Supramolecular Isoguanosine Assemblies Form Hydrogels with Excellent Long-Term Stability

Supramolecular nucleoside-based hydrogels have the potential to be utilized in drug delivery, regenerative medicine and for the construction of nanoscopic devices. Isoguanosine, its 2'-deoxyribonucleoside and the 2'-deoxy-2'-fluororibonucleoside form hydrogels in alkali metal salt solutions. Gel stability depends on the metal ions used (Li⁺ , Na⁺ , K⁺ , Rb⁺ , Cs⁺ ). All isoguanosine gels show long-term stability of several months, whereas guanosine gels collapse within minutes or hours. Rheological data confirm a 15 times higher hydrogel stability for isoguanosine compared to guanosine. Isoguanosine gel stability covers a broad pH range (pH 3-10), and the stability at physiological Na⁺ ion concentration is striking. SEM images reveal that isoguanosine self-assembles into helical stacked fibers that are interconnected whereas guanosine forms discrete ribbons. Moreover, isoguanosine gels display excellent loading and release ability for small molecules.