pH dependence of drug release behavior from metal-organic framework particle with different acid-base resistances

[Display omitted] •Drug delivery systems using metal–organic frameworks was proposed.•The crystal structure of UiO-66-NH2 collapsed under alkaline conditions.•Ibuprofen was included in UiO-66-NH2 pores at 0.16 g IBU/g UiO-66.•Released amount of IBU from UiO-66-NH2 tremendously increased at pH 8.5. Generally, a carrier that contains or binds to a drug is required for DDSs. Although it is common to use liposomes and polymeric micelles as carriers, the loading of drugs in these carriers is relatively low. This study investigates the application of metal–organic frameworks (MOFs), which are a new class of porous materials, to drug carriers. UiO-66-NH2 and ibuprofen (IBU) were selected as model MOF and drug, respectively. The acid/alkaline resistance of each MOF was investigated. Then, liquid-phase adsorption of drugs with MOF particles was conducted to obtain drug-loaded MOF particles. Furthermore, the release behavior of the drug from the MOF particles was investigated under different pH conditions. It was confirmed that the crystal structure of UiO-66-NH2 collapsed under alkaline conditions (pH 13). The model drug IBU was incorporated in the pores of UiO-66-NH2 at a relatively large amount of 0.16 g-IBU/g-UiO-66-NH2. The IBU incorporated in UiO-66-NH2 was immediately released when it was placed in a solution under alkaline conditions (pH 8.5). In addition, it was demonstrated that the release of IBU increased as soon as the pH conditions were changed from 1.5 to 8.5 during the dissolution test. The findings of this study indicate that UiO-66-NH2 has the potential to be a DDS with a large drug inclusion capacity and responsiveness to alkaline conditions.