Crystal Transformation of β-CD-MOF Facilitates Loading of Dimercaptosuccinic Acid.

The β-cyclodextrin-metal-organic framework (β-CD-MOF), a potential drug delivery carrier, presents a densely packed laminated crystal structure (CCDC number 1041782) that prevents drug from entering inside the molecular voids in most CD units. In this paper, it was demonstrated that dimercaptosuccinic acid (DMSA), an instable small molecule chemical drug, was successfully loaded in β-CD-MOF with a high molar ratio of 1:1.35 (β-CD-MOF:DMSA) determined by high-performance liquid chromatography. The drug loading mechanism of β-CD-MOF/DMSA was supported by a series of experimental characterizations and molecular simulations. The morphology observations revealed that crystalline particles of β-CD-MOF transformed to reticular microstructure after drug loading evidenced by powder X-ray diffraction (PXRD), scanning electron microscope (SEM), synchrotron radiation Fourier transform infrared spectroscopy (SR-FTIR), and etc. It is of interest to note that the stability of DMSA was well improved by β-CD-MOF, but decreased by γ-CD-MOF, indicating different protective capacities between the two types of CD-MOFs. Thus, it is hypothesized that the transformation from laminated molecular arrangement of β-CD-MOF to reticular microstructure leads to an enhanced drug-loading capability for delivery of specific drugs.