Functionalized Sugar Hydrogel Associated with Unique Exciplex Emission and Its Reflection in Bioimaging

Abstract

Two fluorescent hydrogels were synthesized with chitosan (green carbo-backbone, Ch) and modified anthracene moieties, 10-benzyl anthracene-9-carbaldehyde (ChAPh) and 10-((benzyloxy)methyl) anthracene-9-carbaldehyde (ChABn). Hydrogel ChAPh shows unique exciplex emission in the THF/water system. Here, the presence of active fluorophores in gel networks shows interesting reciprocation of fluorescence enhancement due to self-assembly in a remote interstitial area with variation of hydrophobic and hydrophilic surroundings. Aggregation-induced emission (AIE) illuminates an emission peak at λem 511 nm with appreciable intense fluorescence to show the formation of exciplex within the ChAPh gel. Aggregations or π–π complexations of -APh/-APh within the ChAPh gel are forced for resettling of fluorophores in hydrophobic solvation with increasing % of water in the THF system. Besides, hydrogel ChABn shows no prominent appearance of emission peak at λem 525 nm. Due to the presence of flexible oxygen (−O−) in -ABn moieties and its H-bonding with water molecules, the exciplex formation is inhibited within the ChABn gel. Thus, hydrogel ChAPh shows a unique exciplex emission within hydrogel networks. The unique exciplex within ChAPh has been established using solvent-dependent and temperature-dependent fluorescence and DLS studies. Additionally, hydrogels ChAPh and ChABn perform successfully as bioimaging gel in fibroblast (human adult dermal fibroblast) cells.