Metal-organic frameworks can be defined as a class of materials having a certain degree of porosity, consisting of metal ions or oligonuclear metal complexes and organic ligands. Pore size plays a fundamental role in the classification of these structures. MOFs, depending on the size of the pores, can be divided into nanoporous, mesoporous, and macroporous. The high surface area, thermal stability, and porosity give metal-organic structures the ability to incorporate neutral molecules, charged molecules, solvents, and gas molecules within their structure. Research in this field has shown numerous potential applications in the development of drug delivery systems.
Initially, MOFs were synthesized by solvothermal techniques, but currently there are several synthetic strategies based on electrochemical, mechanochemical, microwave-assisted, and sonochemical techniques. There are several ways to load the drug into the metal-organic frameworks. A very popular strategy is encapsulation, in which the cargo is introduced inside the pores of MOFs via non-covalent interactions. Another strategy is the directed assembly, characterized by the interaction of coordination bonds between MOFs and cargo, which participates in the synthetic reaction, contributing in part to the construction of MOFs. Furthermore, loading can be performed following a post-synthesis strategy where the cargo molecules are located on the surface of the MOFs.
Considering the numerous experimental and computational studies performed on metal-organic frameworks, significant and encouraging developments are expected for drug delivery. For biomedical applications, numerous studies are still needed, in particular regarding the study of pore size and related toxicity.
References
- Catherine P. Raptopoulou. Metal-Organic Frameworks: Synthetic Methods and Potential Applications, Materials, 2021.
- Bianca Maranescu, Aurelia Visa. Applications of Metal-Organic Frameworks as Drug Delivery Systems, Int. J. Mol. Sci. 2022.