Chitosan modified halloysite nanotubes as emerging porous microspheres for drug carrier

• Halloysite (Hal) nanotubes were chitosan (CTS)-modified to prepare microspheres.
• Pores of microspheres were beneficial to the entrance of aspirin (Asp) molecules.
• Microspheres showed higher loading capacity for Asp than pristine Hal nanotubes.
• Hal-CTS/Asp nanocomposites could have potential application in drug carrier system.

Natural halloysite (Hal) nanotubes were well dispersed and thoroughly emulsified to prepare the porous microspheres Hal-chitosan (Hal-CTS) in a water/oil microemulsion, which was further loaded with aspirin (Asp) as a model drug to investigate the drug release behavior. The charge-mediated adsorption of molecules to the surface of Hal could facilitate the dispersion of Hal in aqueous media and enabled Hal to assemble into microspheres. The microspheres had interconnected pores, large pore volume, high specific surface area and hierarchical pore distribution, which was beneficial to the entrance of Asp molecules. The porous microspheres showed excellent loading capacity for Asp as high as 42.4 wt%, around 20 times higher than the pristine Hal (2.1 wt%). The release results indicated that Hal-CTS/Asp nanocomposites had the lower release in the simulated gastric fluid, whereas more rapid release rate and higher release amount in the simulated intestinal fluid, which could help to maintain effective concentration of Asp in the body and reduce the maximum extent of the side effects to the stomach. The as-prepared Hal-CTS/Asp nanocomposites could have potential application in the drug carrier systems due to their natural and excellent biocompatibility.

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