Supramolecular hydrogels derived from silver ion-mediated self-assembly of 5′-guanosine monophosphate

Abstract

We describe the preparation and properties of supramolecular hydrogels produced by spontaneous self-association of disodium guanosine 5′-monophosphate (Na25′GMP) in the presence of Ag+ ions. Hydrogels with increasing viscosity are prepared by increasing the GMP:Ag stoichiometry from a molar ratio of 1 : 1 to 1 : 2. In each case, the hydrogels comprise an interconnected matrix of nanofilaments that undergo a gel to sol transition between 50–80 °C, depending on the matrix composition. NMR, UV-vis and CD spectroscopy investigations, in combination with XRD and SAXS studies indicate that the nanofilaments are constructed from helically stacked, chiral arrays of Ag-GMP dimers. Cationic dyes such as methylene blue and Hoechst-33258 bind to the Ag-GMP nanofilaments, with the latter dye exhibiting induced chirality transfer and significantly disrupting the hydrogel superstructure. Protein molecules (cytochrome c) can be immobilized within the hydrogels without loss of enzymatic activity. We also show that nanocomposite hydrogels comprising Ag-GMP nanofilaments impregnated with plasmonic Ag nanoparticles can be readily prepared by prolonged exposure to light.