Global ETD Search

1	Integrative Click Chemistry for Tuning Physicochemical Properties of Cancer Cell-Laden Hydrogels Hunter Caleb Johnson (8764017) 30 April 2020 (has links) <p>The pancreas is a vital organ that secretes key metabolic hormones and digestive enzymes. In pancreatic ductal adenocarcinoma (PDAC), one of the leading causes of cancer-related death in the world, limited advances in diagnosis or therapies have been made over decades. Key features of PDAC progression include an elevated matrix stiffness and an increased deposition of extracellular matrices (ECM), such as hyaluronic acid (HA). Understanding how cells interact with components in the tumor microenvironment (TME) as PDAC progresses can assist in developing diagnostic tools and therapeutic treatment options. In recent years, hydrogels have proven to be an excellent platform for studying cell-cell and cell-matrix interactions. Utilizing chemically modified and naturally derived materials, hydrogel networks can be formed to encompass not only the components, but also the physicochemical properties of the dynamic TME. In this work, a dynamic hydrogel system that integrates multiple click chemistries was developed for tuning matrix physicochemical properties in a manner similar to the temporally increased matrix stiffness and depositions of HA. Subsequently, these dynamic hydrogels were used to investigate how matrix stiffening and increased HA presentation might affect survival of PDAC cells and their response to chemotherapeutics. </p> hydrogel cancer cell PDAC
2	Cell-Matrix Tensional Forces Within Cell-Dense Type I Collagen Oligomer Tissue Constructs Facilitate Rapid In Vitro Vascularization of Dense Tissue Constructs for Skin Engineering Kevin P. Buno (5929535) 03 January 2019 (has links) The skin provides protection and maintains homeostasis, making it essential for survival. Additionally, skin has the impressive ability to grow, as observed in children as they grow into adults. However, skin functions are compromised in large skin defects, a serious problem that can be fatal. The gold standard treatment is to use an autologous skin graft; however, due to donor site morbidity and limited availability, when full-thickness defects surpass 2% total body surface area (TBSA), skin substitutes are preferred. Unfortunately, current skin substitutes on the market: are slow to revascularize (2+ weeks), have low graft survival rates (<50% take), and lead to significant scarring and contracture. Fortunately, a promising solution is to prevascularize engineered skin substitutes in vitro, which has been shown to facilitate rapid tissue integration upon grafting by providing an intact vascular network that readily connects to the host’s circulation. However, current approaches for prevascularizing tissue constructs require long in vitro culture times or implement low extracellular matrix (ECM) density tissue constructs – both which are problematic in a clinical setting. To address this, we implemented a novel multitissue interface culture model to define the design parameters that were essential for rapid vascularization of soft tissue constructs in vitro. Here, we identified endothelial colony forming cell (ECFC) density and maintenance of cell-matrix tensional forces as important factors for rapid in vitro tissue vascularization (18% vessel volume percentage after 3 days of culture). We then applied these parameters to achieve rapid in vitro vascularization of dense, oligomer tissue constructs (12, 20, and 40 mg/mL). We demonstrated, for the first time, rapid in vitro vascularization at 3 days within dense matrices (ECM concentration > 10 mg/mL). Lastly, a rat full-thickness excisional wound model was developed to determine the acellular densified oligomer’s (20 and 40 mg/mL) ability to resist wound contraction and facilitate a wound healing response (recellularization and vascularization) when grafted into wounds. Future work will implement the vascularized, dense tissue constructs into the developed animal model to assess the vascularized graft’s efficacy on treating wounds to reduce scarring and contracture outcomes. Biomaterials mechanobiology vasculogenesis oligomers tissue engineering type i collagen in vitro vascularization rapid vascularization
3	The Use of Biopolymers for Tissue Engineering Nelda Vazquez-Portalatin (7424441) 17 October 2019 (has links) <p>Osteoarthritis (OA) is a degenerative joint disease characterized by cartilage damage and loss in the joints that affects approximately 27 million adults in the US. Tissue that is damaged by OA is a major health concern since cartilage tissue has a limited ability to self-repair due to the lack of vasculature in cartilage and low cell content. Tissue engineering efforts aim towards the development of cartilage repair strategies that mimic articular cartilage and are able to halt the progression of the disease as well as restore cartilage to its normal function.</p><p>This study harnesses the biological activity of collagen type II, present in articular cartilage, and the superior mechanical properties of collagen type I by characterizing gels made of collagen type I and II blends (1:0, 3:1, 1:1, 1:3, and 0:1). The collagen blend hydrogels were able to incorporate both types of collagen and retain chondroitin sulfate (CS) and hyaluronic acid (HA). Cryoscanning electron microscopy images showed that the 3:1 ratio of collagen type I to type II gels had a lower void space percentage (36.4%) than the 1:1 gels (46.5%) and the complex modulus was larger for the 3:1 gels (G=5.0 Pa) compared to the 1:1 gels (G=1.2 Pa). The 3:1 blend consistently formed gels with superior mechanical properties compared to the other blends and has the potential to be implemented as a scaffold for articular cartilage engineering.</p> <p>Following the work done to characterize the collagen scaffolds, we studied whether an aggrecan mimic, CS-GAHb, composed of CS and HA binding peptides, GAH, and not its separate components, is able to prevent glycosaminoglycan (GAG) and collagen release when incorporated into chondrocyte-embedded collagen gels. Bovine chondrocytes were cultured and embedded in collagen type I scaffolds with CS, GAH, CS and GAH, or CS-GAHb molecules. Gels composed of 3:1 collagen type I and II with CS or CS-GAHb were also studied. The results obtained showed CS-GAHb is able to decrease GAG and collagen release and increase GAG retention in the gels. CS-GAHb also stimulated cytokine production during the initial days of scaffold culture. However, the addition of CS-GAHb into the chondrocyte-embedded collagen scaffolds did not affect ECM protein expression in the gels. The incorporation of collagen type II into the collagen type I scaffolds did not significantly affect GAG and cytokine production and ECM protein synthesis, but did increase collagen release. The results suggest the complex interaction between CS-GAHb, the chondrocytes, and the gel matrix make these scaffolds promising constructs for articular cartilage repair.</p> <p>Finally, we used Dunkin Hartley guinea pigs, a commonly used animal model of osteoarthritis, to determine if high frequency ultrasound can ensure intra-articular injections of the aggrecan mimic are accurately positioned in the knee joint. A high-resolution small animal ultrasound system with a 40 MHz transducer was used for image-guided injections. We assessed our ability to visualize important anatomical landmarks, the needle, and anatomical changes due to the injection. From the ultrasound images, we were able to visualize clearly the movement of anatomical landmarks in 75% of the injections. The majority of these showed separation of the fat pad (67.1%), suggesting the injections were correctly delivered in the joint space. The results demonstrate this image-guided technique can be used to visualize the location of an intra-articular injection in the joints of guinea pigs and we are able to effectively inject the aggrecan mimic into knee joints.</p><p>All of the work presented here suggests that the addition of the aggrecan mimic to collagen I and collagen I and II scaffolds has shown that this type of construct could be useful for treating cartilage damage in the future.</p> Biochemistry Organic Chemistry Biological Engineering articular cartilage tissue engineering collagen chondroitin sulfate osteoarthritis chondrocytes hydrogels aggrecan ultrasound intra-articular injections elastin
4	TARGETED DELIVERY OF BONE ANABOLICS TO BONE FRACTURES FOR ACCELERATED HEALING Jeffery J H Nielsen (8787002) 21 June 2022 (has links) <div>Delayed fracture healing is a major health issue involved with aging. Therefore, strategies to improve the pace of repair and prevent non-union are needed in order to improve patient outcomes and lower healthcare costs. In order to accelerate bone fracture healing noninvasively, we sought to develop a drug delivery system that could safely and effectively be used to deliver therapeutics to the site of a bone fracture. We elected to pursue the promising strategy of using small-molecule drug conjugates that deliver therapeutics to bone in an attempt to increase the efficacy and safety of drugs for treating bone-related diseases.</div><div>This strategy also opened the door for new methods of administering drugs. Traditionally, administering bone anabolic agents to treat bone fractures has relied entirely on local surgical application. However, because it is so invasive, this method’s use and development has been limited. By conjugating bone anabolic agents to bone-homing molecules, bone fracture treatment can be performed through minimally invasive subcutaneous administration. The exposure of raw hydroxyapatite that occurs with a bone fracture allows these high-affinity molecules to chelate the calcium component of hydroxyapatite and localize primarily to the fracture site.</div><div>Many bone-homing molecules (such as bisphosphonates and tetracycline targeting) have been developed to treat osteoporosis. However, many of these molecules have toxicity associated with them. We have found that short oligopeptides of acidic amino acids can localize to bone fractures with high selectivity and with very low toxicity compared to bisphosphonates and tetracyclines.</div><div>We have also demonstrated that these molecules can be used to target peptides of all chemical classes: hydrophobic, neutral, cationic, anionic, short, and long. This ability is particularly useful because many bone anabolics are peptidic in nature. We have found that acidic oligopeptides have better persistence at the site of the fracture than bisphosphonate-targeted therapeutics. This method allows for a systemic administration of bone anabolics to treat bone fractures, which it achieves by accumulating the bone anabolic at the fracture site. It also opens the door for a new way of treating the prevalent afflictions of broken bones and the deaths associated with them.</div><div>We further developed this technology by using it to deliver anabolic peptides derived from growth factors, angiogenic agents, neuropeptides, and extracellular matrix fragments. We found several promising therapeutics that accelerated the healing of bone fractures by improving the mineralization of the callus and improving the overall strength. We optimized the performance of these molecules by improving their stability, targeting ligands, linkers, dose, and dosing frequency.</div><div>We also found that these therapeutics could be used to accelerate bone fracture repair even in the presence of severe comorbidities (such as diabetes and osteoporosis) that typically slow the repair process. We found that, unlike the currently approved therapeutic for fracture healing (BMP2), our therapeutics improved functionality and reduced pain in addition to strengthening the bone. These optimized targeted bone anabolics were not only effective at healing bone fractures but they also demonstrated that they could be used to speed up spinal fusion. Additionally, we demonstrated that acidic oligopeptides have potential to be used to treat other bone diseases with damaged bone.</div><div>With these targeted therapeutics, we no longer have to limit bone fracture healing to casts or invasive surgeries. Rather, we can apply these promising therapeutics that can be administered non-invasively to augment existing orthopedic practices. As these therapeutics move into clinical development, we anticipate that they will be able to reduce the immobilization time that is the source of so many of the deadly complications associated with bone fracture healing, particularly in the elderly.</div> Genetics not elsewhere classified Nanobiotechnology Animal behaviour Clinical microbiology Endocrinology Nanomedicine Regenerative medicine (incl. stem cells) Solid state chemistry Molecular medicine Proteins and peptides Solution chemistry Radiation and matter Biomaterials Biomechanical engineering bone fracture healing Anabolic Agents/pharmacology Targeted Drug DeliveryDesign Bone fracture targeted drugs Bone theapeutics targeted therapies Growth factors Neuropepetides Extracellular matrix Extracellular matrix fragments spinal fusion Angiogensis Acidic oligopeptides osteoporosic fractures diabetic bone fractures Integrin alpha 5 Acelerated Bone fracture healing Hydroxyapatite Hydroxyapatite targeting Targeting peptides Peptide drugs osteomyelitis (OM) Rheumatoid arthritis Bone fractures osteogenic therapies osteotropic osteotropic nanomedicines osteoinductive capacity Molecular Medicine Organic Chemistry Proteins and Peptides Radiochemistry Solid State Chemistry Solution Chemistry Biochemistry Animal Behaviour Biological Engineering Biotechnology Genetics Medicine Pharmacology Biomaterials Biomechanical Engineering Biomechanics Endocrinology Nanobiotechnology Nanomedicine

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