Nanocellulose-Based Capsules with pH Responsiveness for Colon-Targeted Curcumin Delivery

Nanocellulose-based materials have been widely used to encapsulate and release drugs due to their biocompatibility, high drug-loading capacity, and controllable release profiles. However, effective administration of hydrophobic drugs remains challenging due to the water-insoluble organic compounds that make up many currently available drugs (e.g., anti-inflammatory or anticancer drugs). Here, we developed a pH-responsive coated bacterial cellulose (BC) capsule loaded with the hydrophobic drug curcumin (Cur) as a proof of concept for delivering targeted hydrophobic drugs to the colon. Cur was encapsulated in the hydrophilic capsule through an osmotic gradient phenomenon and then coated with carboxymethyl chitosan. The coating was carried out by adding calcium chloride, which facilitates the cross-linking of carboxymethyl chitosan, forming a stable protective layer. In vitro release analysis using the gastrointestinal medium revealed that the BC capsule coated with the pH-sensitive polymer carboxymethyl chitosan had a release profile activated by pH 6.8, providing efficient and protecting loads from premature release. In vitro experiments were performed with HT29 cells and showed that capsules loaded with Cur were more toxic to cancer cells. Overall, the proposed scalable, inexpensive, and simple manufacturing method has great potential for advanced biomedical applications including targeted therapy for hydrophobic drug delivery.