Engineered photothermal-responsive bacterial platform for in vivo fluorescence imaging-guided photothermal/gene combined breast cancer therapy

   Malignant tumors pose a significant threat to human health, and bacteria-based tumor therapy has made considerable progress in recent years[–6]. Compared with other treatment modalities, this therapeutic approach offers several distinct advantages. Bacteria can be genetically engineered to carry nanomedicines or chemotherapeutic drugs on their surfaces[7], and serve as immune adjuvants to enhance the body's anti-tumor immune response[8,9]. The application of coupling nanophotothermal agents to bacterial surfaces for photothermal therapy has been extensively studied[1–13]. A bio-inorganic system for precise tumor targeting has been developed by covalently linking indocyanine green (ICG)-loaded nanoparticles to the surface of YB1 Salmonella[7]. Reghu and Miyako reported the synthesis of nanoparticle-functionalized bacteria with good biocompatibility and high solubility via a one-step ultrasonication method, which avoids the tedious preparation steps typically required for nanoparticles. The resulting nanoparticles exhibited excellent photothermal conversion capability after incubation with Bifidobacterium[14]. However, the heat generated during high-temperature photothermal therapy may damage surrounding normal tissues and reduce bacterial activity. Therefore, there is an urgent need to develop a safe and effective photothermal approach for tumor therapy.