Chitosan@4,6-Dihydroxyisophthalaldehyde Microgels with Hydrazine-Induced Fluorescence for Cell Imaging Applications

The graft functionalization of chitosan with 4,6-dihydroxyisophthalaldehyde moiety (chitosan@4,6-dihydroxyisophthalaldehyde) molded microgel offers a remarkable self-fluorescence potency due to the extended conjugation of chemically bound hydroxy-aromatic moieties. The microgel has a particle size of 149 nm, and the nanofiber-like 3D architecture shows stable structural integrity established by Fourier transform infrared (FTIR) spectra, field emission scanning electron microscopy, and rheology. Significant uniqueness is found upon adding hydrazine to the microgel solution. An interesting shifting in the circular dichroism (CD) band from 2.04 to 23.48 ellipticity mdeg–1 signifies significant enhancement in the interaction between two parallel layers through the hydrazine bridge by simple Schiff base formation, resulting in more rigid polymeric assembles. Excited-state intramolecular proton transfer induced fluorescence enhancement and extended conjugation are found in the presence of hydrazine, and all observations are confirmed by CD, dynamic light scattering, fluorescence lifetime, FTIR, and time-dependent density functional theory analysis. Further application in human lung fibroblasts (MRC-5) cell lines has been performed to establish nontoxicity, cell adhesion ability, and intense fluorescent cell imaging. The prepared microgel has steady structural integrity and plays a vital role as a multimodal, self-fluorescent material. Indeed, the developed material is promising toward improved gel-based chemical sensing tactics and can accomplish various applications.