Screening of Polysaccharide Films Consisting of pH-Dependent Systems in Combination with Microbial Decomposition-Dependent Systems to Determine the Appropriate Coating for Colonic Drug Delivery

Objective

The study aimed to identify a film sensitive to microbial decomposition to select an appropriate coating for delivering drugs to the colon.

Methods & Materials

Different polysaccharides, including xanthan, inulin, carrageenan, and alginate, were made with Eudragit FS 30 D (EFS) by film formation method. The films were screened by performing mechanical tests, swelling percentage, the reduction of dry film mass, the passage of water vapor through (WVT) of the films, and the permeability of the films to the drug in different media similar to the gastrointestinal tract (GIT). Additionally, the films' characteristics were evaluated based on shape (SEM), Fourier Transform Infrared Spectroscopy (FTIR), and differential scanning calorimetry (DSC).

Results

The film evaluation results revealed that the inulin film had the highest work of failure (WF), % of elongation at break (%E), Tensile strength (TS), and elastic modulus (EM). Also, this film exhibited the highest TS/EM ratio. In contrast, other polysaccharide films exhibited the opposite behavior. The results of the dry film swelling and mass reduction tests in media with 1.2, 6.5, and 6.8 pH, as well as in the SCF medium, showed that in an acidic medium, films containing inulin and alginate have very low swelling and less degraded. In contrast, film containing xanthan showed very high swelling and high dry mass at different pHs. However, the alginate film showed lower swelling and dry mass than the xanthan film at all investigated pHs. The results of evaluating the WVT of the films showed that the highest and lowest WVT related to the films prepared from inulin and alginate, respectively. In addition, the highest ratio of the swelling index in the SCF medium compared to the buffered phosphate medium with pH 6.8 was observed in the film containing inulin. The results of the evaluation of the permeability of the films to the drug in different media similar to the GIT showed that the permeability of the inulin film to the drug in a gastric medium is very low. In contrast, the permeability of this film in the SCF medium significantly increased compared to the buffered medium with pH 6.8. The SEM studies showed that films containing xanthan and carrageenan degraded more than other polysaccharide films at pH 1.2. The evaluation and comparison of films in SCF-containing and non-SCF media showed that the degradation of films in SCF media was more significant. Evaluation of DSC and FTIR showed that the formed film containing EFS polymer lack of interaction with other polysaccharides.

Conclusion

This study showed that inulin film is a suitable polysaccharide for colonic drug delivery systems due to its suitable mechanical properties, low swelling compared to the liquids of the upper parts of the GIT, and sensitivity to the enzymes in the colon. In other words, film coatings consisting of pH-dependent polymers such as EFS in combination with inulin can deliver drugs targeted to the end parts of the GIT.

Graphical Abstract