Carboxymethyl chitosan modified with curcumin: A photodynamic antibacterial agent with good solubility and stability

Curcumin (CCM) is a natural photoinitiator with antioxidant, antibacterial and anti-inflammatory properties. However, hydrophobicity and low stability limit its application. In this study, CCM was coupled with carboxymethyl chitosan (CMCS) by an esterification reaction to obtain a water-soluble derivative (CMCS-CCM). A series of characterization techniques demonstrated the synthesis and aggregation properties of CMCS-CCM. The derivative exhibited good stability, antioxidant properties, and photodynamic antibacterial activity. Under the blue light irradiation of 450 nm, the minimal inhibit concentration (MIC) of CMCS-CCM against Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) were 128 and 512 μg/mL, respectively. Reactive oxygen species (ROS) assay and Scanning electron microscope (SEM) results indicated that the photodynamic antibacterial activity of CMCS-CCM was attributed to the disruptive effect of the generated ROS on the bacterial structure. Furthermore, the derivative did not show significant cytotoxicity and hemolytic activity. These results suggest that the derivatives can be used as a potential antibacterial agent and applied in the food industry.