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Previous issue date: 2016-04-08 / Esta tese foi realizada com o objetivo geral de desenvolver e a caracterizar nanocarreadores
com potencial para sobrepujar as propriedades biofarmac?uticas n?o-favor?veis da
anfotericina B (AmB), uma mol?cula extremamente eficaz no tratamento de infec??es
sistemicas fungicas e leishmaniose, mas dif?cil de formular independentemente da via de
administra??o desejada. Acredita-se que essa mol?cula hidrof?bica possui limita??es devido
a pronunciada tend?ncia de agregar sob condi??es fisiol?gicas humanas. A primeira parte
desta tese foi conduzida pela hip?tese de que o estado de agrega??o da AmB teria um forte
impacto sobre as propriedades farmacocin?ticas da mesma. Por tal raz?o, complexos de
albumina e amB foram produzidos de forma a controlar o estado de agrega??o da AmB. A
estrutura dos coloides obtidos foi caracterizada atrav?s de ensaios de espectroscopia UV-Vis
e dicroismo circular. Adicionalmente, o impacto do estado de agrega??o na permeabilidade
intestinal e no poss?vel reconhecimento dos agregados pelo sistema imunol?gico foram
investigados. A segunda parte deste trabalho teve como objetivo o desenvolvimento de
micro- e nanocarreadores para sobrepor as barreiras para absor??o da AmB ap?s a sua
administra??o pela via oral. Para este fim, AmB foi incorporada em micro- e nanoemuls?es
para observa??o da habilidade destes sistemas de incrementar a permeabilidade intestinal de
mol?culas. Tal habilidade foi avaliada atrav?s do m?todo ex vivo de C?maras de Ussing, onde
o tecido intestinal ? utilizado como barreira entre duas semi-c?maras. Nenhuma permea??o
foi detectada nas condi??es experimentais utilizadas. No entanto, os dados obtidos atrav?s da
medidas eletrofisiol?gicas demonstraram que a velocidade da perda da viabilidade do tecido ?
dependente do estado de agrega??o da AmB em contato com o tecido. Tamb?m foi
observado, atrav?s dos ensaios de permeabilidade que as rotas de absor??o paracelular e
transcelular devem ser rotas marginais quando a absor??o da AmB ? observada in vivo, como
descrito na literatura. Como alternativas, as rotas de absor??o pela captura de agregados e
part?culas pelas placas de Peyer e a rota de absor??o linf?tica t?m sido discutidas. Finalmente,
um otro sistema particulado que objetiva a libera??o em n?vel de col?n e baseada na
utiliza??o da xilana, um biopol?mero natural e enzimaticamente degradado. A xilana ?
polissacar?deo presente em gr?os, cereais e plantas angiospermas que ? especificamente
degradado na regi?o col?nica, especificamente pela microbiota l? presente. A t?cnica
aplicada de forma original consiste na forma??o de uma emuls?o ?gua-?gua de xilana em presen?a de PEG, seguida por uma etapa de reticula??o com o tris?dio trimetafosfato.
Atrav?s da aplica??o desta t?cnica foi poss?vel produzir part?culas ? base de xilana que
podem ter seu tamanho m?dio, de forma controlada, variado entre 380 nm e 4.5 ?m, de
acordo com os par?metros utilizados. Esta t?cnica tamb?m ? livre do uso de solventes
org?nicos e possui potencial aplica??o para a libera??o controlada de AmB em n?vel de
col?n. / This thesis is part of the development and evaluation of nanomedicines potentially able to
overcome unfavorable biopharmaceutical properties of amphotericin B (AmB), a highly
effective molecule used for the treatment of systemic fungal infections and leishmaniasis, but
difficult to formulate efficiently, whatever the route of delivery. It is believed that this
hydrophobic molecule suffers from severe limitations due to its pronounced tendency to
aggregate under physiological conditions. The first part of the thesis was driven on the
hypothesis that the degree of aggregation of AmB could have a strong impact on some of its
pharmacokinetics properties. For this purpose albumin has been used to produce controlled
complexes between albumin and AmB in order to control AmB aggregation states. The
morphological characteristics of the resulting colloidal objects have been carefully
characterized by UV-Vis spectroscopy and circular dichroism. Furthermore, the impact of
aggregation state on both the intestinal permeability and a possibly expected recognition of
the aggregates by the immunological system were investigated. The second part of this work
was focused on the development of micro- and nanocarriers intended to overcome the
absorption barrier raised against AmB after oral delivery. For this purpose, AmB was loaded
into micro- and nanoemulsions to evaluate a possible permeability enhancement effect
through the intestinal membrane, which was evaluated in ratas using the Ussing chamber
model. No detectable permeation was seen in any of the experimental conditions. However,
the electrophysiological data showed tissue viability losses due to the strong toxicity of AmB,
that were dependent on the aggregation state of AmB when in contact with the tissue. It was
also concluded from detailed permeation experiments in healthy tissues that paracellular and
transcellular routes were likely to be only marginal pathways when oral absorption are
observed in vivo, as reported in the literature. The likeness of other possible absorption
pathways, including Peyer's patches capture and lymphatic pathway implication for
aggregated particles has been discussed. Finally, another particulate system intended for
colonic delivery and based on xylan, a natural and enzymatically degradable biopolymer, has
been investigated. Xylan is a polysaccharide present in grains, cereals and angiosperm plants
that is specifically degraded on colon region, by the microbiota. An original process
consisting in a water-in-water emulsion of xylan in presence of PEG followed by a
crosslinking phase using trisodium trimetaphosphate has been developed, making possible the production of xylan-based biocompatible micro- and nanospheres ranging from 380 nm to
4.5 ?m, depending on the parameters in the process. This eco-friendly process is free of
harmful solvents and has potential application for the delivery of AmB at the colonic level.
| Identifer | oai:union.ndltd.org:IBICT/oai:repositorio.ufrn.br:123456789/21539 |
| Date | 08 April 2016 |
| Creators | Marcelino, Henrique Rodrigues |
| Contributors | 38878240400, Vauthier, Christine, 00000000000, Reynaud, Franceline, 00344484971, Degobert, Ghania Hamdi, 00000000000, Ponchel, Gilles, 00000000000, Legrand, Philippe, 00000000000, Egito, Eryvaldo S?crates Tabosa do |
| Publisher | PROGRAMA DE P?S-GRADUA??O EM CI?NCIAS DA SA?DE, UFRN, Brasil |
| Source Sets | IBICT Brazilian ETDs |
| Language | Portuguese |
| Detected Language | English |
| Type | info:eu-repo/semantics/publishedVersion, info:eu-repo/semantics/doctoralThesis |
| Source | reponame:Repositório Institucional da UFRN, instname:Universidade Federal do Rio Grande do Norte, instacron:UFRN |
| Rights | info:eu-repo/semantics/openAccess |
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