Carboxymethyl starch films as enteric coatings: Processing and mechanistic insights

This study proposes the application of carboxymethyl starch derivatives as tablet coatings affording gastro-protection. Carboxymethyl starch (CMS) films were obtained by casting of aqueous filmogenic starch solutions with or without plasticizers and their structural organization was followed using Fourier transform infrared (FTIR), Thermogravimetric analysis (TGA), X-ray diffraction (XRD). Together with data from mechanical tests (tensile strength, elongation, Young’s modulus) the results were used to select filmogenic formulations adapted for coatings of tablets. The behaviour of these films was evaluated in simulated gastric and intestinal fluids. The effect of plasticizers (glycerol and sorbitol) on the starch organization, on the rate of drying of the films and on the water vapor absorption was also analyzed.

Various types of starch have been compared and the best results were found with high amylose starch (HAS) that was carboxymethylated in an aqueous phase to obtain carboxymethyl high amylose starch (CMHAS). The CMHAS coating solutions containing sorbitol or glycerol as plasticizers have been applied with an industrial pan coater and the final tablets exhibited a good gastro-resistance (up to 2h) in simulated gastric fluid followed by disintegration in simulated intestinal fluid (SIF). The CMHAS derivatives present a high potential as coatings for nutraceutical and pharmaceutical solid dosage forms.

Materials

Reagents – Hylon VII® (∼70 % amylose), was a generous gift from Ingredion (Westchester, IL, USA). Lycoat® RS 720 (medium viscosity was gifted by Roquette America Inc. (Keokuk, IA, United States). Sodium monochloroacetate (SMCA), glycerol, iodine, monobasic phosphate, potassium iodine, sorbitol, and the other chemicals were all reagent grade and used as received from Millipore Sigma (Burlington, Massachusetts, USA).

The simulated gastric (SGF) was prepared by adding 7 mL HCl (37% w/w) and 2 g

Marc-André Labelle, Pompilia Ispas-Szabo, Florent Vilotte, Mircea Alexandru Mateescu, Carboxymethyl starch films as enteric coatings: Processing and mechanistic insights, Journal of Pharmaceutical Sciences, 2023, ISSN 0022-3549, https://doi.org/10.1016/j.xphs.2023.09.002.