Synthesis and release studies of ZIF-8 nanoparticles for ascorbic acid delivery in cancer therapy

• ZIF-8 nanoparticles can efficiently intercalate AA molecules within their sodalite structure. • The average particle size increased due to the intercalation of AA, from 90 nm to 160 nm. • AA@ZIF-8 can release AA within two days when used as a drug delivery vehicle at pH 7.4, demonstrating potential for use as a pH-sensitive system in cancer therapy. Metal-Organic Frameworks (MOFs) have recently been used for a wide variety of applications, such as designing nanoparticle-based drug delivery systems. The Zeolite Imidazole Framework (ZIF-8) is a subgroup of these materials. In the current study, ZIF-8 nanoparticles (NPs) were synthesized using the dissolving method in a methanol-based solution, while an in-situ entrapping method was employed to intercalate Ascorbic acid (AA) within the frameworks. Field emission scanning electron microscopy (FESEM) images of ZIF-8 NPs, before and after AA intercalation, showed the particles to be nearly hexagonal with sharp edges. Dynamic light scattering (DLS) measurements revealed that the size range of the as-synthesized NPs was from 90 nm to 160 nm, before and after intercalation, respectively. The X-ray diffraction experiment confirmed that the NPs were formed with perfect crystallinity and retained structural integrity after AA loading. UV-absorbance and FTIR measurements verified the presence of AA molecules within the ZIF-8 NPs. Furthermore, the AA release was investigated by UV-visible spectroscopy at both pH values of 7.4 and 5. Results demonstrated a faster drug release at pH 5, such that approximately the entire amount of AA was released within 10 hours. The release kinetics were mathematically simulated using three conventional models: the first-order, second-order, and parabolic diffusion models. The fitted data indicated that the second-order equation was the most accurate in predicting the rate of AA release over time, with a correlation coefficient (R²) greater than 0.99. Additionally, the first-order and diffusion models could only predict the initial hours of AA discharge from the ZIF-8 NPs effectively.