In this study the viability of using guar gum to form films was investigated along with the effectiveness of the cross-linking process employing 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride (EDC) as the cross-linking agent. In addition, the cross-linked films were evaluated considering the water absorption, thermal stability and mechanical properties. The cross-linking process of guar gum films was confirmed by the low solubility in water and through infrared analysis. The results shown that the properties evaluated were affected by the cross-linking process due to changes in the polysaccharide structure. For example, the swelling behavior and water vapor absorption decreased with an increase in the amount of EDC. The EDC content (10-30%) also affected the polymer structure and hydrogen bond formation, reducing the thermal stability of the system.

Filmes reticulados de gelatina (Gel), caseína (Cas) e a mistura Gel/Cas (1:1, m/m) foram estudados em termos das propriedades térmicas, morfológicas e absorção de água e quanto ao perfil de permeação de p-hidroxiacetanilida (p-HAA ) como fármaco modelo. O grau de reticulação por 1-etil-3-(3-cloridrato) dimetilaminopropil carbodiimida (EDC) foi de 90,6% para filmes de Gel e cerca de 70% para filmes de Cas e misturas Gel/Cas (1:1, m/m). A total solubilidade dos filmes não-reticulados foi reduzida para somente 21 - 22% após reticulação com EDC. Apesar do alto grau de reticulação, o intumescimento dos filmes de Gel (87,2%) foi praticamente o dobro do determinado para filmes de Gel/Cas (1:1, m/m) e Cas. A taxa de permeação de p-HAA seguiu a ordem Gel>Gel/Cas ≅ Cas para filmes reticulados, ou seja, um comportamento consistente com o maior intumescimento da Gel em relação aos outros dois sistemas estudados. Os menores valores de permeação observados para filmes de Cas e Gel/Cas, sugerem que estes sistemas podem ser utilizados para controlar a permeação de fármacos. Considerando os diferentes modelos matemáticos aplicados, os sistemas estudados não mostraram um bom ajuste relativamente a equação de primeira ordem e somente uma parcial correlação com as equações de ordem zero e do modelo de Higuchi. No entanto, uma boa correlação (r² >0,99) foi obtida utilizando a equação da lei das potências (valores de n = 0,70 - 0,87), indicando que a permeação de p-HAA através dos filmes foi controlada principalmente pelo mecanismo de difusão.

Cross-linked films of gelatin (Gel), casein (Cas) and their (1:1, m/m) mixture (Gel/Cas) were studied in terms of their thermal, morphological and water absorption properties and the permeation profile of p-hydroxyacetanilide (p-HAA) as a model drug. The degrees of cross-linking by 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride (EDC) were 90.6% for Gel films and approximately 70% for Cas and Gel/Cas films. The totally soluble non cross-linked films achieved only 21 - 22% of solubility after cross-linking with EDC. Despite the high cross-linking degree, the swelling of Gel films (87.2%) was practically twice that determined for Gel/Cas and Cas films. The permeation rate of p-HAA followed the order Gel>Gel/Cas ≅ Cas for cross-linked films, which is consistent with the Gel film showing a greater swelling than the other two systems studied. Lower permeation rates were observed for Cas and Gel/Cas films, suggesting that these could be used as rate-controlling systems for drug permeation. For the different mathematical models applied, the systems studied did not show a good fit with the first-order equation and only a partial fit with the zero-order equation and Higuchi's model. However, good correlations (r² > 0.99) were obtained using the power law equation (n = 0.70 - 0.87), indicating that the p-HAA permeation through the films was mainly controlled by a diffusion mechanism.