The main question that this thesis addresses is what is the optimal way of producing tissue grown in the peritoneal cavity around a foreign body for its use as a vascular graft? It is known that a foreign body implanted into the peritoneal cavity induces an inflammatory response with cells recruited from within the peritoneal cavity to encapsulate the foreign body. Over the course of two to three weeks these cells produce an organised matrix and differentiate to become myofibroblasts. Tubes of these ‗tissue capsules‘ have been transplanted into the arterial vasculature in several animal models where the tissue capsule differentiates into an arterial structure. This structure consists of a layer of smooth muscle-like cells, adventitia of dense connective tissue including vasa-vasorum and an endothelial layer of flattened mesothelial cells. In order to determine whether the tissue would further differentiate ex vivo in response to mechanical stimulus an in-vitro bioreactor system was built to house tissue capsules produced in a variety of animal models. This bioreactor system could house 4 tissue capsules under physiological conditions including standard pulse rates, pressures and temperatures experienced by an artery. Boiled blood clot (BBC) scaffolds were implanted into the peritoneal cavity of rats to produce tissue capsules. After two weeks of development in the peritoneal cavity, tissue capsules were harvested and implanted into the bioreactor. Tissue capsules grafted into the bioreactor were subjected to mechanical force for a range of time-points, pressure, pulse and flow rates. When analysing tissue immunohistochemically, elastin, myosin, αSMA and desmin were detected. This staining was not consistent across all samples and only present in small parts of some tissue tested. Western analysis did not show any expression of αSMA or myosin. Finally the morphology of the tissue also resembled that of tissue previously implanted into the arterial circulation, but development of mechanical properties were not to the extent that would make the tissue useful as a vascular graft. The bioreactor system was thus modified to be able to house tissue for a period of 3 weeks. This system successfully housed tissue capsules under mechanical force in physiological ranges. Next, a range of materials were tested for their ability to be included into the peritoneal implant device used for the large animal model. Elasteon 80A did not produce any cellular growth or peritoneal pathology in all implanted samples (n = 4). Cloisite, a pro-inflammatory material produced large tissue capsule development over a 2 week implant period in 25% of samples however this tissue was heavily adhered to the greater omentum and dependent on its vascular supply. This data suggested that Elasteon could be used to coat the outer surface of a peritoneal implant device to decrease the rate of peritoneal adhesions. Three devices were designed and fabricated for their use in generating tissue for the modified Mitrofanoff procedure which requires a length of tissue to be implanted between the umbilicus and the bladder as a fistula. In all three cases no implantable material was produced that could be used for this procedure. To modify the device that could be used to produce tissue for any surgical application, a range of devices was produced and the animal model was changed to pigs. Materials incorporated into these devices include Dexon mesh and polyethylene. These devices also did not produce any tissue that could possibly be used as a vascular graft. A novel material, polymer BD347 was then produced for use in developing tissue within the interior of the device to provide greater growth and mechanical properties for developing a vascular graft. In toxicological studies, the replacement rate of cells was unaffected after seven days of incubation of fibroblasts at confluence with the polymer. A range of mechanical properties from pig vasculature was gained so that a sheet of polymer with similar properties to that of a vascular graft could be made. This polymer was fabricated as a tube and implanted into the peritoneal cavity of rats. The implanted polymer remained free-floating with a capsule of tissue in 78% of cases. A device was designed that has the ability to impart a physiological pulsation force on the developing tissue capsule in the peritoneal cavity using a sheep model. When two devices were implanted for a period of 10 days in each animal these devices produced no complications for the animal. Upon harvest all devices were free of adhesion and did not cause any peritoneal or dermal infection. In 100% of cases this device produced tissue that was thick and consistent along the length of the implant. The quality of tissue differed greatly macroscopically between tissue produced around pulsing and non-pulsing scaffolds, but microscopically the structure of both tissues was not significantly different. Approximately 90% of cells in this tissue stained positively for CD45. Tissue in pulsing devices produced a higher amount of vimentin expression in CD45 positive staining cells than tissue in non-pulsing devices. Mechanical properties of tissue in pulsed devices were also much greater than tissue in non-pulsed devices. Two of the pulsed tissues were grafted into the carotid artery of sheep as arterial patches. In one animal tissue lasted a period of 1 week before it ruptured. In the second animal tissue lasted a period of 2 weeks at which time the animal was sacrificed. In this sheep a layer of endothelial cells had migrated to populate areas of the tissue patch. Pulsation of the implant device enhanced the development of tissue capsule in the peritoneal cavity towards arterial properties. These studies provide information on the materials and designs required to produce peritoneal-derived tissue capsules that can be used in a range of surgical applications. These studies also provide information on how this tissue responds to mechanical force and provides an in vitro system for testing this tissue. This work in this thesis has produced a device that is in the stage of pre-clinical development to be used as a potential therapy for cardiovascular disease. This device is a novel development from previous devices used for generating tissue capsules for engraftment and is a significant contribution to work in developing a replacement artery.

Abstract Superabsorbent water beads have found many uses as household decorative items, crafts, and other industrial uses. We report a case of ingestion of several LiquiBlock Rainbow brand superabsorbent beads by a ten month old girl leading to small bowel obstruction requiring laparotomy and removal of the beads.

Persistent lip swelling can be a diagnostic challenge. We report an unusual case of lip edema in the setting of lip surgery 30 years before presentation and because of retained foreign material. This case highlights the importance of accurate historical information and aggressive diagnostic methods in assessing persistent lip swelling.

No description available.

<p>Inflammation and the formation of an avascular fibrous capsule have been identified as the key factors controlling the wound healing associated failure of implantable glucose sensors. Our aim is to guide advantageous tissue remodeling around implanted sensor leads by the temporal release of dexamethasone (Dex), a potent anti-inflammatory agent, in combination with the presentation of a stable textured surface. </p><p>First, Dex-releasing polyurethane porous coatings of controlled pore size and thickness were fabricated using salt-leaching/gas-foaming technique. Porosity, pore size, thickness, drug release kinetics, drug loading amount, and drug bioactivity were evaluated. In vitro sensor functionality test were performed to determine if Dex-releasing porous coatings interfered with sensor performance (increased signal attenuation and/or response times) compared to bare sensors. Drug release from coatings monitored over two weeks presented an initial fast release followed by a slower release. Total release from coatings was highly dependent on initial drug loading amount. Functional in vitro testing of glucose sensors deployed with porous coatings against glucose standards demonstrated that highly porous coatings minimally affected signal strength and response rate. Bioactivity of the released drug was determined by monitoring Dex-mediated, dose-dependent apoptosis of human peripheral blood derived monocytes in culture. </p><p>The tissue modifying effects of Dex-releasing porous coatings were accessed by fully implanting Tygon® tubing in the subcutaneous space of healthy and diabetic rats. Based on encouraging results from these studies, we deployed Dex-releasing porous coatings from the tips of functional sensors in both diabetic and healthy rats. We evaluated if the tissue modifying effects translated into accurate, maintainable and reliable sensor signals in the long-term. Sensor functionality was accessed by continuously monitoring glucose levels and performing acute glucose challenges at specified time points. </p><p>Sensors treated with porous Dex-releasing coatings showed diminished inflammation and enhanced vascularization of the tissue surrounding the implants in healthy rats. Functional sensors with Dex-releasing porous coatings showed enhanced sensor sensitivity over a 21-day period when compared to controls. Enhanced sensor sensitivity was accompanied with an increase in sensor signal lag and MARD score. These results indicated that Dex-loaded porous coatings were able to elicit a favorable tissue response, and that such tissue microenvironment could be conducive towards extending the performance window of glucose sensors in vivo.</p><p>The diabetic pilot animal study showed differences in wound healing patters between healthy and diabetic subjects. Diabetic rats showed lower levels of inflammation and vascularization of the tissue surrounding implants when compared to their healthy counterparts. Also, functional sensors treated with Dex-releasing porous coatings did not show enhanced sensor sensitivity over a 21-day period. Moreover, increased in sensor signal lag and MARD scores were present in porous coated sensors regardless of Dex-loading when compared to bare implants. These results suggest that the altered wound healing patterns presented in diabetic tissues may lead to premature sensor failure when compared to sensors implanted in healthy rats.</p> / Dissertation

Les biopiles enzymatiques miniatures représentent un potentiel important pour la future génération de dispositifs médicaux implantables, utilisés pour le diagnostic, le pronostic et le traitement. Ces derniers fonctionnent actuellement avec des sources d'énergie externes. Ces biopiles utilisant les molécules présentes dans les fluides biologiques sont des dispositifs médicaux prometteurs. Le glucose, qui est abondamment disponible dans le corps, est à l’étude comme biocarburant permettant de produire de l’énergie. Les enzymes utilisées pour produire l'énergie à partir des produits biochimiques sont immobilisées sur des électrodes en or par des médiateurs redox. Cependant, la faible puissance actuellement disponible et la sensibilité des enzymes à l'environnement limitent leur application in vivo. Malgré des recherches intensives, de nombreux problèmes restent à résoudre, notamment l'amélioration de la puissance, de la stabilité et de la biocompatibilité des biopiles.La réaction à corps étranger et l'isolement du dispositif médical par la formation d'une capsule fibreuse peuvent d'une part dénaturer les enzymes et, d'autre part, entraver la diffusion des analytes et de l'oxygène. Le travail décrit dans cette thèse vise à protéger les biopiles fonctionnant à base de glucose. Afin de résoudre les problèmes mentionnés ci-dessus, les hydrogels, actuellement développés pour diverses applications telles que l'administration de médicaments, l'ingénierie tissulaire et les dispositifs médicaux, offrent des propriétés prometteuses en tant que matériaux de revêtement.La première partie de la thèse est centrée sur l'évaluation de différents hydrogels injectables de faible poids moléculaire, en analysant à la fois la gélification in vitro et in vivo, la cinétique de dégradation, la réaction à corps étranger et l'angiogenèse. Les hydrogels présentent une dégradation lente et une intégration tissulaire optimale. Une angiogenèse accrue a été observée en raison de la libération d'une molécule pro-angiogénique pendant la dégradation de l'hydrogel.Dans la seconde partie de la thèse, l'un des hydrogels étudiés a été utilisé pour recouvrir l'électrode en or : le choix de l'enzyme a été basé sur des études de stabilité in vitro. En parallèle, le processus de revêtement a été optimisé, à la fois pour son uniformité et son épaisseur. Même si un revêtement plus épais présente l’avantage de protéger l’électrode contre la réaction à corps étranger, il est nécessaire de limiter l’épaisseur afin de maintenir une diffusion efficace des analytes et de l’oxygène.Les expériences en cours décrites dans la dernière partie de la thèse sont axées sur l'optimisation de l'implantation chez le rat et la mesure de l'activité des biopiles. De plus, les électrodes ont été connectées à une antenne pour établir une communication sans fil ; en effet, cela permettrait une mesure non invasive de l'activité enzymatique.En conclusion, ces travaux ont permis d'identifier un hydrogel pouvant être utilisé pour revêtir les électrodes de biopiles. Le sous-produit libéré lors de la biodégradation favorise l'angiogenèse au voisinage du matériau. Grâce à ce revêtement, on peut donc s'attendre à un échange accru d'analytes et d'oxygène, préalable indispensable à l'activité enzymatique. / Miniature enzymatic biofuel cells hold great potential to power the future generation of implantable medical devices, which are currently working on external power sources used for diagnosis, prognosis and treatment. Enzymatic biofuel cells appear to be promising in harvesting the energy from biochemicals present in physiological body fluids. Glucose, which is abundantly available in the body, is being explored as a biofuel to harvest energy. The enzymes employed to harvest the energy from the biochemicals are electrically wired on gold electrodes by redox mediators. However, the limitation of insufficient power, and the sensitivity of the enzymes towards host environment restrict their in vivo application. Despite several attempts, numerous challenges remain to be addressed such as improved current density, increased stability, and biocompatibility of enzymatic biofuel cells.Foreign body reaction and isolation of the medical device by formation of a fibrous capsule may firstly denature the enzymes, and secondly hinder the diffusion of analytes and oxygen. The work described in this thesis aims at protecting glucose based biofuel cells. As a strategy for combatting the bottlenecks mentioned above, hydrogels, currently developed for various applications such as drug delivery, tissue engineering, and medical device, offer promising properties as coating materials.The first part of the thesis is focused on evaluating different low molecular weight injectable hydrogels by analysing both in vitro and in vivo gel formation, degradation kinetics, foreign body reaction and angiogenesis. The hydrogels exhibit slow degradation, and optimal tissue integration. Enhanced angiogenesis was observed due to a pro-angiogenic molecule released during hydrogel degradation.In the second part of the thesis, one of the studied hydrogels was used to coat the gold electrode functionalised with enzyme: the selection of the enzyme was based on in vitro stability studies. In parallel, the process of coating was optimised, both for uniformity and thickness. Although a thicker coating should protect the electrode against foreign body reaction, it was necessary to limit the thickness in order to maintain an efficient analyte and oxygen diffusion.Ongoing experiments described in the last part of the thesis are focused on the optimisation of implantation in rat and measurement of the biofuel cell activity. In addition, the electrodes were connected to an antenna for wireless communication; indeed, such a device would allow for a non-invasive measurement of enzyme activity.To conclude, this work allowed for the identification of a hydrogel that can be used to coat the electrodes of biofuel cells. The byproduct released during the biodegradation favours angiogenesis in the vicinity of the material. Thanks to this coating, we can therefore expect an enhanced exchange of analytes and oxygen, which is a prerequisite for enzyme activity.

<p>Many implanted devices fail due to the formation of an avascular capsule. Fat is known to promote healing and vascularization. It is possible that isolating and attaching ASCs (adipose stem cells) to an implanted device improves the healing in the adjacent tissue. </p><p> Various attachment methods were studied, and the fibronectin treatment was found comparable to or better than other treatments. Next, bare and ASC coated polyurethane were implanted into rats. The fibrous capsule surrounding the bare polyurethane was thicker and contained more collagen at 8 weeks. Additionally, the microvessel density in the tissue surrounding the ASC coated polyurethane was significantly higher at 4 and 8 weeks. Quantification of glucose sensor response following ASC attachment for 1 week found no measurable significant differences in function.</p><p> The bioluminescence technique, which quantifies the tissue glucose concentration around the implant at the moment of freezing, was used to determine if ASC attachment to biomaterials impacts the tissue glucose concentration profile. ASC attachment to polyurethane and to glucose sensors did not significantly change the glucose profiles in the tissue. However, a quantifiable glucose concentration profile was observed around all glucose sensors.</p><p> The final experiments were performed to identify a possible mechanism that adipose tissue uses to alter the foreign body response. In vitro experiments showed that VEGF (VEGF-A specifically) secretion following ASC attachment to polyurethane was 10-20 times higher than with fibroblast attachment after three days and 40-70 times higher after six days. This high secretion of VEGF would likely have in vivo physiological affects on microvasculature.</p><p> In conclusion, the attachment of ASCs to polyurethane reduced the thickness and collagen content of the fibrous capsule surrounding ASC coated implants and increased the microvessel density in adjacent tissue. In addition, ASC attachment did not enhance glucose sensor function, nor did it decrease the glucose concentration in the adjacent tissue. Finally, ASCs were found to secrete high amounts of pro-vascular cytokines, which likely plays a key role in the observed improvement of the foreign body response.</p> / Dissertation

Cholesterol crystals have been linked to activation of the NLRP3 inflammasome and the formation of foreign body giant cells (FBGCs). It has been hypothesized that FBGCs have a role in advanced atherosclerotic plaque formation. This thesis examined the feasibility of producing stable cultures of FBGCs starting with human monocytes with the goal to examine pterin production by these cells in comparison to human monocyte derived macrophages (HMDMs). The study also investigated the effect of cholesterol crystals on 7,8-dihydroneopterin (7,8-NP) production and modulation of IL-1β levels in macrophages. 7,8-Dihydroneopterin is a potent antioxidant generated by macrophages which also down regulates the expression of macrophage scavenger receptor CD36. The use of alpha-tocopherol and IL-4 as FBGC fusion mediators was explored. Using these mediators, large numbers of FBGC were successfully cultured. The rates of fusion achieved in the cultures were low, and the cells had poor adhesion, which prevented pterin measurement. FBGC, which are thought to remove crystallized cholesterol from the plaque, cleared 21% of cholesterol crystal compared to 50% cleared by HMDM cells. Due to this result, the effect of cholesterol crystals on pterin production in monocytes and macrophages was explored. Cholesterol crystals cause inflammation through the activation of the NLRP3 inflammasome, however, it was unknown whether they could modulate 7,8-NP production. Cholesterol crystals caused an intracellular dose-dependent loss of 7,8-NP to its oxidized form, neopterin, in HMDM cells. Cholesterol crystals induced intracellular synthesis of 7,8-NP in HMDMs. 7,8-NP was released into the supernatant and oxidized to neopterin in media. Monocytes treated with cholesterol crystals released up to 100 nM of neopterin and 120 nM of 7,8-NP in the media after 48 hours. The combination of IFN- and cholesterol crystals appeared to inhibit the release of 7,8-NP into the media for the first 48 hours, after this time 7,8-NP release rapidly increased. The addition of exogenous 200 μM 7,8-NP showed that in the presence of monocytes, cholesterol crystals did not cause the oxidation of 7,8-NP to neopterin, as seen in HMDMs but possibly to 7,8-dihydroxanthopterin or xanthopterin. The presence of 7,8-NP increased IL-1β expression in the presence of cholesterol crystals after 24 hours incubation. FBGCs and the removal of cholesterol crystals may be a key process in the resolution of atherosclerotic plaques. It appears that cholesterol crystals are able to modulate inflammatory processes including activation of the inflammasome and balance of 7,8-dihydroneopterin to the oxidized neopterin. The infiltrating monocytes may provide antioxidant protection against the inflammation induced by cholesterol crystals and the activity of the infammasome.

This MEng (Master of Engineering) research thesis evaluates the capabilities and limitations of line-scan thermography for the non-destructive evaluation of composite structures containing hidden defects. In simple terms, line-scan thermography is a state-of-the-art technique in which a focused line of thermal energy is transmitted into a material. Line-scan thermography has great potential for the rapid and low cost non-destructive inspection of composite structures for aircraft, automobiles and ships. In this project, theoretical research exploring the heat transfer physics was undertaken in conjunction with experimental studies to develop an optimum inspection regime for line-scan thermography. The capability of line-scan thermography to detect impact damage in carbon/epoxy laminates was experimentally investigated in Chapter 3. From the impact side, in all materials, line-scan thermography overestimated the size of the impact damage whereas flash thermography underestimated the size. There was a close relationship between the ultrasonic profile and the line-scan thermographic thermal response curve. New experimental data has been produced and analysed for the ability of line-scan thermography to determine the defect as well as the defect size. It was found that line-scan thermography was able to distinguish back drilled holes, but it was not possible to determine accurate defect sizing due to the depth of the holes from the inspected surface and the limitations associated with the line-scan thermographic apparatus itself. There was excellent correlation between the C-scan ultrasonics intensity curves and the line-scan thermographs as well as excellent correlation with the theoretical results. The relationship between line-scan thermography and foreign body objects were experimentally investigated for carbon/epoxy composites. A major limitation found with line-scan thermography is its limited depth penetration, which is highlighted in the foreign object study using 6 mm and 13 mm diameter Teflon® discs and 13 mm Teflon® strips embedded in carbon/epoxy laminates. Depth penetration allowed only 2 mm resolution for the 13 mm diameter discs and 1.5 mm resolution for the 6 mm discs in a composite panel. The results of the investigation of stainless steel shim objects in carbon/epoxy laminates reveal that line-scan thermography is capable of determining their presence and size close to the surface. There was also excellent correlation between the ultrasonic response curve and the line-scan thermographic intensity curve. The results of the investigation of thermoplastic film foreign body objects in carbon/epoxy laminates show that at present line-scan thermography does not have the capability to determin e such defects. Experimental results show that line-scan thermography is capable of detecting large voids, back drilled holes, some foreign body objects, and impact damage. However, the ability of line-scan thermography to measure the defect dimensions is dependent on the size and type of damage, the distance from the line source, the depth of the defect, and the type of composite material.

Thesis (Ph. D.)--University of Washington, 2004. / Vita. Includes bibliographical references (leaves 113-116).