Thesis (doctoral)--Lund University, 1993. / Added t.p. with thesis statement inserted.

Thesis (Ph. D.)--University of Washington, 1999. / Vita. Includes bibliographical references (leaves 278-286).

Thesis (doctoral)--Lund University, 1993. / Added t.p. with thesis statement inserted.

Thesis (Ph. D.)--Chemical Engineering, Georgia Institute of Technology, 2006. / Chaikof, Elliot, Committee Chair ; Hanson, Stephen, Committee Member ; Lollar, John "Pete", Committee Member ; Sambanis, Athanassios, Committee Member ; Yoganathan, Ajit, Committee Member.

Thesis (Ph. D.)--Biomedical Engineering, Georgia Institute of Technology, 2006. / Pollman, Matthew, Committee Member ; Galis, Zorina, Committee Member ; McIntire, Larry, Committee Member ; Taylor, W Robert, Committee Member ; Jo, Hanjoong, Committee Member ; Nerem, Robert, Committee Chair.

A hiperplasia intimal é uma complicação comum após o implante de stent em artérias periféricas e a influência da homocisteína neste processo ainda é desconhecida. O objetivo deste estudo é comparar o espessamento intimal em aorta de suínos submetidos à hiper-homocisteinemia induzida com suínos normais, após implante de stents auto-expansíveis de nitinol. Foram utilizados 18 suínos da raça Macau, com peso médio de 30 kg. Os animais foram divididos aleatoriamente em dois grupos: o primeiro, grupo C (controle), foi alimentado com dieta normal e o outro, grupo M (metionina), recebeu dieta rica em metionina para induzir hiper-homocisteinemia durante 30 dias. Os stents utilizados para o experimento foram os auto-expansíveis, de nitinol, com 25 milímetros de comprimento e diâmetro final de oito milímetros. Foram realizadas dosagens de colesterol, triglicerídeos, colesterol HDL e homocisteína plasmática em ambos os grupos. A adequação das medidas do stent em relação às dimensões da artéria aorta dos suínos e a sua perviedade, após o implante, foram confirmadas mediante realização de arteriografias seletivas. Trinta dias após o implante do stent, os animais foram submetidos à eutanásia e as peças enviadas para exame anatomopatológico. O exame histológico mostrou intensa hiperplasia intimal no grupo controle e placas formadas por macrófagos espumosos com pouca hiperplasia intimal no grupo metionina. A análise morfométrica digital revelou maior hiperplasia intimal no grupo C em relação ao grupo M. Não ocorreram mudanças significativas nas dosagens de colesterol, triglicerídeos e colesterol HDL, em ambos os grupos. Não ocorreram variações significativas nos níveis de homocisteína plasmática dos suínos do grupo controle e, nos animais do grupo metionina, os níveis plasmáticos de homocisteína aumentaram de 17,47 para 58,90 μmol/l após 30 dias de administração de dieta rica em metionina. Concluindo, em aorta abdominal de suínos, alimentados com dieta rica em metionina por 30 dias, ocorreu uma hiperplasia intimal menor após o implante de stent auto-expansível de nitinol em comparação ao grupo controle. / Intimal hyperplasia is a common complication after stent placement in peripheral arteries and the influence of homocysteine in this process is still unknown. The purpose of this study is to compare the intimal thickening in the aorta of normal and induced hyperhomocysteinemic pigs following placement of self-expanding nitinol stents. The animals used were 18 pigs from the Macau specimen. They were over eight weeks old and average weight of 30 kg. Nitinol stents were self-expandable, 25 mm lenght and expanded diameters of 8 mm. The pigs were divided in two groups, the first (group C) was fed with a normal diet and the second group was fed with methionine rich diet to induce hyperhomocysteinemia (group M) during 30 days. Blood samples were collected for analyses of total cholesterol, triglycerides, and HDL and homocysteine concentrations. Assessment was done by angiography. After 30 days of the procedure, the animals where sacrificed and the abdominal aorta segment was removed for histological and digital morphometry analysis. Microscopic examinations of the aortas of the control group had a significant thicker intima compared with methionin group. In the comparison among groups, intimal thickening of the vessel wall at digital morphometric analysis was higher in group C than group M. There was no significant change in total cholesterol, triglycerides, and HDL concentrations in either group. There was no change in plasma homocysteine levels in group C; and in group M plasma homocysteine levels ranged from 17,47 to 59,80 μmol/l after 30 days with a methionine-rich diet. In conclusion, insertion of self-expandable nitinol stent in pig’s abdominal aorta after 30 days with a methionine-rich diet results in less intimal hyperplasia as compared to normal pigs.

A hiperplasia intimal é uma complicação comum após o implante de stent em artérias periféricas e a influência da homocisteína neste processo ainda é desconhecida. O objetivo deste estudo é comparar o espessamento intimal em aorta de suínos submetidos à hiper-homocisteinemia induzida com suínos normais, após implante de stents auto-expansíveis de nitinol. Foram utilizados 18 suínos da raça Macau, com peso médio de 30 kg. Os animais foram divididos aleatoriamente em dois grupos: o primeiro, grupo C (controle), foi alimentado com dieta normal e o outro, grupo M (metionina), recebeu dieta rica em metionina para induzir hiper-homocisteinemia durante 30 dias. Os stents utilizados para o experimento foram os auto-expansíveis, de nitinol, com 25 milímetros de comprimento e diâmetro final de oito milímetros. Foram realizadas dosagens de colesterol, triglicerídeos, colesterol HDL e homocisteína plasmática em ambos os grupos. A adequação das medidas do stent em relação às dimensões da artéria aorta dos suínos e a sua perviedade, após o implante, foram confirmadas mediante realização de arteriografias seletivas. Trinta dias após o implante do stent, os animais foram submetidos à eutanásia e as peças enviadas para exame anatomopatológico. O exame histológico mostrou intensa hiperplasia intimal no grupo controle e placas formadas por macrófagos espumosos com pouca hiperplasia intimal no grupo metionina. A análise morfométrica digital revelou maior hiperplasia intimal no grupo C em relação ao grupo M. Não ocorreram mudanças significativas nas dosagens de colesterol, triglicerídeos e colesterol HDL, em ambos os grupos. Não ocorreram variações significativas nos níveis de homocisteína plasmática dos suínos do grupo controle e, nos animais do grupo metionina, os níveis plasmáticos de homocisteína aumentaram de 17,47 para 58,90 μmol/l após 30 dias de administração de dieta rica em metionina. Concluindo, em aorta abdominal de suínos, alimentados com dieta rica em metionina por 30 dias, ocorreu uma hiperplasia intimal menor após o implante de stent auto-expansível de nitinol em comparação ao grupo controle. / Intimal hyperplasia is a common complication after stent placement in peripheral arteries and the influence of homocysteine in this process is still unknown. The purpose of this study is to compare the intimal thickening in the aorta of normal and induced hyperhomocysteinemic pigs following placement of self-expanding nitinol stents. The animals used were 18 pigs from the Macau specimen. They were over eight weeks old and average weight of 30 kg. Nitinol stents were self-expandable, 25 mm lenght and expanded diameters of 8 mm. The pigs were divided in two groups, the first (group C) was fed with a normal diet and the second group was fed with methionine rich diet to induce hyperhomocysteinemia (group M) during 30 days. Blood samples were collected for analyses of total cholesterol, triglycerides, and HDL and homocysteine concentrations. Assessment was done by angiography. After 30 days of the procedure, the animals where sacrificed and the abdominal aorta segment was removed for histological and digital morphometry analysis. Microscopic examinations of the aortas of the control group had a significant thicker intima compared with methionin group. In the comparison among groups, intimal thickening of the vessel wall at digital morphometric analysis was higher in group C than group M. There was no significant change in total cholesterol, triglycerides, and HDL concentrations in either group. There was no change in plasma homocysteine levels in group C; and in group M plasma homocysteine levels ranged from 17,47 to 59,80 μmol/l after 30 days with a methionine-rich diet. In conclusion, insertion of self-expandable nitinol stent in pig’s abdominal aorta after 30 days with a methionine-rich diet results in less intimal hyperplasia as compared to normal pigs.

A hiperplasia intimal é uma complicação comum após o implante de stent em artérias periféricas e a influência da homocisteína neste processo ainda é desconhecida. O objetivo deste estudo é comparar o espessamento intimal em aorta de suínos submetidos à hiper-homocisteinemia induzida com suínos normais, após implante de stents auto-expansíveis de nitinol. Foram utilizados 18 suínos da raça Macau, com peso médio de 30 kg. Os animais foram divididos aleatoriamente em dois grupos: o primeiro, grupo C (controle), foi alimentado com dieta normal e o outro, grupo M (metionina), recebeu dieta rica em metionina para induzir hiper-homocisteinemia durante 30 dias. Os stents utilizados para o experimento foram os auto-expansíveis, de nitinol, com 25 milímetros de comprimento e diâmetro final de oito milímetros. Foram realizadas dosagens de colesterol, triglicerídeos, colesterol HDL e homocisteína plasmática em ambos os grupos. A adequação das medidas do stent em relação às dimensões da artéria aorta dos suínos e a sua perviedade, após o implante, foram confirmadas mediante realização de arteriografias seletivas. Trinta dias após o implante do stent, os animais foram submetidos à eutanásia e as peças enviadas para exame anatomopatológico. O exame histológico mostrou intensa hiperplasia intimal no grupo controle e placas formadas por macrófagos espumosos com pouca hiperplasia intimal no grupo metionina. A análise morfométrica digital revelou maior hiperplasia intimal no grupo C em relação ao grupo M. Não ocorreram mudanças significativas nas dosagens de colesterol, triglicerídeos e colesterol HDL, em ambos os grupos. Não ocorreram variações significativas nos níveis de homocisteína plasmática dos suínos do grupo controle e, nos animais do grupo metionina, os níveis plasmáticos de homocisteína aumentaram de 17,47 para 58,90 μmol/l após 30 dias de administração de dieta rica em metionina. Concluindo, em aorta abdominal de suínos, alimentados com dieta rica em metionina por 30 dias, ocorreu uma hiperplasia intimal menor após o implante de stent auto-expansível de nitinol em comparação ao grupo controle. / Intimal hyperplasia is a common complication after stent placement in peripheral arteries and the influence of homocysteine in this process is still unknown. The purpose of this study is to compare the intimal thickening in the aorta of normal and induced hyperhomocysteinemic pigs following placement of self-expanding nitinol stents. The animals used were 18 pigs from the Macau specimen. They were over eight weeks old and average weight of 30 kg. Nitinol stents were self-expandable, 25 mm lenght and expanded diameters of 8 mm. The pigs were divided in two groups, the first (group C) was fed with a normal diet and the second group was fed with methionine rich diet to induce hyperhomocysteinemia (group M) during 30 days. Blood samples were collected for analyses of total cholesterol, triglycerides, and HDL and homocysteine concentrations. Assessment was done by angiography. After 30 days of the procedure, the animals where sacrificed and the abdominal aorta segment was removed for histological and digital morphometry analysis. Microscopic examinations of the aortas of the control group had a significant thicker intima compared with methionin group. In the comparison among groups, intimal thickening of the vessel wall at digital morphometric analysis was higher in group C than group M. There was no significant change in total cholesterol, triglycerides, and HDL concentrations in either group. There was no change in plasma homocysteine levels in group C; and in group M plasma homocysteine levels ranged from 17,47 to 59,80 μmol/l after 30 days with a methionine-rich diet. In conclusion, insertion of self-expandable nitinol stent in pig’s abdominal aorta after 30 days with a methionine-rich diet results in less intimal hyperplasia as compared to normal pigs.

It has been postulated that the control of thrombus formation on molecularly engineered surfaces is an important step in developing clinically durable small-diameter vascular prostheses. This has led to designing a membrane-mimetic assembly that contains physiological regulators of blood coagulation, thrombomodulin (TM) and heparin, to provide strategies for generating actively antithrombogenic surfaces. The membrane-mimetic construct contains polymeric phospholipid monolayer on an alkylated polyelectrolyte multilayer supported by planar substrate such as glass or silicone. When incorporated with TM, the model platform exhibited the biological function by catalyzing activation of protein C. Surface TM activity was extensively investigated at physiologic shear rates (50 sec-1 and 500 sec-1). Significantly, reaction rates become saturated at TM surface densities greater than or equal to ~ 800 fmole/cm2 due to due to a transport limitation. Based on the similar membrane-mimetic construct, a functional heparinized surface was designed as an alternative anticoagulant system. Immobilization of heparin onto membrane-mimetic surfaces was achieved through biotin-streptavidin binding specificity. Activity of surface heparin to facilitate thrombin inactivation was investigated at shear rates of 50 and 500 sec-1. Significantly, rate of thrombin decay becomes saturated when the surface coverage of heparin is higher than 4.4 pmole of heparin per cm2. We further investigated the effects of surface bound TM and heparin on tissue factor (TF) -induced thrombin generation in a flow model. Specifically, TF positioned over a 2 x 6 mm2 upstream region as a trigger for thrombin generation and TM and/or heparin positioned over the remaining downstream (34 x 6 mm2) portion of the test film. Compared to TF alone surface, thrombin generation was profoundly reduced in the presence of surface bound TM and/or heparin. Significantly, thrombin production was maximally inhibited more than 85% in the presence of TM and heparin, possibly due to anticoagulant synergism of both anticoagulants. We believe that current membrane-mimetic systems can potentially create actively antithrombogenic surfaces.

Recombinant synthesis of elastin-mimetic proteins has been employed for several decades, however, long-term biocompatibility and biostability of such proteins was not fully defined. We present virtually crosslinked elastin-mimetic proteins which exhibit exceptional biocompatibility and long-term biostability over a period of at least seven months. This report is the first evidence of a non-chemically or ionically crosslinked system that exhibits long-term in vivo stability. Although, physically crosslinked protein-based materials possess a number of advantages over their chemically crosslinked counterparts, physical crosslinks and the related domains so formed may be deformed or damaged at applied stresses lower than those required to disrupt covalent crosslinks. In this regard, we have synthesized a new class of recombinant elastin-mimetic triblock copolymer capable of both physical and chemical crosslinking. We have demonstrated that chemical crosslinking provides an independent mechanism for control of protein mechanical responses. Specifically, elastic modulus was enhanced and creep strain reduced through the addition of chemical crosslinking sites. A number of reports have described the design of synthetic genes, which encode elastin-like proteins for bacterial expression in Escherichia coli. Although advantages with this expression system exist, significant limitations including the lack of eukaryotic post-translational systems, the tendency to sequester mammalian proteins into inclusion bodies, difficult purification protocols, and endotoxin contamination have been noted. We demonstrate the expression of a recombinant elastin-mimetic protein from P. pastoris. A novel synthetic strategy, monomer library concatamerization, was utilized in designing non-repetitive elastin genes for highly repetitive protein sequences. It is likely that this strategy will be useful for creating large, repetitive genes for a variety of expression systems in order to more closely approach the genetic diversity inherent to native DNA sequences. All told, elastin-based protein polymers are a promising class of material characterized by high degree of biocompatibility, excellent biostability, and a tunable range of mechanical properties from plastic to elastic. A variety of options facilitate the processing of these biopolymers into chemically crosslinked or non-crosslinked gels, films, or nanofibers for any of a number of implant applications including structural components of artificial organs and engineered living tissues, carriers for controlled drug release, or biocompatible surface coatings.