Green metal-organic frameworks (MOFs) for biomedical applications

Metal-organic frameworks (MOFs), known as highly ordered crystalline hybrid structures, are the products of coordination polymerization of transition metals and organic ligands. MOFs are best known for their extensive specific surface area, hierarchically porous and tailorable 1D, 2D, or 3D micro-and nanostructure, and acceptable biocompatibility. Because of the multiplicity of metallic and organic units used in MOFs synthesis, tailor-made MOFs can be synthesized to be served as building blocks of advanced biological materials and systems. Recently, synthesis of green MOFs has received much more attention for nanobiomedicine usage. We review herein synthesis and biomedical application of green MOFs by analyzing their components, including green solvents, ligands, linkers, auxiliary linkers, and sustainable organic precursors. First, MOFs were classified in terms of their general toxicity level and biological behavior by considering the chemistry of ligands, linkers, and green organic precursors. Second, applications of bio-MOFs and nano-MOFs in medicine were categorized. Third, chemistry of green MOFs used as pro-drug and their potential and effects related to bioimaging, drug delivery, and multimodal therapeutics were systematically reviewed and discussed. Fourth, concluding remarks and challenging aspects of future developments of bio-MOFs and nano-MOFs were underlined.