Stimuli-Responsive Nucleotide–Amino Acid Hybrid Supramolecular Hydrogels

Abstract

The ability to assemble chemically different gelator molecules into complex supramolecular hydrogels provides excellent opportunities to construct functional soft materials. Herein, we demonstrate the formation of hybrid nucleotide–amino acid supramolecular hydrogels. These are generated by the silver ion (Ag+)-triggered formation of silver–guanosine monophosphate (GMP) dimers, which undergo self-assembly through non-covalent interactions to produce nanofilaments. This process results in a concomitant pH reduction due to the abstraction of a proton from the guanine residue, which triggers the in situ gelation of a pH-sensitive amino acid, N-fluorenylmethyloxycarbonyl tyrosine (FY), to form nucleotide–amino acid hybrid hydrogels. Alterations in the supramolecular structures due to changes in the assembly process are observed, with the molar ratio of Ag:GMP:FY affecting the assembly kinetics, and the resulting supramolecular organisation and mechanical properties of the hydrogels. Higher Ag:GMP stoichiometries result in almost instantaneous gelation with non-orthogonal assembly of the gelators, while at lower molar ratios, orthogonal assembly is observed. Significantly, by increasing the pH as an external stimulus, nanofilaments comprising FY can be selectively disassembled from the hybrid hydrogels. Our results demonstrate a simple approach for the construction of multicomponent stimuli-responsive supramolecular hydrogels with adaptable network and mechanical properties.

Bioinspired Amino Acid Based Materials in Bionanotechnology: From Minimalistic Building Blocks and Assembly Mechanism to Applications

“…Coassembly can expand the conformational space of supramolecular assemblies in terms of structural and functional complexity, − resulting in tunable mechanical strength and piezoelectric properties, switchable fluorescent emissions, and controllable helicity and orientation of nanostructures. − Ji et al reported an unexpected transition of molecular packing modes from H- to J- and X-aggregation of the simple aromatic molecule 4,4′-bipyridine (BPY) by coassembling with chiral acetylated alanine (AcA) (Figure c). Due to the intermolecular hydrogen bond between −COOH and pyridine (Figure d), the addition of AcA changed the packing mode of BPY from H-aggregation in single crystals to hybrid JX-aggregation in cocrystals (Figure e–g).…”

Gelation in L-Cysteine-Silver Aqueous Solutions Initiated by Iodide Anion

“…Гелеобразование в таких системах может быть инициировано различными факторами -добавкой электролита, изменением рН, нагреванием, облучением и др. Особый интерес представляют процессы самосборки и гелеобразования в результате анионного отклика, что открывает новые возможности в создании и направленном дизайне анион-чувствительных супрамолекулярных органо-и гидрогелей биомедицинского назначения [6][7][8].…”