Enhanced Bactericidal Effect of Chitosan Using Coordinated Transition Metal Ions

Pathogenic bacteria are responsible for causing numerous diseases in humans and plants. Unfortunately, the effectiveness of systematic bactericidal agents is gradually diminishing due to the rise of bacterial resistance. However, a potential solution lies in chitosan, a natural polymer renowned for its remarkable bactericidal properties. In this study, chitosan (CHT)-metal complexes were synthesized using monovalent (Ag + ), bivalent (Ni 2+ , Cu 2+ , Mn 2+ ), and trivalent (Fe 3+ ) metal ions, and their bactericidal activity was investigated against gram-positive and gram-negative bacteria strains. The association of the metal centers in the chitosan backbone increases its bactericidal effect for all tested cases. Notably, the Ag/Chitosan complex displayed the highest bactericidal effect, as expected due to the intrinsic activity of Ag + ions. Intriguingly, even metal ions lacking with intrinsic bactericidal effect, demonstrated enhancement when complexed with chitosan. These findings strongly suggest that the inhibitory properties of the complexes are linked to the nature of the coordinated bond established between the metal center and the chitosan ligand.