A) Chemical structure of chitosan, glutaraldehyde (GA), and crosslinking reaction showing the nucleophilic attack of the amine group of the chitosan to the positively charged aldehyde group of GA forming an imine group in the chitosan hydrogels crosslinked with GA. (ChemDraw Professional 15.1 was used for the chemical drawings). B) Physical appearance of chitosan hydrogels crosslinked with increasing GA concentrations i) 0%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 1%, 2.5%, and 5%; ii) quantification of crosslinking based on GA concentrations measured by the absorption of the hydrogels at 360 nm (n=3). C) FTIR spectra of crosslinking based on GA concentrations.