Doctor of Philosophy, The Ohio State University, 2020, Oral Biology

Background and Objective: Dental implants are commonly made out of titanium or titanium alloys. The expected outcome following dental implant placement surgery is rigid stability due to osseointegration, the bone remodeling at bone/implant fixture interface, and a mucosal seal characterized by the formation of thin junctional epithelium covering the underlying connective tissue at the alveolar crest. A significant number of studies have been published focusing on post-implantation bone healing and various phases of osseointegration. However, limited amount of information is available regarding the formation and long-term integrity of the soft tissue seal. To understand the role of implant properties on soft-tissue responses, a biomimetic model of human gingiva with and without characteristic peri-implantitis is needed. This thesis is aimed to develop a healthy and “diseased” in vitro gingival model system and utilize our well-established clinical model to investigate the peri-implant soft tissue seal, tissue inflammation, and tissue breakdown in various oral-related conditions. Material and Methods: This thesis has three components addressing three specific aims. Following Introduction in Chapter 1, Chapter 2 presents experimental data on the behavior of gingival fibroblasts and epithelial cells on titanium surfaces with different characteristics in the absence and presence of a challenge from supernatants from P.gingivalis biofilm. Chapter 3 reports methodology of engineering gingiva in vitro by the use of gingival fibroblasts and epithelial cells, in a prototype scaffold used for engineering skin. Chapter 4 describes a clinical study conducted by recruiting 77 patients with implant supported dental restorations. These implants were functional at least for 1 year and revealed possible associations between clinical presentation of healthy/diseased peri-implant soft tissue and site-specific cytokine and titanium release. Results: Studies conducted with cultures es (open full item for complete abstract)

Committee: Binnaz Leblebicioglu (Advisor); Heather Powell (Advisor); Dimitris Tatakis (Committee Member); Sudha Agarwal (Committee Member) Subjects: Dentistry; Engineering

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

Master of Science in Biomedical Engineering, Cleveland State University, 2011, Fenn College of Engineering

The flow of nutrients through any biological tissue is important to maintain homeostasis. If the transport process is understood, medical research teams can better design medications, prosthetic implants, and tissue scaffolds. Additionally, transport rates help physicians to better understand disease states and wound healing, including minor injuries such as breaks and sprains, which will aid in better diagnoses. We developed a novel method that measures the rate of diffusion in vitro, of fluorescein sodium salt. Samples were incubated at 37°C in a 5% CO2 atmosphere for various periods of time. Samples were sliced and analyzed using Image-Pro Plus and MATLAB to obtain concentration profiles. The diffusivity was estimated from the data using the model equation for one-dimensional transport in a finite medium. We found that radial diffusivity in canine bone in 1-dimension was 1.27 x 10-7±1.96 x 10-8 cm2/s. As a point of reference, the diffusivity of fluorescein sodium salt in PBS is 2.7 x 10-6 cm2/s. Given the average distance between a Haversian canal and an osteon radius is 250 μm, our data shows it would take approximately 20 minutes for a nutrient of a weight of 376 Da to travel between the two locations. This indicates that the diffusion time of key nutrients, such as vitamin D, with molecular weight of 384 Da, would be about 20 minutes.

Committee: Joanne Belovich PhD (Committee Chair); Surendra Tewari PhD (Committee Member); Ronald Midura PhD (Committee Member) Subjects: Biology; Biomechanics; Biomedical Engineering; Biomedical Research; Biophysics; Fluid Dynamics; Health Sciences; Medicine

Master of Science, University of Akron, 2011, Chemical Engineering

Tissue engineering scaffolds (or matrices) with a controllable degradation profile were fabricated from multiple blends of two L-tyrosine polyurethanes (denoted as PCL1250-HDI-DTH and PEG1000-HDI-DTH ) by means of the electrospinning process. By adjusting the ratios (2:1, 1:1, 1:2, and pure solutions) of the two polymers in the blends, relative control over the scaffolds' degradation properties was achieved without detriment to other scaffold properties. The ability to control the degradation rate allows for scaffold residence time to be design variable when fabricating a medical device intended on mimicking the body. The matrices produced were characterized chemically, morphologically, and mechanically and then subjected to hydrolytic degradation. As theorized, the scaffolds degraded in a predictable and controllable manner. The scaffolds containing the higher proportion of the more resilient PCL1250-HDI-DTH polymer degraded more slowly and to a lesser extent (by mass) than those principally composed of the more hydrophilic PEG1000-HDI-DTH polymer. Specifically, after 60 days of exposure, mass losses (from highest to lowest concentration of PEG1000-HDI-DTH) were approximately 35%, 26%, 21%, 16%, and 9%. Note that decreasing concentration of PEG1000-HDI-DTH correlates to increased resistance to hydrolytic degradation. The mass lost per electrospun scaffold was between 76% and 108% greater than the identical blend in thin film configuration, demonstrating the enhanced degradation characteristics of the structure. Specifically, after 35 days of exposure, mass losses from the electrospun membranes were (from highest to lowest concentration of PEG1000-HDI-DTH) approximately 76%, 85%, 108%, 103%, and 98% greater than those of each blend's thin film counterpart. Morphologically, despite differing polymeric compositions, the scaffolds were fabricated under almost identical conditions and produced similar, acceptable fiber diameters, distributions, and pore sizes with mino (open full item for complete abstract)

Committee: Lingyun Liu Dr. (Advisor); Edward Evans Dr. (Committee Member); Bi-Min Newby Dr. (Committee Member) Subjects: Chemical Engineering

Master of Science, The Ohio State University, 2023, Biomedical Engineering

Development of Tissue-Engineered Vascular Grafts (TEVG's) for use in treatment of pediatric cardiovascular disease offer a promising alternative to current synthetic graft models, which typically result in the patient needing additional surgeries to correct for complications related to the inability of these grafts to assimilate into the body. Understanding this potential for TEVG performance improvement, we saw opportunity in optimizing the scaffolds design. Herein, we utilized an accelerated degradation mechanism in a basic environment to begin to characterize the degradation space of our six novel scaffold variants: comparing their microstructure, chemical composition, and mechanical integrity at nine different timepoints (Day 0 (control), 1, 3, 5, 7, and 9) to our clinical TEVG scaffold. Current analyses have shown differing chemical compositions of PGA, PLA, and PCL for each scaffold at baseline (day 0), as well as similarities and differences between mechanical and microstructural characteristics of each scaffold variant. While initial degradation of samples is complete, data collection and analysis for this study is ongoing. Once complete, this data will be applied to a multiscale fluid-solid growth (mFSG) computational model that can identify future scaffold designs for optimizing the microstructure, degradation rate, and mechanical profile of the TEVG polymeric scaffold.

Committee: Daniel Gallego-Perez (Committee Member); Christopher Breuer (Advisor) Subjects: Biomedical Engineering

Doctor of Philosophy, University of Akron, 2019, Biomedical Engineering

Spinal cord injury (SCI) results in permanent motor and sensory deficits, primarily caused by localized cell death. Treatment strategies which focus on guiding cell behavior (exogenous or endogenous) are attractive. Neural stem cells (NSCs) can contribute to recovery indirectly (secreted neurotrophic factors) or directly (by differentiating into functional cell types). Their efficacy is also clearly enhanced with an active biomaterial carrier to keep them within the site of injury and guide their behavior. Here, a biomaterial-based approach for treating SCI was investigated, consisting of NSCs seeded within a biomimetic scaffold made from methacrylamide chitosan (MAC). The scaffold contained tethered, biotinylated recombinant growth factors to specify the lineage of the encapsulated NSCs. This scaffold showed promising tissue-level improvements but failed to restore locomotor function. Next, a new approach for covalently immobilizing azide-tagged recombinant proteins was developed. This approach was tested on interferon-gamma (IFN-gamma, which induces neuronal differentiation from NSCs) and found to enable immobilization to multiple materials while retaining its bioactivity. A new, open-source gait analysis technique was then adapted to include SCI-specific parameters. This technique was tested on a treatment which is known to be effective, intracellular sigma peptide (ISP, which reduces inhibitory cues from the microenvironment) and found to sensitively measure benefits. The NSC-seeded scaffolds were tested again, with two major improvements: they were primed in subcutaneous tissue prior to transplantation into the spinal cord and ISP was co-administered. This approach was based on a finding that NSC-seeded scaffolds with immobilized IFN-gamma increased the expression of developmental markers after subcutaneous maturation. Ultimately, subcutaneous maturation with ISP was found to improve function. The tissue-level analysis suggested that this was due to an indirec (open full item for complete abstract)

Committee: Nic Leipzig PhD (Committee Chair); Rebecca Willits PhD (Committee Member); Hossein Tavana PhD (Committee Member); Bi-Min Zhang Newby PhD (Committee Member); Adam Smith PhD (Committee Member) Subjects: Biomedical Engineering

Master of Science, The Ohio State University, 2017, Mechanical Engineering

Our current understanding of electrophysiological phenomena is limited by our ability to measure particular processes. There are a number of electrophysiological intracellular and extracellular measuring techniques which currently exist; however, they are not without limitations. These techniques, such as patch-clamping, involve the careful isolation of a singular cell (which removes the cell from its native environment) and subsequent puncturing or suctioning of the cell membrane (which can damage the cellular structure). This research focuses on the development of conducting polymer sensors for in vivo measurements of electrophysiological phenomena. The goal of this work is to create a system by which ion concentration dynamics can be directly measured and analyzed to quantify metrics of biological processes without harming tissues of the organism. Quasi-potentiostatic amperometric sensors were developed using polypyrrole doped with dodecylbenzenesulfonate (DBS) to form PPy(DBS). By applying a cyclic pulse voltage input to the conducting polymer measurement system, and measuring the resulting current response, system parameters can be correlated to deviations from an equilibrium concentration as a function of time. This research will lay the foundation for more complex measurement techniques, both in electrophysiology, as well as in energy storage technology.

Committee: Vishnu Baba Sundaresan (Committee Member); Daniel Gallego-Perez (Committee Member) Subjects: Biomedical Engineering; Cellular Biology; Engineering; Mechanical Engineering; Neurobiology; Neurology; Neurosciences

Doctor of Engineering, Cleveland State University, 2016, Washkewicz College of Engineering

Localized host inflammatory microenvironment resulting from several neuropathologies (e.g., trauma, amyotrophic lateral sclerosis (ALS), glioblastomas) leads to progressive degeneration of neuronal tissue and destruction of axonal tracts in the adult central nervous system (CNS). Failure to reinstate healthy cells and axonal connections under these conditions can severely compromise locomotion and cognitive function, resulting in muscle atrophy, paralysis and even death. Annually, thousands of people are diagnosed with various neuropathologies and a majority of them succumb to these conditions soon after. The adult CNS has a limited ability for self-repair, which necessitates repair strategies focused on ameliorating secondary cellular degeneration, promoting endogenous repair mechanisms, and exogenous cell replacement therapy. Currently, pharmacological and surgical treatments options are limited in their outcomes for these types of ailments. Neural stem cells (NSCs) isolated from the embryonic and adult striatum have the capacity to divide and differentiate into various neuronal and glial lineages, thus demonstrating their utility in regenerating lost neuronal populations. To further investigate their clinical potential, in this work, we first developed and tested the utility of uncrosslinked 3D biological hydrogels (compressive strength < 600 Pa) for their ability to promote murine NSC survival, differentiation into desired lineages and neurite outgrowth, in the presence (or absence) of exogenous cues such as retinoic acid. In the second step, the influence of an activated murine microglia in regulating the phenotype and genotype of murine NSCs within a localized 3D coculture microenvironment was investigated, and the key cytokines and chemokines which regulate NSC survival, differentiation and neurite outgrowth were identified. Finally, in the third step, the effects of paracrine-signaling between adult human NSCs and human pediatric glioblastoma cells within a (open full item for complete abstract)

Committee: Chandra Kothapalli Ph.D. (Committee Chair); Nolan Holland Ph.D. (Committee Member); Xue-Long Sun Ph.D. (Committee Member); Joanne Belovich Ph.D. (Committee Member); Moo-Yeal Lee Ph.D. (Committee Member) Subjects: Biomedical Engineering; Medicine; Neurosciences

Master of Science in Biomedical Engineering, Cleveland State University, 2014, Washkewicz College of Engineering

The field of tissue engineering aims at promoting the regeneration of tissues or replacement of failing or malfunctioning tissue by means of combining a scaffold material, adequate cells and bioactive molecules. Different materials have been proposed for use as three-dimensional porous scaffolds for bone tissue engineering procedures. Among them, polymers of natural origin are one of the most attractive options mainly due to their similarities with the extracellular matrix (ECM), chemical versatility as well as typically good biological performance. In this study, two biocompatible composite scaffolds were developed from natural polymer by tissue engineering approach and tested in vitro. The first Scaffold (SCAF-1) that was developed was composed of human hair keratin protein and human hair fibers (cuticle-cortex). The second scaffold (SCAF-2) was composed of human hair keratin protein, human hair fibers (cuticle-cortex) and hydroxyapatite (HA) particles. SEM and EDX were used to analyze the three dimensional structure, surface chemistry and pore size of the scaffolds. Both scaffolds showed a three-dimensional structure with a pore size ranging from 40-500µm and porosity greater than 50%. Compressive tests were carried out under dry as well as wet conditions for both scaffolds. SCAF-1 showed compressive modulus of 0.009 MPa in wet condition and 0.90 MPa in a dry condition. Likewise, SCAF-2 had compressive modulus of 0.09 MPa in wet condition and 2.7 MPa in dry condition. Cell culture experiments with bone marrow stromal cells demonstrate that the composite scaffolds support cell attachment and proliferation. Overall, human hair keratin scaffolds have been shown to have a porous three-dimensional structure that induces proliferation of GFP- stromal cells for bone tissue regeneration. These preliminary results suggest that human hair keratin, cuticle-cortex fibers and HA composite scaffolds appear to be an interesting structure for potential studies in bone tissue e (open full item for complete abstract)

Committee: Surendra N. Tewari PhD (Committee Chair); Joanne M. Belovich PhD (Committee Member); Chandra Kothapalli PhD (Committee Member) Subjects: Biomedical Engineering

Master of Science, The Ohio State University, 2006, Graduate School

Committee: Not Provided (Other) Subjects:

Master of Science, The Ohio State University, 2007, Graduate School

Committee: Not Provided (Other) Subjects:

PhD, University of Cincinnati, 2024, Engineering and Applied Science: Biomedical Engineering

Severe tissue injuries pose a significant challenge in therapeutic interventions, often resulting in suboptimal functional recovery due to inadequate regenerative signals. Traditional clinical methods, such as autografts, have variable success rates, partly because they fail to provide the necessary cellular and tissue guidance for advanced regeneration. This dissertation investigates the potential of electrospun polyvinylidene fluoride-trifluoroethylene (PVDF-TrFE), a piezoelectric polymer, in creating a conducive environment for tissue regeneration. The inherent piezoelectricity of PVDF-TrFE generates electric charges under mechanical stress, actively engaging tissue cells, including fibroblasts essential for extracellular matrix formation and Schwann cells vital for peripheral nervous system healing, thereby promoting nerve function and broad tissue regeneration. This research focuses on PVDF-TrFE scaffolds, specifically electrospun piezoelectric nanofiber scaffolds, meticulously characterized for their material and electrical attributes. The study explores the incorporation of decellularized extracellular matrix (dECM) to enhance the bioactivity of the scaffolds, introducing bioactive components that provide better functional repair. Additionally, the effects of ultrasonic stimulation on these scaffolds are examined, aiming to induce electrical stimulation through mechanical deformation triggered by sound waves, thereby enhancing cellular activity to aid nerve regeneration. Experiments with NIH-3T3 fibroblast cultures on these scaffolds show increased metabolic activity following ultrasound stimulation, illustrating the scaffold's capability to support cellular processes essential for peripheral nervous system recovery. The dissertation also examines the impact of post-processing annealing on PVDF-TrFE scaffolds, analyzing how different annealing temperatures affect their crystallization behavior, morphology, mechanical properties, and piezoelectric responsivene (open full item for complete abstract)

Committee: Leyla Esfandiari Ph.D. (Committee Chair); Daria Narmoneva Ph.D. (Committee Member); John Martin Ph.D. (Committee Member); Greg Harris Ph.D. (Committee Member) Subjects: Biomedical Engineering

MS, University of Cincinnati, 2024, Engineering and Applied Science: Biomedical Engineering

Peripheral neuropathy is a diverse affliction caused by numerous forms of traumatic injuries and genetic diseases. Damage or mutation in the peripheral nervous system (PNS) can result in unpleasant alterations to normal sensation, such as chronic itch or chronic pain. There is no cure for peripheral neuropathy and research models of the PNS are limited due to its vital nature in an organism and its grand scale. Only in-vitro and in-utero models allow for observing interactions between the distal and proximal ends of sensory neurons (SNs) in tandem. Current three-dimensional (3D) in-vitro models enable simulating the PNS in different tissue environments, such as the skin. However, current innervated models are limited in options for measuring action potentials of SNs in the 3D environment. Such models use non-repeatable measurements or costly experimental measuring apparatuses, making processes that change over time, such as healing or degradation, a significant challenge to observe. In this article we describe the creation of an innervated dermis optimized to provide surface access to SNs so individual neuron action potentials can be clearly distinguished from each other while still achieving transdermic sensation for use with calcium imaging. Next, we develop our own method for repeatably measuring action potentials using our model that provides continuous measurement of action potentials in a non-destructive manner, without the need for a customized imaging apparatus. Our new model can simultaneously measure multiple action potentials from dozens of neurons numerically and continuously across multiple days.

Committee: Stacey Schutte Ph.D. (Committee Chair); Eric Nauman Ph.D. (Committee Member); Greg Harris Ph.D. (Committee Member) Subjects: Biomedical Engineering

Doctor of Philosophy, University of Akron, 2024, Biomedical Engineering

Myocardial infarction commonly known as heart attack, is a type of cardiovascular disease which occurs when the flow of blood is restricted to a part of the heart muscle for a prolonged period, leading to tissue damage or cell death due to lack of oxygen and nutrients. Several tissue engineering strategies have been implemented to regenerate the damaged cardiac tissue and improve cardiac function post myocardial infarction. One of the most promising strategies for cardiac regeneration is using injectable hydrogels derived from decellularized myocardial tissue. Compared with other natural or synthetic biomaterials, the decellularized cardiac extracellular matrix (ECM) hydrogels provide cardiac- specific microenvironment including ECM composition and biochemical cues which supports the cell attachment, growth, migration, and differentiation. Due to these advantages, decellularized cardiac ECM hydrogels have been widely explored for various cardiac tissue engineering applications. However, as the decellularized myocardial tissue is lyophilized and milled into a powder to form hydrogel, the material properties and the ability to induce angiogenesis (formation of new blood vessels) is greatly affected. To address this issue, we developed a hybrid hydrogel (Fn-cECM) by combining decellularized cardiac ECM hydrogel (cECM) solution and fibrin (Fn) solution and investigated their material properties and evaluated their interactions with therapeutic cells. We observed that the Fn-cECM hybrid hydrogel exhibited enhanced degradation, gelation kinetics and storage modulus compared to the cECM hydrogel. Additionally, we observed significant capillary network formation and angiogenic sprouting for human umbilical vein endothelial cells (HUVECs) and human mesenchymal stem cells (hMSCs) spheroids. Based on our promising outcomes, we evaluated the feasibility of fabricating granular hydrogels using cECM and Fn-cECM microgels produced via extrusion fragmentation to overcome the limita (open full item for complete abstract)

Committee: Ge Zhang (Advisor); Ge Zhang (Committee Chair); Qin Liu (Committee Member); Hossein Ravanbakhsh (Committee Member); Weinan Xu (Committee Member); Jiang Zhe (Committee Member) Subjects: Biomedical Engineering; Biomedical Research

Doctor of Philosophy, The Ohio State University, 2023, Biomedical Engineering

Cancer metastasis is a complex, systemic, and non-random process requiring tumor cells to both adapt to and manipulate a multitude of microenvironments. Given this complexity, traditional 2D cell culture models offer insufficient structural and biological relevance, while animal models face obstacles in real-time analysis, experimental control, and translational success. As an alternative to address these barriers, this dissertation discusses development of tissue engineered microfluidic device-based tumor-on-a-chip platforms to isolate phases of metastatic colonization and study premetastatic microenvironmental changes. In this dissertation, this hydrogel-based technology was applied in three different aspects of metastatic progression. First, a thyroid metastasis-on-a-chip model was developed to study metastasis suppressor gene RCAN1-4 and its impact on downstream lung colonization. Second, 3D hydrogel scaffolds were implemented to investigate colorectal cancer-induced collagen remodeling by stromal fibroblasts and pericytes during premetastatic niche development. Third, observations of cancer-induced collagen remodeling were used to inform design of a liver premetastatic niche-on-a-chip model to further interrogate immune-myofibroblast crosstalk in response to colorectal cancer signaling and establish the relationship between this crosstalk and metastatic colonization.

Committee: Aleksander Skardal (Advisor); Daniel Gallego-Perez (Committee Member); Jennifer Leight (Committee Member); Jonathan Song (Committee Member) Subjects: Biomedical Engineering; Biomedical Research; Oncology

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

Schwann cells (SCs) are responsible for axon function and maintenance in the peripheral nervous system (PNS), as well as being a key component to the regeneration process following trauma. Once an injury occurs, SCs respond to both physical and chemical stress cues to modify their phenotype to assist in the regeneration of damaged axons. There is currently a lack of research examining SC response to dynamic changes in the extracellular matrix (ECM) brought on by swelling and the development of scar tissue as part of the body's wound-healing process. Thus, the overall objective of this project is to use a biocompatible, mechanically tunable substrate to mimic changes in the microenvironment. Previously, we have reported that ECM cues such as ligand type and substrate stiffness impact SC phenotype and plasticity, which was demonstrated by culturing SCs on mechanically stable substrates. However, to better realize SC potential for plasticity following traumatic injury, we utilized a UV-tunable PDMS substrate with dynamically changing stiffness to mimic changes in the microenvironment. Through the examination of cell morphology and protein expression, we seek to better understand the relationship between SC plasticity and a dynamically changing microenvironment in both injury and diseased states. This relationship holds the potential for creating future PNS therapies that currently have extremely limited methods of care.

Committee: Greg Harris Ph.D. (Committee Chair); Jason Shearn Ph.D. (Committee Member); John Martin Ph.D. (Committee Member) Subjects: Biomedical Engineering

Doctor of Philosophy, The Ohio State University, 2023, Biomedical Engineering

A trachea defect from malformation or obstruction can result in significant morbidities and mortalities. Long segment tracheal defects, where the length of the defective tracheal segment is >50% for adults and >30% for the pediatric population, are often fatal due to the lack of autologous tissue suitable for reconstruction. Tissue engineered tracheal grafts (TETG) have the potential to be used to replace diseased tracheal tissue. However, TETG success is often limited by delayed epithelial formation and biocompatibility. The Chiang lab developed a partially decellularized tracheal graft (PDTG) that removes the immunogenic epithelium and lamina propria while preserving donor cartilage that is immune-protected. We have previously shown that PDTG can support host-derived neotissue formation but the composition, long-term outcome, and drivers of PDTG neotissue formation have been largely uncharacterized. The characterization of PDTG neotissue will facilitate the translation of PDTG into large animals as we better understand the regenerated tissue and possible drivers behind neotissue formation. This dissertation aims to examine PDTG neotissue using a combination of immunofluorescent and transcriptomic approaches to characterize PDTG neotissue before uncovering drivers of tracheal graft epithelialization. Functional vasculature in PDTG was established by 2 weeks post-implant. Graft epithelialization was reestablished by 1 month. PDTG neo-epithelialization is driven by basal progenitor cells that were able to proliferate and differentiate into secretory and multiciliated cells. This neo-epithelialization process mirrors the epithelial repair processes seen in epithelial injury models. There was also a macrophage-dominant immune response post-implantation for both PDTG and syngeneic transplants. I then examine the immune response associated with graft implantation to study the impact of macrophages on graft epithelialization. To do that, macrophage phenotypes in the (open full item for complete abstract)

Committee: Tendy Chiang (Advisor); Susan Reynolds (Committee Member); Kaitlin Swindle-Reilly (Committee Member); Christopher Breuer (Committee Co-Chair) Subjects: Biomedical Engineering; Medicine

Master of Science in Chemical Engineering, Cleveland State University, 2023, Washkewicz College of Engineering

Existing hydrogel materials used as bioinks in tissue engineering, especially bioprinting, are not engineered specifically for these applications and so have various tradeoffs or disadvantages that create limitations or incompatibilities with various cultures, equipment, or experimental conditions. Typically, naturally derived hydrogels demonstrate good biocompatibility but with poor rheological properties, whereas synthetically produced polymers typically demonstrate excellent printability at the cost of biocompatibility. To bridge these material needs, a triblock copolymer elastin-like polypeptide hydrogel containing RGDS cell binding domains to enhance biocompatibility was designed, produced, and purified through recombinant expression in Escherichia coli. This material was characterized through DLS measurements to understand purification characteristics and the micelle geometry used to estimate a minimum gelation concentration of the novel construct is estimated to be between 10 mM and 0.6 mM (0.3 g/mL and 0.018 g/mL). Further work will involve characterizing the rheological properties of the networked micelle hydrogel.

Committee: Nolan Holland Ph.D. (Committee Chair); Chelsea Monty-Bromer Ph.D. (Committee Member); Metin Uz Ph.D. (Committee Member) Subjects: Biomedical Engineering; Molecular Biology

Doctor of Philosophy, The Ohio State University, 2022, Mechanical Engineering

Direct-write (DW) Additive Manufacturing (AM), holds a great promise in tissue engineering (TE), as it enables the rapid fabrication of complex, porous, three-dimensional (3D) TE scaffolds through precise deposition of biomaterials, cells, and biomolecules. However, in the current TE workflow, scaffolds are fabricated in the lab and then are implanted in the patient via an open surgery. This paradigm invites handling and surgical complications, negating the therapeutic benefits of TE. At this stage of development, it is rational to merge Robotic Assisted Surgery (RAS), AM, and TE to perform minimally invasive TE directly inside the patient body (intracorporeally), through keyhole incisions, using an endoscopic AM tool. Endoscopic AM is radically different from conventional DW AM methods. The material must traverse through a long slender tool to be deposited in 3D on soft tissue deep into the body, at physiological temperature, and in a safe manner. Most of the current biomaterial formulations used in TE either have a very low viscosity at physiological temperature (37 ◦C) and therefore cannot be deposited in 3D, or require crosslinking mechanisms that are unsafe to be used intracorporeally, such as the use of ultraviolet light, or chemical agents. Moreover, flowrate control continues to be a challenge in DW AM, resulting in defects in the manufactured constructs, which are not desired in intracorporeal TE. Towards intracorporeal AM of TE scaffolds, in this dissertation I present, 1. flowrate control in DW AM with pressure feedback, to avoid excess or lack of material deposition for precise intracorporeal TE, 2. development and characterization of a novel biomaterial formulation for DW AM of TE scaffolds in intracorporeal conditions, and robotics methods for scaffold integration on soft tissue, and 3. endoscopic AM of TE scaffolds in a mock surgical environment and the effect of endoscopic AM unique characteristics on the biomaterial printing and cell function.

Committee: David Hoelzle Dr. (Advisor) Subjects: Biomedical Engineering; Mechanical Engineering

Doctor of Philosophy, University of Toledo, 2022, Chemical Engineering

Polysaccharides have attracted much attention in the field of bone tissue engineering as natural scaffolds that mimic the physiological structure of the extracellular matrix (ECM) and provide glycosaminoglycan-like environments with nontoxic degradation products. Moreover, the use of polysaccharides is not limited to mimicking the 3D structure of the ECM but also as bioactive natural macromolecules that can stimulate cell-signalling. Gellan gum (GAGR) is a naturally occurring polysaccharide with repeating units of D-glucose, D-glucuronic acid, and L-rhamnose. Due to its biocompatibility and biodegradability, GAGR has been investigated in biomedical applications, food processing, pharmaceutics, and tissue engineering. In this research, GAGR is investigated not only as a scaffold but also as a bioactive material that stimulates bone regeneration. Culturing pre-osteoblast cells with GAGR resulted in a significant upregulation of genes related to osteogenesis and chondrogenesis, in addition to collagen type I protein formation, which is the main component in the ECM. Thus, to deliver GAGR, various formulations of GAGR, hyaluronic acid, and β-tricalcium phosphate were fabricated. The objective was to develop an ionically crosslinked gel that can be injected and allows GAGR to disintegrate over time from its network structure. Then, the possibility of GAGR diffusion and adsorption in human bone was investigated in vitro by the standard diffusion cell chamber and adsorption isotherms. In vivo, the cross-linked GAGR gel was injected into the femur bone of an ovariectomized rat model. GAGR gel-injected sites showed a significant increase in inward bone growth, resulting in thicker cortical bone, as well as an increase in number of blood vessels. A simulation of the in vivo study using finite element model (COMSOL Multiphysics v 5.4) showed a qualitative agreement to the experimental results, and revealed a significant effect of GAGR molecular weight and adsorption on (open full item for complete abstract)

Committee: Dong-Shik Kim (Committee Chair); Joshua Park (Committee Member); Eda Yildirim-Ayan (Committee Member); Maria Coleman (Committee Member) Subjects: Chemical Engineering