No abstract

Bacterial infections pose a serious threat to human health. Photodynamic therapy is an effective medical treatment to solve the problems raised by antibiotic resistant bacteria. But it is not easy to have photosensitizers (PSs) that can simultaneously produce efficient fluorescence and reactive oxygen species. Traditional PSs show compromised performances due to the aggregation‐caused quenching effect in aqueous media, however, luminogens with aggregation‐induced emission (AIE) can inherently achieve high fluorescence and efficient ROS generation. In addition, electrostatic interaction is generally accepted to be responsible for initial targeting of bacteria. But for AIE PSs, the roles of molecular charges on antibacterial efficiency are rarely considered. Herein, two red‐emissive AIE PSs with the same luminogenic core but carrying different number of positive charges are designed, and their antibacterial performance and the killing mechanism toward Gram‐positive (G(+)) and Gram‐negative (G(−)) bacteria are investigated. The AIE PSs with highly efficient singlet oxygen generation can clearly image and selectively kill bacteria over mammalian cells. With the increase in the positive charges of AIE PSs, the improvement in antibacterial efficiency is great against G(−) bacteria, but it is negligible against G(+) bacteria. This research will provide new insight into the rational design of new antibacterial materials.

Silkworm silk is a promising natural biopolymer for textile and biomedical applications for its remarkable flexibility, excellent biocompatibility and controllable biodegradability. The functionalization of silks makes them more versatile for flexible displays and visible bioscaffolds. However, fluorescent silks are normally fabricated through unstable physical absorption or complicated chemical reactions under harsh conditions. Herein, we developed a simple strategy for preparing fluorescent silks. Five aggregation‐induced emission luminogens (AIEgens) with activated alkynes were synthesized by rational molecular design, and then reacted with silk fibers through facile metal‐free click bioconjugation. The resulting conjugates show bright full‐color emissions and high stability. A white light‐emitting silk was fabricated by simultaneous bioconjugation with red‐, green‐ and blue‐emissive AIEgens. The red‐emissive AIEgen‐functionalized silks were successfully applied for long‐term cell tracking and two‐photon bioimaging, demonstrating great potential for tissue engineering and bioscaffold monitoring.