Guanosine-Derived Supramolecular Hydrogels: Recent Developments and Future Opportunities

Review of α-nucleosides: from discovery, synthesis to properties and potential applications

Nucleic acids play an important role in the genetic process of organisms; nucleosides, the building block of nucleic acids, typically exist in nature in a β configuration. As an anomer of β-nucleoside, α-nucleoside is extremely rare in nature. Because of their unique and interesting properties such as high stability, specific parallel double-stranded structure and some other biochemical properties, α-nucleosides have attracted wide attention. Various methods including but not limited to the mercuri procedure, fusion reaction and Vorbrüggen glycosylation have been used to synthesize α-nucleosides and their derivatives. However, to the best of our knowledge, there is no review that has summarized these works. Therefore, we systematically review the discovery, synthesis, properties, and potential applications of α-nucleosides in this article and look to provide a reference for subsequent studies in the coming years.

A systematic summary of the discovery, synthesis, properties and potential applications of α-nucleosides and their derivatives.

Thermo-Switchable de Novo Ionic Liquid-Based Gelators with Dye-Absorbing and Drug-Encapsulating Characteristics

An ionic liquid-based surfactant with ester functionality self-aggregates in an aqueous medium and forms ionogels at 8.80% (w/v) concentration at physiological pH. The ionogel exhibited a remarkable change in its appearance with temperature from fibrillar opaque to transparent because of the dynamic changes within its supramolecular structure. This gel-to-gel phase transition occurs below the melting point of the solid ionic liquid. The ionogels were investigated using turbidity, differential scanning calorimetry, scanning electron microscopy (SEM), field emission SEM (FE-SEM), inverted microscopy, transmission electron microscopy imaging, Fourier transform infrared spectroscopy, and rheological measurements. The fibrillar opaque ionogel and transparent ionogel were studied for their ability to absorb dyes (methyl orange and crystal violet) and to encapsulate drugs (diclofenac sodium and imatinib mesylate).

Developing a Self-Healing Supramolecular Nucleoside Hydrogel Based on Guanosine and Isoguanosine

Recently, supramolecular hydrogels have attracted increasing interest owing to their tunable stability and inherent biocompatibility. However, only few studies have been reported in the literature on self-healing supramolecular nucleoside hydrogels, compared to self-healing polymer hydrogels. In this work, we successfully developed a self-healing supramolecular nucleoside hydrogel obtained by simply mixing equimolar amounts of guanosine (G) and isoguanosine (isoG) in the presence of K+ . The gelation properties have been studied systematically by comparing different alkali metal ions as well as mixtures with different ratios of G and isoG. To this end, rheological and phase diagram experiments demonstrated that the co-gel not only possessed good self-healing properties and short recovery time (only 20 seconds) but also could be formed at very low concentrations of K+ . Furthermore, nuclear magnetic resonance (NMR), powder X-ray diffraction (PXRD), and circular dichroism (CD) spectroscopy suggested that possible G2 isoG2 -quartet structures occurred in this self-healing supramolecular nucleoside hydrogel. This co-gel, to some extent, addressed the problem of isoguanosine gels for the applications in vivo, which showed the potential to be a new type of drug delivery system for biomedical applications in the future.

A G4·K+ hydrogel made from 5′-hydrazinoguanosine for remediation of α,β-unsaturated carbonyls

A G₄·KCl hydrogel with a nucleophilic 5′ sidechain absorbs α,β-unsaturated carbonyls via formation of cyclic adducts.