vivo control of mineralization and architecture. Imaging uncovered a fibrous architecture within the enthesis that controls trade-offs between strength and toughness. In vivo models of pathology revealed architectural adaptations that optimize these trade-offs through cross-scale mechanisms including nanoscale protein denaturation, milliscale load-sharing, and macroscale energy absorption. Results suggest strategies for optimizing architecture for tough bimaterial attachments in medicine and engineering.

Radiation Effect on Poly(ε-Caprolactone) Nanofibrous Scaffold

2007 ◽  
Vol 119 ◽  
pp. 95-98
Author(s):  
Youn Mook Lim ◽  
Joon Pyo Jeun ◽  
Chan Hee Jung ◽  
Jae Hak Choi ◽  
Phil Hyun Kang ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Tissue Engineering ◽  
Radiation Effect ◽  
Average Diameter ◽  
Nanofibrous Scaffolds ◽  
Biomimetic Scaffolds ◽  
Biodegradable Poly ◽  
Γ Ray

Nano- to micro-structured biodegradable poly(ε-caprolactone) nanofibrous scaffolds (PCL NFSs) were prepared by an electrospinning. Electrospinning has recently emerged as a leading technique for generating the biomimetic scaffolds for tissue engineering applications. The average diameter of the electrospun PCL NFSs ranged from 0.5 to 2 ㎛ depending on the solvent/nonsolvent mixture. PCL NFSs were irradiated using γ-ray and their mechanical properties and biodegradability were measured. In vitro/vivo degradation studies of the scaffolds as a function of the radiation dose were performed. The scaffolds were degraded more slowly in vitro than in vivo.

Shear Wave Propagation of the Ferret Brain at Multiple Frequencies In Vivo

2012 ◽  
Author(s):  
Yuan Feng ◽  
Yulin Chang ◽  
Erik H. Clayton ◽  
Ruth J. Okamoto ◽  
Philip V. Bayly
Keyword(s):  
Mathematical Modeling ◽  
Mechanical Properties ◽  
White Matter ◽  
Loss Modulus ◽  
Tissue Properties ◽  
In Vivo Measurement ◽  
Dissipative Effects ◽  
Multiple Frequencies ◽  
The Brain

Mathematical modeling and computer simulations are widely used for understanding traumatic brain injury (TBI). However, accurate tissue parameters are needed, especially for the brain in vivo. In this study, we used the ferret as the animal model because it is the smallest mammal with a folded brain and significant white matter tracts. Magnetic resonance elastography (MRE) has proven useful for in vivo measurement of biological tissue properties. Mechanical properties of the ferret brain over a range of frequencies from 400–800 Hz were studied using MRE. Experiment results show both that storage and loss modulus increases with frequency and that dissipative effects in the white matter (characterized by the loss modulus G″) were significant larger than in gray matter.

scholarly journals Identification of in vivo nonlinear anisotropic mechanical properties of ascending thoracic aortic aneurysm from patient-specific CT scans

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Minliang Liu ◽  
Liang Liang ◽  
Fatiesa Sulejmani ◽  
Xiaoying Lou ◽  
Glen Iannucci ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Aortic Aneurysm ◽  
Thoracic Aortic Aneurysm ◽  
Aortic Wall ◽  
Inverse Methods ◽  
Ct Scans ◽  
Patient Specific ◽  
Accurate Identification ◽  
Anisotropic Mechanical Properties

Abstract Accurate identification of in vivo nonlinear, anisotropic mechanical properties of the aortic wall of individual patients remains to be one of the critical challenges in the field of cardiovascular biomechanics. Since only the physiologically loaded states of the aorta are given from in vivo clinical images, inverse approaches, which take into account of the unloaded configuration, are needed for in vivo material parameter identification. Existing inverse methods are computationally expensive, which take days to weeks to complete for a single patient, inhibiting fast feedback for clinicians. Moreover, the current inverse methods have only been evaluated using synthetic data. In this study, we improved our recently developed multi-resolution direct search (MRDS) approach and the computation time cost was reduced to 1~2 hours. Using the improved MRDS approach, we estimated in vivo aortic tissue elastic properties of two ascending thoracic aortic aneurysm (ATAA) patients from pre-operative gated CT scans. For comparison, corresponding surgically-resected aortic wall tissue samples were obtained and subjected to planar biaxial tests. Relatively close matches were achieved for the in vivo-identified and ex vivo-fitted stress-stretch responses. It is hoped that further development of this inverse approach can enable an accurate identification of the in vivo material parameters from in vivo image data.

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