Positively Charged Semiconductor Conjugated Polymer Nanomaterials with Photothermal Activity for Antibacterial and Antibiofilm Activities In Vitro and In Vivo

Biofilm infections are associated with most human bacterial infections and are prone to bacterial multidrug resistance. There is an urgent need to develop an alternative approach to antibacterial and antibiofilm agents. Herein, two positively charged semiconductor conjugated polymer nanoparticles (SPPD and SPND) were prepared for additive antibacterial and antibiofilm activities with the aid of positive charge and photothermal therapy (PTT). The positive charge of SPPD and SPND was helpful in adhering to the surface of bacteria. With an 808 nm laser irradiation, the photothermal activity of SPPD and SPND could be effectively transferred to bacteria and biofilms. Under the additive effect of positive charge and PTT, the inhibition rate of Staphylococcus aureus (S. aureus) treated with SPPD and SPND (40 μg/mL) could reach more than 99.2%, and the antibacterial activities of SPPD and SPND against S. aureus biofilms were 93.5 and 95.8%. SPPD presented better biocompatibility than SPND and exhibited good antibiofilm properties in biofilm-infected mice. Overall, this additive treatment strategy of positive charge and PTT provided an optional approach to combat biofilms.