Core–shell hydrogel with synergistic super absorption and long-term acid resistance stability: a novel gastric retention drug delivery carrier

Traditional natural polysaccharide-based hydrogels, when used as drug carriers, often struggle to maintain long-term stability in the extremely harsh gastric environment. This results in unstable drug release and significant challenges in bioavailability. To address this issue, this study utilized inexpensive and safe natural polysaccharides-chitosan (CS) and high methoxyl pectin (HM)-as raw materials. Dynamic chemical bonds and anion-cation electrostatic interactions were employed to successfully prepare a super absorbent gel bead substrate (CS-HM), which serves as the "core" structure. Subsequently, another low-density hydrophilic polysaccharide, sodium carboxymethyl cellulose (CMCNa), was used to coat and crosslink the outer layer of the core, increasing the number of ionic groups. This enhancement raises the osmotic pressure inside the gel network, improving its absorption capacity. At the same time, the core-shell structure provides an energy dissipation mechanism, allowing the material to remain more stable in a strong acid environment. Due to its super absorption, high modulus, and continuous floating release properties, CS-HM@CMCNa-as a new type of acid-resistant super absorbent core-shell material-possesses the key characteristics required for gastric retention sustained-release systems. It is expected to become an ideal drug carrier for the treatment of clinical chronic diseases.