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Mucoadhesive polymers
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A mucoadesão é definida como a adesão entre a superfície da mucosa e macromoléculas, que podem ser de origem sintética ou natural. A mucoadesão é explicada por um mecanismo complexo que depende de interações intermoleculares. As macromoléculas mucoadesivas podem ser integradas em formulações farmacêuticas, tornando-as também, mucoadesivas.
O mecanismo de mucoadesão é dividido em dois passos, a fase de contacto e a fase de consolidação. Na primeira, há contacto entre a formulação mucoadesiva e a superfície da mucosa. A segunda começa quando a camada mucoadesiva é ativada pelo contacto com a humidade da mucosa, e são estabelecidas ligações entre o muco e o polímero.
Há vários fatores que afetam a mucoadesão: hidrofilicidade, peso molecular do polímero, concentração do polímero, flexibilidade, peso molecular do polímero, conformação espacial, carga do polímero e pH do meio.
Relativamente às propriedades dos polímeros mucoadesivos, variam consoante o tipo de polímero, como a sua carga, solubilidade em água e tipo de forças que promovem a bioadesividade. Apesar das diferenças, os polímeros devem ser biocompatíveis, não tóxicos, não irritantes da mucosa, e devem aderir, facilmente, ao tecido húmido.
Um dos polímeros mais usados é o quitosano, que demonstra grande mucoadesividade. É catiónico, o que facilita a adesão, visto que o muco tem carga negativa. Outros exemplos de polímeros mucoadesivos são: ácido poliacrílico, alginato, carboximetilcelulose, pectina, álcool polivinílico e goma xantana.
Estes polímeros podem ser usados em formulações farmacêuticas, melhorando-as. Considerando os sistemas de libertação de fármacos, estes têm algumas desvantagens, por exemplo, a libertação precoce ou tardia do fármaco. Um sistema de libertação de fármacos com um polímero mucoadesivo, irá ter um tempo de contacto prolongado com a mucosa.
Os sistemas de libertação de fármacos com propriedades mucoadesivas têm potencial para serem utilizados em patologias tão diferentes, como por exemplo, doenças intestinais, pulmonares, vaginais ou orais.
Esta revisão bibliográfica resume estudos sobre mucoadesão, polímeros mucoadesivos e o seu o potencial em integrar as formulações de libertação de fármacos, contribuindo na preparação de soluções farmacêuticas para algumas doenças.
Mucoadhesion is defined as the adhesion between a mucosal surface and, natural or synthetic, macromolecules. Mucoadhesion is a complex mechanism and it depends intermolecular interactions. The adhesive macromolecules can be part of a pharmaceutical formulation, turning it in a mucoadhesive preparation as well. The mucoadhesion mechanism is divided into two steps, the contact stage and the consolidation stage. In the contact stage, there is contact between the mucoadhesive formulation and the mucus membrane. The second step starts once the mucoadhesive layer is triggered by the presence of the moisture, and bonds, between the mucus layer and the polymer, are established. There are several factors to be taken into account when it comes to mucoadhesion: hydrophilicity, polymer molecular weight, swelling, flexibility, spatial conformation, concentration of polymer, charge of polymer and pH. Concerning mucoadhesive polymers, there are several properties that vary depending on the polymer, such as its charge, solubility in water and type of bioadhesive forces. Despite these differences, the polymers should be biocompatible, non-toxic, non-irritating and should, easily, adhere to moist tissue. One of the most used polymers is chitosan, which exhibits good mucoadhesive properties. It is cationic, so the mucoadhesion is easier, since the mucus has negative charge. Some other examples are: polyacrylic acid, alginate, carboxymethylcellulose, pectin, polyvinyl alcohol and xanthan gum. The mucoadhesive properties can be added to formulations, improving them. Drug delivery systems have some drawbacks, like earlier or late release of the drug. Mucoadhesive drug delivery systems have an increased residence time at the site of absorption. Drug delivery systems with mucoadhesive properties have potential to be used in different fields, such as intestinal, pulmonary, vaginal and oral diseases. This review describes the research about mucoadhesion and its mechanism, polymers potential role in drug delivery and how they can contribute to solve some health challenges.
Mucoadhesion is defined as the adhesion between a mucosal surface and, natural or synthetic, macromolecules. Mucoadhesion is a complex mechanism and it depends intermolecular interactions. The adhesive macromolecules can be part of a pharmaceutical formulation, turning it in a mucoadhesive preparation as well. The mucoadhesion mechanism is divided into two steps, the contact stage and the consolidation stage. In the contact stage, there is contact between the mucoadhesive formulation and the mucus membrane. The second step starts once the mucoadhesive layer is triggered by the presence of the moisture, and bonds, between the mucus layer and the polymer, are established. There are several factors to be taken into account when it comes to mucoadhesion: hydrophilicity, polymer molecular weight, swelling, flexibility, spatial conformation, concentration of polymer, charge of polymer and pH. Concerning mucoadhesive polymers, there are several properties that vary depending on the polymer, such as its charge, solubility in water and type of bioadhesive forces. Despite these differences, the polymers should be biocompatible, non-toxic, non-irritating and should, easily, adhere to moist tissue. One of the most used polymers is chitosan, which exhibits good mucoadhesive properties. It is cationic, so the mucoadhesion is easier, since the mucus has negative charge. Some other examples are: polyacrylic acid, alginate, carboxymethylcellulose, pectin, polyvinyl alcohol and xanthan gum. The mucoadhesive properties can be added to formulations, improving them. Drug delivery systems have some drawbacks, like earlier or late release of the drug. Mucoadhesive drug delivery systems have an increased residence time at the site of absorption. Drug delivery systems with mucoadhesive properties have potential to be used in different fields, such as intestinal, pulmonary, vaginal and oral diseases. This review describes the research about mucoadhesion and its mechanism, polymers potential role in drug delivery and how they can contribute to solve some health challenges.
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Mucoadhesion Polymer Drug delivery system Mestrado integrado - 2020