Michael J. McClure, Ph.D.

VCU Biomedical Engineering professor awarded grant for research on muscle reinnervation

VCU  online

2018-09-04

Michael McClure, Ph.D., has received a $500,000 Defense Medical Research and Development Neuromusculoskeletal Injuries Rehabilitation Research Award through the U.S. Department of Defense to develop a strategy that could allow a patient to regain use of a severely damaged muscle. McClure, an assistant professor in the Department of Biomedical Engineering in Virginia Commonwealth University’s College of Engineering, is working with Jonathan E. Isaacs, M.D., professor and chair of the Division of Hand Surgery in the VCU Department of Orthopaedic Surgery, to develop a way to reinnervate the muscle through neurotization. In some cases, multiple nerves serve the same purpose for a single muscle group. McClure said surgeons can move a redundant nerve and implant it into the muscle graft, while connecting its other end to the main nerve bundle. “It’s a live nerve and as soon as you implant it into the muscle graft, it’s going to sprout new axons and start a signaling process that’s going to be advantageous,” he said. “It could be a perfect storm for regeneration.” Researchers hope that this strategy of using decellularized muscle grafts — tissue that has been stripped of its cells, leaving behind the matrix and structure — will improve muscle and nerve regeneration and reinnervation. Improving function may also lead to the body building more muscle fibers. An article about the research appears in the August 2018 issue of the Journal of Tissue Engineering.

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Proposed Standard Supports Muscle Regeneration

ASTM  online

2018-12-31

ASTM International’s committee on medical and surgical materials and devices (F04) is developing a standardized guide for pre-clinical testing considerations for materials used to regenerate muscle. This guide (WK64460) will provide scientifically-based information concerning repairing and regenerating muscle when defects are caused by trauma, such as blast injuries. “These types of injuries can range widely, from relatively small to those that require entire muscles to be removed,” says ASTM International member Barbara Boyan, dean of the engineering college at Virginia Commonwealth University. The guide will present the strengths and weaknesses of animal models used to demonstrate effectiveness. Boyan noted that by creating this guide, the committee hopes that scientists in industry and academia will have a better structure to inform their approach to develop products for muscle regeneration. Labs and manufacturers, she says, could use the standard as a roadmap to determine approaches with higher success. Regulatory bodies and consumers could also find this guide useful in determining effectiveness of materials. ASTM welcomes participation in the development of its standards. Become a member at www.astm.org/JOIN. The next meeting of ASTM International committee on medical and surgical materials and devices is November 6-9 at the Washington Hilton; Washington, DC, USA. INDUSTRY SECTORS:Medical ISSUE MONTH: September/October ISSUE YEAR: 2018 COMMITTEE: F04

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Innovation Gateway supports six new projects with the Commercialization Fund

Virginia Commonwealth University  online

2022-06-28

By Emily Komornik Office of the Vice President for Research and Innovation A Virginia Commonwealth University researcher who switched from cardiovascular bioengineering to skeletal muscle research after seeing how difficult it was for some U.S. veterans injured in Iraq and Afghanistan to lift a cup of coffee is among six researchers who received a VCU Commercialization Fund award from Innovation Gateway. While working at the Hunter Holmes McGuire Veterans Affairs Medical Center, Michael McClure, Ph.D., now an assistant professor at the Department of Biomedical Engineering in the College of Engineering, shifted his postdoctoral studies to study muscle tissue, wanting to improve the veterans’ quality of life by restoring their full range of motion. McClure began his effort by studying volumetric muscle loss injuries and then transitioning that research to one of the most common muscle injuries: the rotator cuff. Patients with rotator cuff injuries lose the “bridge” between the muscle and tendon, hindering their ability to complete simple tasks and limiting their range of motion. He is developing a technology that uses scaffold materials that target that bridge, reconnecting the muscle and tendon and allowing the patient to build muscle instead of losing it. This will lead to a better recovery in rotator cuff injury patients. Although there are other technologies that use similar singular cell scaffolds, none is muscle specific. They focus more on the tendons and bones. “There's not really anything else like this that’s out there in the market,” McClure said. “I firmly believe that something that's muscle specific will give you muscle specific outcomes that are going to be well received by the surrounding tissue,” which will result in better recovery in these types of injuries. With support from the Commercialization Fund, McClure will be able to enhance the technology further, researching how different cells react with the scaffold. That will guide his research team to determine how cells in the body will actually react when the technology is implanted. The other five researchers who received funding this spring from Innovation Gateway span across disciplines and departments throughout the university. Two recipients’ proposals focus on virtual reality technologies. Nicholas Thomson, Ph.D., a developmental psychologist and assistant professor in the Department of Psychology in the College of Humanities and Sciences and in the Department of Surgery in th

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Skeletal Muscle Trauma

Develop decellularized muscle grafts for the replacement of volumetric muscle loss.

Skeletal Muscle Aging

Determine how aging affects skeletal muscle extracellular matrix and develop therapeutics to target proteins in the matrix.

Muscle and Nerve Integration

Investigate the interaction between muscle and nerve in the context of muscle regeneration.

Myoblast fusion

Determine how muscle extracellular matrix alignment regulates fusogens and integrin signaling.

Estrogen Receptor and Muscle Regeneration

Determine how estrogen signaling regulates muscle fiber regeneration following injury.

Air Impedance Electrospinning for Controlled Porosity

WO2012006072 A3

2012-04-12

Electrospun materials are fabricated using air-flow impedance technology, which results in the production of scaffolds in which some regions are dense with low porosity and others regions are less dense and more porous. The dense regions provide structural support for the scaffold while the porous regions permit entry of cells and other materials into the scaffold, e.g. when used for tissue engineering.

Stem cell interactions with decellularized muscle allografts for replacement of large defects

Musculoskeletal Transplant Foundation $284,000

Regenerative medicine strategies using adult stem cells present a way to build new muscle tissue and improve quality of life for those affected by these types of muscle injuries. Adipose derived stem cells and satellite stem cells are multipotent cells with potential to repair skeletal muscle. However, their ability to do so has been limited by availability of suitable delivery systems. A common approach is to inject the stem cells into an injured muscle. Unfortunately, the injected cells fail to engraft well. Scaffolds such as collagen, polyglycolic acid, and poly-L-lactic acid have also been used for stem cell delivery, but with limited success. A possible factor in the limited success of scaffolds is that the unique extracellular matrix structure present in muscle is not present in these scaffolds to provide appropriate signals for myocyte development. 2016-2019

Neurotization to Improve Graft Reinnervation and Recovery Following Severe Muscle Injuries

Department of Defense $498,000

Intramusclular neural architecture disruption is an underappreciated cause for poor muscle recovery following traumatic muscle injury. Tissue grafting of segmental muscle loss has shown promise but only partially innervates the regenerated tissue. Neurotizaton was shown to improve motor function after nerve injuries. We propose to improve innervation and function of decellularized muscle graft-mediated muscle regeneration using neurotization. 2018-2021

Applied Physiology for Biomedical Engineers

Applied Physiology for Bioengineering is a course that models and describes physiological systems using applied mathematics and engineering principles. Physiological systems will include a comprehensive study of muscle, nervous, cardiovascular, respiratory, renal, gastrointestinal, and endocrine physiology, beginning with applied biophysical concepts in cell anatomy and physiology leading into the various physiological systems. This course also incorporates a laboratory that uses the knowledge-base tools gained through lecture and implements them in practice using exercises in biochemical and physiological calculations, osmosis, electrical network simulation of diffusion, EEG, blood pressure, ECG, spirometry, and joint anatomy.

Introduction to Cellular and Molecular Engineering

Cell and tissue culture techniques are becoming increasingly important in academic laboratories and companies involved in regenerative medicine. This laboratory-based course is designed to introduce basic, hands-on cell culture concepts and techniques needed for academia and industry. Students will first model cell culture conditions using diffusion and transport equations. Students will be expected to learn molecular engineering techniques by designing and purifying plasmids for mammalian cell transfection. Using mathematical models, students will calculate how much transfection reagent is required for mammalian cells and measure gene and protein levels in the resulting transfections. Lectures will reinforce basic concepts in cell culture and bioengineering, while the laboratory will be used to practice concepts learned in lecture. Knowledge will be tested midterm and with a comprehensive final exam. As a final project, students will co-culture mammalian cells transfected with different genes.

Integrin-α7 signaling regulates connexin 43, M-cadherin, and myoblast fusion

Michael J McClure, Allison N Ramey, Mashaba Rashid, Barbara D Boyan, Zvi Schwartz

2019-06-01

Regenerative medicine treatments for severe skeletal muscle injuries are limited, resulting in persistent functional deficits. Clinical options include neglecting the wound with the expectation that fibrosis will develop or using an autologous muscle graft with minimal functional improvement. A regenerative matrix can be used, but muscle fiber development on these matrices remains a challenge in vivo. Here, we explored the fundamental mechanisms that mediate cell-substrate signaling and its effect on cell-cell communication during myoblast fusion and tube formation to improve outcomes following implantation of matrices used to stimulate muscle regeneration. We previously reported that integrin-α7 was increased on anisotropic biomaterials, suggesting a role for α7β1 signaling in myoblast communication via connexin 43 and M-cadherin. Our results demonstrated that α7 silencing blocked expression of myogenic differentiation factor 1 (Myod), myogenin (Myog), myogenic factor 6 (Myf6), myosin heavy chain type 1 (Myh1), and transmembrane protein 8c (Tmem8c), indicating that myoblast fusion was inhibited. Expression of α5 and M-cadherin decreased but β1 and connexin 43 increased. We examined protein production and observed reduced extracellular-signal regulated kinase 1/2 (ERK) in α7-silenced cells that correlated with upregulation of connexin 43 and M-cadherin, suggesting a compensatory pathway. These results indicate that α7 signaling plays a critical role in ex vivo fusion and implicates a relationship with connexin 43 and M-cadherin.

Regulation of extracellular matrix vesicles via rapid responses to steroid hormones during endochondral bone formation

Niels Asmussen, Zhao Lin, Michael J McClure, Zvi Schwartz, Barbara D Boyan

2019-02-01

Endochondral bone formation is a precise and highly ordered process whose exact regulatory framework is still being elucidated. Multiple regulatory pathways are known to be involved. In some cases, regulation impacts gene expression, resulting in changes in chondrocyte phenotypic expression and extracellular matrix synthesis. Rapid regulatory mechanisms are also involved, resulting in release of enzymes, factors and micro RNAs stored in extracellular matrisomes called matrix vesicles. Vitamin D metabolites modulate endochondral development via both genomic and rapid membrane-associated signaling pathways. 1α,25-dihydroxyvitamin D3 [1α,25(OH)2D3] acts through the vitamin D receptor (VDR) and a membrane associated receptor, protein disulfide isomerase A3 (PDIA3). 24R,25-dihydroxyvitamin D3 [24R,25(OH)2D3] affects primarily chondrocytes in the resting zone (RC) of the growth plate, whereas 1α,25(OH)2D3 affects cells in the prehypertrophic and upper hypertrophic cell zones (GC). This includes genomically directing the cells to produce matrix vesicles with zone specific characteristics. In addition, vitamin D metabolites produced by the cells interact directly with the matrix vesicle membrane via rapid signal transduction pathways, modulating their activity in the matrix. The matrix vesicle payload is able to rapidly impact the extracellular matrix via matrix processing enzymes as well as providing a feedback mechanism to the cells themselves via the contained micro RNAs.

Platelet-Rich Plasma and Alignment Enhance Myogenin via ERK Mitogen Activated Protein Kinase Signaling

Michael J. McClure, Nicholas M. Clark, Zvi Schwartz, and Barbara D. Boyan

2018-07-02

Volumetric muscle loss is debilitating and involves extensive rehabilitation. One approach to accelerate healing, rehabilitation, and muscle function is to repair damaged skeletal muscle using regenerative medicine strategies. In sports medicine and orthopedics, a common clinical approach is to treat minor to severe musculoskeletal injuries with platelet-rich plasma (PRP) injections. While these types of treatments have become commonplace, there are limited data demonstrating their effectiveness. The goal of this study was to determine the effect of PRP on myoblast gene expression and protein production when incorporated into a polymer fiber. To test this, we generated extracellular matrix mimicking scaffolds using aligned polydioxanone (PDO) fibers containing lyophilized PRP (SmartPReP® 2, Harvest Technologies Corporation, Plymouth, MA). Scaffolds with PRP caused a dose-dependent increase in myogenin and myosin heavy chain but did not affect myogenic differentiation factor-1 (MyoD). Integrin α7β1D decreased and α5β1A did not change in response to PRP scaffolds. ERK inhibition decreased myogenin and increased Myod on the PDO-PRP scaffolds. Taken together, these data suggest that alignment and PRP produce a substrate-dependent, ERK-dependent, and dose-dependent effect on myogenic differentiation.

Decellularized muscle supports new muscle fibers and improves function following volumetric injury

2018-02-12

Current strategies to treat volumetric muscle loss use primarily pedicle or free muscle transfers, but these grafts fail to adequately regenerate functional tissue. Decellularized soft tissue grafts possess physical and chemical cues to promote muscle regeneration, suggesting their potential for use in large muscle defects. In this study, we developed a decellularized muscle matrix (DMM) graft using rat gastrocnemius. Anisotropy and chemical components of the extracellular matrix were retained, including laminin, fibronectin, and collagen. We compared the ability of DMM, autologous muscle grafts (clinical standard), and type I collagen plugs (negative control) to support muscle regeneration. DMM supported regeneration over a 56-day period in 1x1cm and 1.5x1cm gastrocnemius defects in rats. Muscle function tests demonstrated improved muscle recovery in rats with DMM grafts when compared to collagen. Histological sections were assessed using morphometrics and immunostaining. DMM supported muscle regeneration with less fibrosis and more de novo neuromuscular receptors than either autograft or collagen. Overall, our results indicate that DMM may be used as a muscle replacement graft based on its ability to improve muscle function recovery, promote muscle regeneration, and support new neuromuscular junctions.

Regulation of extracellular matrix vesicles via rapid responses to steroid hormones during endochondral bone formation

2017-12-30

Endochondral bone formation is a precise and highly ordered process whose exact regulatory framework is still being elucidated. Multiple regulatory pathways are known to be involved. In some cases, regulation impacts gene expression, resulting in changes in chondrocyte phenotypic expression and extracellular matrix synthesis. Rapid regulatory mechanisms are also involved, resulting in release of enzymes, factors and micro RNAs stored in extracellular matrisomes called matrix vesicles. Vitamin D metabolites modulate endochondral development via both genomic and rapid membrane-associated signaling pathways. 1α,25-dihydroxyvitamin D3 [1α,25(OH)2D3] acts through the vitamin D receptor (VDR) and a membrane associated receptor, protein disulfide isomerase A3 (PDIA3). 24R,25-dihydroxyvitamin D3 [24R,25(OH)2D3] affects primarily chondrocytes in the resting zone (RC) of the growth plate, whereas 1α,25(OH)2D3 affects cells in the prehypertrophic and upper hypertrophic cell zones (GC). This includes genomically directing the cells to produce matrix vesicles with zone specific characteristics. In addition, vitamin D metabolites produced by the cells interact directly with the matrix vesicle membrane via rapid signal transduction pathways, modulating their activity in the matrix. The matrix vesicle payload is able to rapidly impact the extracellular matrix via matrix processing enzymes as well as providing a feedback mechanism to the cells themselves via the contained micro RNAs.

Galectin-1 promotes an M2 macrophage response to polydioxanone scaffolds

2017-06-15

Regulating soft tissue repair to prevent fibrosis and promote regeneration is central to creating a microenvironment conducive to soft tissue development. Macrophages play an important role in this process. The macrophage response can be modulated using biomaterials, altering cytokine and growth factor secretion to promote regeneration. Electrospun polydioxanone (PDO) fiber scaffolds promoted an M2 phenotype when macrophages were cultured on large diameter, highly porous scaffolds, but an M1 phenotype on smaller diameter fibers. In this study, we investigated whether incorporation of galectin-1, an immunosuppressive protein that enhances muscle regeneration, could promote the M2 response. Galectin-1 was incorporated into large and small fiber PDO scaffolds during electrospinning. Galectin-1 incorporation increased arginase-1 and reduced iNOS and IL-6 production in mouse bone-marrow derived macrophages compared with PDO alone for both scaffold types. Inhibition of ERK mitogen-activated protein kinase did not alter galectin-1 effects on arginase-1 and iNOS expression, but reversed IL-6 suppression, indicating that IL-6 is mediated by a different mechanism. Our results suggest that galectin-1 can be used to modulate macrophage commitment to a pro-regenerative M2 phenotype, which may positively impact tissue regeneration when using small diameter PDO scaffolds.

Role of Integrin α7β1 Signaling in Myoblast Differentiation on Aligned Polydioxanone Scaffolds

2016-07-15

The aligned structural environment in skeletal muscle is believed to be a crucial component in functional muscle regeneration. Myotube formation is increased on aligned biomaterials, but we do not fully understand the mechanisms that direct this enhanced fusion. Previous studies indicate that the α7 integrin subunit is upregulated during myoblast differentiation, suggesting that signaling via α7β1 mediates the effect of alignment. To test this hypothesis, we took advantage of an in vitro model using random and aligned polydioxanone (PDO) matrices and C2C12 myoblasts.

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The Influence of Platelet Rich Plasma on Myogenic Differentiation.

2016-04-01

The ability to expand and direct both precursor and stem cells towards a differential fate is considered extremely advantageous in tissue engineering. Platelet-rich plasma (PRP) possesses a milieu of growth factors and cytokines, which have the potential to have either a differentiative or proliferative influence on the cell type tested. Here, we investigated the effect of PRP on C2C12 myoblasts. A range of PRP concentrations in differentiation media was used to determine whether a concentration dependence existed, while PRP embedded in fibres of aligned electrospun polydioxanone and polycaprolactone was used to determine whether this presence of fibres would cause any differences in response.

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Electrospinning collagen/chitosan/poly( L -lactic acid- co -ϵ-caprolactone) to form a vascular graft: Mechanical and biological characterization

2013-05-01

For blood vessel tissue engineering, an ideal vascular graft should possess excellent biocompatibility and mechanical properties. For this study, a elastic material of poly (L-lactic acid-co-ϵ-caprolactone) (P(LLA-CL)), collagen and chitosan blended scaffold at different ratios were fabricated by electrospinning. Upon fabrication, the scaffolds were evaluated to determine the tensile strength, burst pressure, and dynamic compliance.

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Tri-layered vascular grafts composed of polycaprolactone, elastin, and silk: Optimization of graft properties.

2012-06-01

The purpose of this study was to create seamless, acellular, small diameter bioresorbable arterial grafts that attempt to mimic the extracellular matrix and mechanical properties of native artery using synthetic and natural polymers. Silk fibroin, collagen, elastin, and polycaprolactone (PCL) were electrospun to create a tri-layered structure for evaluation.

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The use of air-flow impedance to control fiber deposition during electrospinning.

2011-11-01

Electrospun non-woven structures have the potential to form bioresorbable vascular grafts that promote tissue regeneration in situ as they degrade and are replaced by autologous tissue. Current bioresorbable grafts lack appropriate regeneration potential since they do not have optimal architecture, and their fabrication must be altered by the manipulation of process parameters, especially enhancing porosity. We describe here an air-impedance process where the solid mandrel is replaced with a porous mandrel that has pressurized air exiting the pores to impede fiber deposition.

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Bioengineered Vascular Grafts: Improving Vascular Tissue Engineering Through Scaffold Design.

2011-12-01

Arteriosclerosis has accounted for three quarters of the deaths related to cardiovascular disease (CVD). Arteriosclerosis is a vascular disease that is characterized by a thickening of the arterial wall and subsequent decrease in the arterial lumen, eventually causing loss of circulation distal to the site of disease.

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Preliminary Investigation of Airgap Electrospun Silk-Fibroin-Based Structures for Ligament Analogue Engineering.

2010-07-01

The process of electrospinning has proven to be highly beneficial for use in a number of tissue-engineering applications due to its ease of use, flexibility and tailorable properties. There have been many publications on the creation of aligned fibrous structures created through various forms of electrospinning, most involving the use of a metal target rotating at high speeds. This work focuses on the use of a variation known as airgap electrospinning, which does not use a metal collecting target but rather a pair of grounded electrodes equidistant from the charged polymer solution to create highly aligned 3D structures.

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Tri-layered electrospinning to mimic arterial architecture using polycaprolactone, elastin, and collagen: A preliminary study.

2011-01-04

Throughout native artery, collagen and elastin play an important role, providing a mechanical backbone, preventing vessel rupture, and promoting recovery under pulsatile deformations. The goal of this study was to mimic the structure of native artery by fabricating a multi-layered electrospun conduit composed of poly(caprolactone) (PCL) with the addition of elastin and collagen with blends of 45-45-10, 55-35-10, and 65-25-10 PCL-ELAS-COL to demonstrate mechanical properties indicative of native arterial tissue, while remaining conducive to tissue regeneration.

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A three-layered electrospun matrix to mimic native arterial architecture using polycaprolactone, elastin, and collagen: A preliminary study.

2010-07-01

Throughout native artery, collagen, and elastin play an important role, providing a mechanical backbone, preventing vessel rupture, and promoting recovery under pulsatile deformations. The goal of this study was to mimic the structure of native artery by fabricating a multi-layered electrospun conduit composed of poly(caprolactone) (PCL) with the addition of elastin and collagen with blends of 45–45–10, 55–35–10, and 65–25–10 PCL–ELAS–COL to demonstrate mechanical properties indicative of native arterial tissue, while remaining conducive to tissue regeneration.

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Electrospinning-Aligned and Random Polydioxanone-Polycaprolactone-Silk Fibroin Scaffolds: Geometry for a Vascular Matrix.

2009-10-01

Extracellular matrices are arranged with a specific geometry based on tissue type and mechanical stimulus. For blood vessels in the body, preferential alignment of fibers is in the direction of repetitive force. Electrospinning is a controllable process which can result in fiber alignment and randomization depending on the parameters utilized. In this study, arterial grafts composed of polycaprolactone (PCL), polydioxanone (PDO) and silk fibroin in blends of 100:0 and 50:50 for both PCL:silk and PDO:silk were investigated to determine if fibers could be controllably aligned using a mandrel rotational speed ranging from 500 to 8000 revolutions per minute (RPM).

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Electrospun polydioxanone-elastin blends: potential for bioresorbable vascular grafts.

2006-06-01

An electrospun cardiovascular graft composed of polydioxanone (PDO) and elastin has been designed and fabricated with mechanical properties to more closely match those of native arterial tissue, while remaining conducive to tissue regeneration. PDO was chosen to provide mechanical integrity to the prosthetic, while elastin provides elasticity and bioactivity (to promote regeneration in vitro/in situ). It is the elastic nature of elastin that dominates the low-strain mechanical response of the vessel to blood flow and prevents pulsatile energy from being dissipated as heat. Uniaxial tensile and suture retention tests were performed on the electrospun grafts to demonstrate the similarities of the mechanical properties between the grafts and native vessel. Dynamic compliance measurements produced values that ranged from 1.2 to 5.6%/100 mmHg for a set of three different mean arterial pressures. Results showed the 50:50 ratio to closely mimic the compliance of native femoral artery, while grafts that contained less elastin exceeded the suture retention strength of native vessel. Preliminary cell culture studies showed the elastin-containing grafts to be bioactive as cells migrated through their full thickness within 7 days, but failed to migrate into pure PDO scaffolds. Electrospinning of the PDO and elastin-blended composite into a conduit for use as a small diameter vascular graft has extreme potential and warrants further investigation as it thus far compares favorably to native vessel.

Electrospinning of Collagen / Biopolymers for Regenerative Medicine and Cardiovascular Tissue Engineering

2009-10-05

The process of electrospinning has seen a resurgence of interest in the last few decades which has led to a rapid increase in the amount of research devoted to its use in tissue engineering applications. Of this research, the area of cardiovascular tissue engineering makes up a large percentage, with substantial resources going towards the creation of bioresorbable vascular grafts composed of electrospun nanofibers of collagen and other biopolymers. These bioresorbable grafts have compositions that allow for the in situ remodeling of the structure, with the eventual replacement of the graft with completely autologous tissue. This review will highlight some of the work done in the field of electrospinning for cardiovascular applications, with an emphasis on the use of biopolymers such as collagens, elastin, gelatin, fibrinogen, and silk fibroin, as well as biopolymers used in combination with resorbable synthetic polymers.

Cross-linking methods of electrospun fibrinogen scaffolds for tissue engineering applications.

2008-12-01

The purpose of this study was to enhance the mechanical properties and slow the degradation of an electrospun fibrinogen scaffold, while maintaining the scaffold's high level of bioactivity. Three different cross-linkers were used to achieve this goal: glutaraldehyde vapour, 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride (EDC) in ethanol and genipin in ethanol. Scaffolds with a fibrinogen concentration of 120 mg ml(-1) were electrospun and cross-linked with one of the aforementioned cross-linkers. Mechanical properties were determined through uniaxial tensile testing performed on scaffolds incubated under standard culture conditions for 1 day, 7 days and 14 days. Cross-linked scaffolds were seeded with human foreskin fibroblasts (BJ-GFP-hTERT) and cultured for 7, 14 and 21 days, with histology and scanning electron microscopy performed upon completion of the time course. Mechanical testing revealed significantly increased peak stress and modulus values for the EDC and genipin cross-linked scaffolds, with significantly slowed degradation. However, cross-linking with EDC and genipin was shown to have some negative effect on the bioactivity of the scaffolds as cell migration throughout the thickness of the scaffold was slowed.

Suture-reinforced electrospun polydioxanone-elastin small-diameter tubes for use in vascular tissue engineering: a feasibility study

2008-01-01

This study characterizes the cross-linking of electrospun elastin and the mechanical properties of suture-reinforced 1.5mm internal diameter electrospun tubes composed of blended polydioxanone (PDO) and soluble elastin. Several tube configurations were tested to assess the effects of reinforcement on tube mechanical properties. Between the electrospun layers of each double-layered prosthetic, zero, one or two 6-0 sutures were wound, maintaining 1mm spacing with a pitch of 9 degrees . Single-layered tubes without suture were also examined. Samples were cross-linked and tested for compliance and burst strength. Compliance decreased significantly (p

Polydioxanone, Elastin, and Collagen Vascular Scaffolds: Uniaxial Cyclic Distension

2009-06-01

The development of vascular grafts requires the matching of material and viscoelastic properties to those of native artery. The hypothesis of this study was to subject electrospun tissue engineering scaffolds composed of polydioxanone, elastin, and collagen to cyclic loading in order to quantify the hysteretic properties, uniaxial tensile mechanical properties of conditioned scaffolds, and stress relaxation properties over a period of 400 cycles when compared to ePTFE, one of the most popular vascular prosthetic materials, and decellularized pig artery. In the electrospun graft, polydioxanone would provide a mechanical backbone, providing tensile support and preventing vessel rupture; while the elastin would provide elasticity and collagen would provide bioactivity (promote regeneration in vitro/in situ).

Cross-linking Electrospun Polydioxanone-Soluble Elastin Blends: Material Characterization

2008-03-01

The purpose of this study was to establish whether material properties of elastin co-electrospun with polydioxanone (PDO) would change over time in both the uncross-linked state and the cross-linked state. First, uncross-linked scaffolds were placed in phosphate buffered saline (PBS) for three separate time periods: 15 minutes, 1 hour, and 24 hours, and subsequently tested using uniaxial materials testing. Several cross-linking reagents were then investigated to verify their ability to crosslink elastin: 1-ethyl-3-(dimethylaminopropyl)-carbodiimide (EDC), ethylene glycol diglycidyl ether (EGDE), and genipin. Uniaxial tensile testing was performed on scaffolds cross-linked with EDC and genipin, yielding results that warranted further investigation for PDO-elastin blends. Material properties of the cross-linked scaffolds were then found within range of both pig femoral artery and human femoral artery. These results demonstrate PDO-elastin blends could potentially be favorable as vascular grafts, thus warranting future in vitro and in vivo studies.

Thermal and mechanical properties of electrospun PMMA, PVC, Nylon 6, and Nylon 6,6

2007-08-07

Poly(methyl methacrylate) (PMMA), poly(vinyl chloride) (PVC), Nylon 6, and Nylon 6,6 have been electrospun successfully. The nanofibers have been characterized by scanning electron microscopy (SEM), confirming the presence of bead free and fiber-bead free morphologies. Thermogravimetric analysis (TGA) indicated differences between the thermal stability of PMMA nanofibers and PMMA powder. However, no significant differences were observed between the starting physical form (powder or pellet) of PVC, Nylon 6 and Nylon 6,6, and their corresponding electrospun nanofibers. Differential scanning calorimetry (DSC) demonstrated a lower glass transition temperature (Tg) and water absorption for PMMA electrospun nanofibers. Furthermore, electrospun Nylon 6 and Nylon 6,6 had a slight decrease in crystallinity. Tensile testing was performed on the electrospun nanofibers to obtain the Young modulus, peak stress, strain at break, and energy to break, revealing that the non-woven mats obtained had modest mechanical properties that need to be enhanced.

Extracellular matrix regenerated: tissue engineering via electrospun biomimetic nanofibers.

2007-09-10

While electrospinning had seen intermittent use in the textile industry from the early twentieth century, it took the explosion of the field of tissue engineering, and its pursuit of biomimetic extracellular matrix (ECM) structures, to create an electrospinning renaissance. Over the past decade, a growing number of researchers in the tissue engineering community have embraced electrospinning as a polymer processing technique that effectively and routinely produces non-woven structures of nanoscale fibers (sizes of 80 nm to 1.5 µm). These nanofibers are of physiological significance as they closely resemble the structure and size scale of the native ECM (fiber diameters of 50 to 500 nm). Attempts to replicate the many roles of native ECM have led to the electrospinning of a wide array of polymers, both synthetic (poly(glycolic acid), poly(lactic acid), polydioxanone, polycaprolactone, etc.) and natural (collagen, fibrinogen, elastin, etc.) in origin, for a multitude of different tissue applications. With various compositions, fiber dimensions and fiber orientations, the biological, chemical and mechanical properties of the electrospun materials can be tailored. In this review we highlight the role of electrospinning in the engineering of different tissues and applications (skin/wound healing, cartilage, bone, vascular tissue, urological tissues, nerve, and ligament), and discuss its potential role in future work.

Polymer scaffold architecture is a key determinant in mast cell inflammatory and angiogenic responses

Daniel Abebayehu, Andrew J Spence, Michael J McClure, Tamara T Haque, Kevin O Rivera, John J Ryan

2019-04-01

Implanted polymer scaffolds can induce inflammation leading to the foreign body response (FBR), fibrosis, and implant failure. Thus, it is important to understand how immune cells interact with scaffolds to mitigate inflammation and promote a regenerative response. We previously demonstrated that macrophage phenotype is modulated by fiber and pore diameters of an electrospun scaffold. However, it is unclear if this effect is consistent among other innate immune cells. Mast cells are inflammatory sentinels that play a vital role in the FBR of implanted biomaterials, as well as angiogenesis. We determined if altering electrospun scaffold architecture modulates mast cell responses, with the goal of promoting regenerative cell-scaffold interactions. Polydioxanone (PDO) scaffolds were made from 60 mg/mL or 140 mg/mL PDO solutions, yielding structures with divergent fiber and pore diameters. Mouse mast cells plated on these scaffolds were activated with IL-33 or lipopolysaccharide (LPS). Relative to the 60 mg/mL scaffold, 140 mg/mL scaffolds yielded less IL-6 and TNF, and greater VEGF secretion. Pores >4-6 μm elicited less IL-6 and TNF secretion. IL-33-induced VEGF regulation was more complex, showing effects of both pore size and fiber diameter. These data indicate parameters that can predict mast cell responses to scaffolds, informing biomaterial design to increase wound healing and diminish implant rejection.