Silver ions blocking crystallization of guanosine-based hydrogel for potential antimicrobial applications.

In this work, the detailed crystallization process of 2'-deoxy-2'-fluoroguanosine ( F G d ) hydrogel has been studied using single crystal X-ray diffraction, variable-temperature nuclear magnetic resonance (VT-NMR), and scanning electron microscopy (SEM). Both solid and solution results indicated that the K + -mediated G-quartet structures were unstable and easily resulted in the breakdown of the hydrogel to form linear ribbon structures by forming mimic reverse Watson-Crick base pairs between the two faces with an intermolecular hydrogen-bond (N10H-O11). Accordingly, Ag + was introduced to block the crystallization of F G d to form long lifetime stable supramolecular hydrogel (>6 months) and possible silver-ions-mediated base pair motifs were suggested via NMR, UV, and mass spectroscopy (MS) in combination with powder X-ray diffraction (PXRD) and circular dichroism spectroscopy (CD). Furthermore, F G d Ag hydrogel exhibited low toxicity for normal oral keratinocyte cells (NOK-SI) and good antibacterial activities for Fusobacterium nucleatum in vitro .