Diffusion and birefringence of bioactive dyes in a supramolecular guanosine hydrogel

Transparent self-standing supramolecular hydrogels were readily prepared by the potassium-ion-mediated self-organization of guanosine and 8-bromoguanosine whilst the individual components precipitated within a few hours. VT-NMR spectroscopy showed that bromoguanosine was a superior gelator compared to guanosine. XRD analysis showed that gel formation was caused by stacked G-quartets. AFM analysis revealed dendritic architectures of the nanofibers in the two-component hydrogel network. DSC profiles showed that the hybrid hydrogels underwent sol-gel transition at lower temperature than the pure guanosine and bromoguanosine hydrogels. Interestingly, bioactive dyes, such as rose bengal, rhodamine-6-G, and fluorescein, could be diffused and released in a controlled manner. UV/Vis absorption and fluorescence spectroscopy and CLSM were used to investigate the diffusion behavior of dyes in the hydrogel network. These dyes exhibited strong birefringence in the gel network (0.07-0.1) as a result of the anisotropic organization.