A single-layer film coating for colon-targeted oral delivery

Most pH-sensitive polymer coating studies for potential colonic delivery systems apply multiple layers to protect the active agent from degradation and early release in the stomach and small intestine. This study designed a single-coat pH-sensitive layer for colon-specific delivery with a potential biopolymer, namely, zein. The tablets were coated with a pH-sensitive film combining zein and Kollicoat® MAE 100P. A scanning electron microscope (SEM) was used to study the surface characteristics of the coating layers, and Fourier transform infrared spectroscopy (FTIR) was used to investigate the molecular interactions between these coating materials. The delivery system showed its potential to prevent the release of drug in gastric and small intestinal simulated media for the delayed release of drug at the expected pH of the colon. The SEM pictures of the coated tablets showed the uniformity of the coating film, although there were some small pores on the surface. The FTIR spectra confirmed that no chemical interaction occurred between two coating materials. The percentage of zein in the coating solution along with the amount of coating were important factors that should be carefully considered during the preparation of the coated tablets to achieve the purpose of this study. This strategy provides a promising design that can effectively carry drugs to the targeted site and also reduce the preparation time.