Loading and in vitro release of ibuprofen in tubular halloysite

Halloysite (Hal) and 3-aminopropyltriethoxysilane (APTES)-modified Hal were used as drug carriers for the loading and release of ibuprofen (IBU). IBU exhibited a low loading capacity and a fast release in unmodified Hal because of the weak interaction (hydrogen bonds) between IBU and the unmodified halloysite. APTES modification increased the loading capacity of IBU and slowed the release of IBU by introducing a strong affinity through electrostatic attraction, which was generated between the carboxyl groups of IBU and the introduced aminopropyl groups of the grafted APTES. The release profiles of IBU were well fitted with the modified Korsmeyer–Peppas model. The release mechanism of IBU from unmodified and APTES-modified Hal, indicated by the exponent of the modified Korsmeyer–Peppas model, was Fickian diffusion and non-Fickian diffusion, respectively.