abstract: Following diagnosis of a glioblastoma (GBM) brain tumor, surgical resection, chemotherapy and radiation together yield a median patient survival of only 15 months. Importantly, standard treatments fail to address the dynamic regulation of the brain tumor microenvironment that actively supports tumor progression and treatment resistance. Moreover, specialized niches within the tumor microenvironment maintain a population of highly malignant glioblastoma stem-like cells (GSCs). GSCs are resistant to traditional chemotherapy and radiation therapy and are likely responsible for near universal rates of tumor recurrence and associated morbidity. Thus, disrupting microenvironmental support for GSCs could be critical to more effective GBM therapies. Three-dimensional (3D) culture models of the tumor microenvironment are powerful tools for identifying key biochemical and biophysical inputs that may support or inhibit malignant behaviors. Here, we developed synthetic poly(N-isopropylacrylamide-co-Jeffamine M-1000® acrylamide) or PNJ copolymers as a model 3D system for culturing GBM cell lines and low-passage patient-derived GSCs in vitro. These temperature responsive scaffolds reversibly transition from soluble to insoluble in aqueous solution by heating from room temperature to body temperature, thereby enabling easy encapsulation and release of cells in a 3D scaffold. We also designed this system with the capacity for presenting the cell-adhesion peptide sequence RGD for adherent culture conditions. Using this system, we identified conditions that promoted GBM proliferation, invasion, GSC phenotypes, and radiation resistance. In particular, using two separate patient-derived GSC models, we observed that PNJ scaffolds regulated self-renewal, provided protection from radiation induced cell death, and may promote stem cell plasticity in response to radiation. Furthermore, PNJ scaffolds produced de novo activation of the transcription factor HIF2α, which is critical to GSC tumorigenicity and stem plasticity. All together, these studies establish the robust utility of PNJ biomaterials as in vitro models for studying microenvironmental regulation of GSC behaviors and treatment resistance. / Dissertation/Thesis / Doctoral Dissertation Biomedical Engineering 2017

Ce sujet est d’actualité suite à une évolution rapide des types de conception de structures élancées utilisées dans les installations provisoires. C’est seulement depuis une vingtaine d’années que ces structures sont préfabriquées en cadres multidirectionnels (de sections tubulaires en acier ou en aluminium). Ces structures sont légères et leur stabilité réside seulement dans les raideurs internes au niveau des files de montants et au niveau horizontal par les planchers ainsi que dans les liaisons avec l’ouvrage. Ce travail concerne l’étude des instabilités (flambement-déversement) en tenant compte de différents types d’imperfections. De nouvelles courbes de flambement ainsi que les facteurs d’imperfection associés sont proposés dans cette thèse. Ces courbes sont obtenues en imposant une déformée initiale représentant les défauts géométriques et mécaniques (contraintes résiduelles). Les résultats expérimentaux confrontés avec les prévisions théoriques de l’Eurocode 3 montrent que les valeurs des imperfections figurant dans la littérature sont extrêmement exagérées. Les valeurs préconisées dans ce travail pourraient présenter un certain intérêt pour une modification éventuelle des courbes européennes de flambement pour ce type de structure. En ce qui concerne l’instabilité latérale, une méthodologie originale d’essais en vraie grandeur de poutres à treillis formés d’éléments tubulaires a été également mise au point. Le système de chargement à « roues libres » développé permet de libérer le point d’application de l’effort dès le début de l’instabilité. Cette technique conduit à des mesures plus précises du moment critique de déversement. / This subject becomes topical following a rapid evolution of design procedures for slender structures used widely in the temporary installations. Only through the last twenty years that these structures are prefabricated of multidirectional frames (steel or aluminium tubular sections). These structures are lightweight and their stability lies only in the internal stiffness at rows of posts and horizontally by the planking as well as the links with the building. This work concerns the study of instabilities (buckling - lateral torsional buckling) taking into account different types of imperfections. New buckling curves and the associated imperfection factors are proposed in this thesis. These curves are obtained by imposing an initial deformed representing the geometrical and mechanical defects (residual stress). The experimental results were confronted with theoretical predictions of Eurocode 3 which show that the values of the imperfections in the literature are extremely exaggerated. The values advocated in this work could be of interest for a possible adjustment of the European buckling curves for this type of structure. Regarding the lateral instability, an original methodology in real scale tests of trusses consist of tubular elements was also developed. The developed loading system of "free wheels" allows releasing the point of application of the force from the beginning of instability. This technique leads to more accurate measurements of the critical lateral torsional buckling moment.

Indiana University-Purdue University Indianapolis (IUPUI) / The aim of this current study was to determine if the exposure of human dental pulp stem cells (HDPSC) to the DynaMatrix membrane will result in an increased production of angiogenic cytokines that are critical for pulp/root regeneration. Angiogenesis cytokine arrays have been established as a viable method for assessing expression of cytokines.20 HDPSC were chosen as they are expected to be found in the apical papilla and the infected immature root canal system of teeth that current regenerative endodontic techniques are designed to treat.

Indiana University-Purdue University Indianapolis (IUPUI) / EFFECTS OF DYNAMATRIX® ON ANGIOGENIC CYTOKINE EXPRESSION FROM HUMAN DENTAL PULP FIBROBLASTS: AN IN VITRO STUDY by Joseph Benjamin Adams Indiana University School of Dentistry Indianapolis, IN Introduction: An exogenous scaffold may lead to more predictable pulp tissue regeneration and continued root formation in a regenerative endodontic procedure. DynaMatrix® is a natural membrane scaffold made of porcine small intestine, currently used in periodontal regenerative surgeries. Objective: The purpose of this study was to investigate if human dental pulp fibroblasts (HDPFs) seeded on DynaMatrix® membrane would result in an increase in the expression of angiogenic cytokines. Materials and Methods: HDPFs (75,000 per well) were seeded in 6-well plates. Three groups were tested: Group 1 (C): HDPFs in 70 media only; Group 2 (M): DynaMatrix® (Cook Biotech, Indianapolis, IN) alone in media; and Group 3 (C+M): HDPFs seeded on DynaMatrix® membranes. After 72 hours of incubation in serum positive, the conditioned media were collected and analyzed for the expression of 20 angiogenic cytokines utilizing RayBiotech Inc., arrays per the manufacturer’s instruction. The data were analyzed by ANOVA. Results: Group M was significantly higher than C for bFGF (p = 0.0023). C+M was significantly higher than M for ANG (p = 0.0104); GRO (p = 0.0003); IFN-γ (p = 0.0023); IL-6 (p = 0.0003); IL-8 (p = 0.0003); Leptin (p = 0.0003); MCP-1 (p = 0.0104); TIMP-1 (p = 0.0190); TIMP-2 (0.0123). C was significantly higher than C+M for ANG (p = 0.0104); MCP-1 (p = 0.0104); and THPO (p = 0.0308). Cytokines such as b-FGF, ANG, and leptin promote angiogenesis, and stimulate migration and proliferation of cells. Conclusion: The cytokine expression profile from the cells seeded on DynaMatrix® suggests that it might be a suitable scaffold for regenerative endodontic procedures. It could improve vascularization by increasing angiogenic cytokines in the microenvironment of the treated root canal and supporting tissue regeneration.

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The ever increasing need for technology development requires the integration of inexpensive, light weight and high strength materials which are able to meet the high standards and specifications for various engineering applications. The intention of this work is to show that the suitable material selection and the utilization of plasma spray processing can be of potential interest to a large number of industrial, biomedical and everyday life applications. This research demonstrates also that plasma processing is a promising engineering tool for multifunctional coatings and near-net-shape manufacturing. Further, the theoretical and experimental results are combined in order to explain the mechanisms behind nanostructure retention and enhanced properties. Proper design of experiments, an appropriate material selection and experimental methodology are discussed herein. The experimental conditions were optimized in order to achieve the best materials properties according to their explicit properties and functions. Specific materials were consolidated according to their prospective performance and applications: 1) Plasma spraying of nano-Ceria-stabilized Zirconia free form part for stem cells scaffolds, 2) Plasma spraying of FeCrAlY on Ti-alloy plate, additionally coated with nano-size Hydroxyapatite for bone tissue engineering, 3) Wire-arc spraying of nano-based steel wires for aerospace and automotive applications. The performance and characteristics of all of the developed coatings and free-form-parts are evaluated using state-of-the art characterization techniques.

In this study, we integrated different calcium sources into sol-gel hybrid glass scaffolds with the aim of producing implants with long-lasting calcium release while maintaining mechanical strength of the implant. Calcium(II)-release was used to introduce bioactivity to the material and eventually support implant integration into a bone tissue defect. Tetraethyl orthosilicate (TEOS) derived silica sols were cross-linked with an ethoxysilylated 4-armed macromer, pentaerythritol ethoxylate and processed into macroporous scaffolds with defined pore structure by indirect rapid prototyping. Triethyl phosphate (TEP) was shown to function as silica sol solvent. In a first approach, we investigated the integration of 1 to 10% CaCl2 in order to test the hypothesis that small CaCl2 amounts can be physically entrapped and slowly released from hybrid glass scaffolds. With 5 and 10% CaCl2 we observed an extensive burst release, whereas slightly improved release profiles were found for lower Calcium(II) contents. In contrast, introduction of melt-derived bioactive 45S5 glass microparticles (BG-MP) into the hybrid glass scaffolds as another Calcium(II) source led to an approximately linear release of Calcium(II) in Tris(hydroxymethyl)aminomethane (TRIS) buffer over 12 weeks. pH increase caused by BG-MP could be controlled by their amount integrated into the scaffolds. Compression strength remained unchanged compared to scaffolds without BG-MP. In cell culture medium as well as in simulated body fluid, we observed a rapid formation of a carbonated hydroxyapatite layer on BG-MP containing scaffolds. However, this mineral layer consumed the released Calcium(II) ions and prevented an additional increase in Calcium(II) concentration in the cell culture medium. Cell culture studies on the different scaffolds with osteoblast-like SaOS-2 cells as well as bone marrow derived mesenchymal stem cells (hMSC) did not show any advantages concerning osteogenic differentiation due to the integration of BG-MP into the scaffolds. Nonetheless, via the formation of a hydroxyapatite layer and the ability to control the pH increase, we speculate that implant integration in vivo and bone regeneration may benefit from this concept.

Acute Lymphoblastic Leukemia (ALL) is one of the most common type of hematologic malignancy in children, characterized by an excessive proliferation of unfunctional immature lymphoblasts in the blood and the bone marrow, which leads to a range of severe blood-related complications. Given the remarkable increase in the prevalence of leukemia in the past 20 years, there has been a particular interest in the development of in vitro experimental models for cancer research. Ultra-short self-assembling peptides have shown to be a promising class of synthetic biomaterials due to their biocompatibility, tunable mechanical properties, and the possibility of controlling the scaffold composition. The objective of this study was to create a bioactive but well-defined synthetic 3D model of the bone marrow (BM) microenvironment for the simulation of ALL using biofunctionalized ultrashort self-assembling peptide scaffolds. Different bioactive motifs derived from integral extracellular matrix (ECM) constituents that are known to enhance cell-matrix adhesion, including RGDS from fibronectin, YIGSR from laminin, and GFOGER from collagen, were incorporated into the parent peptide IIZK. These peptides demonstrated to be capable of generating stable hydrogel structures composed of fibrous porous networks, each with unique nanofiber morphology and mechanical properties. All the peptide scaffolds that were investigated in this study exhibited optimal characteristics concerning the cytocompatibility of multiple BM niche cells, including human bone marrow mesenchymal stem cells (MSCs), human umbilical vein endothelial cells (HUVECs), and patient derived ALL cells. The suitability of the scaffolds as drug screening platforms was evaluated, demonstrating their potential as versatile tools for the assessment of drug efficacy.

Numerous eye diseases are linked to biomechanical dysfunction of the retina. However, the underlying forces are almost impossible to quantify experimentally. Here, we show how biomechanical properties of adult neuronal tissues such as porcine retinae can be investigated under tension in a home-built tissue stretcher composed of nanostructured TiO2 scaffolds coupled to a self-designed force sensor. The employed TiO2 nanotube scaffolds allow for organotypic long-term preservation of adult tissues ex vivo and support strong tissue adhesion without the application of glues, a prerequisite for tissue investigations under tension. In combination with finite element calculations we found that the deformation behavior is highly dependent on the displacement rate which results in Young’s moduli of (760–1270) Pa. Image analysis revealed that the elastic regime is characterized by a reversible shear deformation of retinal layers. For larger deformations, tissue destruction and sliding of retinal layers occurred with an equilibration between slip and stick at the interface of ruptured layers, resulting in a constant force during stretching. Since our study demonstrates how porcine eyes collected from slaughterhouses can be employed for ex vivo experiments, our study also offers new perspectives to investigate tissue biomechanics without excessive animal experiments.