Novel terephthaloyl thiourea cross-linked chitosan hydrogels as antibacterial and antifungal agents

Four novel terephthaloyl thiourea chitosan (TTU-chitosan) hydrogels were synthesized via a cross-linking reaction of chitosan with different concentrations of terephthaloyl diisothiocyanate. Their structures were investigated by elemental analyses, FTIR, SEM and X-ray diffraction. The antimicrobial activities of the hydrogels against three species of bacteria (Bacillis subtilis, Staphylococcus aureus and Escherichia coli) and three crop-threatening pathogenic fungi (Aspergillus fumigatus, Geotrichum candidum and Candida albicans) are much higher than that of the parent chitosan. The hydrogels were more potent in case of Gram-positive bacteria than Gram-negative bacteria. Increasing the degree of cross-linking in the hydrogels resulted in a stronger antimicrobial activity.