Micropartículas de goma gelana revestidas com filmes de amido resistente/pectina como estratégia para administração oral de insulina
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Data
2016-01-14
Autores
Meneguin, Andreia Bagliotti [UNESP]
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Editor
Universidade Estadual Paulista (Unesp)
Resumo
O desenvolvimento de um sistema que possibilite a administração oral da insulina (INS) constitui um grande desafio, já que esta pode ser degradada nas porções superiores do trato gastrintestinal (TGI). Seu encapsulamento no interior de matrizes poliméricas baseadas em goma gelana (GG) deve oferecer significante proteção contra as condições adversas do TGI, além do estabelecimento de interações mucoadesivas. O revestimento de formas farmacêuticas sólidas com amido resistente tipo 3 é uma estratégia tecnológica racional para se alcançar a liberação cólon específica de fármacos. A pectina também agrega propriedades importantes nesse sentido, já que é resistente à proteases e amilases. O objetivo deste trabalho foi a obtenção e caracterização de micropartículas (MP) de GG (1,5, 2,0 ou 2,5%), reticuladas com Al3+ (3 ou 5%) e revestidas com filmes de amido resistente/pectina para a administração oral de INS. O método de obtenção empregado foi eficiente com rendimento máximo de 99,10%, além de ter possibilitado a obtenção de MP com elevada eficiência de encapsulação (máximo de 89,11%). As MP apresentaram diâmetro médio de 1012 a 1197 μm e circularidade variando de 0,68-0,81. A análise de microscopia eletrônica de varredura indicou que o aumento da concentração de GG foi responsável pela obtenção de MP mais esféricas e que a INS alterou o rearranjo das estruturas. A seção transversal mostrou um revestimento contínuo e intacto. De acordo com os dados de difração de raios-X, as MP apresentaram estruturas semicristalinas. A absorção de líquidos foi menor em meio ácido (218-615%) do que em tampão fosfato pH 7,4 (432-812%) e 6,8 (373-703%) e o modelo cinético de Korsmeyer-Peppas foi o que melhor retratou o mecanismo de penetração de líquidos nas amostras, indicando que esse ocorreu por difusão Fickiana (caso-I). Ensaios de degradação enzimática revelaram que o sistema desenvolvido foi capaz de proteger a INS contra a degradação em até aproximadamente 80% após 120 min de incubação com tripsina e α-quimotripsina. Os estudos de liberação in vitro da INS foram realizados em aparato I e IV e os resultados demonstraram que o revestimento desenvolvido ofereceu um maior controle da liberação da INS, com reduzidas taxas de liberação em meio ácido, além de prolongar a liberação nos outros meios estudados. Os perfis de liberação originados a partir de ensaio em aparato I e IV tiveram melhor ajuste aos modelos cinéticos de Weibull e Korsmeyer-Peppas e Higuchi e Korsmeyer-Peppas, respectivamente. Ensaios ex vivo de bioadesão indicaram que as amostras obtidas com 2,0 e 2,5% de GG geram maiores forças mucoadesivas (Fma). A permeação ex vivo da INS foi realizada através das técnicas de intestino invertido e intestino não invertido, tendo esta última revelado a importância do revestimento para o aumento da permeabilidade da insulina, a qual alcançou valores de até 84%. As MP foram capazes de modular a abertura das junções paracelulares, contribuindo para o aumento da permeação da INS através das células Caco-2. Todas as MP produzidas induziram um importante efeito hipoglicemiante, com redução máxima da glicemia sanguínea de 51%. O efeito foi mantido por até 7h. O conjunto de resultados sugere o uso das MP de GG revestidas com amido resitente/petina como um sistema carreador da INS, contornando problemas específicos, como os de permeabilidade intestinal e biodisponibilidade oral.
The development of a system that enables the oral administration of insulin (INS) is a major challenge, since the INS can be degraded in the upper portions of gastrintestinal tract (GIT). Its encapsulation within polymer matrices based on gellan gum (GG) should offer significant protection against the adverse conditions of the GIT, in addition to establishing mucoadhesive interactions. The coating of solid dosage forms with type 3 resistant starch is a rational strategy to achieve the colon specific drug delivery. Pectin also adds important properties in this sense, since it is resistant to proteases and amylases. The aim of this work was to obtain and to characterize GG MP (1.5, 2.0 or 2.5%), crosslinked with Al3+ (3 or 5%) and coated with films resistant starch/pectin for the oral administration of INS. The method employed was effective with a maximum yield of 99.10%, besides having allowed the obtaining of MP with a high encapsulation efficiency (up to 89.11%). The MP showed a mean diameter from 1012 to 1197 μm and circularity ranging from 0.68 to 0.81. The scanning electron microscopy indicated that the increase of the concentration of GG is responsible for obtaining more spherical MP and that INS is responsible for changing the rearrangement structures. The cross section showed a continuous and intact coating. According to the data of X-ray diffractograms, the MP have semi-crystalline structures. The liquid uptake was lower in acid media (218-615%) than in phosphate buffer pH 7.4 (432-812%) and 6.8 (373-703%) and the Korsmeyer-Peppas model was the best fitting for the liquid penetration mechanism in the samples, indicating that this occurred by Fickian diffusion (case-I). Enzymatic degradation tests showed that the system is able to protect the INS against degradation by up to approximately 80% after 120 min of incubation with trypsin and α-chymotrypsin. The in vitro release studies of INS were performed in apparatus I and IV, and the results showed that the coating developed offered a greater control of INS release, with reduced release rates in acidic medium, besides prolonging the release in the other media studied. Release profiles derived from the test apparatus I and IV fitted better to the kinetic model Weibull and Korsmeyer-Peppas and Higuchi and Korsmeyer-Peppas, respectively. Ex vivo bioadhesion test indicated that the samples obtained with 2.0 and 2.5% GG generate higher mucoadhesive forces (FMA). The ex vivo INS permeation was analyzed by the techniques of inverted and non-inverted intestine, and the latter revealed the importance of the coating to the increase of INS permeability. MP showed to modulate the opening of tight junctions, contributing for the INS permeation in both Caco-2 cells and in excised rat intestinal tissues. All MP induced a significant hypoglycemic effect with a maximum reduction in blood glucose of 51%. The effect was kept for up to 7h. The set of results suggests the use of the GG MP coated with resistant starch/pectin as INS carrier to enhance its permeability through the intestinal epithelium and its bioavailability after oral administration.
The development of a system that enables the oral administration of insulin (INS) is a major challenge, since the INS can be degraded in the upper portions of gastrintestinal tract (GIT). Its encapsulation within polymer matrices based on gellan gum (GG) should offer significant protection against the adverse conditions of the GIT, in addition to establishing mucoadhesive interactions. The coating of solid dosage forms with type 3 resistant starch is a rational strategy to achieve the colon specific drug delivery. Pectin also adds important properties in this sense, since it is resistant to proteases and amylases. The aim of this work was to obtain and to characterize GG MP (1.5, 2.0 or 2.5%), crosslinked with Al3+ (3 or 5%) and coated with films resistant starch/pectin for the oral administration of INS. The method employed was effective with a maximum yield of 99.10%, besides having allowed the obtaining of MP with a high encapsulation efficiency (up to 89.11%). The MP showed a mean diameter from 1012 to 1197 μm and circularity ranging from 0.68 to 0.81. The scanning electron microscopy indicated that the increase of the concentration of GG is responsible for obtaining more spherical MP and that INS is responsible for changing the rearrangement structures. The cross section showed a continuous and intact coating. According to the data of X-ray diffractograms, the MP have semi-crystalline structures. The liquid uptake was lower in acid media (218-615%) than in phosphate buffer pH 7.4 (432-812%) and 6.8 (373-703%) and the Korsmeyer-Peppas model was the best fitting for the liquid penetration mechanism in the samples, indicating that this occurred by Fickian diffusion (case-I). Enzymatic degradation tests showed that the system is able to protect the INS against degradation by up to approximately 80% after 120 min of incubation with trypsin and α-chymotrypsin. The in vitro release studies of INS were performed in apparatus I and IV, and the results showed that the coating developed offered a greater control of INS release, with reduced release rates in acidic medium, besides prolonging the release in the other media studied. Release profiles derived from the test apparatus I and IV fitted better to the kinetic model Weibull and Korsmeyer-Peppas and Higuchi and Korsmeyer-Peppas, respectively. Ex vivo bioadhesion test indicated that the samples obtained with 2.0 and 2.5% GG generate higher mucoadhesive forces (FMA). The ex vivo INS permeation was analyzed by the techniques of inverted and non-inverted intestine, and the latter revealed the importance of the coating to the increase of INS permeability. MP showed to modulate the opening of tight junctions, contributing for the INS permeation in both Caco-2 cells and in excised rat intestinal tissues. All MP induced a significant hypoglycemic effect with a maximum reduction in blood glucose of 51%. The effect was kept for up to 7h. The set of results suggests the use of the GG MP coated with resistant starch/pectin as INS carrier to enhance its permeability through the intestinal epithelium and its bioavailability after oral administration.
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Palavras-chave
Micropartículas, Goma gelana, Amido resistente, Pectina, Insulina, Liberação cólon-específica, Microparticles, Gellan gum, Resistant starch, Pectin, Insulin, Colon specific delivery