Synthesis and short DNA in situ loading and delivery of 4 nm-aperture flexible organic frameworks

Five water-soluble flexible organic frameworks have been synthesized from a pyridinium-derived tetracationic tetraaldehyde and five diacylhydrazines (1 : 2) through the quantitative formation of a hydrazone bond in water at ambient temperature. Dynamic light scattering experiments reveal that the homogeneous frameworks display hydrodynamic diameters ranging from 68 nm to 167 nm, which can be tuned by changing the concentration of the components. Molecular modelling shows that, when adopting an ideal, extended conformation, the frameworks form an aperture of 4 nm diameter. The new flexible frameworks are generally of low cytotoxicity. Fluorescence imaging and flow cytometric analysis demonstrate that the new flexible porous frameworks can quickly include single and double stranded DNA of 21 nucleotides and deliver the included DNA into both normal and cancer cells, with the percentage of delivered cells reaching up to 99.5%.