Self-assembly of guanosine and deoxy-guanosine into hydrogels: monovalent cation guided modulation of gelation, morphology and self-healing properties

Abstract

In this study, we report the effect of monovalent cations including Na⁺, K⁺, Rb⁺, Ag⁺, Au⁺, Tl⁺, Hg⁺ and NH₄⁺ on the stimulation of purine nucleosides guanosine (G) and deoxy-guanosine (dG) to self-assemble into hydrogels. The gelation properties in terms of gel crystallization, lifetime stability, thermo-reversibility, minimum gelation concentration, gel melting temperature, thixotropic property and others were thoroughly investigated and compared not only between two nucleosides but also among different metal ions. A few metal ions were found to induce G/dG to form gels with much improved lifetime stability. The results revealed that dG is a much better gelator than G for introduction of a thixotropic property. Interestingly, morphological, fluorescence and rheological (thixotropic) properties of the gels were found to modulate significantly by changing the metal ions. In the presence of K⁺ ions, G produces a self supporting tight gel but it has poor lifetime stability. In contrast, the presence of K⁺ ions stimulates dG to form a very loose gel but with excellent lifetime stability and thixotropic property. In this context, we have successfully engineered a self-supporting stable co-gel using a simple co-gelation method by mixing an equimolar amount of K⁺ induced G and dG gels and this co-gel shows long lifetime stability, self-healing and injectable properties which may allow for a broad range of biological applications. Furthermore, an Ag⁺ induced G gel was exploited for the light triggered in situ fabrication of uniform AgNPs within a gel to make a nano–bio hybrid material.