Amritha K. Venkatesh [1], Fabian Benencia [2]
[1] Department of Chemical and Biomolecular Engineering, Ohio University, Athens, Ohio
[2] Department of Biomedical Sciences, Ohio University, Athens, Ohio
The toll-like receptors are a family of innate immune receptors that elicit inflammatory reactions by triggering a cascade of cytokines upon the recognition of a specific ligand. While these responses are helpful in combating microbial and viral infections, they prove to be detrimental to different kinds of cancers and autoimmune diseases. For instance, the role of TLR3 has been indicated in malignant melanomas, thyroid cancer and pancreatic cancer. Having shown the expression of TLR3 in breast cancer cells, we hypothesized that TLR3-mediated signaling in breast cancer plays a role in the recruitment of antigen presenting cells to the tumor microenvironment. For the experiments, we used the 4T1 mouse breast cancer model, derived from BALB/c mouse. 4T1 cells were treated with different concentrations of poly I:C, a synthetic ligand for TLR3, and the supernatant was analyzed by ELISA for the expression of chemokines - RANTES, SDF-1α, MIP-3α, MIP-3β. These molecules were selected, since their respective receptors are present on antigen presenting cells. Following this, a real-time PCR analysis was performed to detect the mRNA level expression of these molecules in poly I:C treated cells. Subsequently, protein array and PCR array analyses were done to detect the change in the expression of other important chemokines and cytokines. Results: The ELISA and real-time PCR analyses revealed that RANTES is upregulated upon treatment with poly I:C in 4T1 cells. Further, the protein array results showed an increase in RANTES, IL6 and MIP2 and a reduction in the matrix metalloprotease inhibitor TIMP1. Also, the PCR array showed an increase in 10 other important cytokines that are capable of collaborating with disease progression. These results indicate the potential role of TLR3 in initiating leukocyte infiltration in breast cancer. Further experiments to observe the effect of inhibiting TLR3 in breast cancer cells on migration will help establish an approach to alleviate leukocyte infiltration in breast cancer.
Austin P. Bishop [1], Madhusudhana Gargesha, Ph.D [1], Michael W. Jenkins, Ph.D. [1], Andrew M. Rollins, Ph.d. [1]
[1] Department of Biomedical Engineering, Case Western Reserve University, Cleveland, Ohio
Using Optical Coherence Tomography (OCT), we have acquired time series of 2D images from beating embryonic quail hearts. High-throughput image segmentation from this real time, in vivo imaging data would help determine very accurately dynamic parameters involved in early heart development (e.g., shear stress, wall velocity). Level set methods have been used in the past for image segmentation, but are prone to errors in regions where image gradients cannot be reliably estimated and suffer from convergence problems especially with noisy data. We propose an improvement to a recently proposed level set method and apply it to OCT image data. Briefly, knowing a priori the maximum heart wall velocity, we estimate the maximum displacement (in pixels) of points on a user-defined initial heart contour per unit time. Then, the evolving 3D level set function is constrained using this maximum displacement estimate. We also exploit temporal correlation in images by setting the starting level set contour for a 2D image at a given time equal to the final contour of the previous time point, thereby reducing computational overhead. Our technique has greatly improved computation speed and accuracy of semi-automatic segmentation as compared to previously reported methods on 2D OCT images.
Ya Chen [1], Wen Li [1], Wei Li [1], Xin Yu [1]
[1] Department of Biomedical Engineering,Case Center for Imaging Research,Case Western Reserve University,Cleveland, OH
Calcium channel mediated Ca2+ cycling is central to the excitation-contraction coupling (ECC) in heart. Abnormal Ca2+ cycling is associated with contractile dysfunction and arrhythmogenesis. However, current investigation of ECC has largely relied on the characterizing of Ca2+ handling in isolated cells using fluorescence dyes. Manganese is a potent MRI contrast agent that enters the cell through the L-type calcium channels. Manganese-enhanced MRI (MEMRI) thus provides the potential for in vivo evaluation of Ca2+ uptake in myocardium. The objective of this study was to quantify manganese (Mn2+) uptake in hearts under altered physiological and biochemical conditions. We aimed to investigate that whether altered Ca2+ concentration can also change the dynamics of Mn2+ accumulation in myocardium.
Akhilesh K. Gaharwar, M.S [1], Patrick Schexnailder, Ph.D [1], Gudrun Schmidt, Ph.D [1]
[1] Weldon School of Biomedical Engineering, Purdue University, West Lafayette, Indiana
One of the goals in tissue engineering is to control the interaction between materials (scaffold) and cells to provide instructive clues for tissue regeneration. In particular, there is a great need for new biomaterials that not only withstand the demanding mechanical forces imparted within the biological milieu but also facilitate the formation of functional tissues. Nature offers inspiration for creating high-performance biomaterials from soft polymer and hard nanoparticle components. We have designed a set of silicate cross-linked poly(ethylene oxide) nanocomposites with a spectrum of physical, chemical and biological properties. Nanocomposites with properties ranging from viscoelastic soft and porous to hard and dense were developed. Enhanced surface interactions between polymer and nanoparticle result in unique property combinations that are not easily achieved by conventional methods. Addition of silicate significantly improves the stiffness of nanocomposites. Polymer crystallinity and hydration degree of nanocomposites decreases with an increase in silicate concentration. Degradation and drug elution properties of nanocomposites can be controlled by changing the cross-linker (silicate) concentration. Preliminary in vitro cell growth studies were performed on the nanocomposite formulations to evaluate the extent of cell-nanocomposite interactions. Addition of silicate promotes cell adhesion, spreading and proliferation of preosteoblast cells. Cell viability remains unchanged, regardless of the nanocomposite composition. Moreover, addition of silicate enhances alkaline phosphatase activity of the attached cells, indicating that the osteoblast phenotype was conserved. Our study also demonstrates the ability of silicate cross-linked nanocomposites to enhance the formation of mineralized extracellular matrix, thus offering new strategies for creating bioactive scaffolds. A strong correlation between microstructure, mechanical properties and cellular activity is observed. In the process, we have developed a new class of bioactive materials that can have potential applications in the regeneration of orthopedic tissues at the interface regions.
Sean Connell [2], Jian Gao [3], Jun Chen [3], Riyi Shi [1]
[1] Department of Basic Medical Sciences, Purdue University, West Lafayette, Indiana
[2] Weldon School of Biomedical Engineering, Purdue University, West Lafayette, Indiana
[3] School of Mechanical Engineering, Purdue University, West Lafayette, Indiana
Blast-induced neurotrauma (BINT) is the signature injury modality associated with the current war efforts and increasing levels of terrorist activity. Exposure to the shock-wave generated by explosive devices is responsible for many of the war related pathologies, including traumatic brain and spinal cord injury. The mechanism responsible for producing the injury is unknown. Recent evidence, however, suggests the forces generated by the shock-wave impact may be a critical component. Deformation of neuronal tissue in response to compressive and tensile forces generated by the shock-wave impact could cause permanent deficits by disrupting the structural integrity of axons. The following research investigates this hypothesis by developing a novel model system to introduce a small-scale shock-wave to an isolated section of rat spinal cord. High-speed shadowgraphy is used to visualize the propagating shock-wave and the impact event. Surface deformation of the tissue is correlated with the applied load to measure internal stresses and strain rates. Anatomical deficits are quantified by measuring axonal membrane integrity using a dye-exclusion assay. Ensuing functional deficits are measured using a double sucrose gap recording chamber to evaluate the electrophysiological properties of the spinal cord. This approach illustrates a clear relationship concerning the shock-wave impact, tissue deformation and resulting anatomical and functional deficits. Further application of this novel model will expose the pathogenesis of BINT and identify therapeutic targets to treat blast victims.
Elaine L. Lee, M.S. [1], Horst A. von Recum, Ph.D. [1]
[1] Department of Biomedical Engineering, Case Western Reserve University, Cleveland, OH
Cells implanted after injury may remodel undesirably with improper mechanical stimulation from surrounding tissue. Proper conditioning of tissue engineered constructs before implantation can lead to tissue architectures that more closely mimic native tissue. Additionally, cell implantation without bulky polymeric scaffolding is desirable. Previous researchers have created devices capable of applying mechanical forces to cells (eg, stretch), but cellular removal from these devices, such as by trypsin, results in irreversible damage. Conversely, devices are available that can detach intact cells, but are non-stretchable substrates. We have created a cell culture platform that allows for mechanical conditioning with subsequent non-damaging cell sheet detachment. We modified silicone culture surfaces with thermally responsive polymers of N-isopropylacrylamide (NIPAAm) to create an elastic substrate that can also change surface properties with temperature. The thermally responsive nature of P(NIPAAm) allows for cell attachment at 37degC, and spontaneous detachment at room temperature, allowing for cell removal from a culture surface without using damaging enzymes. A copolymer of NIPAAm and acrylic acid was conjugated to a commercially available amine-bonded silicone surface using carbodiimide chemistry. To determine detachment capability both before and after mechanical stretching, 3T3 and HL-1 cells were allowed to detach as the culture media was brought to room temperature over the course of 1 hr. Cells were conditioned using the Flexcell FX-4000 Tension System at 5% strain, 1 Hz for 24 hrs. Both before and after mechanical conditioning, cell sheets were able to attach to the resulting surfaces at 37degC and showed detachment by rounded morphology at 25degC. Cells also demonstrated greater alignment after stretching. This work has potential impact on future therapies using embryonic stem cells to construct replacement tissue, such as myocardium damaged in heart attacks.
Katie A. Ewing, B.S.E. [1], Miriam A. Manary, M.S. [2], Lawrence W. Schneider, Ph.D [2]
[1] Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI
[2] University of Michigan Transportation Research Institute, Ann Arbor, MI
INTRODUCTION: Many students with special healthcare needs remain in their wheelchairs during transport on school buses. Good fit of a crashworthy lap/shoulder belt is necessary to enhance occupant protection. However, belt restraints for wheelchair-seated drivers are often unused or misused due to a lack of knowledge of best-practice procedures. Although different standards that address school bus transportation exist, there are no defined zones for preferred locations of upper shoulder-belt anchor points that are expressed relative to landmarks in school buses where the same station must accommodate many wheelchair users. The purpose of this study is to define fore-aft locations and adjustment ranges for upper shoulder-belt anchor points in school buses relative to rear tiedown strap anchor points using optimal upper anchor point location data from 342 frontal-impact tests.
METHODS: During a frontal-impact test, the upper shoulder-belt anchor point is fixed to achieve optimal upper torso restraint, defined by a side-view angle between 30 and 45 degrees to the horizontal from the top of the occupant’s shoulder to the upper anchor point. Quantitative analysis of pre-test side-view set-up photos for a range of wheelchair types and crash-dummy sizes was performed. The interiors of two school buses were inspected and the heights of the window tops measured in order to determine the physical locations of the upper shoulder-belt anchor points.
RESULTS: Points corresponding to ± two standard deviations from the average horizontal distance of the upper shoulder-belt anchor point forward of the rear tiedown anchor point were graphed. The intersections of 30 and 45 degree lines through these points and the horizontal lines corresponding to the top-of-window heights for the two school buses gives the range of upper anchor point locations needed to achieve good shoulder-belt fit on potential student passengers seated in wheelchairs. This preferred range runs from approximately 737 mm (29 in) behind the rear wheelchair tiedown anchor points to 508 mm (20 in) forward of the rear tiedown anchor points.
CONCLUSION: The defined fore-aft adjustment ranges for upper shoulder-belt anchor points relative to wheelchair rear tiedowns will benefit school bus manufacturers, bus modifiers, and transportation providers by providing guidelines for where to locate upper anchor points to accommodate various wheelchair-seated occupants.
Hui Ouyang, B.S. [1], Yan Fu, Ph.D [1], Ji-Xin Cheng, Ph.D [1], Eric Nauman, Ph.D [3], Riyi Shi, M.D., Ph.D [2]
[1] Weldon School of Biomedical Engineering, Purdue University, West Lafayette, Indiana
[2] Department of Basic Medical Science, Purdue University, West Lafayette, Indiana
[3] School of Mechanical Engineering, Purdue University, West Lafayette, Indiana
Crush to the mammalian spinal cord leads to primary mechanical damage followed by a series of secondary biomolecular events. The chronic outcomes of spinal cord injuries have been well detailed in multiple previous studies. However, the initial mechanism by which constant displacement injury induces conduction block is still unclear. We therefore investigated the anatomical factor(s) that may directly contribute to electrophysiological deficiencies in crushed cord. Ventral white matter strips from adult guinea pig spinal cord were compressed 80% either briefly or continuously for 30 minutes. Immunofluorescence imaging and coherent anti-Stokes Raman spectroscopy (CARS) were used to visualize key pathological changes to ion channels and myelin. Compression caused electrophysiological deficits, including compound action potential (CAP) decline that was injury duration dependent. Compression further induced myelin retraction at the Nodes of Ranvier. This demyelination phenomenon exposed a sub-class of voltage-gated potassium channels (kv1.2). Application of a potassium channel blocker, 4-Aminopyridine (4-AP), restored the CAP to near pre-injury levels. To further investigate the myelin detachment phenomenon, we constructed a three-dimensional finite element model (FEM) of the axon and surrounding myelin. We found the von Mises stress was highly concentrated at the paranodal junction. Thus, the mechanism of myelin retraction may be associated with stress concentrations that cause debonding at the axoglial interface. In conclusion, our findings implicate myelin disruption and potassium channel pathophysiology as culprits to compression-mediated conduction block. This result highlights a potential therapeutic target for compressive spinal cord injuries.
Punkaj Ahuja [1], Sumitha Nair, Ph.D [1]
[1] Department of Biomedical Engineering, Case Western Reserve University, Cleveland, OH
We have recently developed an optical sensor array called the “sliver sensor” for simultaneous monitoring of electrolytes and metawwwbolites. The sensing scheme is based on color change of optode beads in response to changes in analyte concentration. Glucose sensing is achieved through an enzyme based pH-linked scheme. The response time to a change in glucose level is in the order of 5 minutes. With further optimization of the sensor design this could be improved further, desirable for some in vivo clinical applications. This optimization includes characterization of the individual optode beads for their response time, and dispersion of the beads in the sensor to ensure that analyte diffusion to the individual beads is fast. In this work we tested the beads individually for response time and their reversibility to pH changes. The results of the static and dynamic calibration experiments show that the beads are reversible and they respond in the order of a few seconds within the 5.0 to 8.0 pH range. These findings indicate that with proper dispersion of the beads within the glucose sensing capsule of the sliver sensor an overall sensor response time in the order of 2 minutes can be achieved for glucose sensing.
Akshay S. Pai, M.S. [1], Venkata S. Potunuru [1], Ravi K. Samala [1], Sergio D. Cabrera [1], Wei Qian [1]
[1] Department of Electrical and Computer Engineering, University of Texas at El Paso, El Paso, Texas
X-ray mammography is the current standard for breast cancer detection. It poses some heath risks owing to the ionizing radiations involved. Microwave imaging (MWI) can be a painless, non ionizing alternative. It relies on the high dielectric contrasts between normal and malignant tissues in the GHz frequency range. To add to the credibility of MWI, it is observed that the dielectric properties of the breast tissues from patient to patient do not vary significantly. A study of using the scatter signals for classification of the tumor presence is conducted numerically here. We use an Electromagnetic (EM) simulator to build a phantom breast model. A resistively loaded Ultra-Wide Band (UWB) dipole antenna is scanned to create a synthetic array around the phantom breast. This directional antenna is used to transmit and receive the UWB pulse signals in the frequency range of 4-8 GHz. The differences in the dielectrics of the tumor (5±9%) and breast tissue (50±7%) are useful to reduce the bias of the algorithm. Our classification is a two step model. In the first stage, due to the high number of data points generated during simulations, we need to identify the “informing” data set from it. This is performed using a multiscale wavelet principal component analysis. Due to its multiscale nature, they efficiently denoise the signal by soft thresholding. Thresholding kills the effect of the noise without killing the effect of the signal i.e. data containing significant contributions from events whose behavior is dependent on frequency are preserved in this case. In the second stage a neural network is used for classification which evaluates the average rate of correct classification as a performance measure. A near full detection rate was obtained at each wavelet resolution. This characterization of the scattered data could also be extended in classifying the shape and size of the target in conjunction with the main imaging procedure.
Sagar D. Joshi, M.S. [1], Lance A. Davidson, Ph.D [2]
[1] Department of Bioengineering
[2] Departments of Bioengineering and Developmental Biology, University of Pittsburgh, Pittsburgh, PA
Cell contraction is major developmental step by which cells shape tissues during morphogenesis. Cells actively deform 2D cell sheets into 3D pipes, furrows and ridges that provide a starting tissue structure to forming rudimentary organs. Previous studies in cell contraction have relied on the endogenous cell shape changes during development. We have devised two complementary approaches to induce contractions in embryonic epithelial cell sheets: laser-ablation of a single cell in a large sheet and nano-perfusion of cell lysate over the entire embryonic surface (1). We have identified that F-actin cytoskeleton reorganizes independently in response to both stimuli and the contractions occur over similar time-scales (1 to 2 min). We utilize these two systematic approaches to induce contractions where we can identify signalling factors (using nano-perfusion) and downstream sub-cellular changes (using laser-ablation). We have now identified extracellular ATP as one of the signaling factors in cell lysate responsible for triggering induced contractions. Current results demonstrate the importance of endogenous cellular contractility and the adverse effects of excessive contractions on development. The knowledge gained through these studies can prove to be very significant in building 3D tissue engineered constructs from 2D cell cultures.
1. Joshi, S. D., von Dassow, M., and Davidson, L. A., Experimental control of excitable embryonic tissues: three stimuli induce rapid epithelial contraction. Exp Cell Res 316 (1), 103 (2010).
Arun P. Mohan, M.S [1], Kinam Park, Ph.D [1], Ann Rundell, Ph.D [1]
[1] Weldon School of Biomedical Engineering, Purdue University, West Lafayette, Indiana
The objective of this research investigates the correlation between the glucose concentration in exhaled breath condensates (EBC) and that in blood for human subjects. A breath condensing unit was designed and built that controls the temperature of the system, flow rate, removes dead space and measures the volume of expired air while condensing the breath. The breath condensing unit consists of a preliminary chamber and condensing chamber. In the preliminary chamber a CO2 analyzer was built and placed in the system to ensure that dead space was removed, a one-way controllable valve served to make sure that the exhaled breath passed through the condensation chamber at a slow controlled flow rate, and both of these components were housed inside a chamber maintained at 37 degrees Celsius. This ensured that the exhaled breath did not condense in any region outside of the condensation chamber. The condensation chamber consisted of a polystyrene 20 mL pipette surround by dry ice. A pnuemotachograph was used to measure the total volume of expired air that passed through the dry ice condensation chamber. The breath condensing unit sought to control experimental variables and remove material interference that affected breath samples in previous designs of the experimental setup. Preliminary studies have found that we can condense 80 uL of EBC from 3 liters of expired air. A fluorometric assay used to measure the glucose present in the EBC was modified to increase its sensitivity due to the low-levels of glucose found in the EBC. The glucose levels in the EBC were found to be as low as 0.02 mg/dL. Ongoing IRB approved human subject studies in the Weldon School of Biomedical Engineering at Purdue University involve a collection of EBC and finger prick blood sample from volunteers before and after a meal to determine if there is a repeatable functional relationship between the glucose concentrations in exhaled breath and glucose concentrations in blood. It is expected that this relationship can be established for individual subjects, so that a new, non-invasive glucose measuring device using exhaled breath condensates (EBC) can be developed to provide diabetics with a more patient-friendly and non-invasive method to measure and regulate their glucose levels.
Madhumitha Ravikumar [1], Timothy Wong [1], Anirban Sen Gupta, PhD [1]
[1] Department of Biomedical Engineering, Case Western Reserve University, Cleveland, Ohio
Platelet transfusion plays a major role in the treatment of thrombocytopenia in patients with hematologic and oncologic platelet disorders. The clinically used transfusion therapies with allogenic platelet concentrates suffer from biologic infections, febrile non-hemolytic transfusion reactions, alloimmunization-induced refractoriness, and possibility of transfusion-associated immunosuppression. Moreover, the complex platelet-harvesting, processing, and storage methods are expensive, and the short shelf-life (5-7 days) of platelet concentrates result in severe shortages in supply. Hence, there is a significant clinical interest in designing a synthetic platelet substitute that can mimic hemostatic functionalities of platelets, while providing advantages of large-scale preparation, reproducible quality, long storage life, and absence of biologic infections. The two most important hemostatic functions of platelets are to form (1) a stable adhesion to specific matrix proteins (collagen and vWf) under physiological shear and (2) to aggregate via fibrinogen-mediated platelet bridging. Both functions require unique synergistic ligand-receptor interactions, and mimicking these interactions on a liposome platform provides a way to develop a synthetic platelet substitute. With this rationale, we have developed liposomes surface-modified with a fibrinogen-mimetic RGD peptide, having specificity to platelet integrin GPIIb-IIIa, and a GPIbá protein fragment having specificity to vWf. In-vitro studies were performed using fluorescently-labeled RGD-liposomes and GPIbá-liposomes under static and dynamic conditions, to test their binding to activated platelets and vWf-coated surfaces respectively. Furthermore, we have integrated these functionalities on a single liposome to study liposome-mediated aggregation of activated platelets on vWf-coated surfaces under shear. We envision that these hemostatically active liposomes can be effective in treating thrombocytopenia.
Todd Rickett [2], Vipuil Kishore, Ph.D. [1], Jorge Uquillas [1], Ozan Akkus, Ph.D. [1], Riyi Shi, M.D., Ph.D. [3]
[1] Weldon School of Biomedical Engineering, Purdue University, West Lafayette, Indiana
[2] Indiana University School of Medicine, Indianapolis, Indiana
[3] Department of Basic Medical Science, Purdue University School of Veterinary Medicine, West Lafayette, Indiana
When peripheral nerves are injured, patients can suffer loss of movement, sensation, and even permanent paralysis. For compound nerve injuries, conventional therapy consists of nerve autografts. Using native neural tissue provides an extracellular matrix that guides nerve regeneration through physical and chemical cues. However, removing autogenous nerve induces patient functional deficits and can cause painful neuromas. Artificial nerve grafts can be engineered to use materials native to the neural environment and to stimulate nerve healing. The predominant protein in peripheral nerve, collagen, is used in existing conduits, though their manufacture fails to impart any physical cues. We have prepared fibers of aligned collagen that we expect will provide contact guidance to improve nerve healing relative to grafts of randomly oriented collagen.
These collagen fibers were prepared through a process of isoelectric focusing, aligning protein fibrils prior to being crosslinked . The control fibers were prepared by polymerizing sheets of collagen deposited without a charge gradient. Atomic force microscopy showed that fiber diameters ranged from 300-600 µm, and the surfaces of the experimental scaffolds demonstrated a high degree of alignment compared to controls. The underlying orientation was shown to influence cells cultured on these fibers. Glial cells cultured on aligned surfaces were more oriented than on random scaffolds, while dorsal root ganglia extended neurites that were 111% longer. Alignment increased the rate of Schwann cells migration by 35%.
Collagen fibers were implanted into a 1 cm gap in rat sciatic nerves and compared to autograft. Animals were allowed to recover for 9 weeks before nerve function was assessed through electrophysiological stimulation and walking track analysis. Immunohistology of excised grafts showed a high density of axons within the collagen implants. For all measures, the synthetic grafts were found to perform at levels comparable to autograft.
In summary, cultures of dorsal root ganglia and Schwann cells grew significantly longer and straighter on aligned substrates than non-oriented collagen. Also, cell proliferation and migration were found to be accelerated by fiber alignment. In the rat sciatic nerve transaction model, functional recovery through the collagen grafts occurred commensurate with autograft, and histological regeneration was similar between the experimental and standard therapies.
Anil K. Thota, M.S. [1], Dominique Durand, Ph.D. [1]
[1] Department of Biomedical Engineering, Case Western Reserve University, Cleveland, Ohio
Deep brain stimulation (DBS) has become a standard therapy for treating advanced Parkinson’s disease (PD), Essential tremor (ET), Dystonia and several psychopathological conditions such as depression and obsessive compulsive disorder. Successful treatment of the pathological symptoms of these diseases depends on the accurate positioning of electrode leads in the target area and optimization of the stimulation parameters post operatively. Accurate positioning of the electrode leads has been most successful by using CT/MRI image guiders in combination with intra-operative microelectrode recordings. However, programming the stimulators for optimal settings is still underachieved as this process is empirical and depends on the experience of the programmer and the subjective assessments of motor function where clinically the Unified Parkinson Disease Rating Scale (UPDRS) is often used.
We have designed an adaptive deep brain stimulator circuit that can automatically adjust the stimulation parameters by utilizing tremor as a control signal. This device consists of 1) an accelerometer for measuring the tremor signal 2) full wave rectifier, low pass filter and adder for signal processing and 3) frequency generator and pulse width modulator for stimulator pulse generation. This hardware circuit was tested with three signals: 1) imitated hand tremor signal generated by an able bodied subject, 2) signals generated by a tuning fork tapping gently on the prongs and 3) simulated sinusoidal signals (2-100Hz). As the imitated hand tremor amplitude increases, the pulse width of the stimulation pulses increased from 80 to 300 microseconds while tuning fork tremor pulse width increased up to 400 microseconds. The stimulator output pulse widths increased with increasing sinusoidal frequencies and reached a plateau after 10 Hz. These results indicate that tremor signals can be used as a control signal for generating adaptive deep brain stimulation pulses.
This adaptive stimulation approach can be scaled and implemented in patients who are currently using DBS therapy. The system ccould be tailored to each patient’s unique electrode placement, anatomy of the brain targets and pathological conditions. Successful implementation could substantially reduce the subjective input of the DBS programmer in PD or ET patients. The output current should be robust since it is based upon a quantitative analysis of pathological symptoms rather than the qualitative nature of the UPDRS. This approach of adaptive stimulation could be important not only for a better treatment but are also cost effective and time caring. Financial support was provided by the Biomedical Engineering department of CWRU.
Srividya Sundararaman, MS [1], Vinod Labhasetwar, PhD [2], Marc S Penn,MD, PhD [1]
[1] Stem Cell and Regenerative Medicine, Cleveland Clinic, Cleveland OH
[2] Biomedical Engineering, Cleveland Clinic, Cleveland OH
[3] Cleveland State University, Cleveland, OH
Gene therapy has evolved as a promising option to deliver pro-angiogenic proteins to infarct zones, thus providing cardiac benefit. We have identified a gene design without viral promoters, using the ubiquitously-expressing CMV promoter and transcription enhancers, to improve the length and magnitude of gene expression as compared to traditional naked plasmid deliveries. Using this design, we delivered therapeutic levels of a pro-angiogenic protein, Stromal Derived Cell Factor-1 (SDF-1), in rodents and pigs with chronic heart failure, by direct injection in the border zone, thereby improving cardiac function. To target cardiac myocytes in the infarct zone, we generated a vector with a cardiac-specific αMHC promoter with increased expression of the gene using the transcriptional enhancers, to provide therapeutic levels of SDF-1 in the infarct zone.
However, to deliver the SDF-1 plasmid, via intra-venous infusion, and for targeting it to the infarct zone, we have developed nanoparticulate gene (drug) carriers bearing an infarct-specific peptide. The infarct-specific peptide was identified with the help of phage panning. Briefly, rats were infused with 10(x11) colony forming units of M13 bacteriophage, each bearing a 7-amino acid peptide sequence. The peptides that attached to the infarct region of the heart were identified, amplified, and re-panned for 3 cycles to identify a 7-mer sequence. Studies, in rats with ischemic cardiomyopathy, using i.v. infusion of this peptide coupled with a 6-His tag revealed no binding to the lung, liver, spleen or kidney.
In order to test the delivery system, we encapsulated a fluorescent dye, 6-Coumarin (6C), in poly(lactic-co-glycolic acid) (PLGA) nanoparticles, and targeted them to the infarct zone, with the infarct-specific peptide bound to the nanoparticle surface. Infusion of these nanoparticles, in vivo, revealed significantly greater uptake of the 6-coumarin in the infarct zone, as compared to the healthy heart, indicating successful encapsulation, as well as, targeting.
By replacing 6C with αMHC driven SDF-1 gene, we will be able to implement cardiac gene transfer via i.v. delivery and improve cardiac function, which may be translatable to the clinical setting.
Hyun-Joo Park, M.S. [1], Dominique Durand, Ph.D. [1]
[1] Department of Biomedical Engineering, Neural Engineering Center, Case Western Reserve University, Cleveland, Ohio
Functional electrical stimulation (FES) can restore volitional motor control of patients with spinal cord injury or neurological diseases by stimulating the paralyzed muscles directly or the peripheral nerves innervating the muscles. Flat Interface Nerve Electrode (FINE) is a type of nerve cuff electrode which improves the fascicular and subfascicular selectivity by reshaping a nerve trunk and realigning the fascicles inside the nerve. There have been many researches regarding the improved selectivity of FINE. However, the motion control of neuromuscular skeletal systems using a multi-contact nerve electrode such as FINE is a challenging problem due to inherent complex properties of the systems and nerve electrode interface. In addition, it is practically implausible to obtain an accurate mathematical model for control purposes due to the lack of noninvasive methods to measure the muscle force and fascicular distribution inside a nerve. In this research a novel motion control algorithm for FES has been developed without time consuming mathematical modeling procedure. The proposed algorithm finds an inverse dynamic model of a redundant neuromuscular skeletal system efficiently by separating the static and dynamic properties. To show the validity of the proposed control algorithm, both simulation study and animal experimental study were conducted. The human computational model has the ankle joint system with 12 muscles and the finite element model of the sciatic nerve with a 16 contact FINE. In the animal experimental study, a FINE was placed on the rabbit sciatic nerve to control the motion of the ankle joint. The results in both the simulation study and the animal experiments showed the good tracking performance of the proposed controller within 10% RMS errors for various reference trajectories.
Shriram Raghunathan, B.S [1], Sumeet K. Gupta, M.S [2], Kaushik Roy, Ph.D [2], Pedro P. Irazoqui, Ph.D [1]
[1] Weldon school of Biomedical Engineering, Purdue University, West Lafayette, Indiana
[2] School of Electrical and Computer Engineering, Purdue University, West Lafayette, Indiana
Epilepsy is currently the second largest neurological disorder in the world after stroke. Roughly 2% of the world’s population and over 2 million people in the United States alone are diagnosed with epilepsy. Neurostimulation is a promising new therapy that is rapidly emerging as an alternative therapy for the 30% of epileptics that do not respond to pharmacological treatment or are not candidates for resective surgery. Efficient seizure detection algorithms will enable development of closed-loop epilepsy prostheses by stimulating the epileptogenic focus within an early onset window. Stimulation on demand, or responsive stimulation, is expected to reduce neuronal desensitization over time and lead to longer-term efficacy.
We have been developing solutions for a miniature implantable epilepsy prosthesis that combine electrical stimulation with an efficient combination of real-time seizure detection algorithms on an integrated circuit package that can be powered by a standard battery. Integrating the signal processing capabilities at the recording source eliminates the need to transfer data out of the patient, thereby removing the wireless data rate bottleneck and also the need for cables connecting to the patient. However, the signal processing capabilities are significantly limited by the amount of power that the battery powered device can consume. We have proposed an event-based detection algorithm that trades off computational complexity for low-power hardware feasibility using digital CMOS circuit blocks. The proposed algorithm can also be used in combination with multiple detection algorithms to significantly decrease the false positive rates, with a negligible increase in hardware cost.
We present animal validation results for the event-based detection algorithm and also present preliminary results that use the algorithm in combination with previously reported seizure detection features to demonstrate its role in improving the efficacy at minimal additional hardware cost. The algorithm was fabricated using 180nm CMOS digital circuits on the MIT FD-SOI process and designed to operate with a supply voltage of 250mV consuming less than 350nW of power from extracted simulations. The microchip is currently under fabrication at the MIT Lincoln Lab foundries. The design trade-offs reported would facilitate the development of multi-algorithm detection modules that share common hardware that is optimized for low-power operation, enabling the rapid development of implantable epilepsy prostheses.
Sarah McBride, MS [1], Ulf Knothe, MD [3], Stefano Brianza, DVM, PhD [1], Scott Dolejs, BS [1], Melissa Knothe Tate, PhD [1]
[1] Department of Biomedical Engineering, Case Western Reserve University, Cleveland, OH
[2] Department of Mechanical and Aerospace Engineering, Case Western Reserve University, Cleveland, OH
[3] Cleveland Clinic Foundation, Cleveland, OH
[4] AO Foundation, Davos Switzerland
The periosteum, a bilayer membrane that envelopes bones, is a major contributor of progenitor cells during bone fracture and segmental defect healing. Recent in vitro cell studies show that mesenchymal stem cells and osteochondroprogenitor cells are 1000× more sensitive to mechanical stimuli than terminally differentiated cells such as osteoblasts. We hypothesize that areas of periosteum subjected to tensile or low compressive strain will exhibit more bone formation within a large defect in the first two weeks after surgery than areas subjected to high compressive strain.
Sheep femora were treated surgically (IACUC approved in the Canton of Grisons, Switzerland), identical to previous studies, and then subjected to compression via the femoral head, while strains were measured optically via digital image correlation (MatLab, Mathworks, Natick, MA) of high definition digital images (PDW-7000, Sony Co., NY). Strains from all views for all bones (n=3) were evaluated and compiled to estimate the strain distribution around the circumference of the central periosteal flap during loading. Then, histological samples from a parallel in vivo study were analyzed to relate areas of new bone formation to the strain distribution measurements of the current study. Cross sections (~4 sections per bone, n = 4 bones) from the center of the defect zone were imaged at high resolution (Leica DMIRE2, Mannheim, Germany) and analyzed using MatLab to determine the spatial distribution of the calcein green label, an intravitally administered fluorochrome label that chelated to mineralizing bone at 1-2 weeks, with respect to the anterior, posterior, medial and lateral axes.
Image processing and analysis allowed us to determine relationships between strain distribution and initial bone apposition in the one-stage bone transport technique. In the one stage bone transport procedure, cells within the periosteum surrounding the critical sized defect are exposed to a spatially and temporally varying strain field as the sheep bears weight on the operated limb. Loading of the femur in compression subjects the posterior side of the periosteal sheath to tension, while all other observed areas experience compression. Areas of greatest proliferative woven bone generation in the first two weeks after surgery correspond to areas exposed predominantly to tensile or low compressive strains.
Zhilei L. Shen, M.S.Eng. [1], Mohammad Reza Dodge, Ph.D. [1], Harold Kahn, Ph.D. [2], Roberto Ballarini,Ph.D. [3], Steven J. Eppell,Ph.D. [1]
[1] Department of Biomedical Engineering, Case Western Reserve University, Cleveland, Ohio
[2] Department of Materials Science and Engineering, Case Western Reserve University, Cleveland, Ohio
[3] Department of Civil Engineering, University of Minnesota, Minneapolis, Minnesota
To fully understand the mechanical behavior of collagenous tissues such as bone and tendon, and to predict their behavior using biomimetic multiscale models, requires mechanical tests at different length scales. However, experimental data are lacking on collagen fibrils with diameters of a few hundred nanometers. To fill this gap, we developed a novel method based on Microelectromechanical Systems (MEMS) technology allowing in vitro uniaxial tensile tests to fracture type I collagen fibrils isolated from sea cucumber dermis. Thirteen fibril specimens with diameters of 210-910 nm and gauge lengths of 6.0-18.0 µm were monotonically stretched to fracture in 1X phosphate buffered saline (PBS) at room temperature. We found substantial variability in mechanical behavior among the specimens and grouped them into three types: (I) a relatively linear region all the way up to brittle fracture, (II) multiple linear regions prior to brittle fracture, (III) an initial linear region, followed by a yield region and a step-wise post-yield region prior to fracture. The elastic modulus obtained from least-squares fits to the initial linear regions of the fibrils was 470 ± 410 MPa, significantly lower than that obtained from previous in air experiments (860 ± 450 MPa). The fracture strength was 230 ± 160 MPa, while the fracture strain was 80% ± 44%. To our knowledge, these are the first measurements of in vitro fracture behavior of isolated collagen fibrils.
This work was funded by National Science Foundation grant 0532320 and National Institutes of Health grant 1 R21 EB004985-01A1.
Yunzhou Shi [1], Terry Huff, Ph.D [1], Sungwon Kim, Ph.D [1], Kinam Park, Ph.D [1], Ji-Xin Cheng, Ph.D [1]
[1] Weldon School of Biomedical Engineering, Purdue University, West Lafayette, IN
[2] Department of Chemistry, Purdue University, West Lafayette, IN
[3] Department of Industrial and Physical Pharmacy,Purdue University, West Lafayette, IN
Spinal cord injury (SCI) is the damage to the spinal cord that results in devastating functional deficit such as mobility, breathing, bladder control and pain sensation. Approximately 450,000 people are now living with SCI in the US with an annual incidence of 12,000 new cases. There are no standard effective therapies for SCI as yet due to the complication of the pathology. The goal of our research is to understand the pathology and develop effective treatments for SCI.
To image the dynamics after SCI with high resolution, we developed an in vivo imaging platform with micron range resolution based on nonlinear optical microscopy. We have applied the imaging platform to demyelination and remyelination in rats after SCI. To further analyze the chemical changes after SCI, we adopted a newly developed desorption electrospray ionization imaging mass spectrometry method. These tools allowed us to investigate the molecular dynamics after SCI that could not be detected before, as well as screen the potential treatments and evaluate the therapeutic effects.
Meanwhile, we have also been focusing on the repair of SCI by sealing the damaged membranes in the early stage. We have shown that axonal membranes injured by compression can be effectively repaired by using nanosized monomethoxy poly(ethylene glycol)-poly(D,L-lactic acid) di-block copolymer micelles (60 nm diameter). Intravenously injected micelles effectively recovered the locomotor function and reduced the volume and inflammatory response of the lesion in SCI rats. The micelles showed no adverse effects after systemic administration to live rats.
With the new treatment we have discovered, we will further examine its clinical relevance and subsequently improve the formulation. We hope that our advances in the analytical tools will help us to discover more fundamentals in SCI and facilitate drug screening.
Jainu Jogani, B.E. [1], Jacob Sony, M.D. [2]
[1] Department of Biomedical Engineering, Wayne State University, Detroit
[2] Division of Cardiology, Wayne State University, Detroit.
Permanent implantable Cardiac Rhythm Devices (CRDs) like Pacemakers and Implantable Cardioverter Defibrillator (ICDs) are more frequently used for arrhythmic disorders. Roughly, about 160,000 ICDs and 280,000 pacemakers were implanted in patients in North America alone as of 2006. The current devices are built in with more sophisticated features including reduced size and wireless communication. Although, the convenience of data storage, retrieval and communication is evident, the risk of less security to the device communication strategies is a concern to patient safety.
The CRD circuit consists of programmable micro-circuit with a trans-receiver antenna & magnetic switch. The magnetic switch can either be a reed switch or giant magnetic resistor that gates the communication of the rest of circuit with external programmer. When kept in a magnetic field of appropriate strength, the devices communicate with the programmer after ‘handshaking’. The list below shows the magnetic field and handshaking frequency:
Magnetic Field (mT) Handshake Frequency
Medtronic 3.0 175Khz
Boston Scientific (Guidant) 1.0 50kHz
St. Jude Medical 2.25 8kHz
ELA Medical 1.35 8kHz
Biotronik 2.0 32kHz
We made a simple RC series antenna circuit to test the CRD’s the output signal on a 4 GSa/s oscilloscope. Seven CRDs from the five major manufacturers were tested: The signals from all the CRDs were decoded to extract information. Besides being dependent on distance, the signal strength was also dependent on the position of the magnet. Some devices required continuous magnet placement for interrogation, however, others emitted the signal up to 10s even after the magnet was removed. This concludes that if these devices are made to communicate at their particular frequency, entrenching and re-programming can possibly be done. Thus data access and device identification can be done easily by decoding this signal.
The easy accessibility of the communication signal spectrum of the devices makes the safety of CRDs very vulnerable. Innovations and more research are warranted in this area to protect these signals from being interacted other than any authentic device.