Green Synthesis of Cyclodextrin-Based Metal–Organic Frameworks through the Seed-Mediated Method for the Encapsulation of Hydrophobic Molecules

Abstract

Metal-organic frameworks (MOFs) are attracting considerable attention as a result of their unique structural properties, such as a high surface area, highly porous topology, and tunable size and shape, which enable them to have potential applications as a new class of carriers for functional agent or drug delivery. However, most of the MOFs and the polymers used are not pharmaceutically acceptable. For the first time, this study successfully conducted the rapid synthesis of cyclodextrin metal-organic frameworks (CD-MOFs) through a facile and green seed-mediated method. The size control, crystal structure, and thermal properties of CD-MOFs with and without seeds were investigated. When 1 mg/mL seed was added, the size of γ-CD-MOF crystals decreased from 6.2 ± 0.8 to 1.8 ± 0.4 μm. The CD-MOFs synthesized though the seed-mediated method had higher crystallinity and thermal stability than those that were not. Furthermore, the CD-MOFs could encapsulate hydrophobic molecules, such as Nile red (NR), which was chosen as a model, and the interaction mechanism between γ-CD-MOFs and NR was investigated. Results showed the formation of a 1:1 complex between NR and CD-MOFs, demonstrating the potential of these polymers as carriers for hydrophobic drug delivery applications.

Metal-organic frameworks for advanced drug delivery

“…However, the disadvantage of CTAB lies in its potential toxicity and it is difficult to be removed from the MOF particles. Recently, a seed-mediated method was employed to produce this CD-MOF using short-chain starch NPs instead of CTAB to have crystals with monodispersed size about 2 μm 183 . However, this method was not able to scale-down the particles to the nano-regime.…”

Cyclodextrin-Based Metal-Organic Frameworks (CD-MOFs) in Pharmaceutics and Biomedicine

“…These investigations have further expanded, which enriched the family of CD-MOFs and induced researchers to explore additional applications of CD-MOFs [70]. Recently, Qiu et al proposed a facile and green seed-mediated method to rapidly synthesize γ-CD-MOFs [71]. The results showed that the crystal structure was not changed, while the size of the MOF was observed to decrease when the seed was added.…”

Metal-Organic Frameworks for Bioimaging: Strategies and Challenges

“…Besides, the synthesis methods of MOFs also include seed-mediated method [59], post-modification method [60], in situ diffusion synthesis [61], microwave-assisted coprecipitation [62], etc. It is worth noting that the synthesis will be affected by many factors, including metal center, organic ligand, reaction solvent, synthesis temperature, pH value of reaction solution, reactant ratio counterion, etc.…”