Bioengineered skin substitutes have been developed to treat burn and non-healing wounds; however limitations still hinder their clinical success rates. Optimizing these current design strategies requires an understanding of how biochemical and topographical features of the native tissue modulate keratinocyte processes involved in tissue functionality. In this thesis, a novel bioengineered skin substitute was developed that contains a microfabricated basal lamina analog that recapitulates the native microenvironment found at the dermal-epidermal junction (DEJ). In native skin, this microenvironment consists of both biochemical and topographical cues which play critical roles in maintaining tissue architecture and overall homeostasis with the external environment. Therefore, we hypothesize that microfabricated basal lamina analogs with extracellular matrix cues and three-dimensional features that mimics the cellular microenvironment of the DEJ will promote enhanced epithelialization and increase epidermal stem cell clustering on the surface of bioengineered skin substitutes. We determined that the extracellular matrix protein fibronectin (FN) found in the cellular microenvironment of the DEJ enhanced keratinocyte attachment, proliferation, and epithelialization of a collagen based basal lamina analog. It was also found that the collagen material used to create the basal lamina analog as well as the FN conjugation strategy to this material significantly influenced the bioactivity of FN and its ability to modulate keratinocyte functions through integrin based mechanism. To investigate spatial tissue organization and the role it plays in the cellular microenvironment of the DEJ on epithelialization and epidermal stem cell localization, we used photolithography coupled with materials processing techniques to create microfabricated basal lamina analogs. It was determined that epidermal thicknesses found in narrow channels of microfabricated basal lamina analogs (50 µm and 100 µm widths with 200 µm depths) were similar to cultures on de-epithelialized acellular dermis and native foreskin tissues after 7 days of in vitro culture. We also determined that the microfabricated basal lamina analogs created an epidermal stem cell niche that promoted epidermal stem cell clustering in the channels which is critical for longevity of the tissue. Overall, we developed a platform technology that was specifically used to produce a highly functional bioengineered skin substitute with regenerative capacity that mimics native skin. We anticipate through the use of this technology, we can further improve bioengineered skin substitutes by incorporating epidermal structures of native skin including hair follicles and sweat glands as well as improve overall cosmetic appearance. Additionally, this novel bioengineered skin substitute can serve as a model system to further our understanding of pathological conditions and diseases of the skin as well as facilitate robust preclinical screenings of epidermal responses to new therapeutic agents as well as to cosmetic and chemical products.

Efficiency of current cell cultures producing biological products is limited due to accumulation of the product and waste on the cells. A previous work aims at assisting bioengineers in solving this problem by introducing a new set of cells which possess the ability to connect to one another and thus form a network. Once created, the network of cells can help the initial cellules by removing their waste and product as well as nourishing them. Our project explores a technique to be able to create the best network of such cells; hence maximizing the amount of metabolic product in the cell culture.

No description available.

No description available.

Decellularized lung tissue has been recognized as a potential platform to engineer whole lung organs suitable for transplantation or for modeling a variety of lung diseases. However many technical hurdles remain before this potential may be fully realized. Inability to efficiently re-endothelialize the pulmonary vasculature with a functional endothelium appears to be the primary cause of failure of recellularized lung scaffolds in early transplant studies. This dissertation research aims to enhance the re-endothelialization of decellularized rodent lung scaffolds with rat lung microvascular endothelial cells. This was achieved by adjusting the posture of the lung to a supine position during cell seeding through the pulmonary artery. The supine position allowed for significantly more homogeneous seeding and better cell retention in the apex regions of all lobes than the traditional upright position, especially in the right upper and left lobes. Additionally, the supine position allowed for greater cell retention within large diameter vessels (proximal – 100 µm to 5,000 µm) than the upright position, with little to no difference in the small diameter distal vessels. Endothelial cell adhesion in the proximal regions of the pulmonary vasculature in the decellularized lung was dependent on the binding of endothelial cell integrins, specifically α1β1, α2β1 and α5β1 integrins to, respectively, collagen type-I, type-IV and fibronectin in the residual ECM. Following in vitro maturation of the seeded constructs under perfusion culture, the seeded endothelial cells spread along the vascular wall, leading to a partial re-establishment of endothelial barrier function as inferred from a custom-designed leakage assay. The results of this dissertation research suggest that attention to cellular distribution within the whole organ is of paramount importance for restoring proper vascular function. / Bioengineering

The potential of physiologically relevant in vitro cell culture models for studying physiological and pathophysiological phenomena has been widely recognized as replacements for animal and conventional in vitro models. To create models that accurately replicate the structure and function of tissues and organs, it is essential to comprehend the biophysical and mechanical features of the extracellular matrix (ECM) and incorporate them into the in vitro cell culture models. Therefore, we first aimed to investigate how nanotopography can modulate cell behaviors by studying cell behaviors on nanostructures of various aspect ratios on a cobalt-chromium-molybdenum (CoCrMo) alloy surface. We also explored the impact of nanofibrous membranes on the formation of alveolar epithelium, which is critical for lung alveolar interstitium chips. In addition, we investigated the effect of mechanical stretch on cell behaviors and focused on how the dimensionality of the stretch affects cell behaviors. To create physiologically relevant in vitro models based on our findings, we engineered a stem cell niche using a combination of nanofibrous membranes, mechanical stretch, and a soft substrate, and evaluated its impact on stem cell behaviors. Finally, we created a biomimetic human lung interstitium chip for application in physiological and pathophysiological in vitro studies.

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The National Bioengineered Food Disclosure Standard (PL 114-216) will require nearly all foods sold in the U.S. to bear a statement disclosing whether they contain genetically modified (GM) material. Past studies suggest the presence of such a statement could have profound effects on consumers; however, research comparing consumer response towards different GM-disclosure statements is scarce. PL 114-216 states that GM foods shall not be considered more or less safe than their non-bioengineered counterparts, nevertheless it would benefit regulators and food manufacturers to be aware of the possible effects such disclosures might have on consumers. In a nationwide survey, multiple disclosure statements with varying degrees of public familiarity were compared to evaluate consumer perceptions and attitudes associated with each statement. Average consumer knowledge level of GM processes was also measured. The statements were then paired with actual food items to determine whether specific product categories influenced consumer responses. A select few of these statements and foods were included in a taste panel, allowing researchers to analyze if disclosure statements affected a consumer's sensorial experience. Results suggested that consumers were most favorable towards statements indicating the absence of GM-material, however they also responded less negatively towards new disclosure statements that do not have negative connotations. Additionally, consumers may react differently depending on the food accompanying a particular disclosure, although the taste panel data found no evidence that statements affected actual eating experience. Importantly, data from both surveys and taste panel suggested a disclosure statement may affect consumer willingness to buy a product.

91f. / Submitted by Suelen Reis (suziy.ellen@gmail.com) on 2013-04-23T13:36:16Z No. of bitstreams: 1 Dissertacao Ana Emilia.pdf: 3842407 bytes, checksum: 06b8d72eed292f7ebdf42b0a223ed0f6 (MD5) / Approved for entry into archive by Rodrigo Meirelles(rodrigomei@ufba.br) on 2013-05-08T11:44:00Z (GMT) No. of bitstreams: 1 Dissertacao Ana Emilia.pdf: 3842407 bytes, checksum: 06b8d72eed292f7ebdf42b0a223ed0f6 (MD5) / Made available in DSpace on 2013-05-08T11:44:00Z (GMT). No. of bitstreams: 1 Dissertacao Ana Emilia.pdf: 3842407 bytes, checksum: 06b8d72eed292f7ebdf42b0a223ed0f6 (MD5) Previous issue date: 2010 / A bioengenharia tecidual tem possibilitado o desenvolvimento de biomateriais e técnicas inovadoras capazes de restituir a qualidade de vida aos pacientes com perdas ósseas, após a remoção de grandes tumores ósseos, traumas e em algumas doenças metabólicas. Dentre os biomateriais empregados nas terapias regenerativas destacam-se as biocerâmicas sintéticas, na forma de microesferas. Estas microesferas constituem um arcabouço que possibilita, no interstício formado entre as esferas, a difusão de fatores de crescimento e angiogênicos, a migração de cálulas osteogênicas essenciais à regeneração deste tecido. Ainda apresentam características físico-químicas semelhantes ao componente inorgânico do tecido ósseo e biocompatibilidade. O objetivo deste trabalho foi avaliar a regeneração de defeitos ósseos críticos, em calvária de rato. Para tanto, utilizou-se uma amostra composta de 60 animais, dividida em quatro grupos: Gl - defeito sem biomaterial, preenchido por coágulo; Gll - microesferas de hidroxiapatita e alginato (HA - Alg); Glll - microeferas de hidroxiapatita dopadas com estrôncio (HASr); GlV - microesferas de hidroxiapatita dopadas com estrôncio e alginato (HASr -Alg), avaliados aos 15, 45 e 120 dias de pós operatório. As análises histológicas, por microscopia de luz, demonstraram neoformação óssea mais evidente no grupo Gll em todos os pontos biológicos quando comparado aos demais grupos. As microesferas implantadas nos grupos lll e lV apresentaram maior fragmentação quando comparadas com as do grupo ll, provavelmente devido à adição de estrôncio à estrutura da HA. A neoformação óssea caracterizada pela osteocondução foi observada de permeio a esses fragmentos do biomaterial. No grupo lll, a ausência do alginato tornou as microesferas mais porosas, com formação de septos de tecido conjuntivo e células fusiformes no interior das microesferas. Em conclusão, os biomateriais apresentaram potencial osteogênico e osteocondutor formando um arcabouço tridimensional que favoreceu a neoformação óssea. A HA associada ao alginato apresentou características histológicas mais evidentes quanto a biocompatibilidade e a osteogênese, quando comparada a HA dopada com estrôncio. / Salvador

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