Preparation of enteric capsules with pulsatile drug delivery potential using pullulan and polyacrylic acid resin III

In this study, the enteric swelling layer of capsules was prepared by optimizing the ratio of pullulan to gellan gum. The enteric-coating solution was prepared by dissolving polyacrylic acid resin III in 85 % ethanol, and the two were combined to form pullulan enteric-coated capsules (PECs). To elaborate further, Pullulan entericcoated thin films (PEFs) were fabricated using the casting method, and their oxygen permeability (OP) and water vapor permeability (WVP) were assessed. Enteric capsules were prepared employing a secondary impregnation method. The cap gap and surface roughness of the capsules were characterized using Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM). The water content and hygroscopicity of the capsules were examined by employing the drying weight loss method. The pullulan-based enteric capsules (PECs) exhibited attributes such as low water content, hygroscopicity, brittleness, leakage resistance, and high impermeability. Finally, the in vitro release of aspirin from the enteric capsules was investigated. Results demonstrated the excellent combination of the enteric-coating layer and the swelling layer in the PECs. Compared with Gelatin enteric-coated capsules (GECs) on the market, it had a smaller cap gap, lower brittleness, weaker moisture absorption, and a good dissolution effect. Thus, it met the requirements of Chinese pharmacopeia, i.e., the ability to maintain integrity for 2 h in simulated gastric fluid and a drug-release rate reaching 80 % within 30 min in simulated intestinal fluid. This capsule also exhibited certain characteristics of a pulsatile drug-delivery system. This work proposed a potential method of preparing enteric hard capsules by using pullulan combined with polyacrylic acid resin III.