bluuebunny/crossref_metadata_2025 huggingface dataset:
Finite Element Modeling of Joint Contact Mechanics With Quadratic Tetrahedral Elements
Authors: Maas Steve A. , Ellis Benjamin J. , Rawlins David S. , Weiss Jeffrey A.
Published: January 2014

Tetrahedral elements are one of the most popular finite element (FE) modeling primitives for complex, biological geometries, partially due to the availability of automatic meshing schemes for creating tetrahedral meshes. However, constant strain tetrahedral elements require a very fine mesh to obtain accurate solutions, and these elements can lock, yielding overly stiff results [1].
Computational Hemodynamic Assessment of a Novel Modular Anastomotic Valve Device for Improving Hemodialysis Vascular Access Patency
Authors: McNally Andrew , Akingba A. George , Sucosky Philippe
Published: January 2014

End-stage renal disease (ESRD) occurs as a result of any renal injury that chronically decreases renal excretory and regulatory function. ESRD patients are most commonly treated with hemodialysis (HD) to manage their renal failure while awaiting kidney transplant. Current practices for maintenance of HD vascular access consist of arteriovenous fistulas (AVFs) or grafts (AVGs), which are both fraught with problems that compromise the patency and use of these surgically created shunts. The major cause of shunt failure is thrombosis caused by occlusion of the outflow venous anastomosis and draining vein. Intimal hyperplasia (IH), which consists of the thickening of the innermost layer of the vessel wall, is the initial pathological event leading to shunt stenosis/thrombosis and has been associated with the presence of flow disturbances and abnormal wall shear stress (WSS) at the graft-vein anastomosis. Therefore, the improvement of HD via the enhancement of vascular access patency requires the development of a novel vascular access technology preserving the normal hemodynamics of the native vein.
Cellular Traction Forces Measured With Microposts Made by Hot Embossing of Polystyrene
Authors: Bielawski Kevin S. , Sniadecki Nathan J.
Published: January 2014

Polydimethylsiloxane (PDMS) has become a highly utilized tool to study the forces that cells generate, although, outside of lab on chip devices, it is not widely used and requires protein coatings to encourage cell adhesion1. Furthermore, PDMS suffers from changes in composition and stiffness with different curing conditions2. Alternatively, polystyrene is a common substrate that promotes cell adhesion and has mostly consistent properties; however, polystyrene is typically challenging to form without special equipment and expensive molds. Previously, a hot embossing method3 has been proposed to manufacture polystyrene devices using a PDMS negative mold and polystyrene chips. A moderate amount of pressure and temperatures above the glass transition temperature of polystyrene enable the polystyrene to flow into the mold. In this paper, we fabricate microposts out of polystyrene and successfully seed cells on top of the posts.
Numerical Modelling of the Mass Transport of Blood-Borne Species in Cerebral Aneurysms of the Basilar Artery
Authors: Costelloe J. A. , Larrabide I. , Frangi A. F. , Walsh M. T.
Published: January 2014

The rupture of a cerebral aneurysm can have devastating effects, with approximately 50% of patients dying within one month of rupture [1]. Aneurysms of the basilar artery are among the most prevalent of posterior circulation cerebral aneurysms [2]. Although the exact mechanisms behind their formation, growth and rupture are unknown, it is believed that hemodynamics plays an important role [3].
Surrogate Knee Contact Modeling Using Artificial Neural Networks
Authors: Eskinazi Ilan , Fregly Benjamin J.
Published: January 2014

Contact models can be incorporated into multi-body simulations to compute the loads resulting from surface-surface interactions. In musculoskeletal biomechanics, the need to model contact arises when bone-bone, foot-ground, implant-implant, and human-orthotic interactions occur. However, contact models are computationally expensive and thus can be prohibitive for studies that require repeated function evaluations, such as optimizations and forward dynamic simulations.
Impact Behavior of Graded Porous Hip Joint
Authors: Ali M. , Hoffman J. , Hayes P. , Matthews T.
Published: January 2014

The occurrence of primary and revision total hip and knee arthoplasty in the United States is increasing [1] due to several factors which include aging population and longer life expectancies [2]. The hip joint is one of the most commonly replaced joints with more than 120,000 artificial hip joints being implanted in the United States [3]. Complications associated with hip replacements include aseptic failure and prosthetic-joint infection [4]. Implant failure is known to cause significant morbidity, pain on weight-bearing, and increased health care costs [2, 5].
A Novel Multi-Stimuli Bioreactor for Tissue Engineering Cartilage
Authors: Carmona-Moran Carlos A. , Wick Timothy M.
Published: January 2014

The demand for tissue engineered articular cartilage for implantation in patients with osteoarthritis requires the development of stable and robust large scale production systems. This can be accomplished through the use of a bioreactor that applies mechanical loading and regulates nutrient transport to promote cell growth, cell differentiation and tissue production. In the present work we have developed a shear stress and perfusion bioreactor (SSPB) capable of providing multiple stimuli to facilitate large-scale production of tissue engineered cartilage.
Noninvasive Mapping of Strain Fields in a Human L4-L5 Intervertebral Disc Under Physiologically-Relevant Axial and Bending Loads
Authors: Gossett Paull C. , Chan Deva D. , Butz Kent D. , Nauman Eric A. , Neu Corey P.
Published: January 2014

Back pain is a leading cause of lost productivity in the United States and is the most common reason for worker compensation claims [1]. Back pain often occurs in the lower (lumbar) spine due in part to the higher loads placed on it compared to the rest of the spine, including large moments during lifting activities [2]. The prevalence and debilitating nature of back pain drives the need to study the mechanical behavior of the spine under physiologically-relevant loading conditions, e.g. axial compression and anterior bending.
Bioengineered SDF-1a Analogue Delivered as an Angiogenic Therapy Significantly Normalizes Elastic and Viscoelastic Material Properties of Infarcted Cardiac Muscle
Authors: Trubelja Alen , MacArthur John W. , Sarver Joseph J. , Cohen Jeffrey E. , Shudo Yasuhiro , Fairman Alexander S. , Patel Jay , Hiesinger William , Atluri Pavan , Woo Y. Joseph
Published: January 2014

Heart disease is a leading cause of death worldwide, and coronary heart disease causes 1 of every 6 deaths in the United States [1]. Following a myocardial infarction, scar tissue gradually replaces myocardium that is lost through a process of collagen deposition and an increase in tensile strength of the tissue [2]. This leads to infarct expansion, adverse ventricular remodeling and dysfunction, and ultimately heart failure. Dilation of the left ventricle (LV) leads to increased LV wall stress and is ultimately responsible for adverse ventricular remodeling. LV dilation causes stretching and thereby increased wall stress, prohibiting cardiomyocytes from effectively contracting, which leads to further dilation, and ultimately a decrease in cardiac pump efficiency [3]. Previously, it has been shown that using a tissue filler to modify the material properties of an infarct limits the process of ventricular remodeling [4]. Angiogenesis is another mechanism by which adverse ventricular remodeling can be limited. Previously, our group developed engineered stromal cell-derived factor-1α (ESA), a computationally designed analog of an established endothelial progenitor cell chemokine, SDF-1α, and demonstrated that ESA injection enhances LV function by promoting angiogenesis and retains the native properties of the extracellular matrix (ECM) [5] [6]. In this study, we propose that injection of ESA to infarcted cardiac muscle improves the tensile strength and viscoelastic properties of ventricular muscle.
Preliminary Fabrication Capabilities of a 2-Axis Photolithography System Based on Optical Drive Motors and Laser Diodes
Authors: Bell Alex , Nistor Vasile
Published: January 2014

Photopolymerization methods such as multiphoton polymerization have been used successfully to create bioactive patterned scaffolds with micron-scale resolution capable of supporting cell growth and differentiation for engineered tissue. [1] They have also been shown effective for fabrication of a variety of MEMS devices. [2] Currently, multiphoton polymerization and similar technologies require a bulky and expensive optical system based on a femto- or picosecond pulsed laser and an XYZ arrangement of high-resolution translating stages. [3] Such systems are currently prohibitive in both cost and effort required to assemble, calibrate, and maintain. Consolidating optical components and motors into a smaller, less-complex device may facilitate the manufacture of customized tissue engineered constructs and MEMS devices on-site in more remote locations on an as-needed basis.
Swelling of Collagen-Hyaluronic Acid Tissue-Equivalents: An Experimental Model to Evaluate Residual Stress in Soft Tissues
Authors: Lai Victor K. , Lake Spencer P. , Kim Bumjun , Weiss Emily M. , Tranquillo Robert T. , Barocas Victor H.
Published: January 2014

Collagen gel tissue-equivalents (TEs), which are simple model tissues with tunable properties, have been used to explore many properties of soft tissues, such as how structural and compositional properties affect mechanical function [1–4]. One aspect not captured in previous TE formulations is residual stress due to interactions among components, which has an important functional role in many tissues (e.g., blood vessels [5], ligaments [6], annulus fibrosus [7]). Since the in vivo stress state of native tissues is not easily replicated in TE fabrication, a different method for “pre-stressing” collagen networks of TEs was necessary. To this end, co-gel TEs were fabricated by adding hyaluronic acid (HA) to reconstituted Type-I collagen (Col) gels. When placed in solutions of varying osmolarity, HA-Col TEs swell as the HA binds water, which in turn will stretch (and stress) the collagen network. In this way, TEs with residual stress (i.e., pre-stressed collagen fibers) can be fabricated and evaluated in order to elucidate relationships between residual stress and functional properties. Therefore, the goals of the present study were to fabricate HA-Col TEs, make initial measurements of their swelling properties, and quantify the mechanical response and changes in microstructural organization under applied tensile load.
Role of Lateral Interactions in Type IV Collagen Network Mechanics
Authors: Gyoneva Lazarina , Hadi Mohammad F. , Segal Yoav , Dorfman Kevin D. , Barocas Victor H.
Published: January 2014

The basement membrane is a specialized part of the extra-cellular matrix. It is usually characterized as a scaffold for epithelial cells but in some tissues it serves other, mechanical, roles [1]. The mechanical properties of the basement membrane are mainly determined by one of its main constituents — type IV collagen. Unlike the well-known fibrous type I collagen, collagen IV assembles into planar networks (Fig. 1) [2]. The α 1(IV) and α 2(IV) collagen IV chains assemble into the so-called major chain network, present in all basement membranes. The α 3(IV), α 4(IV), α 5(IV) collagen IV chains form the minor chain network which is found only in the adult basement membranes of the kidney glomerular capillaries (GBM), ocular lens (LBM), cochlea, and the testes [3]. The minor chains have a higher number of cysteine residues, allowing them to form a higher number of lateral interactions. In the minor chain network, the greater potential to interact laterally manifests in the formation of super-coils, which are rarely observed in the major chain network [4]. Increasing the number of cross-links in a polymeric material is known to increase material stiffness; therefore, it is believed that the minor chain network confers basement membranes with additional strength and stability [5]. In the hereditary disease Alport syndrome, a mutation causes the absence of the minor chain network. The GBM and LBM of Alport patients appear weakened and unable to meet their mechanical demands, further supporting this theory [6]. The objective of this study was to evaluate the importance of cross-linking in the minor chains for the mechanical properties of type IV collagen networks, specifically in the GBM and LBM where the absence of the minor chains has an observed mechanical effect.
Using a Biphasic Finite Element Model of the Human Knee Joint to Identify Robust Designs for a Meniscal Substitute
Authors: Leatherman Erin R. , Guo Hongqiang , Maher Suzanne A. , Santner Thomas J.
Published: January 2014

The menisci of the knee are C-shaped fibrocartilage disks with a cross-sectional wedge-shape that occupy the periphery of the knee joint. Although surgical treatment of the damaged meniscus is the most commonly performed orthopaedic procedure in the US, surprisingly few treatment options exist. This is in part because the structural properties of a meniscal substitute required to ensure function across a wide patient population has not been established.
Electrospun Hyaluronic Acid Scaffolds Containing Microspheres for Protein Delivery to Support Peripheral Nerve Growth
Authors: Whitehead Tonya J. , Sundararaghavan Harini G.
Published: January 2014

Peripheral nerve injury can cause lifelong pain, loss of function, and decreased quality of life. The gold standard of repair is a nerve autograft; however this requires additional surgeries and can cause donor site morbidity. As an alternative, nerve growth conduits are being developed to guide he existing nerves to cross these injured gaps. Electrospinning has emerged as a popular method to produce fibrous scaffolds for use in tissue engineering applications. However, limited work has been done electrospinning Hyaluronic Acid (HA) a major component of the extra cellular matrix. Cells respond to several factors in their environment including chemical, mechanical, topographical and adhesion cues.1 Using electrospinning along with microspheres allows us to control mechanical, topographical, and chemical signals within our scaffold. Axons are known to respond to topographical cues, prefer ‘soft’ substrates and grow faster in the presence of Nerve Growth Factor (NGF). We can precisely control the mechanics of our scaffold by conjugating methacrylates to the HA backbone and crosslinking under UV light. We also use the rotation speed of the collection mandrel to create fibers that are aligned along one axis. Adhesivity is achieved by coating the finished scaffold with fibronectin. Microspheres are included to release protein and create a chemical signal. These characteristics combined mimic the natural environment of nervous tissue.
The Use of Stentrievers in Acute Ischemic Stroke: Performance Evaluation in a Patient-Specific Vascular Replica
Authors: Chueh Ju-yu , Kuhn Anna Luisa , Puri Ajit S. , Wakhloo Ajay K. , Gounis Matthew J.
Published: January 2014

Expedited revascularization through pharmacologic dissolution and/or mechanical thrombectomy is the principle goal of treatment of ischemic stroke [1]. Pharmacologic therapy consists of intravenous thrombolysis with tissue plasminogen activator and is limited by a narrow time window within which to administer the medication, resulting in less than 10% utilization in stroke patients. Mechanical thrombectomy provides another option for flow recanalization. Four thrombectomy devices are cleared by the FDA to restore blood flow in ischemic stroke patients, namely, the Merci retriever, the Penumbra aspiration system, the Solitaire FR revascularization device, and the Trevo device. While several completed and ongoing clinical trials have shown enhancement in the design of thrombectomy devices and increase in recanalization rate [2–4], the recanalization rate and, more importantly, the clinical outcome achieved with current thrombectomy devices still remain to be optimized.
Progression of Abdominal Aortic Aneurysm: Effect of Lagrangian Transport and Hemodynamic Parameters
Authors: Arzani Amirhossein , Suh Ga Young , McConnell Michael V. , Dalman Ronald L. , Shadden Shawn C.
Published: January 2014

Abdominal aortic aneurysm (AAA) is a permanent, localized enlargement of the abdominal aorta that accompanies disturbed blood flow, which is thought to perpetuate aneurysm progression. AAA rupture is a leading cause of death in the elderly and an exact intervention decision for this disease has always been associated with uncertainty. There is currently no medicinal treatment of AAA, however lower extremity exercise has been a proposed therapy. Specifically, elevated flow rates in the abdominal aorta, reduced retrograde flow, higher mean wall shear stress, and lower oscillatory shear index resulting from exercise have been hypothesized as beneficial in preventing or slowing AAA. Computational fluid dynamics (CFD) has recently been used to model flow conditions inside AAA with an aim to better understand the biomechanical underpinnings of this disease. Recent studies have used patient-specific computational models, however few studies have looked in detail to AAA transport topology or correlated their results with aneurysm progression data. This study aims to (1) compare the flow topology between rest and exercise conditions in patients with small AAA to understand specifically how blood transport changes from rest to exercise, and (2) compare flow parameters obtained by CFD to the aneurysm progression.
Effects of Spine Soft Tissue Stiffening on Biomechanics of Lumbar Spine: A FEA Study
Authors: Kiapour A. , Kiapour A. M. , Goel V. K. , Sairyo K.
Published: January 2014

Spine stiffening or also called Ankylosing Spondylitis (AS) is a type of progressive arthritis that leads to a chronic inflammation affecting spinal column and sacroiliac joints (SI). Long-term inflammation of the spinal joints (called Spondylitis) leads to calcium deposits forming on the ligaments and around the intervertebral discs. Subsequent tissue inflammation resulted from deposition of calcium, causes the spine to stiffen and potential mobility loss. This may result in clinical sequelae such as long-term disability and in complete fusion of vertebral column (Ankylosis) in severe cases [1]. Current literature on AS and its effects on segmental biomechanics is not known. Hence, this study designed to investigate the biomechanical effects of spine stiffening through changing the stiffness of soft tissue (ligaments & discs) across lumbar spine using finite element (FE) analysis.
In Vivo Measurements of Blood Transport Patterns and Stasis in the Human Left Ventricle
Authors: Hendabadi Sahar , Bermejo Javier , Benito Yolanda , Yotti Raquel , Fernández-Avilés Francisco , del Álamo Juan C. , Shadden Shawn C.
Published: January 2014

Because the left ventricle (LV) is not completely emptied during systole, oxygenated blood from the left atrium interacts with residual blood from preceding cycles. It is hypothesized that LV flow is optimal for transporting blood under normal conditions; yet proving this remains a challenge. Furthermore, clinical evaluation of LV hemodynamics has tremendous diagnostic importance for patients with cardiomyopathy. We have performed Doppler-echocardiography on 6 patients with dilated cardiomyopathy and 6 healthy volunteers. Using novel processing of the color-Doppler data, bi-directional velocity field maps in the apical long axis plane were derived. Resulting flow data was used to perform Lagrangian coherent structure (LCS) computation, which enabled novel characterization of the transport topology in the LV during filling and ejection. This framework was used to quantify stasis in the LV, which can be used as a surrogate for diagnosing pumping deficiencies and thrombosis risk. This framework also enables characterization of LV vortices, which have previously received much attention using Eulerian characterizations. The framework presented here uncovers the well-defined boundaries to both E-wave and A-wave filling vortices, which has not been previously reported.
Predilections of Cardiogenic Embolic Transport to the Cerebral Versus Peripheral Arteries
Authors: Shadden Shawn C. , Carr Ian A. , Nemoto Naohiko , Schwartz Robert S. , Lesser John R.
Published: January 2014

One of the most compelling scenarios of embolic transport is for cardiogenic particles. These emboli are a major cause of death and disability, resulting in an estimated 20%–30% of ischemic brain strokes. Whether cardiogenic emboli continue distally in the descending aorta, or travel into the aortic branch arteries has critical consequences for stroke. Previous studies found that embolic particles tend to favor larger diameter arteries at bifurcations, which suggests that cardiogenic emboli should be preferentially transported to the descending aorta, even beyond expectations due to flow rate. However, extrapolating previous findings to this scenario is questionable because previous models do not represent the unique fluid dynamics and morphology of the ascending aorta. We utilized medical imaging and computational modeling to better understand the transport of cardiac emboli to the cerebral arteries. Results indicate that particle transport to aortic branch arteries, and subsequently the arteries to the head, has a strong size-destination predilection that varies markedly from volumetric blood flow distribution.
In Vivo Testing of the Viscoelastic Properties of Uterine Suspensory Tissue in Women With Pelvic Organ Prolapse
Authors: Luo Jiajia , Smith Tovia M. , Ashton-Miller James A. , DeLancey John O. L.
Published: January 2014

Pelvic floor dysfunction has resulted in 11% of women undergoing surgery [1] during their lifespan in the USA. Over 200,000 prolapse operations are performed yearly [2] and the annual estimated cost for these operations exceeds US $1 billion [3].
Observation of Traction Forces During Galvanotaxis
Authors: Taparia Nikita , Sniadecki Nathan J.
Published: January 2014

Cell migration plays a critical role in many biological functions within multicellular organisms such as wound healing, immune response, and embryogenesis. A cell’s inability to migrate can cause severe complications such as inflammatory or autoimmune diseases, defective wound healing or cancer metastasis [1].
3D In Vivo Bone Dynamic Imaging of PTH’s Anabolic Action
Authors: Altman Allison R. , Huh Beom Kang , Chandra Abhishek , Tseng Wei-Ju , Qin Ling , Liu X. Sherry
Published: January 2014

Aging shifts bone remodeling toward a negative balance between bone formation and resorption, causing bone loss and increased fracture risk. Anti-resorptive agents are commonly used to inhibit bone resorption and stabilize bone mass. While they are effective to prevent further bone loss, there is also a great need for anabolic agents which can reverse bone deterioration and regain lost skeletal integrity. Intermittent parathyroid hormone (PTH) treatment is the only FDA-approved anabolic treatment for osteoporosis, which greatly stimulates bone formation. Combined therapy of anti-resorptive drugs, such as alendronate (ALN), and PTH have been proposed and are expected to further stimulate bone formation. However, studies show conflicting results regarding the effectiveness of combined treatments: some have reported the addition of ALN to impair PTH function [1, 2], while others suggest an improvement over PTH monotherapy [3, 4]. The first objective of this study is to document the immediate changes of individual trabecular structures due to PTH and combined therapy within 12 days using in vivo micro computed tomography (μCT). As PTH is typically prescribed for 1 to 3 years to osteoporotic patients, a treatment of 12 days for rats (approximately equivalent to one year of human life) may be more clinically relevant than long-term treatment studies on rats. The secondary purpose of this study was to gain insight into the mechanism of combined versus PTH treatments through a bone dynamic imaging strategy to track events over an individual remodeling site. We hypothesized that PTH and combined treatments would immediately enhance bone formation on the trabecular surface.
Spatiotemporal Intracellular Deformation of Cells During Freezing-Induced Cell-Fluid-Matrix Interactions
Authors: Ghosh Soham , Dutton J. Craig , Han Bumsoo
Published: January 2014

Freezing of biomaterials is emerging as one of the key biotechnologies in cell/tissue engineering, medicine and biology. Its applications include — 1) preservation of cell/tissue engineering products, 2) quality control of biospecimens cryopreserved in tissue banks and repositories, and 3) synthesis procedures of biomaterials such as decellularization of native tissues to create acellular (i.e., cell-free) complex three-dimensional extracellular matrices (ECMs). Traditionally, research efforts have focused on determining optimal freeze/thaw (F/T) protocols with chemical additives, so called cryoprotective agents, for a given cell/tissue-type by comparing the outcomes of F/T protocols, which are mainly gauged by cell viability. Although cell viability is the major constituent, it has recently been recognized that other features beyond viability are also critical to the functionality of biomaterials, including the microstructure of the ECM, the status of cell-matrix adhesion, and the cytoskeletal structure and organization [1, 2, 3].
Temporally-Stiffening Hydrogel Regulates Cardiac Differentiation via Mechanosensitive Signaling
Authors: Young Jennifer L. , Kretchmer Kyle , Engler Adam J.
Published: January 2014

Stiffness of the extracellular matrix (ECM) surrounding cells plays an integral role in affecting how a cell spreads, migrates, and differentiates, in the case of stem cells. For mature cardiomyocytes, stiffness regulates myofibril striation, beating rate, and fiber alignment, but does not induce de-differentiation [1,2]. Despite improved myocyte function on materials which mimic the ∼10 kPa heart stiffness, the heart does not begin as a contractile ∼10 kPa material, but instead undergoes ∼10-fold myocardial stiffening during development [3]. Thiolated hyaluronic acid (HA) hydrogels have been used to mimic these stiffening dynamics by varying hydrogel functionality and component parameters. Recently, we have shown that pre-cardiac mesodermal cells plated on top of these stiffening HA hydrogels improves cardiomyocyte maturation compared to static, compliant polyacrylamide (PA) hydrogels [3]. While active mechanosensing causes maturation, the specific mechanisms responsible for responding to time-dependent stiffness remain unknown. Here we examined protein kinase signaling and mechanics in response to dynamic vs. static stiffness during the commitment process from embryonic stem cells (ESCs) through cardiomyocytes to better understand how developmentally-appropriate temporal changes in stiffness regulate cell commitment.
WPI iCREATE: Innovation and Translation in Senior Level Biomedical Engineering Course
Authors: Gaudette Glenn R. , Hoy Frank , Billiar Kristen L.
Published: January 2014

Traditional engineering programs provide an excellent foundation in technical knowledge and skills. However, to be effective problem solvers, today’s engineering students need to develop an innovation mindset. With this goal in mind, a group of faculty from WPI Engineering Departments and from the Business School formed WPI iCREATE: iCREATE: Innovation Center for REsearch And Technology Entrepreneurship. This new center is focused on bringing innovation and entrepreneurship to both undergraduate and graduate courses, partially through the development of teaching modules.
Flow Diverted Aneurysmal Hemodynamic Simulations and Validation With Experiments
Authors: Dholakia R. J. , Sadasivan C. , Fiorella D. J. , Woo H. H. , Lieber B. B.
Published: January 2014

Brain aneurysms occur due to abnormal ballooning of cerebral arteries. Rupture of the cerebral aneurysms can result in subarachnoid hemorrhage and may prove fatal for patients [1]. Surgical clipping is a highly invasive option for treatment of aneurysms. Endovascular flow diverting stents have recently emerged as a less invasive treatment for cerebral aneurysms. Flow diverters for intracranial aneurysms, are porous metallic mesh tubes deployed across the neck of the aneurysm to exclude the aneurysm from the circulation [2–4]. By producing a substantial reduction of flow inside the aneurysm and by promoting activation of platelets that cross the device into the aneurysm, intra-aneurysmal thrombus is generated and the aneurysm is eventually excluded from the circulation.
Un-Tethered, Active Ankle-Foot Orthotic
Authors: Schiotis Patricia , Reardon Shane , Hosig Sam , Williams John , Ellsworth Robert , Kjolner Dana , DeBartolo Elizabeth
Published: January 2014

Foot drop, or the inability to dorsiflex the foot (i.e., point your toe upward) is a fairly common lasting side-effect of a stroke, affecting approximately 20% of stroke survivors (∼1.3 million people each year). The customers have adopted the use of Ankle Foot Orthotics (AFOs) in order to aid in the dorsi-flexion of the foot. These passive devices do not allow users to safely move down inclines or stairs as the user’s foot will always be pointed upwards when off the ground.
Distributions During Cryoprotective Agent Loading in a Microchannel
Authors: Scherr Thomas F. , Pursley Shelby , Monroe W. Todd , Nandakumar Krishnaswamy
Published: January 2014

Cryopreservation of cells and tissues is critical to long term storage and off the shelf availability of biomaterials for a variety of disciplines[1]. Typical cryopreservation protocols aim to remove intracellular water by exposing the sample to a cryoprotective agent (CPA) to create an osmotic pressure gradient[2]. While CPAs are useful in preventing cell damage due to intracellular ice formation, the dehydration process can induce harmful osmotic shock[3].
Experimental Determination of the Mechanical and Biological Properties of Carotid Artery Plaques
Authors: Mulvihill J. J. , Cunnane E. M. , Kavanagh E. , Walsh M. T.
Published: January 2014

Atherosclerosis is a cardiovascular disease that occurs within the walls of arteries and can result in a reduction of the lumen diameter. This reduction can cause a decrease in blood flow to the brain which can lead to a stroke event. Carotid angioplasty stenting (CAS) is a minimally invasive surgical treatment for stroke prevention and has been found to show equivalency to the highly invasive open artery repair which is a more commonly used surgical technique (Brott et al. 2010). Development in the design of stent and angioplasty devices is necessary for the continuous improvement of minimally invasive treatments of carotid artery disease. However, a major concern with regard to this treatment is the rupture of the plaque due to the almost instantaneous inflation of the stent device. To further improve the design of these devices a better understanding of the mechanical behaviour and failure of the plaque during minimally invasive treatment in the circumferential direction is required. A limited amount of data exists regarding the mechanical behaviour of atherosclerotic plaques under physiological conditions. Studies undertaken by Maher et al. (2009) and Teng et al. (2009) have tested the tensile properties of the plaque in the circumferential direction but these studies employed unphysiological strain rates which limit the true representation of the global properties of the plaque. This current study aims to biologically and mechanically characterise the whole plaque tissue and to determine if a correlation exists between the mechanical behaviour and the pre-operatively identified biological content of the plaque.
Mechanical Effects of Myofibril Disarray on Cardiac Function
Authors: Veress A. I. , Giannakidis A. , Gullberg G. T.
Published: January 2014

Myocardial disarray is a fiber distribution that deviates away from the tightly organized, parallel alignment of myocardial fibers that characterizes the normal myocardium. This coherently-organized distribution of the myofibers results in the twisting contraction of the normal left ventricle (LV). With myofiber disarray, the fibers have random directionality, either locally or globally, within the LV.
Prediction of Abdominal Aortic Aneurysms Using Sparse Gaussian Process Regression
Authors: Ijaz A. , Choi J. , Lee W. , Baek S.
Published: January 2014

Abdominal Aortic Aneurysms (AAA) is a form of vascular disease causing focal enlargement of abdominal aorta. It affects a large part of population and has up to 90% mortality rate. Since risks from open surgery or endovascular repair outweighs the risk of AAA rupture, surgical treatments are not recommended with AAA less than 5.5cm in diameter. Recent clinical recommendations suggest that people with small aneurysms should be examined 3∼36 months depending on size to get information about morphological changes. While advances in biomechanics provide state-of-the-art spatial estimates of stress distributions of AAA, there are still limitations in modeling its time evolution. Thus, there is no biomechanical framework to utilize such information from a series of medical images that would aid physicians in detecting small aneurysms with high risk of rupture. For the present study, we use series of CT images of small AAAs taken at different times to model and predict the spatio-temporal evolution of AAA. This is achieved using sparse local Gaussian process regression.
Predictions of Drug Distribution During Infusions Into the Brain Using an Axisymmetric Finite Element Biphasic Model That Includes Backflow
Authors: Orozco Alejandro , Smith Joshua H. , García José Jaime
Published: January 2014

Convection-enhanced delivery is a technique to infuse therapeutic agents into the brain under positive pressure for the treatment of disorders of the central nervous system. Recent clinical trials [1] have shown limited efficacy of this procedure, attributed to poor distribution of the infused agent that may be due to backflow, in which the infused fluid preferentially flows along the outside of the catheter toward the surface of the brain.
Development of a Shape Memory Patch for Vascular Injuries
Authors: Boire Timothy , Gupta Mukesh , Lynch Brendan , Sung Hak-Joon
Published: January 2014

There is a high risk of surgical complications when treating vascular injuries such as ruptures and ischemia associated with strokes, aneurysms, and other vascular diseases. Moreover, it is still challenging to repair injuries of small diameter blood vessels through currently available therapeutic approaches because of limited access and small path length. To address these issues, a vascular patch made of biodegradable shape memory polymers (SMPs) can be deployed to the injured or ruptured site in a minimally invasive manner via a catheter or laparoscope, as shown in Figure 1. SMPs are capable of achieving minimally-invasive implantation and repair vascular injuries because they can be fixed into a temporary shape (i.e. an injectable shape for placement through a laparoscope) and recover their original, permanent shape (i.e. a ruptured tissue-specific shape) when triggered by an external stimulus such as heating above its melting temperature (T m).
A New Interdisciplinary PhD Program in Bioinnovation at Tulane University
Authors: Gaver Donald P. , Job Anne-Marie Jacob
Published: January 2014

Graduate education in the sciences and engineering rarely offers the training and experiences necessary to fully prepare graduates to enter directly into non-academic research and leadership positions. Tulane’s NSF IGERT-funded Interdisciplinary PhD Program in Bioinnovation challenges this paradigm by creating a program in that will cultivate our trainee’s abilities to develop clinically relevant biomedical technologies and devices leading to commercial products. This program couples research with extensive training in entrepreneurship and regulation to develop graduates who can lead the creation of innovative and cost-effective solutions to complex biomedical problems.
Primary Cilia Knockdown Reduces the Number of Stromal Cells in Three Dimensional Ex Vivo Culture
Authors: Coughlin Thomas R. , Haugh Matthew , Voisin Muriel , Birmingham Evelyn , McNamara Laoise M. , Niebur Glen L.
Published: January 2014

Mesenchymal stem cells (MSCs) are multipotent stromal cells that reside in the bone marrow and differentiate into connective cell lines, such as adipocytes and osteoblasts [1]. An appropriate balance of MSC differentiation toward adipocytes and osteoblasts is vital to bone homeostasis [6]. In vitro work demonstrates that differentiation of MSCs is influenced by mechanical stimuli [2, 3]. In a mouse model, the ratio of adipocytes to MSCs in the marrow was 19% lower compared to controls following treatment by low magnitude mechanical signals (LMMS) [4]. In mice, LMMS increased MSC number by 46% and the differentiation capacity of MSCs was biased towards osteoblastic compared to adipogenic differentiation [5]. Thus, mechanobiological stimuli may play an important role in maintaining balanced MSC differentiation.
Estimation of Atherosclerotic Plaque Material Properties: A Mixed Method of Strain Imaging and Inverse Finite Element Analysis
Authors: Akyildiz A. C. , Hansen H. H. G. , de Korte C. L. , Speelman L. , Wentzel J. , van der Steen A. , Gijsen F.
Published: January 2014

Atherosclerosis is a cardiovascular disease characterized by plaque formation in the vessel wall. Plaque rupture initiates thrombus formation and may lead to myocardial infarction, stroke and eventually, to sudden death [1]. A plaque ruptures when the mechanical stress in the plaque exceeds its strength. Thus, biomechanical models have a great potential to predict plaque rupture. For reliable prediction models, correct material properties of plaque components at large strains are prerequisite. However, the data available in literature are limited and show a wide range.
Innovative Design and Manufacturing Techniques for Patient Specific Abdominal Aortic Aneurysm Flexible Benchtop Models
Authors: Stefanov Florian , Delassus Patrick , McGloughlin Tim , Morris Liam
Published: January 2014

Abdominal aortic aneurysm (AAA) represents an asymptomatic cardiovascular type of disease, that is diagnosed in elder people over 60 years old. It is characterised by a ballooning of the abdominal aorta, which grows, at different rates in different patients. If left untreated, it will rupture causing severe internal bleeding, which can lead to shock or death [1]. Medical devices such as bifurcated stent grafts (SG) are used for the treatment of this disease. To help improve SG performance, biomedical engineers design benchtop models for testing.
The Activation of Zebrafish Sperm Cells in a Micromixer
Authors: Scherr Thomas F. , Knapp Gerald , Tiersch Terrence , Monroe W. Todd , Nandakumar Krishnaswamy
Published: January 2014

The freshwater fish, Danio rerio (zebrafish), have become widely used as a model organism for vertebrate development, DNA mutation, and human disease studies [1]. Maintaining live colonies of the numerous developed strains of zebrafish under investigation can be prohibitively costly. As such, there is a growing need to catalog their reproductive cells and have them available on demand [2]. Thus cryopreservation of model strain gametes has become an important endeavor, where evaluation of freezing and thawing techniques is currently a bottleneck to these procedures.
Quantitative In Vivo Evaluation of Neointimal Hyperplasia Using High-Resolution Contrast-Enhanced Cone-Beam Computed Tomography
Authors: van der Bom Imramsjah M. J. , Strittmatter Lara , Hendricks Gregory H. , Kühn Anna Luisa , Wakhloo Ajay K. , Gounis Matthew J.
Published: January 2014

Intracranial atherosclerotic disease (ICAD) is the most common cause of stroke throughout the world. Patients with severe arterial stenosis and a recent stroke or transient ischemic attack are at high risk of recurring stroke. In an attempt to improve the clinical outcome of patients with severe, symptomatic ICAD, percutaneous transluminal angioplasty and intracranial stenting have become treatment options over the last years. Follow-up imaging of patients with ICAD that underwent intracranial stenting is generally done using 2D digitally subtracted angiography. Since often the vessel path is curved and the neointimal hyperplasia (NH) is eccentric, in-stent restenosis (ISR) may be under- or overestimated using 2D techniques.
Treatment With Non-Nucleoside Reverse Transcriptase Inhibitor Efavirenz Leads to Increase of Carotid Intima-Media Thickness in Mice
Authors: Caulk Alexander W. , Gleason Rudolph L.
Published: January 2014

Since the advent of highly active antiretroviral therapy (HAART), patients infected with human immunodeficiency virus-1 (HIV-1) are living longer lives. However, HIV-1-positive (HIV-1+) patients are now experiencing many non-AIDS related comorbidities including myocardial infarction, atherosclerotic lesions, and other preclinical markers of atherosclerosis including increased carotid intima-media thickness (cIMT), arterial stiffness, and impaired flow-mediated dilation (FMD). Studies have implicated the virus, the treatment, or both in the progression of these co-morbidities, causing the exact mechanisms of cardiovascular disease progression to remain unclear.
Age-Related Changes in the Non-Linear Mechanical Strain Response of Human Peripapillary Sclera
Authors: Fazio Massimo A. , Grytz Rafael , Morris Jeffrey S. , Bruno Luigi , Girkin Christopher A. , Downs J. Crawford
Published: January 2014

In glaucoma, the optic nerve head (ONH) is the site of damage to the retinal ganglion cell axons that transmit the visual information from the eye to the brain. Results of several randomized prospective trials showed that intraocular pressure (IOP), age 1, increased optic disc cupping, corneal thickness, and African ancestry 2 are independently associated with glaucomatous progression. All of these risk factors have a biologically plausible association with either the level of IOP, the severity of disease, or biomechanical properties of the ONH. Importantly, age is the only risk factor other than IOP that is independently associated with the onset and progression of glaucoma across all of the major prospective clinical trials conducted over the past twenty years. In addition, every population-based survey conducted to date has demonstrated a strong relationship between the prevalence of glaucoma with advancing age, despite almost no studies showing IOP changes with age. These findings indicate that the aging ONH becomes increasingly vulnerable to glaucomatous injury at similar levels of IOP.
Selective Electrical Stimulation of Adult Cardiomyocyte for Studying Intercellular Mechanical Transmission
Authors: Zhang Xu , Zhao Yi
Published: January 2014

Heart diseases rank the top among the leading causes of death in the United States, and account for nearly 40% of all deaths 1. As the most important component of heart muscle, cardiac myocytes are the basic units to generate contractile forces and regulate heart function. There are extensive molecular and electrophysiological studies suggesting that the defective intercellular communication in cardiac myocytes is an underlying cause of left ventricular dysfunction in several heart diseases 2,3. However, there are limited evidences in terms of mechanical contractility and electromechanical transmission, which are the direct measures of intercellular communication in myocardium. This is largely due to the lack of appropriate tools that can quantitatively assess the mechanical performance of adult cardiac myocytes. In this study, a microengineered device is developed for quantitative assessment of cardiac mechanical performance in isolated adult myocytes. This device is capable of applying electrical stimulation to selected cardiac myocytes, measuring mechanical force generation in single cells, and examining intercellular mechanical transmission in longitudinally connected doublets of adult cardiac myocytes.
Investigation of the Fatigue Properties of Mitral Valve Leaflets
Authors: Shahmansouri Nastaran , Javid Farhad , Pasini Damiano , Angeles Jorge , Amabili Marco , Mongrain Rosaire
Published: January 2014

Annulus dilation is one of the main causes of functional mitral regurgitation. Although the annulus dilation is usually accompanied by left ventricle dilation and dysfunction, the mechanical relation between them is not fully elucidated yet. In this paper, the assumption is made that the ventricular dysfunction increases the cyclic loading conditions on the mitral valve apparatus. This effect may cause fatigue and weaken the tissue. This hypothesis is investigated in vitro by applying increased cyclic loadings to the tissue and evaluating the tissue stiffness during the cycles. The results of this study show that the tissue loses its strength after cyclic fatigue loadings.
A Walker With Integrated Toilet Seat and Stroller Capabilities for the Disabled
Authors: Moelmann Connor , Davis Phillip , Getz Josh , Pham Alex , Wobith David , Shih Albert , Sarns Dick
Published: January 2014

With the baby boomers reaching retirement, we anticipate a large increase in demand of health care products for the elderly. As people age, bones become fragile and balance becomes impaired, which puts older people at increased danger with longer recovery times. Dick Sarns, the sponsor of this project and co-founder and CEO of NuStep, a rehabilitation equipment manufacturer, wanted to create a walker for his wife, Norma Sarns, who suffers from multiple sclerosis.
AView: A Clinical Tool for Hemodynamic and Morphological Analysis of Intracranial Aneurysms
Authors: Xiang Jianping , Varble Nicole , Siddiqui Adnan , Antiga Luca , Meng Hui
Published: January 2014

Neurointerventionists are routinely faced with the dilemma whether or not to treat unruptured intracranial aneurysms. Hemodynamic and morphological characteristics have become important considerations for aneurysm rupture-risk assessment [1]. Clinicians require an integrated tool that analyzes these parameters to help make treatment decisions in clinical workflow, however such a tool does not exist. To this end, Toshiba Stroke and Vascular Research Center (TSVRC) at University at Buffalo and Orobix Srl (Italy) have developed a prototype of a computational workflow system. Termed AView, it is an integrated, image-based vascular analysis tool for rapid assessment of aneurysmal hemodynamics, morphometrics, rupture risk assessment, and treatment planning.
Research-Focused Undergraduate Laboratory Exercises in Biomechanics
Authors: Buckley Jenni M. , Higginson Jill S. , Bucha Amy C. , Khandha Ashu , Elliott Dawn , Buchanan Thomas
Published: January 2014

Undergraduate laboratory exercises in core engineering courses do not always subscribe to the Problem Based Learning approaches advocated by the educational community [1–3]. Common shortcomings include “cookie cutter” labs where students are not engaged in experimental design as well as a general detachment from the “real world” application of the laboratory exercise. Soft skills like proper documentation during experiments as well as scientific writing may also be overlooked in lab curricula. This is unfortunate, as the undergraduate laboratory experience is a perfect opportunity to develop essential research skills as well as inspire and excite students about their chosen field.