In Vivo Imaging of Dynamic Shear Modulus of Rodent Mammary Tumors Using Ultrasound

Biomechanical properties of living tissue are very important in maintaining normal tissue function, cellular and extracellular structural integrity. Therefore, the quantitative determination of biomechanical properties of breast tissue, especially in vivo, serves an important role in clinical diagnosis.

A Quantitative Analysis of Kinetic Energy Harvesting for Hybrid Power Supplies

This study presents a quantitative analysis of experimental data for extracting energy from human body motion and its possibility of powering portable electronic devices, such as consumer electronics or biomedical monitoring sensors. Since portable electronic devices are typically limited by the size and lifespan of batteries, energy harvesting shows potential as alternative for extending battery life. The acceleration was collected experimentally from 10 subjects while walking and running at different velocities on a treadmill. The acceleration results were studied and a figure of merit consisting of the acceleration-squared-to-frequency was found to determine, in addition to the quality factor, as the important factors for optimal energy harvesting. It was determined that from average walking an energy harvester can produce a power output density greater than 1mW/cm3.

Ovarian Cancer Cell Invasiveness Correlates With Increased Cell Deformability

Cancer cells undergo a variety of biochemical and biophysical transformations when compared to identical cells displaying a healthy phenotypic state, cancer cells show a drastic reduction of stiffness upon malignancy[1, 2] and change of stiffness of single cells can indicate the presence of disease [3–6]. Besides, metastatic cancer has a higher deformability than their benign counterparts[7, 8]. Using atomic force microscopy, we demonstrated that cancerous ovarian cells (OVCAR3, OVCAR4, HEY and HEYA8) are substantially softer than the healthy immortalized ovarian surface epithelium (IOSE) cells. In addition, within the different types of cancerous ovarian cells, increased invasiveness and migration are directly correlated with increased cell deformability. These results indicate that stiffness of individual cells can distinguish not only ovarian cancer cells from healthy cells types, but also invasive cancer types from less invasive types. Stiffness may provide an alternative and convenient biomarker to grade the metastasis potential of cancer cells.

Comparison of Methods to Predict Scapular Notching From Radiographs After Reverse Total Shoulder Arthroplasty

Scapular notching is a complication of reverse total shoulder arthroplasty (rTSA) that results in bone loss on the lateral border of the scapula. Notching has been reported in up to 86% of patients at 5 year follow-up [1], and is graded 1–4 as a function of progressive bone loss [2]. Notching may arise from impingement, erosion, periprosthetic osteolysis, stress shielding or a combination of these [1]. Glenosphere position can mitigate notching by limiting hardware impingement [3–5], but may increase the forces required to abduct the arm [6]. Clinicians might optimize patient range of motion and function via implant placement if susceptibility to notching was known a-priori.

Dynamic Mechanical Properties Control Adult Stem Cell Fate

Stem cells respond to many microenvironmental cues towards their decisions to spread, migrate, and differentiate and these cues can be incorporated into materials for regenerative medicine.1 In the last decade, matrix stiffness alone has been implicated in regulating cellular functions such as migration, proliferation and differentiation. With this in mind, a variety of natural and synthetic polymer systems were used in vitro to mimic the elasticity of native tissues. Despite helping to develop this important field and gather valuable information, these substrates are primarily static and lack the dynamic nature that is observed during many cellular processes such as development, fibrosis and cancer. Thus, it is of great interest to temporally manipulate matrix elasticity in vitro to better understand and develop strategies to control these biological processes. In this work, we utilize a sequential crosslinking approach (initial gelation via addition reaction, secondary crosslinking through light-mediated radical polymerization) to fabricate hydrogel substrates that stiffen (e.g., ∼3 to 30 kPa) either immediately or at later times and in the presence of cells. We demonstrate the utility of this technique by investigating the short-term (several minutes to hours) and long-term (several days to weeks) stem cell response to dynamic stiffening

Stiffness as an Effector of Lung Branching Morphogenesis

Growing evidence suggests that physical microenvironments and mechanical stresses direct cell fate in developing tissues. However, how these physical properties affect morphogenesis remains unknown. We show here that ECM mechanical properties, i.e. stiffness, reproduced by using hydrogel, guide tissue morphogenesis in the developing lung bud. In particular, decreasing substrate stiffness in cultured lung buds resulted in an inhibition of appropriate cleft formation and a resulting enlargement of epithelial buds. These findings suggest that the magnitude of mechanical stiffness across the lung bud alters the branching pattern. Additionally, physically designed hydrogel material is a valuable tool for producing the specific microenvironment to explore how physical cues affect and alter tissue morphogenesis for in vitro study.

A Comprehensive Tool for Patient-Specific AAA Geometry and Biomechanics Assessment

Annual mortality from ruptured abdominal aortic aneurysm (AAA) in the United States alone is approximately 150,000, which is currently ranked as the 13th leading cause of death and the 10th leading cause of death in men over 55 years of age [1]. The vascular surgeon needs to weigh the risk of AAA rupture against the risk of surgical intervention to decide the best course of treatment. Several steps are involved when using computational techniques to evaluate risk of rupture [2], namely medical image segmentation, 3D reconstruction, finite element mesh generation, derivation of boundary conditions, specification of tissue material properties, etc. Currently, computational analysis of AAA biomechanics includes the use of multiple third-party commercial software tools to accomplish each of these steps, which makes its clinical implementation impractical, time-consuming and requiring to interface multiple software tools as this demands an engineering skill set. Additionally, the versatility of general purpose off-the-shelf software comes at the cost of simplifying assumptions regarding geometric modeling, limited user control and boundary conditions. This makes subsequent computational results vulnerable to inaccuracies. In this work, we describe the software tool AAAVASC, built on a MATLAB platform, with an integrated approach for image-based modeling and a novel pipeline that facilitates both geometry quantification and computational analysis of AAA biomechanics.

Assessment of the Effect of Coronary Occlusion on Aortic Valve Dynamics Using a Global 3D FSI Model

Coronary artery disease (CAD) is considered to be a major cause of mortality and morbidity in the developing world. It has recently been shown that aortic root pathologies such as aortic stiffening and calcific aortic stenosis can contribute to the initiation and progression of this disease by affecting coronary blood flow [1,2]. Such pathologies influence the distensibility of the aortic root and therefore the hemodynamics of the entire region. As a consequence the coronary blood flow and velocity profiles will be altered [3,4,5] which could accelerate the development of an existing coronary artery disease. However, it would be very interesting to see if an occluded coronary artery would have a mutual impact on valvular dynamics and aortic root pathologies. This bi-directionality could aggravate and contribute to the progression of both the coronary and aortic root pathology.

Pure Moment Testing for Spinal Biomechanics Applications: Fixed Versus 3D Floating Ring Cable-Driven Test Designs

For spine biomechanical tests, the cable-driven system in particular has been widely used to apply pure bending moments. The advantages to pure moment testing lie in its consistency as an accepted standard protocol across previous literature and its ability to ensure uniform loading across all levels of the spinal column. Of the methods used for pure moment testing, cable-driven set-ups are popular due to their low requirements and simple design. Crawford et al [1] were the first to employ this method, but prior work by our group indicated a discrepancy between applied and intended moment for this system in flexion-extension only [2]. We hypothesize that this discrepancy can be observed in other bending modes and minimized with a second-generation floating ring design to eliminate off-axis loads.

Surgical Variability of Resection Parameters During Total Knee Arthroplasty

There is intrinsic surgical variability in the practice of total knee arthroplasty (TKA), and thus computational analyses of TKA should account for this variability to ensure clinical applicability and robustness of results. Statistical inputs within computational analyses have been used to assess the biomechanical characteristics of TKA implants [1], and such methodologies are promising when applied to morphological analysis of TKA in order to motivate component design, assess current designs, and improve the understanding of surgical outcomes. Analyses to date either directly use actual TKA component placement or bone resection data [2], or assume a single set of parameters for placement and resection across the entire specimen group that was investigated [3], and thus do not account for surgical variability. This could be due to a lack of available data to quantify clinical variability in TKA component placement.