Evaluation of synergistic effects of carvacrol-loaded bovine serum albumin nanoparticles and visible light on mixed biofilms of Candida tropicalis and Pseudomonas aeruginosa.

Treating biofilm-associated infections is considerably more challenging in the presence of polymicrobial communities comprising bacterial and fungal species. This underscores the need for innovative therapeutic strategies. This study evaluated the antimicrobial and immunomodulatory efficacy of carvacrol-loaded bovine serum albumin nanoparticles (CAR@BSANPs) against single- and mixed-species biofilms of Candida tropicalis and Pseudomonas aeruginosa, both alone and in combination with visible light. We assessed antimicrobial photodynamic activity and reactive oxygen species (ROS) production in planktonic cells and biofilms. Then, we validated the results in vivo using a Galleria mellonella infection model. We performed survival analysis, measured haemocyte density, examined immune gene expression, and determined microbial burden. CAR@BSANPs demonstrated strong antimicrobial, antibiofilm, and ROS-generating activities, particularly under visible light exposure. Gene expression analysis revealed downregulation of HWP1, LASR, and PELA, as well as upregulation of TUP1. In vivo, the combined treatment significantly improved larval survival, increased haemocyte density, upregulated gallerimycin and cecropin, and decreased microbial load. Overall, these findings suggest that CAR@BSANPs combined with visible light are an effective nanotherapeutic approach for overcoming biofilm-associated resistance in single- and mixed-species infections.