Structural modification induced hydrogelation and antibacterial properties in supramolecular gels

Low molecular weight N-oxide hydrogelators were synthesized by incorporating N-oxide moieties into hydrazone/semicarbazone groups, which was obtained by the modification of the pyridyl functional groups of hydrazone/semicarbazone compounds. The properties of the N-oxide compounds were compared with the pyridyl compounds, and the results showed that the structural modification of the pyridyl-hydrazides to pyridyl-N-oxide hydrazides enhanced the water solubility of the hydrazone gelator. The relative stability of the gels was analyzed by minimum gelation concentration, gel-to-sol transition temperature and rheology, and the morphologies were analyzed by scanning electron microscope (SEM). The stimuli-responsive properties of the gels in the presence of various salts were analyzed by adding different potassium salts, and the hydrazone gels showed a selective response towards cyanide ion. The hydrazone gels displayed antibacterial activity against both Gram-positive and Gram-negative bacteria, whereas semicarbazone gels were inactive. Furthermore, the gels were found to be biocompatible, which can be used as antibacterial agents.