The goal for this thesis was to apply electrospun biomimetic coatings on implantable glucose biosensors and test their efficacy as mass-transport limiting and tissue engineering membranes, with special focus on achieving reliable and long sensing life-time for biosensors when implanted in the body. The 3D structure of electrospun membranes provides the unique combination of extensively interconnected pores, large pore volumes and mechanical strength, which are anticipated to improving sensor sensitivity. Their structure also mimics the 3D architecture of natural extracellular matrix (ECM), which is exploited to engineer tissue responses to implants. A versatile vertical electrospinning setup was built in our workshop and used to electrospin single polymer - Selectophore™ polyurethane (PU) and two polymer (coaxial) – PU and gelatin (Ge) fibre membranes. Extensive studies involving optimization of electrospinning parameters (namely solvents, polymer solution concentration, applied electric potential, polymer solution feed flow rate, distance between spinneret and collector) were carried out to obtain electrospun membranes having tailorable fibre diameters, pore sizes and thickness. The morphology (scanning electron microscopy (SEM) and optical microscopy), fibre diameter (SEM), porosity (bubble point and gravimetry methods), hydrophilicity (contact angle), solute diffusion (biodialyzer) and uniaxial mechanical properties (tensile tester) were used to characterize certain shortlisted electrospun membranes. Static and dynamic collector configurations for electrospinning fibres directly on sensor surface were optimized of which the dynamic collections system helped achieve snugly fit membranes of uniform thickness on the entire surface of the sensor. The biocompatibility and the in vivo functional efficacy of electrospun membranes off and on glucose biosensors were evaluated in rat subcutaneous implantation model. Linear increase in thickness of electrospun membranes with increasing electrospinning time was observed. Further, the smaller the fibre diameter, smaller was the pore size and higher was the fibre density (predicted), the hydrophilicity and the mechanical strength. Very thin membranes showed zero-order (Fickian diffusion exponent ‘n’ ~ 1) permeability for glucose transport. Increasing membrane thickness lowered ‘n’ value through non-Fickian towards Fickian (‘n’ = 0.5) diffusion. Thin electrospun PU membranes (~10 μm thick) did not affect, while thicknesses between 20 and 140 μm all decreased sensitivity of glucose biosensor by about 20%. PU core - Ge shell coaxial fibre membranes caused decrease in ex vivo sensitivity by up to 40%. The membranes with sub-micron to micron sized pore sizes functioned as mass-transport limiting membranes; but were not permeable to host cells when implanted in the body. However, PU-Ge coaxial fibre membranes, having <2 μm pore sizes, were infiltrated with fibroblasts and deposition of collagen in their pores. Such tissue response prevented the formation of dense fibrous capsule around the implants, which helped improve the in vivo sensor sensitivity. To conclude, this study demonstrated that electrospun membrane having tailorable fibre diameters, porosity and thickness, while having mechanical strength similar to the natural soft tissues can be spun directly on sensor surfaces. The membranes can function as mass-transport limiting membranes, while causing minimal or no effect on sensor sensitivity. With the added bioactive Ge surfaces, evidence from this study indicates that reliable long-term in vivo sensor function can be achieved.

Orientador: Cecília Amélia de Carvalho Zavaglia / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica / Made available in DSpace on 2018-08-24T09:00:21Z (GMT). No. of bitstreams: 1 Uebelhart_Beatriz_M.pdf: 3346622 bytes, checksum: f0a455713e558d11ecb3ef1e865148a0 (MD5) Previous issue date: 2013 / Resumo: Uma Bomba de Sangue Centrífuga Implantável (BSCI) está sendo desenvolvida para ser utilizada como assistência circulatória em pacientes com doenças cardiovasculares graves (DCVs). Para algumas doenças cardíacas, a única forma de tratamento é o transplante cardíaco. Um Dispositivo de Assistência Circulatória (DAV) pode ser utilizado para manter a vida do paciente enquanto ele aguarda na fila de espera por um transplante. A BSCI consiste de um DAV e é composta de protótipo, cânulas, motor, controlador, e fonte de energia. A complexidade geométrica de seu rotor dificulta sua construção através de processos de usinagem convencionais. Ao mesmo tempo, o aperfeiçoamento e construção de novos protótipos é essencial, pois permite a realização da análise de seu funcionamento, identificação e correção de falhas. A tecnologia selecionada que permite a construção rápida de um modelo tridimensional de geometria complexa é a prototipagem rápida (PR). Neste trabalho foram utilizados três diferentes tipos de processos de PR no desenvolvimento de protótipos da BCI para realização de testes "In Vitro" e "In Vivo". Os modelos físicos foram construídos através dos processos de Sinterização Seletiva a Laser (SLS), de Modelagem por Fusão e Deposição (FDM) e Estereolitografia (SLA). Através de análises qualitativas selecionou-se um dos processos para confecção dos protótipos da BSCI. Os protótipos foram submetidos a testes "In Vitro" e experimentos "In Vivo". A tecnologia de PR selecionada foi a Estereolitografia. O resultado do teste de desempenho hidrodinâmico apresentou-se satisfatório quando comparado a estudos anteriores. O teste em simulador demonstrou uma melhora nas condições fisiológicas simuladas quando um organismo simulado é submetido a assistência da BCI. Através dos testes "In Vivo" foi possível analisar o comportamento do protótipo e estudar técnicas de implante da BCI, os resultados se apresentaram satisfatórios / Abstract: An Implantable Centrifugal Blood Pump (ICBP) is being developed to be used as circulatory assistance in patients with severe cardiovascular diseases. For certain heart diseases, the only treatment is the heart transplant. A Ventricular Assist Device (VAD) can be used to maintain the patient's life while he waits for a heart transplant. ICBP consists of a VAD and is composed of a prototype, cannulae, motor, controller and energy source. Due the complexity of spiral geometry of the impeller, ICBP prototypes construction is difficult through conventional manufacturing processes. At the same time, the improvements and construction of new prototypes is essential because allows the performance analysis, identification and correction of failures. The chosen technology that allows fast construction of 3D models with complex geometry is Rapid Prototyping (RP). In this study were used three different technologies of RP to develop new ICBP prototypes and perform "In Vitro" and "In Vivo" tests. The physical models were constructed through the processes of Selective Laser Sintering (SLS), Fused and Deposition Modeling (FDM) and Stereolithography (SLA). Through qualitative analysis, between processes, one was selected to construct the ICBP 3D models. "In Vitro" and "In Vivo" tests were performed. SLA rapid prototyping process was selected to construct ICBP models. Hydrodynamic tests results presented satisfactory when compared with previous studies. Cardiovascular Simulator test results presented an improvement in simulated physiological conditions when the organism was submitted to ICBP assistance. Through "In Vivo" tests was possible to analyze the ICBP prototype performance and study ICBP implant techniques, and the results presented satisfactory / Mestrado / Materiais e Processos de Fabricação / Mestra em Engenharia Mecânica

Deciphering exogenous cues that determine stem cell fate decisions is a persisting challenge of cell biology and bioengineering. In an effort to unravel the role of spatial constraints in the cell-instructive characteristics of bone marrow microenvironments, murine hematopoietic stem and progenitor cells (HSPC) were exposed to fibronectin-coated microcavities in vitro. Microcavity sizes were chosen to allow for the inclusion of either individual or multiple cells. Repopulation experiments using lethally irradiated mice showed that the maintenance of functional HSPC in culture critically depends on cavity dimensions. Short-term repopulating hematopoietic stem cells (ST-HSC) were found to be best supported within single-cell sized compartments while long-term repopulating HSC (LT-HSC) were maintained within both cavity sizes. In sum, the reported data reveal spatial restriction to be a simple but powerful means for directing HSPC fate ex vivo.

Dissertação(mestrado)- Universidade Federal do Rio Grande, Programa de Pós-Graduação em Engenharia e Ciência de Alimentos, Escola de Química e Alimentos, 2010. / Submitted by Caroline Silva (krol_bilhar@hotmail.com) on 2012-08-15T21:29:59Z No. of bitstreams: 1 dissertao.final.lidiane.pdf: 1460415 bytes, checksum: 6f8a2a7217fb18e07210cc2a3ead7b12 (MD5) / Approved for entry into archive by Bruna Vieira(bruninha_vieira@ibest.com.br) on 2012-09-03T19:03:03Z (GMT) No. of bitstreams: 1 dissertao.final.lidiane.pdf: 1460415 bytes, checksum: 6f8a2a7217fb18e07210cc2a3ead7b12 (MD5) / Made available in DSpace on 2012-09-03T19:03:03Z (GMT). No. of bitstreams: 1 dissertao.final.lidiane.pdf: 1460415 bytes, checksum: 6f8a2a7217fb18e07210cc2a3ead7b12 (MD5) Previous issue date: 2010 / Spirulina é uma cianobactéria que vem sendo produzida e estudada devido suas propriedades nutricionais e benéficas à saúde. Atualmente, a Legislação brasileira recomenda, como limite máximo de consumo diário por pessoa, 1,6g de Spirulina (BRASIL, 2009). O presente trabalho tem como objetivo geral avaliar o efeito de dietas adicionadas de diferentes concentrações de Spirulina LEB-18 sobre os perfis bioquímicos, hematológicos, nutricionais e fisiológicos de ratos machos da linhagem Rattus norvegicus cepa Wistar/UFPel. Atendendo todas as necessidades bioclimatológicas, tanto de micro como macro ambientes, o bioensaio, aprovado pela Comissão de Ética da Universidade Federal de Pelotas – UFPel (processo nº 23110. 008077/2009-22) foi conduzido na Sala de Experimentação Animal do Departamento de Ciência dos Alimentos da UFPel. O experimento foi realizado durante 45 dias, sendo os 5 primeiros para adaptação dos animais ao ambiente e à dieta controle e os demais para a realização, em paralelo, de dois experimentos (I e II). No experimento “I”, com duração de 40 dias, os animais (n=24) foram distribuídos em 4 tratamentos, conforme dieta ofertada: C (caseína como fonte protéica); S1 (1,6g Spirulina/dia); S2 (3,2g Spirulina/dia); e S3 (4,8g Spirulina/dia). No experimento II, durante 10 dias, os animais (n=23) receberam uma dieta aprotéica (A). Posteriormente foram redistribuídos em 4 grupos (C, S1, S2 e S3) para recuperação nutricional durante 30 dias. No decorrer e ao término do experimento foram observados peso dos animais e ingestão diária de dieta; coletados materiais biológicos, como, excretas, sangue e órgãos para posteriores determinações. Dentre as concentrações estudadas, a S1, caracterizada pelo limite descrito pela ANVISA, apresentou melhores resultados. Apesar de algumas diferenças entre os tratamentos adicionados de Spirulina, a microalga mostrou-se eficaz ao desenvolvimento dos animais e não causou reações adversas, conforme determinações, condições e período de realização desta pesquisa. / Spirulina is a cyanobacteria that has been produced and studied for its nutritional properties and health benefits. Presently, Brazilian legislation recommends a maximum consumption limit of 1.6g of Spirulina daily per person (BRAZIL, 2009). This study has the general objective of evaluating the effect of diets supplemented with different concentrations of Spirulina LEB-18 on biochemical profiles, hematologic, nutritional and physiological characteristics of male rats of the classification Rattus norvegicus strain Wistar/UFPel. Given all the bioclimatological needs, both micro and macro environments, the bio-assay, approved by the Ethics Committee of Pelotas Federal University (UFPEL) (processo nº 23110. 008077/2009-22), was conducted in the Hall of Animal Experimentation at the Department of Food Science, UFPEL. The study was carried out over 45 days, with the first 5 days for the adaptation of the animals to the environemnt and dietary control. Over the remaining 40 days, two experiments (I and II) were carried out in parallel. In experiment “I”, lasting 40 days, the animals (n=24) were distributed into the following 4 groups of diet preparation offered: C (casein as a protein source); S1 (1,6g Spirulina/day); S2 (3,2g Spirulina/day); and S3 (4,8g Spirulina/day). In experiment “II”, lasting 10 days, the animals (n=23) received an aproteic diet (A). Afterwards, they were distributed into four groups offered the diet preparations C, S1, S2 and S3 cited above, for nutritional recovery lasting 30 days. In the course of the experiment and at the end, animal weight and daily dietary intake were observed; biological materials, (such as feces, blood and organs), were collected for subsequent analysis. Amongst the concentrations studied, the S1 group, characterised by the limit described by ANVISA, showed better results. Despite some differences amongst the groups, supplementation with Spirulina microalgae proved effective for animal development and caused no adverse reactions, as prescribed within the conditions and duration of this research.