Chlorin e6 conjugated chitosan as an efficient photoantimicrobial agent.

The development of antibacterial agents with high bacteria-binding capability and antibacterial efficiency is highly desirable. Herein, cationic polysaccharide chitosan (CS) was combined with photosensitizer Chlorin e6 (Ce6) to construct a novel photodynamic antibacterial agent (CS-Ce6 conjugates) for combating gram-positive bacteria Staphylococcus aureus (S. aureus) and gram-negative bacteria Escherichia coli (E. coli). CS-Ce6 conjugates with different degrees of substitution (DS) were synthesized and characterized by a spectroscopic method and organic elemental analysis to understand the relationship between structure and antibacterial effect. CS-Ce6 conjugates revealed good reactive oxygen species (ROS) generation ability and photodynamic antibacterial effect. Meanwhile, they both were positively correlated with DS in the range of 4.81% ~ 11.56% resulting in stronger photodynamic antibacterial ability. These findings highlight that CS-Ce6 conjugates have the potential as an effective photodynamic bactericidal agent in the antibacterial field.