Abstract
AbstractStructural variety, tunable porosity and opportunities for functionalization make metal‐organic frameworks (MOFs) promising materials for applications in medicine as drug delivery systems. In this minireview, an overview of chemical stability of MOF nanocarriers at simulated body conditions is presented. Parameters such as a choice of buffer, pH value, nanoparticle size or surface modification are discussed, as well as analytical methods and approaches suitable to determine the material stability. Last but not least, examples of tuning and improving the chemical stability of MOF nanoparticles for solution‐based drug delivery (oral and intravenous) are presented and examples of MOFs as pH‐responsive drug nanocarriers are given.
Highlights
When reporting on results of chemical stability, the exposure conditions (i. e. type of the operating environment and its strength, temperature, concentration, time and the experimental set-up in general) need to be specified, because they effect the results as demonstrated on the examples given in the following paragraphs
Demel et al reported on a comprehensive study comparing the stability of UiO-66 in different buffers, namely 2-amino-2(hydroxymethyl)-1,3-propanediol (TRIS), 4-(2-hydroxyethyl) piperazine-1-ethane sulfonic acid (HEPES), N-ethylmorpholine (NEM) and phosphate buffer (PB).[32]
The results suggested that the metal-organic frameworks (MOFs) nanoparticles were stable in water with a very low amount of the ligand released after 24 h (2.5 0.4 wt%), but much less stable in phosphate buffered saline (PBS) exhibiting a faster initial degradation of 22.3 2.1 wt% during the first 6 h and a smoother degradation profile unto 29.9 2.1 wt% after 24 h
Summary
Conventional drugs based on small molecules are often distributed at high concentrations in order to reach target tissues at a therapeutic concentration This can lead to a nonselective biodistribution within the body, which might result in a tissue damage. MOFs are porous coordination polymers constructed from organic ligands and metal-containing nodes.[11] Due to their structural and functional tunability,[12,13] they have been considered as promising materials for various applications including gas storage and separation,[14,15] catalysis,[16,17] sensing,[18,19] electrical and proton conduction,[20,21] and as nanocarriers in drug delivery.[5,6,7,8,9,10] For many of the applications, a high chemical and thermal stability is required and is often a crucial aspect when considering the commercialization of the materials. The influence of the buffer choice (with regard to its composition) is discussed in detail in the corresponding paragraph of this minireview
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