Crystalline and Amorphous Zeolitic Imidazolate Framework Nanoparticles for Controlled Drug Release

Zeolitic imidazolate frameworks (ZIFs), such as ZIF-8, offer interesting possibilities for use in drug delivery applications due to high porosity. In this study, we provide insights into the delivery performance of calcein drug loaded into crystalline ZIF-8 and released from both crystalline and amorphous ZIF-8. Based on previous work, the hypothesis is the crystalline state will ensure high loading capacity, while the amorphous state will allow for a more gradual release compared to that from the crystalline state. We transform the crystalline ZIF-8 to the amorphous state via ball milling. The prepared materials are characterized by different techniques, including field emission scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction, Fourier transform infrared spectroscopy, thermogravimetric analysis, and Brunauer–Emmett–Teller (BET) analysis. The drug loading and delivery studies are performed in vitro, while the amount of adsorbed drug is measured using optical spectroscopy. Through more than 20 days, we observe controlled release of calcein drug. We also characterize the cytotoxicity of the different materials. We conclude that the use of both crystalline and amorphous states of ZIF-8 offer interesting potential for drug delivery applications.