Efficient Antibacterial Performance and Effect of Structure on Property Based on Cationic Conjugated Polymers

Cationic conjugated polymers (CCPs) have attracted more and more attention in antibacteria and tumor treatment based on photodynamic therapy (PDT). However, the main chain structure–antibacterial activities relationship has been rarely reported. Herein, we designed and synthesized four cationic conjugated polymers: one poly(fluorine phenylene) derivative (PFP) and three poly(fluorene- co -phenylene ethynylene) derivatives (PFE-1, PFE-CN-2, and PFE-NP-3). PFP and PFE-1 have the same side chains but bear different conjugated backbones. PFE-CN-2 (π-A) and PFE-NP-3 (A-π-A) are modified with electron-donating and/or electron-withdrawing groups. Three PFEs can produce reactive oxygen species (ROS) faster than PFP. The order of antibacterial activities of the four CCPs is as follows: PFE-CN-2 > PFE-1 ≫ PFE-NP-3 ≈ PFP, which is coincident with the generation rate of ROS. In addition, CCPs with D-π-A structure is more advantageous than A-π-A in ROS production and in antibacterial performance. These results provide an important base for designing more efficient PDT agents for antibacteria and antitumor.