Layered composite based on halloysite and natural polymers: a carrier for the pH controlled release of drugs

We have prepared new biohybrid materials based on halloysite nanotubes and natural polymers (alginate and chitosan) for the controlled and sustained release of bioactive species. A functional nanoarchitecture has been designed allowing us to generate a layered tablet with a chitosan/halloysite nanocomposite film sandwiched between two alginate layers. The assembly of the raw components and the final structure of the hybrid tablet have been highlighted by the morphological and wettability properties of the prepared materials. Since the biohybrid has been designed as a smart carrier, halloysite nanotubes have been first loaded with a model drug (sodium diclofenac). The effect of the tablet thickness on the drug release kinetics has been investigated, confirming that the delivery capacity can be controlled by modifying the alginate amounts of the external layers. A simulation of the typical pH conditions along the human gastro-intestinal path has been carried out. Strong acidic conditions (pH = 3, typical in the stomach) prevent the drug release. In contrast, the drug was released at pH = 5.7 and 7.8, which simulate the duodenum/ileum and colon paths, respectively. These results demonstrate that the proposed nanoarchitecture is suitable as a functional material with tunable delivery capacity.