A removable photothermal antibacterial “warm paste” target for cariogenic bacteria

Dental caries, as one of the most common persistent disease, affects people of all ages. However, the effectiveness of treatment is not satisfactory because of incomplete mechanical removal of cariogenic plaque and side effects such as antimicrobial resistance. Overcoming the problems of traditional antibacterial agents, photothermal therapy (PTT) upon near infrared (NIR) irradiation possesses the advantages of a deep tissue penetration depth and non-drug-resistance and has great potential in dental application. Even so, multiple colonies in oral cavity and the toxicity of residual nanomaterials bring challenges for the treatment. Here, we developed removable photothermal antibacterial “warm paste” nanoagents by the modification of Fe3O4 nanoparticles with polydopamine (PDA), silver, PDA, and glycol chitosan in sequence (FePAgPG). Second PDA layer can slow down the excessive release of Ag+ and reduce the damage to normal tissues. While in acidic microenvironment, the FePAgPG nanoparticles efficiently target the pathological bacteria based on pH responsive activity. Followed by that, nanoparticles are irradiated by NIR to realize effective sterilization through Ag-assisted PPT strategy, similar with antibacterial “warm paste”. Finally, the nanomaterials are removed by the magnetic field. Specifically, FePAgPG achieves excellent antibacterial effects (over 95%) against cariogenic bacteria at a relatively lower temperature (53 °C) in short time (10 min), enhanced ability to inhibit biofilm formation, and great cell compatibility. This strategy can provide a reference for the design of removable photothermal nanomaterials applied in other open wound infections.