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Previous issue date: 2018-03-20 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior - CAPES / The present study focuses on the development of nanoparticles with an iron oxide magnetic core, with different biocompatible coatings, and on a comparative study of their toxicities. Uncoated and dextran-, chitosan-, polyethylene glycol- and silica-coated nanoparticles were synthesized. The addition of optical markers of the benzo-thiazoles class was also accomplished. The physico-chemical properties of the nano-particles were characterized, including their magnetic, optical and contrast properties in nuclear magnetic resonance imaging (relaxivities). In the particular case of nanopar-ticles functionalized with 6-OH-BTA-1 molecules, the affinity to the beta-amyloid pep-tide was also investigated. A second step was to evaluate the toxicological effects of these nanoparticles in vitro (using in VERO cells), and in vivo with zebrafish as an animal model. The size of the nanoparticles with the coatings ranged from 13 to 30 nm. Their crystalline structure was consistent with the ferrite spinel. The nanoparticles, independent of the coating, did not present residual magnetization and hysteresis, in-dicating superparamagnetic behaviour. For most nanoparticles, the r2 transverse re-laxivity values ranged from 76-64 mM-1.s-1, exceptfor uncoated and chitosan-coated nanoparticles, which present higher values, possibly due to the aggregation. The val-ues of r1 were similar for all nanoparticles (12.6 to 18 mM-1.s-1), with the exception of silica-coated nanoparticles (r1=2.1 mM-1.s-1). The r2/r1 ratios were between 4 and 17, typical of commercially available negative contrast-agents. The nanoparticles function-alized with benzothiazoles showed fluorescence with a Stokes shift of the emission peak of ~ 197 nm. The interaction of the beta-amyloid peptide with the 6-OH-BTA-1 molecule analyzed by fluorescence suppression is characterized by a static mecha-nism and Stern-Volmer constants of 1.53x104 mM-1 for the monomeric form, 1.40x104 mM -1 for oligomers) and 1.33x104 mM -1 for amyloid plaques.The in vitro toxicity assays indicated acceptable values of cell viability for iron concentration up to 2 mmol.L-1. The nanoparticles with the carboxysilane and polyethylene glycol showed higher biocom-patibility and silica-coated nanoparticles had the highest cytotoxicity. The in vivo as-says did not show significant changes in survival and hatchability rates, except for doses greater than 2 mmol.L-1 in the case of the chitosan-coated nanoparticles. The percentages of animals with anatomical alterations were similar between the treated and control groups. In the locomotion and exploration tests, only chitosan- and silica-coated nanoparticles induced significant changes. / O presente trabalho aborda o desenvolvimento de nanopart?culas compostas por um n?cleo magn?tico de ?xido de ferro com diferentes revestimentos biocompat?-veis e estudo comparativo de suas toxicidades. Foram sintetizadas nanopart?culas de ?xido de ferro sem revestimento e com revestimentos de dextrana, quitosana, polieti-lenoglicol e s?lica, e com a adi??o de marcadores ?pticos da classe dos benzotiaz?is. As propriedades f?sico-qu?micas das nanopart?culas foram caracterizadas, incluindo as suas propriedades magn?ticas, ?pticas e de contraste em imagens por resson?ncia magn?tica nuclear (relaxividades), bem como a afinidade ao pept?deo beta-amiloide, no caso particular de funcionaliza??o com a mol?cula 6-OH-BTA-1. Em uma segunda etapa, foram avaliados os efeitos toxicol?gicos dessas nanopart?culas em ensaios bi-ol?gicos in vitro em c?lulas VERO, e in vivo tendo como animal modelo o peixe zebra. O tamanho das nanopart?culas com revestimentos variou entre 13 a 30 nm, e estrutura cristalina coerente com o espin?lio de ferrita. As nanopart?culas n?o apresentaram magnetiza??o residual e histerese, indicando superparamagnetismo, independente do revestimento. Para a maioria das nanopart?culas, os valores de relaxividade transver-sal r2 variaram de 76-64 mM-1.s-1, com exce??o das nanopart?culas sem revestimento e de quitosana, os quais foram mais elevados, possivelmente devido ao efeito de agrega??o. Os valores de r1 foram semelhantes para todas as nanopart?culas (12,6 a 18 mM-1.s-1), com exce??o das nanopart?culas de s?lica (r1 = 2,1 mM-1.s-1). As raz?es r2/r1 foram entre 4 e 17, valores t?picos de agentes de contraste negativos comercial-mente dispon?veis. As nanopart?culas funcionalizadas com os benzotiaz?is mantive-ram sua fluoresc?ncia com deslocamentos de Stokes na ordem de 197 nm para o pico de emiss?o. As an?lises da intera??o do pept?deo beta-amiloide com a mol?cula 6-OH-BTA-1, mostraram valores de constante de Stern-Volmer para supress?o de fluo-resc?ncia de 1,53x104 mM-1 (mon?mero), 1,40x104 mM-1 (olig?mero) e 1,33x104 mM-1 (placa), indicando quenching por um mecanismo est?tico. O pept?deo na forma mo-nom?rica demonstrou maior facilidade de acesso ?s mol?culas de 6-OH-BTA-1. Os resultados dos ensaios in vitro indicaram valores aceit?veis de viabilidade celular para concentra??o de ferro inferior a 2 mmol.L-1. As nanopart?culas com o carboxisilano e polietilenoglicol demostraram maior biocompatibilidade e as nanopart?culas de s?lica tiveram a maior citotoxicidade. Os resultados dos ensaios in vivo n?o mostraram alte-ra??es significativas na taxa de sobreviv?ncia e de eclos?o do corium, exceto para as doses maiores que 2 mmol.L-1 das nanopart?culas revestidas com quitosana. Os per-centuais de animais com altera??es anat?micas foram similares entre os grupos tra-tados e de controle. Nos ensaios de locomo??o e explora??o, apenas as nanopart?cu-las de quitosana e de s?lica induziram altera??es adversas significativas.
| Identifer | oai:union.ndltd.org:IBICT/oai:tede2.pucrs.br:tede/8073 |
| Date | 20 March 2018 |
| Creators | Oliveira, Elisa Magno Nunes de |
| Contributors | Papal?o, Ricardo Meurer |
| Publisher | Pontif?cia Universidade Cat?lica do Rio Grande do Sul, Programa de P?s-Gradua??o em Engenharia e Tecnologia de Materiais, PUCRS, Brasil, Escola Polit?cnica |
| Source Sets | IBICT Brazilian ETDs |
| Language | Portuguese |
| Detected Language | English |
| Type | info:eu-repo/semantics/publishedVersion, info:eu-repo/semantics/doctoralThesis |
| Format | application/pdf |
| Source | reponame:Biblioteca Digital de Teses e Dissertações da PUC_RS, instname:Pontifícia Universidade Católica do Rio Grande do Sul, instacron:PUC_RS |
| Rights | info:eu-repo/semantics/openAccess |
| Relation | -7432719344215120122, 500, 500, 600, 4518971056484826825, 2075167498588264571 |
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