Exosome-Coated Metal–Organic Framework Nanoparticles: An Efficient Drug Delivery Platform

Drug delivery systems aim at a reduction of side effects in chemotherapy. This is achieved by encapsulation of drugs in nanocarriers followed by controlled release of these drugs at the site of the diseased tissue. Though inorganic or polymeric nanoparticles (NPs) are often used as nanocarriers,(1, 2) hybrid nanomaterials such as metal−organic framework (MOF) NPs have recently emerged as a valuable alternative.(3-6) They are synthesized from inorganic and organic building block units to create porous three-dimensional frameworks. Because of this building principle, the composition and structure of these materials are highly tunable.(7-10) Furthermore, both external and internal surfaces can be functionalized independently. With these properties, MOF NPs can be designed to fit the specific requirements of the desired application.(3, 11) For drug delivery purposes these so-called “design materials” have been synthesized with high porosity allowing for high drug loading capacities. They also have been designed to be biodegradable. Specifically, iron-based MOF NPs have attracted great attention. In addition to the above-mentioned properties, they can be detected via magnetic resonance imaging (MRI), rendering them an ideal platform for theranostics.(12-14) In our study, we focus on one of these iron-based MOFs, namely MIL-88A NPs, which are composed of iron(III) and fumaric acid.(15, 16) Both compounds can be found in the body and the NPs are reported to be nontoxic.(12) Additionally, MIL-88A NPs have been shown to efficiently host chemotherapeutic drugs.(12) Thus, they represent a promising nanocarrier.