Construction of layer-by-layer self-assembly coatings based on hemicyanine derivative for photodynamic antimicrobial application

Two-component composite films containing hemicyanine (C3) and indigo carmine (IC) dye were prepared via layer-by-layer self-assembly. The positively charged C3 has a conjugate backbone and hydrophilic groups, which could capture negatively charged bacteria on the surface of substrate by electrostatic and hydrophobic interactions. In addition, the donor-receptor structure of C3 also promotes intramolecular charge transfer to boost the generation of reactive oxygen species (ROS) for antibacterial therapy. Under the irradiation of white light, the three-layer film can display prominent photodynamic antibacterial activity, and the inhibition efficiency against the ampicillin resistant (Ampr) E. coli strain is as high as 90% with killing 3.6 × 108 of E. coli cells per cm2.