Towards a novel pullulan and pullulan-enteric hard capsules: Study of drug release and crucial capsule features

Abstract

Pullulan, a natural polymer, is often used as a plant-based alternative polymer for gelatin to produce hard capsules. To the best of our knowledge, there have been negligible studies on the performance of enteric pullulan capsules. Hence, this paper describes a new formulation for enteric pullulan hard capsules that can resist the acidic environment of the stomach and release the drug in the small intestine without the need for an exterior coating. This formulation consists of three polymers, including pullulan, Eudragit L100, and κ-carrageenan, which are used to develop resistance against acid and facilitate gelation to form capsules. With regards to the humidity assessment of target hard capsules, it is estimated that the prepared capsules possess an appropriate potential for target utilizations. The capsules were tested using esomeprazole as a model drug for dissolution testing. The results demonstrated that the enteric hard-shell capsules remained stable for 2 h in 0.1 N HCl at a pH of 1.2 and then ruptured upon entering a phosphate buffer (simulated small intestine) medium at a pH of 6.8. The FESEM and cross-sectional analysis revealed that no drug was released due to the absence of pores on the surface. Rheological examinations also revealed that the prepared solution have a desirable property. It is certified that the NMR spectrum proposes the existence of crosslinking and polymerization of pullulan which signifies appropriate existing interactions polymeric binders and gelling agent. TGA and DSC evaluations are in well accordance with the strong cross-linked structure generated by comprising pullulan polymer with the Eudragit pH-sensitive Polymer. Overall. this new formulation has potential feature for utilization in drug delivery systems where controlled release is desired, especially for drugs that are sensitive to acidic environments in the stomach.