Enhanced photocatalytic and antibacterial activity of acridinium-grafted g-C3N4 with broad-spectrum light absorption for antimicrobial photocatalytic therapy

As a metal-free polymeric photocatalyst, graphitic carbon nitride (g-C3N4) has attracted great attention owing to its high stability and low toxicity. However, g-C3N4 suffers from low light harvesting ability which limits its applications in antimicrobial photocatalytic therapy (APCT). Herein, acridinium (ADN)-grafted g-C3N4 (ADN@g-C3N4) nanosheets are prepared via covalent grafting of ADN to g-C3N4. The obtained ADN@g-C3N4 exhibits a narrow optical band gap (2.12 eV) and a wide optical absorption spectrum (intensity a.u. > 0.30) ranging from ultraviolet to near-infrared region. Moreover, ADN@g-C3N4 would produce reactive oxygen species (ROS) under light irradiation to exert effective sterilization and biofilm elimination activities against both gram-negative and gram-positive bacteria. Molecular dynamics simulation reveals that the ADN@g-C3N4 may move toward, tile and insert the bacterial lipid bilayer membrane through strong van der Waals and electrostatic interaction, decreasing the order parameter of the lipid while increasing the conducive of ROS migration, inducing ADN@g-C3N4 with improved antimicrobial and antibiofilm performance. Moreover, ADN@g-C3N4 could efficiently eradicate oral biofilm on artificial teeth surfaces. This work may provide a broad-spectrum light-induced photocatalytic therapy for preventing and treating dental plaque diseases and artificial teeth-related infections, showing potential applications for intractable biofilm treatment applications. An acridinium-grafted g-C3N4 (ADN@g-C3N4) with a narrow band gap and broad-spectrum light absorption was synthesized. The narrow optical band gap and improved electrostatic interaction with bacterial lipid bilayer membrane of ADN@g-C3N4 strengthened the ROS generation and facilitated the diffusion of ROS to bacteria surface, leading to enhanced photocatalytic and antibacterial activity against bacteria and corresponding biofilm under light irradiation. STATEMENT OF SIGNIFICANCE: An acridinium-grafted g-C3N4 (ADN@g-C3N4) with a narrow band gap and broad-spectrum light absorption was developed as an antimicrobial photocatalytic therapy agent. The ADN@g-C3N4 exhibited enhanced photocatalytic and antibacterial activity against bacteria and corresponding biofilm under light irradiation, showing potential applications for intractable biofilm treatment.