Supramolecular Synthesis of Hybrid Metal-Organic Framework-Dye Composites as Bioimaging Probes

Fluorescence microscopy enables the visualization of complex biological systems and processes. However, the utilization of organic dyes as bioimaging agents presents several challenges such as stability in biological environment, reduced photostability, and lower quantum yields. Substantial effort has gone into the improvement of the photophysical properties of biocompatible fluorescent molecules (fluorophores).1,2Metal-organic frameworks (MOFs) are crystalline materials comprised of metal ion clusters linked by organic ligands. These nanomaterials are characterized by their large surface area, high porosity, tailorable a priori chemical design and post synthetic tunability. Selective encapsulation of fluorophores in porous nanoparticles to form emissive nanocomposite materials results in increased dye photostability and quantum yields, longer lifetimes, and better organization of the dye molecules, meanwhile providing a convenient solution to issues related to the low biocompatibility or scarce solubility of the dyes in physiological buffer. Furthermore, post synthetic functionalization of the nanostructures with targeting agents can direct precise accumulation within cells via endocytosis. In principle, this simple protocol can evolve into a general strategy to deliver intracellularly functional molecular components for targeted bioimaging applications.