Kanav Jain [1], Taylor B. Updegrove [2], Roger M. Wartell [2]
[1] The Wallace H. Coulter Department of Biomedical Engineering at Georgia Tech and Emory, Atlanta, Georgia
[2] School of Biology, Georgia Institute of Technology, Atlanta, Georgia
Small RNA (sRNA) segments in bacteria have been found to bind to the 5’ leader region of messenger RNAs (mRNAs) and regulate the translation that follows the start codon. In turn, sRNA-mRNA interaction is modulated in numerous ways by Hfq, a hexameric sRNA-binding protein. In one case, DsrA sRNA is thought to bind to the leader region of the RpoS stress-sigma factor mRNA in order to regulate its translation. However, when the pair is run through partition-function-based interaction site prediction software RNAup (http://rna.tbi.univie.ac.at/cgi-bin/RNAup.cgi), the lowest free energy site found in silico does not match that found in vivo and in vitro. Permutational stem loop mutations made in the software analysis – i.e., running every possible set of nucleotides for the length of one side of hairpin stem I in place of the wt DsrA – returned an accurate binding location for select permutations. Hfq could be the factor destabilizing the hairpin stems, and this could be checked in vitro; in melting curve analyses, 1.5 µM Hfq was found to lower the Tm of DsrA domain I from 62°C to 51°C. The permutation algorithm can easily be extended to more cases to ultimately determine which mutations will ultimately modulate translation.
Muhammad Qasim, B.S. [1], Jae T. Hong, MD, PhD [2], Raghu N Natarajan, PhD [3]
[1] Department of Bioengineering, University of Illinois at Chicago, Chicago, IL, USA
[2] Department of Neurosurgery, Catholic University of Korea, St. Vincent’s Hospital, Suwon, South Korea
[3] Department of Orthopedic Surgery, Rush University Medical Center, Chicago, IL, USA
Posterior cervical screw instrumentation has been broadly used for cervical spine instability and spinal deformity and has been reported to induce higher fusion rates and obviates the need for rigid external mobilization. Lateral mass screws are relatively safe but screw loosening has been documented as a failure mechanism particularly in the lower cervical spine. Screw fixation into the cervical pedicle has been proposed as an alternative to lateral mass. However, their use in the cervical spine region can be technically difficult and potentially dangerous, as the cervical pedicle is small and is immediately surrounded by delicate structures: vertebral artery (VA), spinal cord, and adjacent nerve roots. Recently, intralaminar screws have been used as an alternative to traditional fusion constructs. This technique has two key advantages over the currently used surgical options: first, it is simpler and does not require the use of any navigational instruments, and second, it is not limited by the position of known vascular structures. However, to date, no biomechanical comparisons of the C7 intralaminar screw technique with lateral mass screw or pedicle screw technique have been performed.
A three dimensional finite element model of an intact C6-C7 cervical spine segment was developed using serial axial CT scans. The vertebrae, endplates and the intervertebral disc were modeled as 3D solid element with free-form meshing. The facets were modeled as 3D solid moving contact surface element with free-form meshing between the superior and the inferior surfaces. Five ligaments: anterior longitudinal ligament, posterior longitudinal ligament, interspinous ligament, ligamentum flavum and capsular ligaments were modeled. Material properties were adopted from literature. Finite element models representing three different cervical anchor types (C7 intralaminar screw, C7 lateral mass screw, C7 pedicle screw) were developed by modifying the intact model. Range of motion (ROM) and maximum von Mises stresses in the vertebra for the three screw techniques were compared under pure moments in flexion, extension, lateral bending and axial rotation.
The study demonstrated that the pedicle screw fixation is the strongest instrumentation method for C7 fixation. However, if C7 pedicle fixation is not favorable, the C7 laminar screw can be a better option compared to C7 lateral mass screw because the stress and ROM of C7 laminar screw construct is smaller than those of C7 lateral mass screw construct.
Paul A. Shields B.S. [1], Jeff VanOss, B.S. [1], Anderson Peck, B.S. [1], Chris Dickson, B.S. [1]
[1] Padnos School of Engineering, Grand Valley State University, Allendale, Michigan
INTRODUCTION: Laparoscopic surgery is a minimally invasive surgical technique in which operations are performed in the abdomen using one or more small incisions and a specialized camera system. Demand for safe and efficient training techniques has been met with primitive inexpensive “box trainers” and more physiologically accurate but prohibitively expensive virtual reality systems. The purpose of the Electronic Laparoscopy Trainer is to provide an addition to existing box trainers that allows training efficiency increases in a cost effective package.
METHODS AND MATERIALS: A new device designed with input from surgeons and educators at Grand Rapids Medical Education Partners was developed. The device consists of a circuit board with an Atmel AVR Xmega series microcontroller that controls interactive light up tiles with touch sensors. An LCD display and USB interface provide feedback and data collection. The Electronic Laparoscopy Trainer creates an interactive programmable surface inside an existing box trainer. The device can light up any number of its twenty-four touch sensitive tiles on its 5.5”x3.5” play surface with up to seven colors indicating desired input from the trainee. Data gathered from the accuracy and speed of the trainee’s responses is collected and displayed or stored for later evaluation.
CONCLUSIONS: The Electronic Laparoscopy Trainer is versatile and capable of being programmed to simulate a large variety of games and training procedures. The device is being evaluated by surgeons and educators at Grand Rapids Medical Education Partners.
Amit Paul, B.S. [1], Sumaira Yahya, B.S. [1], Shan Sun, Ph.D [1], Michael Cho, Ph.D [1]
[1] Department of Bioengineering, University of Illinois at Chicago, Chicago, Illinois
Cellular mechanics play a crucial role in the fundamental cellular functions such as adhesion and migration, proliferation, and differentiation. Recent evidence suggests that stem cell differentiation can be regulated by modulation of the cell's biomechanics. The cytoskeletal structures and arrangements in mesenchymal stem cells (MSCs) undergoing differentiation are dramatically altered, and these altered mechanics are lineage-dependent. As a specific example, during adipogenic differentiation of human MSCs, the actin stress fibers are reorganized rapidly in order to support the round cell morphology of adipocytes, and this results in a lower Young's modulus of the cell. The complexity of events associated with the transformation of these precursor cells leaves many questions unanswered about morphological, structural, proteomic, and functional changes in differentiating stem cells. A thorough understanding of stem cells' behavior, both experimentally and computationally, would allow development of more effective approaches to the expansion of stem cells in vitro and for the regulation of their commitment to a specific phenotype. We have therefore investigated the lineage-dependent mechanical changes in stem cells using quantitative fluorescence microscopy, atomic force microscopy (AFM), and laser optical tweezers (LOT). With the abundance of quantitative experimental data, we also developed a sophisticated model utilizing the cellular image analysis programs MetaMorph and CellProfiler, as well as the computational cellular modeling software SimBiology (Matlab program) that can predict critical changes in the stem cells and simulate experimental results.
Chia-Fang Chang, B.S. [1], Ameya S. Walimbe, B.S. [1], Jeremy C. Koehler, B.S. [2], John J. Whalen, B.S. [1]
[1] Department of Biomedical Engineering, University of Michigan, Ann Arbor, Michigan
[2] Department of Mechanical Engineering, University of Michigan, Ann Arbor, Michigan
Each year, 5.7 million Americans are clinically diagnosed with refractory Gastroesophageal Reflux Disease (GERD), characterized by chronic stomach acid reflux that is insensitive to both lifestyle modifications and pharmaceutical treatments. The most widely available treatments for these patients are endoluminal anti reflux procedures, including EndoCinch plication and EsophyX transoral incisionless fundoplication, and the more drastic Nissen Fundoplication. These endoluminal treatments involve stitching the gastroesophageal tissue in order to restore the natural anti reflux barrier of the lower esophageal sphincter (LES), a ring of muscle regulating entry to the stomach, although their efficacy in terms of decreasing long-term acid exposure has not been established. As such, patients often must rely on Nissen Fundoplication for relief. However, because Nissen Fundoplication is invasive, irreversible, and can lead to complications such as dysphagia and bloating, new methods to effectively treat refractory GERD are necessary. We propose a novel, long-term solution to treat refractory GERD by using an esophageal prosthesis to prevent retrograde acid flow while maintaining normal physiological function. Our device, a silicone band molded over a nitinol frame strengthens the anti reflux barrier by adding a compressive pressure on the LES. The prosthesis deforms to allow food to pass uninhibited during swallowing and opens to release air and vomit during eructation and regurgitation, respectively. In the absence of these events, however, the band compresses the LES to prevent acid reflux from damaging esophageal tissue. As the prosthesis will be inserted laparoscopically around the distal esophagus, and can be adjusted or removed at a later time if necessary, it is both minimally-invasive and reversible. The device successfully established a physiologic pressure differential in an ex-vivo porcine esophagus as well as passed a representative food bolus test. Further development of this design concept is warranted to achieve the goal of long-term acid reflux prevention in refractory GERD patients.
John Paderi, Ph.D [2], Kate Stuart, Ph.D [2], Alyssa Panitch, Ph.D [1]
[1] Weldon School of Biomedical Engineering, Purdue University, West Lafayette, IN
[2] Glytrix LLC, West Lafayette, IN
Borrowing from biology, we have designed synthetic molecules inspired by native tissue components, which have wide application for tissue healing and regeneration. The engineered biomimetic molecules, termed collagen-binding peptidoglycans, mimic native proteoglycans that are ubiquitous in collagenous tissues. The peptidoglycan binds specifically to collagen where it has numerous functions including 1) coating collagen and preventing platelet adhesion and activation 2) preventing MMP mediated collagen degradation 3) modulating collagen architecture and enhancing tissue mechanical properties 4) stimulating endothelial cell adhesion/migration through activation of local growth factors FGF-2 and FGF-10. The peptidoglycan has been engineered for use in dermal wounds, with demonstrated efficacy for scar-free healing in a rat model. It has also been formulated for use during balloon angioplasty where it is delivered through a drug-eluting balloon and has shown great promise for safely preventing thrombosis and intimal hyperplasia in a pig model. It can be used with or without stents, and is thus able to address needs in peripheral, cerebral, and coronary artery disease. The synthetic peptidoglycans can be easily manufactured in large quantities and therefore have great potential for development and translation to clinical use.
Codie T. Wilson, M.S. [1]
[1] Department of Electrical and Computer Engineering, Grand Valley State University, Grand Rapids, Michigan
Surface EMG was recorded from the medial hamstrings of eight subjects during voluntary concentric contraction against minimal weight resistance at a velocity of approximately 120 deg/s, and passive extension by a physical therapist at velocities of approximately 120 deg/s and 350 deg/s. Four of the subjects had typical development (TD), and four had cerebral palsy (CP) and spasticity in the hamstrings with a Modified Ashworth Score (MAS) >= 2. Both the continuous wavelet transform (CWT) and the Choi-Williams distribution were used to produce instantaneous median frequency (IMDF) curves for each activity, from which statistical observations were made. Results show that the median frequency and 95% bandwidth of the EMG signals were consistently higher in subjects with CP then with TD when comparing voluntary contraction. The slopes of the regression lines fitted to the IMDF curves were greater for the group with CP than for the group with TD during voluntary contraction in all cases as well. Within the group with CP, passive extension yielded consistently lower median frequencies and regression line slopes than during voluntary contraction. It is concluded that this type of analysis may lead to clinically relevant information regarding spasticity. Additionally, while both the CWT and Choi-Williams distribution gave similar qualitative results, the CWT was found to be a better analysis tool for this study.
Golnar Doroudian, B.S. [1], Anjulie Gang [1], Matthew Curtis, M.S. [1], Brenda Russell, Ph.D [1]
[1] Department of Bioengineering, University of Illinois at Chicago, Chicago, Illinois
[2] Department of Physiology and Biophysics, University of Illinois at Chicago, Chicago, Illinois
Human bone-marrow-derived mesenchymal stem cells (hMSCs) are an attractive cell source for regeneration of damaged tissue. The objective is to understand how mechanical cues affect the proliferation and differentiation of hMSCs into heart, muscle, bone or nerve cell lineages. The approach used is to deliver known mechanical inputs to hMSCs grown in culture on flat two-dimensional surfaces, or on substrata with microposts measuring 15 micrometer high and spaced 75 micrometer apart. These were mounted in a BioFlex device to provide cyclic straining (10%) at 1Hz frequency for 48 h (n=5). The effects of cyclic strain and microtopography on hMSC behavior were compared by shape and size of nuclei and cells, cytoskeletal organization with actin staining, and microarray analysis. When the combination of stimuli was provided, cells were elongated and spanned from micropost to micropost; whereas with only microtopography, the cells were more rounded and clustered near the microposts. The length/width ratio of the nuclei was highest with both strain and microtopography, and the nuclear surface area was greater on flat surface with or without straining. Microarray analysis showed approximately 6000 genes were significantly affected by cyclic strain with or without microtopography. Pathways of actin cytoskeletal organization, bone development and cell growth were altered with cyclic strain alone. However, the addition of microtopography had no effect on genes for migration, hypoxia, skeletal system and heart development. Interestingly, combined cues of strain and topography were most notable in cell proliferation. The protein/RNA/DNA ratio was the same in all conditions suggesting that cells change in number but not in size or protein mass. Altogether, the results show that physical stimuli of cyclic strain and microtopography differentially affect the biological processes of hMSCs. Therefore, attention to mechanical stimuli in the creation an artificial stem cell niches is essential for advanced applications for regenerative medicine. (Funded by NIH HL0905230).
Amy E. Ross [1], Mary Tang [2], Bao-Shiang Lee [3], Richard A Gemeinhart [2]
[1] Department of Bioengineering, University of Illinois at Chicago, Chicago, Illinois
[2] Department of Biopharmaceutical Sciences, University of Illinois at Chicago, Chicago, Illinois
[3] UIC Research Resources Center, University of Illinois at Chicago, Chicago, IL
Matrix metalloproteinase-2 (MMP-2) is an extracellular matrix (ECM) degrading enzyme that is overactivated in many forms of cancer, including brain tumors. We have developed an implantable chemotherapy system in which the drug is attached throughout the matrix of a poly(ethylene glycol) diacrylate (PEGDA) hydrogel via an MMP-2 cleavable peptide. MMP-2 cleaves the peptide, resulting in drug release from the hydrogel.
PEGDA hydrogels (Mn=3400) were fabricated using the MMP cleavable peptide sequence GPLGVRG with the model drug, fluorescent molecule tetramethyl rhodamine (TAMRA), attached to the C-terminus of the peptide. Hydrogels were swollen in deionized water to determine the swelling ratio and mesh size. Release studies with MMP-2 were conducted by incubating the hydrogels in tris-buffered saline with or without MMP-2 and measuring the buffer fluorescence. These studies demonstrated a greater release of TAMRA in the presence of MMP-2. In vitro studies were conducted by inserting the hydrogels in collagen with embedded U-87 MG cells to provide a 3-D model of a tumor environment. Gelatin zymography confirmed the production of MMP-2 by U-87 MG cells. High-pressure liquid chromatography (HPLC) and mass spectrometry (MS) demonstrate cleavage of the peptide released from the hydrogel in the presence of cells. These data indicate that MMP-2 can be utilized to mediate release from a hydrogel-based controlled drug delivery system.
Darcy E. Wagner, B.S. [1], Joseph Lawrence, PhD. [1], Sarit Bhaduri, PhD. [1]
[1] Department of Biomedical Engineering, University of Toledo, Toledo, Ohio
[2] Department of Mechanical, Industrial, and Manufacturing Engineering, University of Toledo, Toledo, Ohio
[3] Department of Mechanical, Industrial, and Manufacturing Engineering and Department of Surgery, University of Toledo, Toledo, Ohio
Calcium phosphate transfection has been a standard laboratory procedure for transfection of a variety of cell lines. The inconsistencies often reported are predominantly due to the high variability that can exist during the synthesis of calcium phosphate nanoparticulates. The previously reported methods rely on a chemical precipitation method performed at room temperature to synthesize spherical nanoparticles. The particles produced from these methods are largely amorphous and therefore have low stability in aqueous environments. Additionally, the nanoparticulates tend towards the hydroxyapatite (HA) phase which has limited biodegradation. Other phases of the calcium phosphate system may be more efficient due to their potential to interact uniquely with the cellular environment. Here, we introduce a novel synthesis method to produce highly crystalline calcium phosphate nanowhiskers (ie. high aspect ratio) of HA, tricalcium phosphate (TCP) and the biphasic variant for nonviral gene delivery. The nanowhiskers were produced by a microwave assisted combustion synthesis method using NaNO3, Ca(NO32-4H2O, KH2PO4, HNO3, and urea. The different compositions vary from one another in their ratio of calcium to phosphate (Ca/P). The Ca/P of HA and TCP, are 1.67 and 1.5, respectively, while biphasic nanowhiskers contain both HA and TCP. Calcium phosphates, in particular hydroxyapatite, are known to be major constituents of bone and are bioactive both in vitro and in vivo. In addition, TCP is known to be biodegradable. Therefore, it may be advantageous to utilize different CaP phases to create nanoparticles with the optimal properties. The nanowhiskers were characterized using XRD, SEM, and TEM to confirm their compositions and morphology. Plasmid DNA encoding a BMP2-GFP fusion protein under the CMV promoter was complexed to the nanoparticulates and incubated with simulated body fluid (SBF) to enhance attachment efficiency. The coating also serves to protect the DNA from degradation during transfection. BMP2 is known to induce bone formation so these complexes may be used to promote bone regeneration. The complexes were used to transfect mouse osteoblasts (7F2, ATCC). The GFP domain of the protein was visualized using fluorescence microscopy after 24 and 48 hours to confirm transfection. DAPI counterstaining of nuclear DNA was used to measure transfection efficiency.
Vikrant Jagadeesan, B.S. [1], Amit Paul, B.S. [1], Quanglong Truong, B.S. [1], Greg Czaplewski, B.S. [1], Terry Layton, Ph.D. [1]
[1] Department of Bioengineering, University of Illinois at Chicago, Chicago, Illinois
Chronic Total Occlusion (CTO) is an advanced form of coronary artery disease that affects approximately 33% of all patients referred for coronary angiography. This disease develops through the deposition of fatty substrates such as cholesterol, other lipid components, and extracellular matrix molecules on the backdrop of vascular inflammation and hardening. The net result is the progressive narrowing of the arterial lumen leading to reduced blood flow and myocardial ischemia. CTO is characterized by a severely calcified, complete occlusion of a major artery for a minimum of 30 days. The favorable treatment option is percutaneous coronary intervention (PCI) employing balloon angioplasty to re-establish coronary blood flow to the distal myocardium. However, the success rate of this treatment is limited by the physician’s ability to control the catheter head positioning at the proximal end of the CTO. The purpose of this project was to design a macroscale model of a novel catheter system with a mechanism for catheter head stabilization within the artery at the proximal cap of the CTO in order to prevent arterial perforation and other potential adverse events. The ability to stabilize and center the catheter head would allow for safe drug delivery and facilitate guide wire crossing for intraluminal treatment of the CTO. The prototype consists of a retractable shell controlled by the physician that deploys anchoring mechanisms at the catheter head to increase stability. Once secured, the physician is able to advance any inner delivery device to the center of the CTO. COMSOL Multiphysics Modeling and Simulation software was used to verify the absence of any turbulent stresses in the blood flow dynamics that are possible with catheters. The prototype is functional at the macroscale level, but future work should be directed toward manufacturing the catheter system on the scale of the human cardiovascular system.
Vitaly O. Kheyfets, Ph.D. Candidate [1], Sarah L. Kieweg, Ph.D. [1]
[1] Department of Mechanical Engineering, University of Kansas, Lawrence, KS
HIV is a growing concern worldwide. With slow progress in the development of a vaccine, researchers have turned to alternate methods of preventing the spreading of HIV as a result of unprotected sexual intercourse.
Developing a mechanism, such as a microbicide, that is capable of protecting the vaginal or rectal epithelium from sexually transmitted pathogens is an important step in the prevention of HIV infection. A microbicide is a topical formulation that can come in the form of a polymeric gel, which provides a physical barrier and acts as a delivery vehicle for an active pharmaceutical ingredient. Published findings of the Microbicide Development Strategy (MDS) have documented that vehicle design is a current priority gap in the development of an effective microbicide. A formulation with a hydroxyethylcellulose (HEC) gelling agent, a linear polymer with no net charge or antiviral properties, has been implemented as a universal placebo for clinical trials. In order for the microbicide to be an effective barrier and delivery vehicle it must have the capability to coat the epithelium for a specific amount of time and sustain its structural integrity under the influence of gravity and other perturbation forces. In addition, to be used as a drug delivery vehicle the microbicide must serve the following functions: coat the surface completely without leaving any of the surface exposed; remain on the surface while influenced by external forces such as gravity and squeezing; and be able to contain potent concentrations of one or more active microbicidal ingredients.
In this study, we will present a novel experimental apparatus and software for conducting gravity induced flow experiments of polymeric fluids and obtaining spreading characteristics and surface topography as a function of time. In addition, we will present a derivation and numerical solution of a partial differential equation (PDE) that governs the free surface of a non-Newtonian fluid spreading under the influence of gravity.
We will show that using the power-law constitutive equation, with parameters obtained from fitting to the rheological data, can provide a reliable approximation of the axial spreading characteristics of HEC gels. In addition, we will present simulations of both 3D and 2D spreading and show that accounting for lateral propagation will significantly improve agreement between theory and experiment.
Anamika Chaudhary, M.S. [1], Dr. Bharata Mitra, PhD [1]
[1] Department of Biochemistry and Molecular Biology, Wayne State University, School of Medicine, Detroit, MI
ZntA from Escherichia coli is a member of the PIB-type ATPase family of transporters. ZntA confers resistance to Pb2+, Cd2+ and Zn2+ by pumping these ions out of the cytoplasm. ZntA has two metal binding sites one in the hydrophilic N-terminal region and the other in the transmembrane region. Sequence analysis showed that PINA (pineal night specific ATPase) is identical to the C-terminal half of ATP7B, which is a copper transporting ATPase that is encoded by the Wilson Disease gene. In vivo studies have suggested that although the N-terminal region and half the transmembrane helices in PINA are absent, PINA may be able to transport copper in yeast. So far, very little is known about the role of the first four transmembrane helices in PIB ATPase; with the discovery of PINA, the objective was to test a similar truncated form of ZntA that lacked the amino terminal domain and the first four transmembrane helices, Del231-ZntA, in order to investigate if the loss of upstream four transmembrane helices would affect the activity and the metal binding ability of the transporter. Del231-ZntA consists of the important element of P-type ATPases such as the phosphorylation domain, the ATP binding domain and the conserved CPC motif, which is important in metal binding in both P1 subfamilies. In the present study, the expression and purification conditions of this truncated form of ZntA are being optimized.
Akhilesh K. Gaharwar [1], Sandhya A. Dammu [1], Jamie M. Canter [1], Chia-Jung Wu [1], and Gudrun Schmidt, Ph.D. [1]
[1] Weldon School of Biomedical Engineering, Purdue University, West Lafayette, Indiana
Hydrogels that can be injected and cross-linked in situ are of great interest in tissue engineering and drug delivery applications as they can be implanted in a minimum invasive manner. However, inferior mechanical properties of these hydrogels to biological tissues significantly limit their uses in load bearing tissues. Our approach to improve the mechanical properties of hydrogels is to develop nanocomposite hydrogels in which nanoparticles can reinforce polymer networks. We formulate polyethylene glycol diacrylate (PEG-DA) and hydroxyapatite nanoparticles (nHA) into injectable solutions that can be photocrosslinked under UV to form mechanically tough and extensible hydrogels (PEG-nHA hydrogels.) These PEG-nHA hydrogels show improved mechanical properties in terms of modulus, elongation and toughness compared to PEG hydrogels. In addition, preosteoblasts can readily adhere to the PEG-nHA hydrogel surface, while hydrogels without nHA are cell repellant. These improved properties are attributed to that the addition of nHA provides physical crosslinkings to the PEG networks as well as cell adhesion sites for preosteoblast to adhere. The superior mechanical properties and cell adhesion suggest the potential of PEG-nHA hydrogels for their uses as injectable biomaterials in orthopedic tissue engineering applications.
Aman Gupta, B.S. [1], Weiguo Li, Ph.D. [2], Glenn T. Stebbins, Ph.D. [3], Richard L. Magin, Ph.D. [1], Vincent M. Wang, Ph.D. [4]
[1] Department of Bioengineering, University of Illinois at Chicago, Chicago, Illinois
[2] Department of Radiology, Northwestern University,Chicago, Illinois
[3] Department of Neurological Sciences,Rush University Medical Center,Chicago, Illinois
[4] Department of Orthopedics,Rush University Medical Center,Chicago, Illinois
Low grade tendon and ligament injuries are challenging to delineate on conventional MRI grayscale images. Diffusion tensor imaging (DTI) is a well established MRI approach for assessing tissue microstructure by quantifying 3D diffusion of water within tissues. DTI has been used to quantify orientation of white matter tracts in the brain and the matrix organization of skeletal tissues such as muscle, IVD and articular cartilage; however, very few DTI data are available for tendons or ligaments. Our study investigates high field DTI of rabbit medial collateral ligament (MCL) and semitendinosus (SemiT) tendon, with a focus on quantifying DTI metrics and fiber tractography.
Contralateral pairs of SemiTs and MCLs from three male, skeletally mature New Zealand White rabbits were imaged. Scans were conducted at 11.74T in a 56mm vertical bore Bruker magnet. DTI was performed using a 3D spin echo DTI sequence (TR/TE = 1000/15 ms, δ/Δ = 2/8 ms, NEX = 1, FOV = 9.6 x 3.2 mm, six diffusion directions, b= 600 s/mm2, resolution=50x50x200µm). Fractional anisotropy (FA), mean diffusivity (MD), axial diffusivity (AD) and radial diffusivity (RD) values were extracted from the experimental data and collagen fiber tracts were generated.
Average FA and MD values for the six SemiTs were 0.67±0.04 and 1398.3±97.5 x10-6 mm2/s respectively, and corresponding values for the six MCLs were 0.66±0.03 and 1423.3±88.5 x10-6 mm2/s respectively. Average AD and RD values for the six SemiTs were 2623.3±85 x10-6 mm2/s and 786±107 x10-6 mm2/s respectively and these values for six MCls were 2666.7±207.7 x10-6 mm2/s and 800±49.4 x10-6 mm2/s respectively. 3D fiber tractography graphically depicted the spatial distribution of parallel, well organized individual fiber tracts in the tissues.
To our knowledge, this is the first study that investigates the microstructure of these tissues using 3D DTI at high fields. FA, MD, AD and RD show excellent repeatability and imaging results confirm the known microstructural organization of collagen bundles in these tissues. FA values are higher than corresponding reported values for articular cartilage, anulus fibrosus and skeletal muscle, consistent with the highly organized collagenous structure of these tissues. Ongoing work in our laboratory is examining sensitivity of DTI metrics to mechanically-induced damage. DTI metrics can provide insight into 3D tissue integrity and fiber tractography graphically supplements the quantitative DTI data. The quantitative and graphical capabilities of DTI provide more rigorous information regarding tendon and ligament microstructure compared to conventional MRI.
Kvar C.L. Black [1], Ji Yi [1], Jose G. Rivera [1], Phillip B. Messersmith [1]
[1] Department of Biomedical Engineering, Northwestern University, Evanston, Illinois
Cancer therapeutics that target growth factor receptors and apoptosis pathways are in clinical use for cancers, however, these treatments may fail and cause more invasive, drug resistant tumors. Therefore, quantification of response and design of more robust therapies are needed to undermine cancer morbidity. An emerging paradigm that treats cancer progression as a Darwinian process offers strategies to positively intervene in the evolutionary process at multiple points in the cell-environment interaction, by for example targeting pro-apoptotic drugs to growth factor receptors. Nanoparticles, with sizes between molecule and cell, offer the ability to target cancer tissue through the enhanced permeability and retention effect and affect cellular processes and therefore modulate the evolution of cancer into benign directions. Surface plasmon resonant metal nanoparticles have broad potential in diagnostic and therapeutic modalities with proper control over their electromagnetic and biofunctional properties, due to their relative inertness, sub-100 nm size, and strong optical tunability. To fully realize the potential of such materials, however, a strategy to easily tune the optical properties of metal nanoparticles, react therapeutic molecules onto their surfaces, and stabilize them in physiological environments is needed.
Polydopamine (PD) can coat and metalize many materials using mussel mimetic mechanisms, making it a versatile aqueous adhesive. PD gives a versatile chemical repertoire to form evolutionary modulatory metal nanoparticles. In this study, PD was polymerized onto the surface of gold NRs to form a multifunctional, multicomponent anticancer surface. Specifically, silver was deposited into the PD layer to modulate toxicity and tune the plasmons throughout the visible and near-infrared portions of the electromagnetic spectrum. PEG was reacted into the PD layer to inhibit non-specific interactions and increase solubility in physiological conditions. The proteasome inhibitor bortezomib was coordinated to catechols in the PD layer to provide a pro-apototic effect, and the anti-EGFR antibody erbitux was reacted through quinone-mediated cross-linking reactions to provide NPs with specific targeting and growth factor pathway inhibition. NRs were identified on oral cancer cells with bright field microscopy, optical coherence tomography, and 2-photon excited confocal microscopy. Finally, targeted NR-mediated photothermal therapy was performed. Importantly, the NPs provides multiple mechanisms of treatment, including specific targeting and inhibition of EGF pathways, toxicity from silver, pH-dependent release of bortezomib in acidic cancer microenvironments, and thermal heating to cause necrosis and permeabilize membranes to increase drug uptake. Taken together, these catechol-based metal nanoparticles provide multimodal imaging and synergistic therapy for cancer.
Ying-Hui Lee, Ph.D [1]
[1] Department of Biomedical Engineering, Illinois Institute of Technology, Chicago, Illinois
Cardiovascular diseases are a leading cause of death in the United States and thrombosis is the precipitating event in these conditions. Circulating tissue factor (TF)-bearing MPs may play a critical role in thrombosis. Clinical studies have shown that elevated monocyte-derived MPs in blood are associated with cardiovascular disease. Monocyte-derived MPs could contribute to mural thrombosis due to the transport of MPs to the vessel wall and the resultant exposure of TF and/or negatively charged phospholipids on their surface. Little is known of the mechanisms by which MPs are transported to surfaces. Blood flow modulates the transport of platelets to biomaterials or the site of vessel injury, thus, we hypothesize that flow can influence MP transport to surfaces. To elucidate the effect of flow on MP transport processes, the adhesion of MPs generated from a promonocytic cell line (THP-1) to bare glass surfaces was evaluated microscopically at a range of wall shear rates. The concentration of MPs in suspensions was determined by flow cytometry and the suspensions were perfused over glass coverslips in a 2D parallel plate flow chamber. Perfusion was performed at physiologically representative wall shear rates of 100, 400 and 1600 s-1. The fluorescently labeled MPs that adhered to surface were visualized by epifluorescence microscopy and MP adhesion was quantified based on the MP size using Image J software. The rate of initial adhesion of MPs increased with increasing wall shear rate. Particles were tightly bound and could not be removed by increasing the wall shear rate by an order of magnitude. Adhesion appeared to be non-specific (charge dependent) and was reduced by decreasing the ionic strength of the suspending buffer. Comparison of the experimental rates of MP adhesion with the theoretical expression for mass transport indicated that MP adhesion was diffusion-controlled at wall shear rates between 100 and 400 s-1. At the higher shear rates the deposition rate appeared dependent on both diffusion and kinetic parameters. To further delineate the MP transport mechanism, additional wall shear rates will be evaluated and red blood cells will be added to the suspension.
Malvika Bhatia [1], Tiffany S. Chen [1], Gillian E. Henker [1], Christopher L. Maue, B.S.E [1]
[1] Department of Mechanical Engineering, University of Michigan, Ann Arbor, Michigan
[2] Department of Biomedical Engineering, University of Michigan
[3] Department of Obstetrics and Gynecology, Komfo Anokye Teaching Hospital, Kumasi, Ghana
Improving maternal health was identified in 2000 as one of the Millennium Development Goals by the United Nations, in large part due to the challenges facing maternal healthcare in resource-limited settings. One of the key working areas of the World Health Organization (WHO) for achieving this goal is coordinating research, with wide scale application that focuses on improving maternal health in pregnancy, during delivery, and after childbirth. Based on clinical observations with local mentors at Komfo Anokye Teaching Hospital (KATH) in Kumasi, Ghana, labor and delivery beds were determined to provide an opportunity for design innovations that could improve care. The existing set-up requires women to be transferred from a labor bed to a delivery bed during the physically and mentally crucial moment of delivery. Additionally, these beds are non-adjustable, ill-fitting, and create undue stress on women’s bodies. Thus, the team identified an opportunity to innovate a novel delivery device for resource-limited settings in which women could safely and comfortably transition through the stages of childbirth.
An improved design was developed based on user requirements gathered through interviews with Ghanaian and American clinicians. Top criteria included: safety, low cost, ability to make quick adjustments, ability of the back to incline, support for the woman’s legs, and access to the pelvis. The resulting design is a compact, foldable seat with an attachment system at its base that allows it to be affixed to any surface it is placed on. The design also includes side rails for arm support and leverage, foot rods for adequate leg support, and a simple lever mechanism for back inclination. In addition to being portable, the device is extremely low-cost compared to alternatives such as standalone reconfigurable beds and therefore has a much wider range of applications. For example, it can be attached to existing beds that are not reconfigurable for delivery; it can be used as for emergency deliveries in non-ideal locations; it can be used by midwives working in rural settings without access to the appropriate resources; and it can also be used for pelvic examinations and post-delivery vaginal repairs.
During a return visit to KATH to evaluate this initial design, we received feedback on specific design features, and were able to validate the functionality, feasibility, and cultural acceptance of the design. Based on this feedback, we are currently iterating the design and planning a route to local (in-country) manufacture and post-implementation sustainability.
Huan Zhou, Ph.D [1]
[1] Department of Bioengineering, University of Toledo, Toledo, Ohio
In this study, alendonate sodium (AS), a bisphosphonate (Bp) to fight against osteoporosis was incorporated into biomimetic carbonated calcium deficient hydroxyapatite (CDHA) coatings. Three possible loading methods of AS to CDHA coatings was systematically studied and compared. The results demonstrated the possibility to deposit CDHA-AS coatings via co-precipitation process, resulting AS incorporated in inner layers of deposited CDHA coatings to produce stable and sustained release of AS. The influences of applied AS dosage to CDHA coatings were studied using XRD and SEM. In vitro tests indicated AS content on CDHA coatings plays a role in osteoblast cells proliferation. It is foreseen that the CDHA-AS coatings can have potential applications in bone tissue engineering applications.
May Kaewken [1], Vu Nguyen [1], Ying Hsu [1], Madhawa Hettiarachchi [1], Andreas Linninger [1]
[1] Laboratory for Product and Process Design (LPPD), Department of Bioengineering, University of Illinois at Chicago, Chicago, IL
Bypassing the blood brain barrier, intrathecal drug delivery is an efficient way of administering drugs directly into the central nervous system by infusion of therapeutic agents into the cerebrospinal fluid filled subarachnoid space in the spine. The cerebrospianl fluid pulsates in the spinal canal at the frequency of the heart beat due to periodic expansions of the cerebrovasculature. Compared with pure diffusion in stagnant fluid, pulsatile flow enhances species transport three to five fold. Inside the complex anatomical structures of the spinal canal, drug transport is mainly due to this convective pulsatile flow of cerebrospinal fluid; transport by drug molecular diffusion is usually negligible. However, obstacles in the spinal canal such as nerve roots and fine arachnoid trabeculae further enhance drug transport due to intensive micromixing.
In this study, we aim to quantify the effect of anatomical fine structures on enhanced micromixing inside the spinal canal. Computational models of the human spinal canal that incorporate protruding nerve bundles and arachnoid trabeculae were constructed. The dimensions of the nerve roots, trabeculae and parameters of intrathecal infusion match published clinical values. To study the effect of these obstacles on pulsatile fluid flow and drug transport, the Navier Stokes and Species Transport equations were solved with direct numerical simulations. After simulating intrathecal infusion of a spinal anesthetic, drastically enhanced micromixing was observed in the spinal canal model with nerves and trabeculae, compared to a control model without these structures. Nerves and trabeculae in the spinal canal greatly enhance drug mixing in the presence of pulsatile cerebrospinal fluid flow.
Nerves and micro-scale trabeculae are significant for accurate quantification of intrathecal drug distribution inside the spinal canal; drug mixing is drastically enhanced by microstructures in pulsatile cerebrospinal fluid flow. A future goal is to construct a computational model of human central nervous system which features anatomical accuracy and reproduces cerebrospinal fluid flow dynamics validated with CINE MRI flow measurements. The final stage is to build a computer model for prediction of drug dispersion in a patient’s central nervous system. Before administering intrathecal infusion therapy on patients, this computer model will enable anesthesiologists to optimize infusion parameters for assessing toxicity threshold and evaluating infusion outcomes a priori.
Paul Skelton, B.S. [1], Haojie Mao, Ph.D [1], King H. Yang, Ph.D [1]
[1] Department of Biomedical Engineering, Wayne State University, Detroit, Michigan
Background: Traumatic brain injury (TBI) affects an estimated 1.7 million people per year. It is estimated that TBI contributes to one third of all injury-related deaths in the United States. Therefore, studying the etiology and therapy for TBI is a primary concern for public health. Controlled cortical impact (CCI) on rodents is a common experiment used to further investigate the mechanisms and therapy methods for TBI. However, different research groups use different CCI parameters, making comparison of experimental findings very difficult. Furthermore, many animals are sacrificed during preliminary trial-and-error stages until the desired brain injury severity is reached. The object of this study is to develop a finite element (FE) mouse brain model to analyze tissue-level biomechanical responses during CCI injury without animal sacrifice.
Methods: The mouse brain geometry was extracted from a set of MRI images with spatial resolution 100 microns and constructed using Materialise’s Mimics 14.0 software. Block meshing, an emerging meshing method for generating high quality hexahedral elements, was used to create a hexahedral mouse brain mesh while maintaining geometric precision. Material properties for the mouse brain were determined from literature review. The FE model was then used to simulate CCI, with the FE solver LS-DYNA. Both flat and hemispherical impactors were tested in a CCI setting with a constant velocity 3.5 m/s and a brain compression depth of 1 mm for analysis of intracranial pressure and strain.
Results and Discussion: An all-hexahedral FE mouse brain model was created with high mesh quality - 99% of total elements with Jacobian values above 0.7. It was found that the brain pressure was diffusely increased during CCI, while concentrated high strains were induced below the impact site. The flat impactor tended to generate high strains near the edge of the impactor, which indicated more cell death along the impactor edge compared to that below the impact center. The hemispherical impactor, however, induced an ellipse shape strain concentration beneath the impactor. It would be of great value to efficiently analyze findings from different labs in order to avoid redundant tests using animal (mouse) subjects. Since the brain tissue-level responses have been well demonstrated in the literature to correlate well with injury outputs, the computer predicted brain internal responses could work as a uniform platform, i.e., quantitative description of intracranial responses, to allow comparisons among different research laboratories, and numerically designing desired injury severities.
Cierra Hall [1], Eric Lueshen [1], Martina Heitzig [1], Andreas Linninger, Ph.D [1]
[1] Department of Bioengineering, University of Illinois at Chicago, Chicago, Illinois
Drug safety and approval processes have recently emphasized a model-based approach for estimating safe drug action and toxicity thresholds in Phase 1 human trials. As a result, there is a need for rigorous mathematical models that are able to utilize experimental animal dose-response data in a way that satisfies the concerns of both safety and toxicity.
We have developed a first principles pharmacokinetics model incorporates mass transport and physiological dimensions in order to rigorously predict the safety and toxicity of drugs. First principles modeling in combination with scaling laws and parameter estimation yields more reliable extrapolation of drug biodistribution from species to species and between individuals of the same species. Estimating biochemical reaction and transport parameters is key to predicting the dose-response curves of a certain drug. We show how experimental dose-response data in rats for the immunosuppressant Cyclosporin are sufficient for predicting the biodistribution of this drug in pigs, monkeys and humans. The predicted drug concentrations extrapolated by our interspecies scaling laws in our first principles model match well with available experimental measurements. These promising results demonstrate that our improved physiologically-based whole-body pharmacokinetic modeling approach not only elucidates the drug mechanisms from a biochemical point of view but offers better scaling precision. Better models can substantially accelerate the introduction of drug leads to human clinical trials and eventually to the market while simultaneously cutting time and resource expenditures.
Sukhraaj S. Basati, B.S. [1], Brian J. Sweetman, M.S. [1], Joe Lancaster, B.S. [1], Andreas A. Linninger, Ph.D. [1]
[1] Department of Bioengineering, University of Illinois at Chicago, Chicago, Illinois
Intracranial dynamics describes the interactions of blood flow, cerebrospinal fluid (CSF) flow, and the deformation of porous brain tissue. Our research group combines experimental measurements with computational models to quantify the flows and pressures in the entire cranio-spinal system. The measurements and computational models have elucidated major differences in CSF flow patterns between normal subjects and patients with hydrocephalus-a disease in which CSF accumulates in the lateral ventricles of the brain. We have observed that the flow in the pontine cistern is about twice that in hydrocephalic patients, whereas flow in the aqueduct is increased about ten times in hydrocephalic patients compared to normal. To better understand normal pressure hydrocephalus we have used our models to show that a reduction in the CSF reabsorption can cause CSF to accumulate. The computational models also provide an explanation that the aqueductal flow reverses direction during accumulation and also that pressure is not a reliable indicator of enlargement. We believe our quantitative approach will improve our understanding of diseases such as hydrocephalus, and in turn lead to better treatment.
The current treatment for hydrocephalus involves surgically implanting a pressure regulated catheter system to drain excess CSF into a cavity within the body. Shunts are implanted into patients worldwide; however their success is limited which often requires numerous revisions due to shunt obstruction, over/under-drainage, or shunt malfunction. The working principle of our sensor is based on the impedance technique, where the high electrical conductivity ratio between CSF and brain tissue is utilized. The fabricated sensor consists of platinum/iridium ring electrodes on a polyimide catheter with an internal shunt for volume control. Volume monitoring is assessed in a hydrocephalic animal model and measurements indicate feasibility. Our vision of an improved therapy consists of incorporating this impedance based volume sensor with a micro-pump for feedback control of CSF volume.
The benefit of applying computational models assists in understanding intrancranial dynamics, design of medical devices, and design of therapy plans. The application of the models developed increase an understanding of brain physics and may lead to improved therapeutic options for patients suffering from brain diseases.
Karthik Ramachandran, B.A. [1], Han-Hung Huang, B.S. [2], Lisa Stehno-Bittel, Ph.D. [2]
[1] Bioengineering Graduate Program, University of Kansas, Lawrence, Kansas
[2] Department of Physical Therapy and Rehabilitation Science, University of Kansas Medical Center, Kansas City, Kansas
Currently, the method for determining success of an islet transplantation is predicted by the volume of transplanted tissue. Islet equivalent (IE) is the standard estimate of islet volume and is loosely based on the assumption that all islets are spherical. Yet, certain populations of isolated islets are ellipsoidal, creating errors in volume measurements. We created and tested a more accurate method to estimate islet volume. Isolated rat islets were dissociated into single cells after being manually separated by size (50, 100, 150, 200, 250, and 300μm). There was an inverse correlation between the cell number per IE and islet size with greater error as the islet size increased. IE calculations overestimated the total tissue volume for large (> 200μm diameter) islets. We modeled the errors, and based on cell number/islet diameter, we created and tested a new calculation to convert islet diameter to volume. When total protein was normalized by IE, there was nearly 3 times more protein/volume in small islets compared to large. However, when total protein was normalized to cell, the large and small islets had equivalent levels. When normalized by IE, large islets showed significantly lower insulin secretion, proinsulin content, and Glut2 level. When the volumes were recalculated based on estimates of cell number, large islets still demonstrated lower insulin secretion, but large and small islets had equal amounts of insulin and Glut2. Normalization of islet volume by IE overestimated the tissue volume of large islets, which lead to some erroneous results. Normalizing islet volume by cell number is a more accurate method for estimating islet volume, especially when comparing islets of different sizes. These calculations pose implications for clinical islet transplantation. A better calculation will lead to more accurate amounts of transplanted tissue, increasing the efficacy of a single transplantation and improving overall success rates.