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Abstract(s)
O kefiran é um exopolissacarídeo presente nos grãos de kefir, sintetizado por várias espécies de Lactobacillus. Este polímero natural tem várias propriedades biológicas interessantes, de entre as quais se destacam as propriedades antibacterianas. A Helicobacter pylori é uma bactéria Gram negativa que infecta o estômago de cerca de 50% da população mundial. É o agente etiológico de várias patologias, como gastrite crónica e é responsável por 90% dos casos de cancro gástrico. A terapia disponível, baseada em antibióticos, é ineficaz em cerca de 20 a 40% dos casos, sobretudo pela elevada taxa de resistência. Este trabalho focou-se na otimização de um método de extração do kefiran, sua caracterização e desenvolvimento de micro/nanopartículas para avaliação do seu efeito contra a H. pylori J99 e 26695. Para tal, alginato ultrapuro foi usado na preparação das nanopartículas devido à sua capacidade de reticular na presença de iões divalentes, permitindo, quando misturado com kefiran, a obtenção de nanopartículas (~100 nm) usando técnicas de microfluídica. Foram também desenvolvidas nanopartículas com um péptido antimicrobiano (MSI-78) com efeito contra a H. pylori. A segurança desta estratégia de bioengenharia foi ainda avaliada em bactérias representativas do microbioma gastro-intestinal, Escherichia coli e a Lactobacillus acidophilus. As nanopartículas de kefiran e alginato sem péptido não tiveram atividade antimicrobiana. Além disso, as nanopartículas com péptido também não demonstraram efeito, sugerindo assim que a libertação do péptido não ocorreu. A citotoxicidade do kefiran contra células do adenocarcinoma gástrico humano foi avaliada (ISO 10993-5;12) e não foi reportada citotoxicidade. Visando o uso de kefiran em aplicações de engenharia de tecidos, foram preparados scaffolds porosos através da técnica de liofilização, tendo sido obtidos scaffolds com estrutura porosa interligada. Os resultados obtidos fornecem novos conhecimentos sobre um polímero natural ainda pouco explorado e potencialmente muito interessante para aplicações biomédicas.
Kefiran is an exopolysaccharide present in kefir grains, which is synthetised by various Lactobacillus species. This natural polymer has several interesting biological properties, among which the antimicrobial properties stand out. Helicobacter pylori is a Gram-negative bacterium that infects the stomach of about 50% of the world’s population. It is the etiologic agent of several pathologies, such as chronic gastritis and is responsible for 90% of gastric cancer cases. The available therapy, based on antibiotics, is ineffective in about 20-40% of cases, mainly due to high rate of resistance. This work focused on the optimization of a kefiran extraction method, its characterisation and development of micro/nanoparticles to evaluate its effect against H. pylori strains J99 and 26695. For this, ultrapure alginate was used in the preparation of nanoparticles due to its ability to crosslink in the presence of divalent ions, allowing, when mixed with kefiran, to obtain nanoparticles (~100 nm) using microfluidics techniques. Nanoparticles loaded with an antimicrobial peptide (MSI-78) with effect against H. pylori were also developed. The safety of this bioengineering strategy was further evaluated in bacteria representative of the gastrointestinal microbiome, Escherichia coli and Lactobacillus acidophilus. Kefiran and alginate nanoparticles non-loaded with MSI-78 peptide had no antimicrobial activity. Moreover, the nanoparticles loaded with MSI-78 also showed no effect, thus suggesting that peptide release did not occur. The cytotoxicity of kefiran against human gastric adenocarcinoma cells was evaluated (ISO 10993-5;12) and no cytotoxicity was reported. Envisaging the possibility of using kefiran in tissue engineering applications, porous scaffolds were prepared using the freeze-drying technique and scaffolds with interconnected porous structure were obtained. The results achieved provide new insights into a natural polymer still little explored that is potentially very interesting for biomedical applications.
Kefiran is an exopolysaccharide present in kefir grains, which is synthetised by various Lactobacillus species. This natural polymer has several interesting biological properties, among which the antimicrobial properties stand out. Helicobacter pylori is a Gram-negative bacterium that infects the stomach of about 50% of the world’s population. It is the etiologic agent of several pathologies, such as chronic gastritis and is responsible for 90% of gastric cancer cases. The available therapy, based on antibiotics, is ineffective in about 20-40% of cases, mainly due to high rate of resistance. This work focused on the optimization of a kefiran extraction method, its characterisation and development of micro/nanoparticles to evaluate its effect against H. pylori strains J99 and 26695. For this, ultrapure alginate was used in the preparation of nanoparticles due to its ability to crosslink in the presence of divalent ions, allowing, when mixed with kefiran, to obtain nanoparticles (~100 nm) using microfluidics techniques. Nanoparticles loaded with an antimicrobial peptide (MSI-78) with effect against H. pylori were also developed. The safety of this bioengineering strategy was further evaluated in bacteria representative of the gastrointestinal microbiome, Escherichia coli and Lactobacillus acidophilus. Kefiran and alginate nanoparticles non-loaded with MSI-78 peptide had no antimicrobial activity. Moreover, the nanoparticles loaded with MSI-78 also showed no effect, thus suggesting that peptide release did not occur. The cytotoxicity of kefiran against human gastric adenocarcinoma cells was evaluated (ISO 10993-5;12) and no cytotoxicity was reported. Envisaging the possibility of using kefiran in tissue engineering applications, porous scaffolds were prepared using the freeze-drying technique and scaffolds with interconnected porous structure were obtained. The results achieved provide new insights into a natural polymer still little explored that is potentially very interesting for biomedical applications.
Description
Keywords
Kefiran Alginato Nanopartículas Helicobacter pylori Péptido Discos Scaffold Alginate Nanoparticles Peptide Discs