Biocompatible cloaking of bacteria for effective tumor imaging and therapy

Bacteria possess distinctive characteristics, such as tropism, motility, and genetic editability, which make them highly attractive for biomedical applications, such as tumor imaging and therapy. However, the immunogenicity triggered by endotoxins may lead to severe adverse effects and prompt quick elimination in the body, thus restricting their clinical applications. In this study, we described a double-layer coating technique employing tannic acid (TA) and albumin (BSA) for bacteria encapsulation. This compact coating effectively shields endotoxin exposure and inhibits endotoxin leakage from bacteria, exhibiting a favorable safety profile. Moreover, bacteria coated with BSA have superior biocompatibility with their surroundings, which prevents phagocytes from eliminating the bacteria, hence prolonging the reservation in vivo. As bacteria grow, the BSA-TA layer progressively detaches after reaching targeted sites, allowing free bacteria to exploit their own advantages. Importantly, the BSA-TA coating strategy protects bacteria against various environmental assaults without compromising their growth, proliferation, or motility, maintaining their inherent characteristics. In murine tumor models, the BSA-TA-coated bacteria demonstrated enhanced long-term tumor imaging and therapeutic efficacy against tumors. Together, the BSA-TA coating strategy improves the biocompatibility of bacteria and has the capacity to expand the range of bacteria for biomedical applications.