For a lay summary of the thesis presented in a 1-minute video format, visit the following link: https://www.youtube.com/watch?v=VhLzt_tEz-s / It is projected that, by 2030, 8% of all adults in the world will have diabetes mellitus and treatment will account for 10% of the total healthcare budget in many countries. Polymeric biomaterial research has led to the design of robust polymer hydrogel capsules to develop curative cell-based therapies for chronic disorders such as diabetes mellitus. Encapsulation of insulin-producing beta cells within synthetic, semi-permeable polymer hydrogels can avoid host immune rejection including fibrotic responses, and thus holds the promise of a long-term curative treatment of this disease. There is a paucity of literature regarding methods available for standardized in vitro screening of synthetic polymer hydrogel capsules to predict host responses in vivo. Thus, the focus of this thesis was to design in vitro assays able to screen for subsequent in vivo fibrotic responses. Two dimensional (‘2D’) (cell attachment to thin film hydrogel coatings) and three dimensional (‘3D’) (cell attachment and protein adsorption to hydrogel capsules) in vitro experiments were designed and tested in an iterative process to assess fibrotic responses to a diverse group of polymer hydrogels. Cell attachment assays included fibroblast (NIH 3T3) and macrophage (RAW 264.7) cell lines, and protein adsorption assays included proteins used to model fibrosis including fibrinogen and lysozyme. For some formulations, in vitro assays were compared with in vivo data on pericapsular cellular overgrowth (PCO) after being implanted into mice. A binomial logistic regression model was designed and validated to assess whether the ‘3D’ in vitro assays correlated with in vivo PCO responses. It was found that the RAW 264.7 cell attachment assay was significantly correlated with PCO outcomes in vivo, demonstrating for the first time a simple, cost-effective, and rapid in vitro cell-based approach to screen and select capsules with lower fibrotic potential to be further tested in animals. / Thesis / Master of Health Sciences (MSc) / In North America, one in eleven adults, or about 415 million people, have diabetes. It is projected that by 2030, around 8% of the world population will be diagnosed with this disease. A common form of treatment is through the frequent injection of insulin, but this is costly, requires multiple daily interventions, and cannot prevent regular excursions from the ideal blood glucose range. Cell-based therapies have a lot of promise in treating several chronic diseases including diabetes. Donor and stem-cell derived islets can be implanted into patients with type 1 diabetes and have been shown to function for over a year, albeit at the price of systematic immune suppression. Alternatively, cells that produce insulin can be placed inside immune-evasive capsules and implanted, potentially providing continuous blood glucose regulation without the need for daily insulin injections. However, this novel form of treatment is limited by the encapsulated cells’ survival once implanted. Cell survival can be affected by the body’s response to a foreign body (the capsule), causing deposition of protein or cells on the capsule surface which can limit the oxygen supply to cells in the capsule and the ability of insulin to leave the capsule in a timely fashion. The goal of this project is to develop assays to screen new capsule formulations. This can advance research by using capsules more readily accepted by the body, leading to a more promising and long-term treatment of diabetes.

Laser-based additive manufacturing is inherently associated with extreme, unprecedented, and rapid thermokinetics which impact the microstructural evolution in a built component. Such a unique, near to non-equilibrium microstructure/phase evolution in laser additively manufactured metallic components impact their properties in engineering application. In light of this, the present work investigates the unique microstructural traits as a result of process induced spatial and temporal variation in thermokinetic parameters in laser directed energy deposited CoCrMo biomedical alloy. The influence of such a unique microstructural evolution in laser directed energy deposited CoCrMo on electrochemical response in physiological media was elucidated and compared with a conventionally manufactured, commercially available CoCrMo component. Furthermore, while investigation of the electrochemical response, such a microstructural evolution in laser directed energy deposited CoCrMo led to in-situ surface modification of the built components in physiological media via selective, non-uniform electrochemical etching. Such in-situ surface modification resulted in enhanced biocompatibility in terms of mammalian cell growth, cell-substrate adhesion, blood compatibility, and antibacterial properties indicating improved osteointegration, compared to a conventionally manufactured, commercially available CoCrMo component.

Biodegradable implants continue to be of interest in orthopaedics for their many potential applications. The magnesium (Mg) alloy WE43 is a biodegradable material with the CE mark approval for clinical application and today mostly used as screws for dental prosthesis. Additional to magnesium, WE43 contains rare earth elements (REEs) of around 7 wt%. These REEs are needed to give the material its mechanical properties and corrosion resistance. Although WE43 is a promising material thought to be used in a diverse number of orthopaedical applications, questions have risen regarding the potential long-term effects of these REEs on the body after the implant degrades. Additionally, with the global demand of REEs rising and a decreasing supply of these elements, there may also be a potential future problem regarding the availability of materials based on REEs. Therefore, new materials containing only elements naturally found in the body are of interest. One such material is the novel Mg-Ca alloy, X0. In this study, a biological comparison was made to answer the question whether the biological performance of X0 is comparable to the already CE approved WE43. Viability, proliferation, and differentiation of MC3T3-E1 (preosteoblast) cells combined with extracts from X0 and WE43, respectively were used. An additional experiment was conducted were X0 was tested against three different versions of WE43 and titanium. In summary, the X0 alloy performed similarly to WE43 in all testing. Both WE43 and X0 showed indications of being bioactive. This led to the conclusion that the X0 alloy showed promise for future use and being a viable alternative to WE43.

M. Tech. (Department of Metallurgical Engineering, Faculty of Engineering Technology), Vaal University of Technology. / Solid titanium (Ti), Ti-6Al-4V (wt.%), and Ti-24Nb-4Zr-8Sn (wt.%) materials were fabricated from powders using spark plasma sintering (SPS). The starting materials comprised of elemental powders of ASTM Grade 4 titanium (Ti), aluminium (Al), vanadium (V), niobium (Nb), zirconium (Zr), and tin (Sn). The powders were initially characterised and milled prior to sintering. The micronpowders were milled in an attempt to produce materials with nanostructured grains and as a result improved hardness and wear resistance. The produced solid Ti-24Nb-4Zr-8Sn alloy was compared to solid titanium (Ti) and Ti-6Al-4V (Ti64) on the basis of density, microstructure, hardness, corrosion, and biocompatibility. Relative densities above 99.0% were achieved for all three systems. CP-Ti and Ti64 had both 100% relative density, and Ti2448 showed a slightly lower density of 99.8%. Corrosion results showed that all three materials exhibited good corrosion resistance due to the formation of a protective passive film. In 0.9% NaCl Ti2448 had the highest current density (9.05 nA/cm2), implying that its corrosion resistance is relatively poor in comparison to Ti (6.41 nA/cm2) and Ti64 (5.43 nA/cm2), respectively. The same behavior was observed in Hank's solution. In cell culture medium, Ti2448 showed better corrosion resistance with the lowest current density of 2.96 nA/cm2 compared to 4.86 nA/cm2 and 5.62 nA/cm2 of Ti and Ti64 respectively. However, the current densities observed are quite low and insignificant that they lie within acceptable ranges for Ti2448 to be qualified as a biomaterial. Cell proliferation test was performed using murine osteoblastic cells, MC3T3-E1 at two cell densities; 400 and 4000 cells/mL for 7 days incubation. Pure titanium showed better cell attachment and proliferation under both conditions suggesting that the presence of other oxide layers influence cell proliferation. No significant difference in cell proliferation was observed between Ti64 and Ti2448.

No description available.

Multifunctional nanomaterials can be engineered to aid in the diagnosis of diseases, enable efficient drug delivery, monitor treatment progress over time, and evaluate treatment outcomes. This strategy, known as theranostics, focuses on the combination of diagnostic and therapeutic techniques to provide new clinically safe and efficient personalized treatments. The evaluation of different nanomaterials’ properties and their customization for specific medical applications has therefore been a significant area of interest within the scientific community. Iron oxide nanoparticles, specifically those based on iron (II, III) oxide (magnetite, Fe3O4), have been prominently investigated for biomedical, theranostic applications due to their documented superparamagnetism, high biocompatibility, and other unique physicochemical properties. The aim of this thesis is to establish a viable set of methods for preparing magnetite (iron oxide) nanoparticles through hydrothermal synthesis and modifying their surfaces with organic functional groups in order to both modulate surface chemistry and facilitate the attachment of molecules such as peptides via covalent bond formations. Modifying their surfaces with biomolecules such as peptides can further increase their uptake into cells, which is a necessary step in the mechanisms of their desired biomedical applications. The methods of nanoparticle synthesis, surface functionalization, and characterization involving electron microscopy (e.g., SEM, TEM), zeta potential measurements, size analysis (i.e., DLS), and FT-IR spectroscopy will be presented. / Bioengineering

Every year, millions of people contract antibiotic-resistant bacterial infections, and tens of thousands die from infection-related complications in the United States alone. Bacterial infections are one of the leading causes of death worldwide, especially in healthcare institutes such as hospitals and nursing homes where people are more susceptible to infection and complications. Bacteria can cause infections in any part of the body and often interact with sugar molecules on the surface of cells; once bacteria are attached, the cells stop functioning properly. When a bacterial infection is suspected, samples from the patient's blood or urine are taken to confirm the diagnosis. If the bacterial infection is sever enough, patients are treated with broad-spectrum antibiotics before the type of bacteria is known, and once it has been identified they are given antibiotics that target the specific bacterial strain. The high death rate associated with bacterial infections is largely due to the emergence of antibiotic-resistant bacterial strains. Although antibiotic resistance is present in some naturally occurring bacterial strains, misuse and over-prescription of antibiotics have accelerated the process. To combat the ever-growing threat of antibiotic-resistant bacteria, antibacterial polymers have been developed. Antibacterial polymers prevent bacterial infections by either killing the bacteria themselves or by preventing them from interacting with the body altogether This dissertation primarily focuses on using sugar-containing polymers to prevent bacterial growth. These materials may potentially be used as a replacement for or supplement to traditional antibiotics. / Doctor of Philosophy / All living cells possess a coating of glycomaterials on, or as critical components of their cell walls. Bacteria, including invasive bacterial pathogens, are no exception and have cell walls comprised of peptidoglycans. Glycomaterials on cell surfaces play a role in critical biological processes such as molecular recognition, cellular interaction, infection, and inflammation. Traditional antibiotic remediations are becoming less effective in treating bacterial infections due to the emergence of antibiotic-resistant strains. The formation of biofilms, an extracellular coating composed of polysaccharides, contributes to the antibiotic resistance of bacteria. The development of novel antibiotics is extremely costly and often unsuccessful, with billions in investment often producing zero new drugs. As a result, antibacterial polymers have been investigated as they are comparatively less expensive and offer unique characteristics to combat bacterial infections. Polymers with inherently antibacterial properties, or those that can be conjugated with antibacterial compounds, offer a replacement for traditional antibiotic remediation. To investigate the role of glycomaterials in antibacterial activity, a series of sugar-containing norbornene homopolymers were prepared and evaluated for their antibacterial activity. Protected glycomonomers consisting of galactose, glucose, N-acetyl glucose, and mannose were prepared in a two- or three-step synthesis by first appending an acrylate to the anomeric carbon through Koenigs-Knorr-type chemistry. After generation of the -anomer, the norbornene carboxylate was prepared by the Diels-Alder reaction of the acrylate with cyclopentadiene. Homopolymers with molecular weights ranging from 25–250 KDa were synthesized using ring-opening metathesis polymerization (ROMP) catalyzed by Grubbs 3rd generation catalyst, and subsequently deprotected to reveal the sugar-norbornene. While the galactose polymers showed no bacterial inhibition, those composed of glucose, N-acetyl glucose, or mannose prevented the growth of Escherichia coli (E. coli) and were effective at concentrations as low as 1.25 mg mL-1. Some strains of pathogenic bacteria, such as Clostridioides difficile (formerly known as Clostridium difficile), interfere with the normal cell functions by indirect means, producing toxins that adversely interact with the surrounding tissue. To sequester the toxins produced by C. difficile before they cause damage to the gastrointestinal (GI) tract, polymers containing the -gal epitope, a naturally occurring trisaccharide, were also prepared. The -gal epitope possessing a propyl azide handle at the anomeric carbon was prepared in a 15-step reaction, followed by reaction with an alkyne-functionalized polymer resin using copper-catalyzed azide-alkyne Huisgen cycloaddition. After global deprotection and thorough washing to remove residual copper from the glycomaterial, cell viability studies showed >80% cell survival. While these materials showed good cell viability, the rigorous synthesis of -Gal and the affinity of the polymer scaffolding for copper was a deterrent to further toxin-binding studies. Non-biological surfaces are also often susceptible to bacterial colonization and fouling. Although such materials may be modified to impart antimicrobial properties, their modification may also be a detriment to other key physical properties. To investigate the tradeoffs between material properties and functionalization, we synthesized a series of poly(arylene ether)s from monomers that possessed a modifiable handle and differed only in the pattern of leaving group on the aromatic ring. These polymers were further modified using post-polymerization thiol-ene reactions to evaluate the effect of the side-chains on the material's properties. The regioisomer incorporated into the polymer was found to influence its thermal properties irrespective of the installed functional group, suggesting that new functionality can be incorporated into these polymers without adversely impacting their physical properties.

Polymeric bone scaffolds are a promising tissue engineering approach for the repair of critical-size bone defects. Porous three-dimensional (3D) scaffolds play an essential role as templates to guide new tissue formation. However, there are critical challenges arising from the poor mechanical properties and low bioactivity of bioresorbable polymers, such as poly(epsilon-caprolactone) (PCL) in bone tissue engineering applications. This research investigates the potential use of cellulose nanocrystals (CNCs) as multi-functional additives that enhance the mechanical properties and increase the biomineralization rate of PCL. To this end, an in vitro biomineralization study of both sulfuric acid hydrolyzed-CNCs (SH-CNCs) and surface oxidized-CNCs (SO-CNCs) has been performed in simulated body fluid in order to evaluate the bioactivity of the surface functional groups, sulfate and carboxyl groups, respectively. PCL nanocomposites were prepared with different SO-CNC contents and the chemical/physical properties of the nanocomposites were analyzed. 3D porous scaffolds with fully interconnected pores and well-controlled pore sizes were fabricated from the PCL nanocomposites with a 3D printer. The mechanical stability of the scaffolds were studied using creep test under dry and submersion conditions. Lastly, the biocompatibility of CNCs and 3D printed porous scaffolds were assessed in vitro. The carboxyl groups on the surface of SO-CNCs provided a significantly improved calcium ion binding ability which could play an important role in the biomineralization (bioactivity) by induction of mineral formation for bone tissue engineering applications. In addition, the mechanical properties of porous PCL nanocomposite scaffolds were pronouncedly reinforced by incorporation of SO-CNCs. Both the compressive modulus and creep resistance of the PCL scaffolds were enhanced either in dry or in submersion conditions at 37 degrees Celsius. Lastly, the biocompatibility study demonstrated that both the CNCs and material fabrication processes (e.g., PCL nanocomposites and 3D printing) were not toxic to the preosteoblasts (MC3T3 cells). Also, the SO-CNCs showed a positive effect on biomineralization of PCL scaffolds (i.e., accelerated calcium or mineral deposits on the surface of the scaffolds) during in vitro study. Overall, the SO-CNCs could play a critical role in the development of scaffold materials as a potential candidate for reinforcing nanofillers in bone tissue engineering applications. / Ph. D.

Biopolymers are becoming more attractive as advanced wound dressings because of their naturally derived origin, abundance, low cost and high compatibility with the wound environment. Arabinoxylan (AX) is a class of polysaccharide polymers derived from cereal grains that are primarily used in food products and cosmetic additives. Its application as a wound dressing material has yet to be realized. In this two-pronged project, arabinoxylan ferulate (AXF) was fabricated into electrospun fibers and gel foams to be evaluated as platforms for wound dressing materials. In the first study, AXF was electrospun with varying amounts of gelatin. In the second study, AXF was dissolved in water, enzymatically crosslinked and lyophilized to form gel foams. The morphology, mechanical properties, porosity, drug release kinetics, fibroblast cell response and anti-microbial properties were examined for both platforms. Carbohydrate assay was conducted to validate the presence of arabinoxylan ferulate in the electrospun GEL-AXF fibers. Swelling and endotoxin quantification studies were done to evaluate the absorptive capacity and sterilization agent efficacy respectively in AXF foams. The results indicated successful fabrication of both platforms which validated the porous, absorptive, biocompatibility and drug release properties. The results also exhibited that silver impregnated AXF scaffolds inhibited growth of Pseudomonas aeruginosa, Staphylococcus aureus and Enterococcus faecalis bacteria species, anti-microbial properties necessary to function as advanced wound dressing materials. Future work will be done to improve the stability of both platforms as well as evaluate its applications in vivo.

Este estudo teve como objetivo avaliar, in vivo, por um período de 24h, a resposta tecidual inflamatória subcutânea após a utilização de cimentos endodônticos. Realizouse a seleção de 75 ratos, machos, da linhagem Wistar, de aproximadamente 90 dias (de vida) e com cerca de 350g (de peso), que foram aleatoriamente distribuídos em 5 grupos (n=20), como se segue: G1 - ActiV GPTM, G2 - Biosealer, G3 - RealSeal®, G4 - RoekoSeal® e G5 - AH Plus®. A resposta inflamatória foi observada pelo teste edemogênico, nos tempos 6, 12 e 24 horas. Como protocolo de aplicação da metodologia, os animais depois de anestesiados, receberam uma injeção do corante vital Azul de Evans na veia lateral caudal. Em seguida, foram tricotomizados em seu dorso e, doses iguais dos materiais estudados foram inseridas subcutaneamente. Ao final de cada período de tempo, realizou-se a remoção da pele dorsal em fragmentos de 15 mm de diâmetro. Os fragmentos foram imersos em solução de formamida P.A., armazenados em estufa a 37ºC, por 48 horas. Nesse momento, os índices de absorbância do corante extraído pelo solvente foram quantificados por meio de espectrofotometria, os resultados convertidos em microgramas (?g) e a concentração de cada substância no infiltrado inflamatório obtida. Os dados obtidos foram submetidos a ANOVA e teste de Tukey (p<0,05). E, de acordo com os resultados obtidos, observou-se que houve diferenças estatisticamente significativas para os fatores em estudo material (p<0,0001) e tempo (p<0,0001), entretanto não houve interação material*tempo (p=0,128). Sendo assim, nas primeiras 6h, a ordem decrescente de irritabilidade dos materiais analisados foi: G3 ? G5 > G1 > G2 > G4. Entretanto, os materiais desempenharam-se de forma semelhante, tanto no tempo de 12h quanto no de 24h, como se segue: G1 ? G3 ? G5 > G2 ? G4. Desta forma, pôde-se concluir que: 1 - o cimento RoekoSeal demonstrou o menor grau de irritabilidade no tempo experimental de 6 horas; 2 - Os cimentos RealSeal e AH Plus apresentaram resposta inflamatória mais intensa no período experimental de 6 horas e 3 - o índice de irritabilidade nas primeiras 6 horas é significativamente superior quando comparado ao período de 24h, independente do material testado. / The aim of this study was evaluate in vivo the earliest 24 hours tissue inflammatory response to five endodontic sealers. In order to this, 75 male rats Wistar with 90 days of age and approximately 350g of weight were divided in 5 experimental groups (n=20): G1 - ActiV GPTM, G2 - Biosealer, G3 - RealSeal®, G4 - RoekoSeal® e G5 - AH Plus®. The inflammatory response was evaluated using the edemogenic test in the experimental periods of 06, 12 and 24 hours. Anesthetized mice received an Evan´s blue dye injection in the lateral caudal vein and were tricotomized in the dorsum where equal amounts of each sealer were subcutaneously inoculated. After experimental period, the mice were sacrified, the dorsal skin was excised and pieces with 15mm of diameter around each inoculated sealer were removed. Each tissue piece was reduced to fragments, immersed in formamide solution and stored at 37ºC during 48 hours. At this moment, the absorbance index of the dye extracted by the solvent was quantified using light absorption spectrometry, the results were converted to micrograms (?g) and their concentration in the inflammatory infiltrated was obtained. The data was submitted to statistical analysis using the ANOVA followed by the Tukey test (p<0.05) and the results showed statistical significant difference for analyzed factors, the material and the time (p<0.001); without interaction between both (p=0.128). Thus, in decrescent order inflammatory response, the groups were scaled: G3 ? G5 > G1 > G2 > G4 for 6 hours, and G1 ? G3 ? G5 > G2 ? G4 for 12 hours and 24 hours. Our findings indicated that: 1 - The RoekoSeal presented the minor inflammatory response value in the 6 hours experimental period; 2 - The RealSeal and AH Plus sealers showed intense inflammatory response in the experimental period of 6 hours; 3 - The inflammatory values at 6 hours were significantly higher compared with results in the period of 24 hours independently of the tested material.