A new class of nitrobenzoic acid-based AIE photosensitizers for highly efficient photodynamic antibacterial therapy

Photodynamic therapy (PDT) has been drawing more and more attention in the antibacterial field. Traditional photosensitizers (PSs) tend to aggregate in aqueous media, which reduces the generation of reactive oxygen species (ROS) and seriously affects the photodynamic efficacy. Many efforts have been made to prevent aggregation of traditional PSs. By contrast, aggregation-induced emission PSs (AIE-PSs) take advantage of aggregation to boost ROS generation and fluorescence intensity. However, the efficacies of the reported antibacterial AIE-PSs are poor. Herein, we report a new class of highly effective antibacterial AIE-PSs based on nitrobenzoic acid structure. TTVBA, a negatively charged AIE-PS, can not only selectively kill spherical bacteria (Staphylococcus aureus (S. aureus)) rather than rod-shaped bacteria (Escherichia coli (E. coli)), but also be easily extended to several AIE-PSs (TTVBP1-3) with positive charges and broad-spectrum antibacterial activity. We demonstrate that TTVBP2 can kill 3.0 log(10) of S. aureus at very low concentration (125 nmol L-1), TTVBP3 can kill 4.7 log(10) of Staphylococcus epidermidis (S. epidermidis) at a concentration of 1 mu mol L-1 and 3.8 log(10) of E. coli at 5 mu mol L-1, thus enabling them among the most effective antibacterial AIE-PSs reported so far. Meanwhile, these AIE-PSs exhibit excellent wash-free imaging ability for bacteria by simple mixing with bacteria. We thus envision that TTVBA, a nitrobenzoic acid-based extendable AIE-PS, provides a new route for the design of AIE-PSs in antibacterial treatment.

Automated summary

Photodynamic therapy (PDT) has gained increasing attention in the antibacterial field. Traditional photosensitizers (PSs) often aggregate in aqueous media, leading to reduced generation of reactive oxygen species (ROS). In contrast, aggregation-induced emission PSs (AIE-PSs) utilize aggregation to enhance ROS generation and fluorescence intensity. The newly developed antibacterial AIE-PSs based on nitrobenzoic acid structure show promising selective antibacterial activity, with TTVBP2 and TTVBP3 being particularly effective against various bacteria strains.