Master of Science, Miami University, 2020, Chemical, Paper and Biomedical Engineering

As the population of the world ages, the field of tissue engineering is becoming increasingly important due to the need for replacement or regeneration of damaged tissues. One proposed solution to this issue is the use of 3D tissue scaffolds to guide cell growth in damaged tissues. A variety of methods have been used to manufacture scaffolds for this purpose, including 3D Bioplotting (3DP) and thermally induced phase separation (TIPS). Both techniques offer opportunities to finely tune the pore size, connectivity, density, and size of the resulting scaffolds. This work describes a hybrid 3DP/TIPS technique used to fabricate highly porous scaffolds made of poly(lactic-co-glycolide) (PLGA) and nano-hydroxyapatite (nHA). The effects of varying compositions of PLGA and nHA were examined on the porosity and mechanical characteristics of the scaffolds. MC3T3-E1 preosteoblast cells were used in both in vitro tests and perfusion bioreactors to assess cell proliferation and differentiation in static and dynamic cell culture environments. CellCeramTM scaffolds were obtained from Sigma Aldrich and subjected to the same cell culture conditions. Flow through the scaffold geometry in a perfusion bioreactor was investigated and modeled in COMSOL. Cell proliferation and differentiation on the scaffolds were then assessed and compared.

Committee: Azizeh Yousefi Moshirabad (Advisor); Paul F James (Advisor); Justin M Saul (Committee Member) Subjects: Biomedical Engineering; Chemical Engineering

MS, University of Cincinnati, 2023, Engineering and Applied Science: Biomedical Engineering

Diabetes mellitus is widely acknowledged as one of the most prevalent metabolic diseases, affecting millions of people around the world. In addition to presenting the generally observed metabolic deficiencies, diabetes can also severely impact other body systems by impairing circulation, promoting neuropathy, and stalling the wound healing process. In particular, the cardiovascular system is often affected by diabetic co-pathologies; these can result from both increased inflammation and actual changes in the structure of cardiac tissue. One such cardiac co-pathology is diabetic cardiomyopathy, or DCM. DCM presents primarily as impaired contraction of cardiac muscle in conjunction with progressive fibrosis, which is characterized by increased collagen deposition, increased cardiomyocyte apoptosis, and/or left ventricular hypertrophy. These observed effects are likely due to alterations within the diabetic microenvironment. Additionally, prior studies in the field of diabetic wound healing have shown that the hyperglycemic environment can alter the behavior of vascular cells, thus stalling the healing process in the chronic inflammatory phase. Since diabetic cardiomyopathy has been linked to increased occurrences of myocardial infarction and more severe post-infarct complications, there is a need for better therapeutic options than the currently employed treatment method, which relies solely on basic glycemic control. This study explores the use of a bioengineered RAD16-II (RARADADARARADADA) peptide nanofiber scaffold as a delivery vehicle for exogenous matrix metalloprotease 2 (MMP-2). This injectable scaffold/protein combination is suggested as a potential therapy for the severely fibrotic phenotype associated with diabetic cardiomyopathy since it has been shown that MMP-2 levels are reduced in diabetic cardiac tissue. Furthermore, MMP-2 primarily functions in maintaining the composition of the extracellular matrix by degrading fibrillar collagen; th (open full item for complete abstract)

Committee: Daria Narmoneva Ph.D. (Committee Chair); Stacey Schutte Ph.D. (Committee Member); T. Douglas Mast Ph.D. (Committee Member) Subjects: Biomedical Research

Master of Science (MS), Ohio University, 2023, Biomedical Engineering (Engineering and Technology)

A study on a solution to repair osteochondral defects was investigated. This work contained the use of a novel collagen-based biomaterial that was structured to mimic the composition and structure of osteochondral tissue. Collagen extraction from the bovine achilles was optimized in terms of atelocollagen yield and stability. It was found that collagen enzymatically digested at a 1.25:10 pepsin to tendon weight ratio in the superior tendon region, gave optimal results in terms of atelocollagen quantity and hydrogel formation. Mineralized collagen scaffolds were fabricated to reflect the composition of subchondral bone. Controlled freezing was applied, which successfully oriented collagen fibers mimicking those in each native zonal tissue. Multiple approaches were attempted to replicate the collagen orientations of osteochondral tissue, ultimately a T-shaped mold was designed to guide directional freezing, resulting in an anisotropic scaffold structure. Native composition of bone hydroxyapatite and cartilage hyaluronic acid were also taken into consideration when fabricating such multizonal scaffolds.

Committee: Mei Wei (Advisor); Shouan Zhu (Committee Member); Doug Goetz (Committee Member); Andrew Weems (Committee Member) Subjects: Biomedical Engineering; Biomedical Research

MS, University of Cincinnati, 2022, Engineering and Applied Science: Chemical Engineering

Conductive polymers are an amazing class of materials with unique electrical and optical properties for polymeric systems. The difficulties of processing conductive polymers is an obstacle to realizing their full potential, motivating novel solutions to increase their solubility, miscibility and stability. In this work, we demonstrate an approach to prepare conductive polymer shells using a lipid conjugated precursor. This is done by leveraging the self-assembly of lipid molecules into vesicular shapes and utilizing the lipid conjugate as an anchor for a surface bound polymer shell to form. We describe the preparation of the conductive polymer precursor, Py-DMPE, demonstrate the polypyrrole coated vesicle spheres. We also detail the preparation of the n-substituted pyrrole upon which this conjugate is based, along with additional substituted polypyrrole products, namely; poly(Py-DSPE) and poly(Py-DCC).

Committee: Jonathan Nickels Ph.D. (Committee Member); Jude Iroh Ph.D. (Committee Member); Gregory Beaucage Ph.D. (Committee Member) Subjects: Chemical Engineering

PHD, Kent State University, 2022, College of Arts and Sciences / Materials Science Graduate Program

Three-dimensional (3-D) tissue scaffolds produce suitable environments for cell growth and proliferation for longer periods of time compared to traditional two-dimensional (2-D) tissue culture and, act as appropriate models for the study of cell-cell/cell-scaffold interactions. 3-D models also allow to study cell activities and their functions as well as to evaluate diseases or tissue damage. Liquid crystal elastomers (LCEs) have intrinsic anisotropy and have shown to promote cell alignment and orientation and the presence of liquid crystals (LCs) at a molecular level with and without the use of external stimuli. The work presented in this thesis is the synthesis, design, and creation of 3-D LCEs scaffolds that support several cell lines to promote tissue regeneration. LCEs scaffolds have shown to meet all tissue scaffold requirements to support cell proliferation and growth since they can potentially be biocompatible, biodegradable and their properties, such as porosity and mechanical properties, can be tuned to adapt and match to different cell lines to obtain a suitable tissue. To tune porosity size and density, a salt leaching method was used. Cellulose nanocrystals (a biocompatible additive) were used as an additive to tune the mechanical properties of LCEs to match the young modulus of specific tissues. Once 3-D LCE scaffolds were produced to specifically match neural-like cell lines, we proceed to co-culture neuroblastoma and a glial cell lines (oligodendrocytes). When neuroblastomas are in presence of oligodendrocytes, myelin sheet is formed around the axon of neurons. We observed myelination of neurons during our co-culturing efforts allowing us to study its formation well over several weeks. Our findings will lead researchers on brain degenerative diseases such as Multiple Sclerosis (MS) to have a more appropriate model to quantify, monitor, and find treatments for demyelination and myelination of neurons. Last but not least, in this thesis we will sho (open full item for complete abstract)

Committee: Elda Hegmann (Advisor); Elda Hegmann (Committee Chair); Robert Clements (Committee Member); Richard Piet (Committee Member); Jennifer McDonough (Committee Member); Edgar Kooijman (Committee Member); Torsten Hegmann (Committee Member) Subjects: Materials Science

Doctor of Philosophy, University of Toledo, 2021, Biology (Cell-Molecular Biology)

Intestinal enterocytes build an apical brush border (BB): a highly ordered collection of actin-based microvilli that promote barrier function and interaction with the luminal environment to facilitate nutrient absorption. The intermicrovillar adhesion complex (IMAC) has been found to drive BB assembly, in which a complex of protocadherin molecules mediate adhesion between neighboring microvillar protrusions to establish a well-assembled, tightly packed array of microvilli. ANKS4B is a scaffold molecule found within the IMAC and is critical in BB assembly; however, its functional properties are not yet fully understood. Recently, it was discovered that ANKS4B utilizes an N-terminal fragment to target to the BB microvilli, but the underlying mechanism of this targeting was not elucidated. Here, we use a structural-functional approach to better understand the role ANKS4B plays in BB targeting and IMAC assembly and address the regulatory roles that dictate ANKS4B function in the intestinal epithelia. We discovered that ANKS4B localizes to the apical BB using a previously cryptic targeting sequence called the linker (LK) domain, and bioinformatic analysis revealed a coiled-coil (CC) motif and a basic-hydrophobic-basic (BHB) membrane binding repeat sequence as main motifs driving the targeting function. In addition, we show that the LK sequence can function as an oligomer. ANKS4B is known to form a stable tripartite complex with two other IMAC components; another scaffolding molecule, USH1C and a myosin motor protein, Myo7b. Myo7b is an unconventional Myth4-FERM (MF) myosin that is thought to be monomeric and employ cargo binding for activation and motility. ANKS4B is the only IMAC components known to form an oligomer and could be responsible for driving Myo7b motility in enterocytes. MF myosins have been shown to play an essential role in both the function and creation of different actin-based membrane protrusion such as microvilli and filopodia. In a quest to better (open full item for complete abstract)

Committee: William Scott Crawley (Committee Chair); Tomer Avidor-Reiss (Committee Member); Rafael Garcia-Mata (Committee Member); Matt Wohlever (Committee Member); Wissam AbouAlaiwi (Committee Member) Subjects: Biology; Health Sciences; Physiology; Public Health

Master of Science in Biological Sciences, Youngstown State University, 2021, Department of Biological Sciences and Chemistry

The calcaneal (Achilles) tendon is capable of handling tremendous tensile loads during locomotion. However, cases of Achilles tendon ruptures have increased in recent years, requiring long healing times. Repaired tendons are more prone to re-rupture after healing, which may negatively impact patient quality of life. Thus, there exists a need for new methods of treatment aimed to improve and accelerate tendon healing. We studied the effect a combination of collagen, platelet-rich plasma (PRP), and mesenchymal stromal cells (MSC) on healing a complete Achilles tendon rupture in a Lewis rat model. The PRP was produced from rat blood collected during exsanguination procedures. MSCs from rat bone marrow met the criteria to be considered stem cells in a rat model, as they were seen to be plastic adherent and capable of tri-lineage differentiation. Rupture was surgically simulated by a full-thickness transection of the tendon, followed by surgical repair. All treatments included a strip of CollaTapeTM wrapped around the repair, acting as a vehicle for the biologics prior to closure of the wound. A single, 100µL subcutaneous injection of MSCs, PRP, or both were administered adjacent to the incision and assigned 1- or 2-week recovery periods before harvesting the operated and unoperated tendons. We observed promising trends which show an increase in gene expression activity in the treated tendons and differences in the expression of Col1a1 and Col3a1 which align with our predicted response to the treatments. However, due to contamination of the GAPDH RT-PCR results, the collagen analysis results remain inconclusive. The biomechanical properties of the tendons were determined using force-extension analysis. When normalized as a percent of the unoperated tendon, a significant improvement was seen in the strain at failure and in ultimate tensile strength after only one week of recovery in the rats who received any biological treatments used in this study, when compared to a sur (open full item for complete abstract)

Committee: Diana Fagan PhD (Advisor); Gary Walker PhD (Committee Member); Carmen Panaitof PhD (Committee Member) Subjects: Biology; Biomechanics; Biomedical Research; Physiology; Surgery

Master of Science, University of Toledo, 2019, Bioengineering

Musculoskeletal tissue injuries affect around 1 in 3 Americans and 1.7 billion people worldwide. This is a huge economic burden, costing an estimated $120 billion in the US alone. With limited success from surgery or subcutaneous injections of medicine, where only temporary relief or complications can occur, alternative measures should be explored. Injectable biologically-loaded hydrogels are one avenue and act as drug delivery systems. They provide a minimally invasive approach to release biologics in a sustained and controlled manner to provide long-lasting relief without toxic effects and with less risk of surgical complications. In this study, the immunological application of a previously-developed nanofibrous PCL-interspersed collagen hydrogel, (PNCOL) was explored by loading PNCOL with the cytokine IL-4 and identifying its effect upon macrophages. Furthermore, the effect of a simulated digestive inflammatory environment (DIE) had upon protein release kinetics as well as scaffold integrity were characterized. Genipin crosslinking was then explored to improve scaffold resistance to degradation, and an optimal genipin concentration was identified to impart sufficient scaffold crosslinking, increased mechanical strength, and a prolonged release profile, with minimal cytotoxic effects. Lastly, the immunomodulatory effect of IL-4 released from crosslinked and uncrosslinked scaffolds were investigated through identifying the impact of IL-4 on macrophage differentiation. The IL-4 released from PNCOL polarized macrophages toward an anti-inflammatory, pro-healing state, while genipin crosslinking with and without IL-4's presence appeared to lower macrophage activity.

Committee: Eda Yildirim-Ayan PhD (Advisor); Eda Yildirim-Ayan PhD (Committee Chair); Halim Ayan PhD (Committee Member); Arun Nadarajah PhD (Committee Member) Subjects: Biology; Biomedical Engineering; Biomedical Research; Cellular Biology; Materials Science

MS, University of Cincinnati, 2019, Engineering and Applied Science: Materials Science

Scaffolds have a variety of applications from batteries to biomedical implants due to their low density and high surface area. Cermet scaffolds in particular are attracting significant attention in the recent past, due to combining the advantageous properties of both metals and ceramics. Cermets have traditionally been used in wear resistant, high temperature resistant, high speed tooling applications. Cermet scaffolds such as Ni-YSZ, Ni-CGO, and Cu-infiltrated-YSZ find applications in solid oxide fuel cells while cermets of calcium silicate with Ti-55Ni and Ti-6Al-4V are used for hard tissue replacements and other biomedical applications. Fabricating such geometrically complex structures via traditional subtractive manufacturing techniques is difficult and even using powder bed additive manufacturing methods poses problems due to poor sintering and high residual stresses. In this study, we aim to assess the feasibility of producing Ni-TiC cermet scaffolds via a particle-based liquid ink extrusion 3D printing approach. The main objective of this thesis was to determine suitable annealing conditions (i.e. time, temperature, atmosphere) to post-process the printed cermet scaffolds and understand the sintering behavior. Ni-TiC (50-50 vol.%) particle inks were prepared by mixing DCM, DBP, 2-Bu and PLGA along with the Ni and TiC powders in the prescribed ratio. DBP served as a plasticizer and 2-Bu served as a surfactant while PLGA was used as a co-polymeric binder to hold the powder particles together. Scaffolds with dimensions of approximately 10-15 mm in diameter, 5-15 mm in height, and a square infill pattern, were printed and subjected to various heat treatment processes. The as-printed and sintered structures were then characterized using conventional metallography techniques to investigate microstructural and compositional changes as a function of time, temperature and environment to qualitatively understand the sintering behavior.

Committee: Ashley Paz y Puente Ph.D. (Committee Chair); Matthew Steiner Ph.D. (Committee Member); Sarah Watzman Ph.D. (Committee Member) Subjects: Materials Science

Doctor of Philosophy, The Ohio State University, 2019, Ohio State University Nutrition

Diabetes mellitus (DM) is a global health problem resulting in 2.2 million yearly deaths by DM-related complications. Insulin, for the past century, has been indispensable for the treatment of both type 1 DM and advanced stages of type 2 DM. However, insulin has relatively low efficacy in the central nervous system (CNS). Currently, DM leads to cognitive learning deficits in children as well as an increased risk of Alzheimer's disease in adults. There is a critical need for the development of a new strategy to improve the efficacy of glucose regulation that will prevent CNS-related complications of DM. Nanotechnology could provide a comprehensive platform for the improvement of insulin efficacy and delivery. Dr. Parquette (OSU) has developed a method to produce nanostructures using amino acid compounds (AACs) with and without various side chains; however, these compounds have not been used for treatment of DM. I anticipated that positively-charged AAC nanostructures could potentially bind negatively charged insulin, protect it from cleavage, and extend its interaction with the insulin receptor (InsR). The aim of my dissertation is to investigate AAC interaction with insulin and its effect on systemic glucose uptake and CNS complications. My overall hypothesis was that candidate AAC improves whole-body glucose uptake and prevents neurological complications in mouse models of DM. The structure-function comparison was performed between two AAC compounds with similarly positively charged lysine backbones that either assemble into nanofibers (AAC2) or lack this ability (AAC6). Zeta potential and microbalance techniques showed a stable binding only between AAC2 nanofibers and insulin, suggesting that this nanofiber structure is critical for the interaction with insulin. Next, I tested cytotoxicity in a range of nanostructures (AAC1-3) using a lactate dehydrogenase activity assay and subsequently excluded cytotoxic AAC3. Then, I compared glucose uptake induction bet (open full item for complete abstract)

Committee: Ouliana Ziouzenkova (Advisor); Martha Belury (Committee Member); Lee Kichoon (Committee Member); Parquette Jon (Committee Member) Subjects: Endocrinology; Nanoscience; Nanotechnology; Neurosciences; Nutrition

Doctor of Philosophy, The Ohio State University, 2019, Biomedical Sciences

A tissue-engineered vascular graft (TEVG) that resists stenosis and grows with its host holds great promise for the field of pediatric congenital heart surgery. This dissertation describes work designed to improve our understanding of the process of cell seeding to assemble TEVGs prior implantation, to inform computational approaches for the rational design of second-generation TEVG scaffolds, to develop methods for the creation of patient-specific TEVGs, to elucidate the natural history of TEVG stenosis and describe its spontaneous reversal, to test the hypothesis that LYST protein expression in macrophages regulates the process of neovessel stenosis and develop novel strategies to modulate its activity in vivo, and to explore the potential of anti-LYST therapy to attenuate cardiovascular fibroproliferative pathologies. The work presented is a collection of peer-reviewed publications, manuscripts under review, and unpublished works in progress spanning studies performed in mice, rats, juvenile lambs, and humans. The findings reported herein provide the foundation for the translation of a readily available, off-the-shelf TEVG with growth capacity that does not require cell seeding and identifies a potent immunomodulatory protein that represents a novel therapeutic target to improve outcomes in the field of cardiovascular surgery.

Committee: Christopher Breuer MD (Advisor); Jeffrey Parvin MD, PhD (Committee Member); Joanna Groden PhD (Committee Member); Ryan Roberts MD, PhD (Committee Member); Jordan Pober MD, PhD (Committee Member) Subjects: Biomedical Research

Doctor of Philosophy, The Ohio State University, 2018, Comparative and Veterinary Medicine

Osteoarthritis (OA) is a progressive disease associated with cartilage injury and is the most common form of arthritis, affecting millions of people worldwide. Most common cartilage healing and treatments have unsatisfactory outcomes due to the inherently limited repair capability of cartilage. The goal here was to produce a sConstruct from decellularized synovial-derived extracellular matrix (sECM) seeded with synovial-derived mesenchymal stem cells (sMSCs) that could house normal or engineered sMSC with little immune reaction while improving cartilage healing. The first part of this work investigates the sMSC migration, differentiation, and distribution into the sECMs as determined by CD90, viability, histologic morphology, expression of GFP, BMP-2, hyaluronic acid (HA), and proteoglycan (PG). At day 14, sMSCs were viable, had multiplied 2.5-fold in the sECMs, had a significant decrease in CD90 expression and significant increases in HA and PG expression. Seeding with BMP-2-sMSCs enhanced the expression of BMP-2, and increased soluble HA and PG. These results indicate sMSC produce anabolic agents and differentiate in the sECM. The second portion of the thesis has two parts; 1) an in vitro model where the sConstructs were co-cultured with chondrocytes, and 2) in vivo, placing sConstructs adjacent to a cartilage lesion in a rat knee. The in vitro study showed increased chondrocyte proliferation, viability, and Col II production, greatest in BMP-2-sConstructs. Chondrocyte co-cultures increased the sConstruct sMSC production of HA, PG, and BMP-2 in a positive feedback loop. 2) In the in vivo study, sECM alone, GFP- or BMP-2-sConstructs were implanted adjacent to clinically created full-thickness rat-knee cartilage lesions. At 5 weeks, the lesion area was resected and gross anatomy, adjacent articulate cartilage growth and subchondral bone repair were scored and peripheral, central and cartilage lesion measurements taken. For all scores and measurements, sConstruct im (open full item for complete abstract)

Committee: Alicia Bertone (Advisor) Subjects: Animal Sciences; Veterinary Services

MS, University of Cincinnati, 2018, Engineering and Applied Science: Materials Science

Children with unilateral alveolar clefts may develop complications, including infection at the secondary surgical site, relapse, and facial asymmetry due to unpredictable post-surgical growth. Because the mineralization rate of osteoblasts is sensitive to strain distributions in the skull, asymmetric strain distribution may lead to unbalanced bone growth. Recently, clinical trials have developed scaffolds with certain porosity to help the growth of the new bones and to alleviate these risks and improve bone healing. Thus, the strain inside the scaffold also influences de novo bone deposition and resorption. The aim of this study is to develop finite element models and conduct detailed computational analyses to decrease experimental animals, we will also explore how scaffold design changes strain distributions in cleft pig skulls. First, we construct two three-dimensional (3D) pig skull models and two different architected scaffolds. Then we perform finite element analysis (FEA) to find ways to decrease the asymmetric strain distributions produced by scaffolds used in the surgery. Finally, these results showed that the asymmetric strain distribution can be effectively reduced by use of different types of scaffolds. We also found that scaffold applied to reconstruct alveolar cleft can be 3D-printed with low stiffness biodegradable material, which also includes significant porosity to facilitate cell infiltration. These results support that FEA can be an effective computational tool to design suitable scaffold for cleft-repairing and predict detailed strain distributions. FEA is beneficial to prepare biodegradable scaffold for in vivo testing and an excellent assistant to surgical operations.

Committee: Gui-Rong Liu Ph.D. (Committee Chair); Yao Fu (Committee Member); Jude Iroh Ph.D. (Committee Member) Subjects: Materials Science

Doctor of Philosophy (Ph.D.), University of Dayton, 2017, Engineering

Conductive biopolymers are starting to emerge as potential scaffolds of the future. These scaffolds exhibit some unique properties such as inherent conductivity, mechanical and surface properties. Traditionally, a conjugated polymer is used to constitute a conductive network. An alternative method currently being used is nanofillers as additives in the polymer. In this dissertation, we fabricated an intelligent scaffold for use in tissue engineering applications. The main idea was to enhance the mechanical, electrical properties and cell growth of scaffolds by using distinct types of nanofillers such as graphene, carbon nanofiber and carbon black. We identified the optimal concentrations of nano-additive in both fibrous and film scaffolds to obtain the highest mechanical and electrical properties without neglecting any of them. Lastly, we investigated the performance of these scaffold with cell biology. To accomplish these tasks, we first studied the mechanical properties of the scaffold as a function of morphology, concentration and variety of carbon nanofillers. Results showed that there was a gradual increase of the modulus and the fracture strength while using carbon black, carbon nanofiber and graphene, due to the small and strong carbon-to-carbon bonds and the length of the interlayer spacing. Moreover, regardless of the fabrication method, there was an increase in mechanical properties as the concentration of nanofillers increased until a threshold of 7 wt% was reached for the nanofiller film scaffold and 1%wt for the fibrous scaffold. Experimental results of carbon black exhibited a good agreement when compared with data obtained using numerical approaches and analytical models, especially in the case of lower carbon black fractions. Second, we examined the influence of electrical properties of nanofillers based on the concentration and the geometry of carbon nanofillers in the polymer matrix using experimental and numerical simulation approaches. The (open full item for complete abstract)

Committee: Khalid Lafdi (Advisor) Subjects: Biomedical Engineering; Engineering; Materials Science

Doctor of Philosophy, University of Toledo, 2017, Biomedical Engineering

Rotator cuff injuries are very common among people over the age of 60, with more than 600,000 surgeries performed annually in the United States for rotator cuff repairs. However, in 20-80% of the cases, the repair fails due to re-rupture of the tendon at the tendon-bone insertion site. The complexity of the tendon tissue in terms of their structure, composition, and function at the tendon-to-bone interface demands for a combinatorial tissue-engineering approach in which cell maturation and function can be directed using bioactive proteins encapsulated within a biomaterial with appropriate material stiffness. Further, since tendons experience routine mechanical strains in their native environment, providing suitable mechanical cues to the engineered scaffold was considered important for the success of rotator cuff repair strategies. The objective of this dissertation was to synthesize and characterize a mechanically-conditioned biphasic composite collagen scaffold to enhance rotator cuff regeneration with (1) controlled delivery of adipose-derived stem cells (ASCs) and platelet-derived growth factor (PDGF) to augment and accelerate tendon healing, and (2) spatial material stiffness to promote gradient mineralization and matrix directionality at the tendon-bone interface. To this end, a mechanical loading bioreactor consisting of unique silicone loading chambers was designed that was capable of applying homogenous uniaxial tensile strains over 60% of the length of cell-encapsulated 3D collagen scaffolds. Uniaxial tensile mechanical loading at 2% strain with 0.1 Hz frequency was identified to be the appropriate loading modality to induce pure ASC tenogenic differentiation, along with enhanced matrix directionality and ECM gene expression within ASC-encapsulated 3D collagen scaffolds. Next, the poor protein retention and matrix stiffness properties of collagen were improved by synthesizing a composite collagen scaffold (PNCOL) interspersed with functionalized polycapr (open full item for complete abstract)

Committee: Eda Yildirim-Ayan (Advisor) Subjects: Biomedical Engineering; Biomedical Research

Master of Science, University of Akron, 2017, Polymer Science

Tissue engineering technology uses the combination of cells, materials and engineering methods, and suitable biochemical and physicochemical factors to improve or replace biological functions. Scaffolds are frequently involved in tissue engineering. Scaffolds are biodegradable materials that have been modified to form new functional tissues for medical purposes. Many studies indicated that silicon is an essential element in bone and connective tissue formation. By functionalizing the biodegradable poly(lactic acid) with silicon, its' application in tissue engineering is available. The silicon-functionalized copolymer used in this study was synthesized by grafting methyl methacrylate and a silicon-containing methacrylate by atom transfer radical polymerization (ATRP) from a brominated poly(lactic acid) (PLB) used as a macroinitiator. The PLB macroinitiator (GPCPSt Mn = 1.6 ×104 Da; Ð = 2.25) was prepared by incorporating 2-bromo-3-hydroxypropionic acid (BrH) as a co-monomer with lactic acid (LA). This polymerization was well controlled using CuBr as the catalyst and bipyridine as the ligand in toluene at 90 °C. The resulting graft copolymer contains PLA, PMMA and 3-(triethoxysilyl)propyl methacrylate (TESPMA). The final scaffolds prepared by compression method showed good integrity in cell culture media.

Committee: Coleen Pugh (Advisor); Abraham Joy (Committee Member) Subjects: Polymer Chemistry; Polymers

Doctor of Philosophy, Case Western Reserve University, 2016, Macromolecular Science and Engineering

Polymeric biomaterials, in the form of fibrous constructs and hydrogels, have received substantial attention in recent years, showing great promise in the field of regenerative medicine. The first half of this dissertation will discuss recent advances in multilayer coextrusion technology to fabricate matrix/fiber polyester composites of poly(ethylene oxide) (PEO) and poly(e-caprolactone) (PCL) and subsequent isolation of highly aligned rectangular fibers with micro- to nano-scale dimensions achieved through post-process uniaxial drawing with two kinetic regimes. Uniaxial drawing resulted in a 2.5-fold increase in specific surface area, a 30-fold increase in elastic modulus, and 10-fold tensile strength. Rectangular coextruded PCL fibers exhibited a 6-fold increase in specific surface area over corresponding circular, electrospun PCL fibers while maintaining similar thermo-mechanical properties. A two-stage distillation process was employed to recover ~100% pure water (95% recovery) and methanol (87% recovery) utilized during PEO removal. The distillation process enabled ~94% recovery of ~100% pure PEO coextruded as sacrificial matrix material that may be reintroduced to the coextrusion process, substantially decreasing process waste. The second segment of this talk focuses on a straightforward in situ post-process PEO crosslinking scheme to fabricate well dispersed, sub-micron scale fiber-reinforced hydrogels. By systematically varying feed rate, hydrogel compressive stiffness was tailored ranging between ~0.5 - 2 kPa, on par with values obtained from articular cartilage. Uniaxial drawing before hydrogel fabrication resulted in a 225% increase in hydrogel stiffness, while use of rigid poly(L-lactic acid) (PLLA) fibers increased gel stiffness 350%. Hydrogels fabricated using the in situ fabrication technique displayed increased stiffness and similar fibroblast cell viability when evaluated against hydrogels developed using electrospun PCL fibers and traditional addi (open full item for complete abstract)

Committee: LaShanda Korley (Advisor); Eric Baer (Committee Member); Gary Wnek (Committee Member); Mark Griswold (Committee Member) Subjects: Chemical Engineering; Polymer Chemistry; Polymers

Doctor of Philosophy, Case Western Reserve University, 2015, Biomedical Engineering

Long-term viability of three-dimensional tissue engineered constructs remains a major hurdle due to challenges associated with mass transfer of oxygen, nutrients, and waste products. To address this shortcoming, this work focuses on designing cell-responsive materials to be utilized in a bioactive tissue engineered construct, with a particular emphasis on vasculogenesis. We hypothesized that highly tunable synthetic materials tailored with the appropriate bioactivity could allow for: cell attachment, cell mediated degradation, and growth factor release in vitro. To accomplish this, bio-inert PEG hydrogels were used as a scaffold substrate. To mimic the properties of the extracellular matrix (ECM), cell-adhesive peptide (CGRGDSP), enzyme-sensitive peptide (CGPQGIAGQC), and bi-functional peptide (CGPQGIAGQCGRGDSP) were incorporated into the hydrogel scaffold. This, in conjunction with multi-arm PEG acrylate and Michael Addition chemistry, allowed for the synthesis of bio-active hydrogels that could be synthesized free of cytotoxic photoinitiator, and had decoupled hydrogel properties for more appropriate comparison between formulations. The resulting hydrogels could bind cells as a function of cell adhesive peptide concentration and degrade as a function of collagenase. Separately, enzymatically degradable growth factor loaded nanoparticles were synthesized using a liposome template technique in conjunction with dehydration-rehydration loading. This allowed for a high concentration of growth factor to be loaded into nanoparticles, while simultaneously preventing the deactiviation of growth factor through extreme processing conditions. Moreover, through the incorporation of enzymatically degradable peptide (VPMSMRGG) into the backbone of these hydrogel nanoparticles, we alter the release profile of the growth factor both as a function of collagenase concentration as well as cell concentration. These bioactive constructs offer the increased ability for cells to (open full item for complete abstract)

Committee: Roger Marchant (Advisor); Kandice Marchant (Advisor); Horst von Recum (Committee Member); Anirban Sen Gupta (Committee Member); Stuart Rowan (Committee Member) Subjects: Biomedical Engineering

Doctor of Philosophy, Case Western Reserve University, 2015, Biomedical Engineering

Cartilage tissue engineers have made great inroads on understanding the factors controlling chondrogenesis, however, the biomechanical properties of tissue engineered cartilage (TEC) are chronically inferior to that of native cartilage. The focus of this dissertation was to determine the ability of scaffold-free TEC to withstand frictional-shear stress, and if needed, to improve that ability to a physiologically relevant level. Frictional-shear testing performed at a sub-physiological normal stress of 0.55 MPa demonstrated that constructs exhibited lubrication patterns characteristic of native cartilage lubrication, but severe damage also occurred. Low absolute collagen content, and a low collagen-to-glycosaminoglycan (GAG) ratio were also found in the same constructs. Reduction in damage was attempted by increasing the collagen content of the ECM. Scaffold-free TEC treated with T4 at 25 ng/ml exhibited increased collagen concentration in a statistically significant manner, and the average collagen-to-GAG ratio was also increased although statistical significance was not achieved. Western blotting showed that type II collagen was increased, type X collagen was not detected. COL2A1, and biglycan gene expression were also found to have increased, no statistically significant difference was found for COLX gene expression. When compared to control constructs, T4 treated constructs exhibited a large and statistically significant decrease in the extent of damage incurred by frictional-shear testing. At the 2.8 MPa normal stress, total damage was reduced by 60% in the 2-month constructs. Correlation coefficients calculated between compositional properties and the amount of damage showed that at the 2.8 MPa normal stress collagen concentration and the collagen-to-GAG ratio exhibited the greatest correlation to damage (correlation coefficient of approximately -0.7 with a 95% confidence interval of approximately -0.87 to -0.38 for both). In conclu (open full item for complete abstract)

Committee: James Dennis Ph.D. (Advisor); Joseph Mansour Ph.D. (Advisor); Horst von Recum Ph.D. (Committee Chair); Eben Alsberg Ph.D. (Committee Member) Subjects: Biomechanics; Biomedical Engineering; Biomedical Research; Engineering; Materials Science

Doctor of Philosophy, The Ohio State University, 2014, Biomedical Engineering

Split-thickness autograft is the standard treatment for full-thickness burns. In large burns, sparse availability of uninjured skin prevents rapid closure of the wound, resulting in increased scar tissue formation or mortality. Tissue-engineered skin (ES) offers promise when autografts are not available. Unfortunately, current generations of ES are orders of magnitude weaker than normal human skin causing them to be difficult to apply surgically, subject to damage by mechanical shear in the early phases of engraftment and less elastic and weaker once grafted. To enhance and tune ES biomechanics, a coaxial (CoA) electrospun scaffold platform was developed from polycaprolactone (PCL, core) and gelatin (shell). CoA ES exhibited increased cellular adhesion and metabolism versus PCL alone or gelatin-PCL blend and promoted the development of well stratified skin with a dense dermal layer and a differentiated epidermal layer. Biomechanics of the scaffold and ES scaled linearly with core diameter suggesting that this scaffold platform could be utilized to tailor ES mechanics for their intended grafting site and reduce graft damage in vitro and in vivo. To further enhance the mechanics of the coaxial scaffold, CoA scaffolds with cores of polylactic acid (PLA) and PCL and shells of gelatin were fabricated along with pure gelatin scaffolds and grafted onto athymic mice. Coaxial scaffolds were effective at preventing wound contracture but were not stable on the animal with the human epidermis largely replaced with mouse epidermis by week 10. The strength and stiffness of the ES were significantly greater than pure gelatin in vitro however after engraftment, mechanics of the gelatin improved greatly whereas little change was observed for the coaxial groups. Large quantities of macrophages were also seen in the coaxial groups throughout the entire duration of the study. Though coaxial scaffold could provide tailored mechanics in vitro, they elicited a strong host respon (open full item for complete abstract)

Committee: Heather Powell (Advisor); Samir Ghadiali (Committee Member); Douglas Kniss (Committee Member); Abigail Shoben (Committee Member) Subjects: Biomedical Engineering