Genetically engineered Escherichia coli Nissle 1917 enabling on-site melanin synthesis attenuates radiation enteritis through ferroptosis inhibition and gut microbiota modulation

Radiation enteritis (RE) poses a clinically-relevant therapeutic challenge with limited effective interventions. Engineered probiotic drug delivery systems offer innovative strategies for precise treatment of inflammatory disease. However, both the practical efficacy and therapeutic mechanism of engineered probiotic agents for RE alleviation remains largely unclear. Herein, the melanin with natural radioprotective function was applied to modify engineered Escherichia coli Nissle 1917 that contains the Tyrosinase gene (EcN-Tyr), which were further formulated into orally administrable microspheres (EcN-Tyr (A/C)₁) with natural sodium alginate and chitosan coatings via microfluidic approach. Notably, EcN-Tyr (A/C)₁ microspheres could successfully withstand gastric acid and actively target inflammatory lesions in the intestine. Mechanistically, EcN-Tyr (A/C)₁ microspheres enabled Ferroptosis inhibition through reducing lipid peroxidation to protect the host from radiation damage. As a result, EcN-Tyr (A/C)₁ effectively alleviated radiation-induced intestinal inflammation, and reduced DNA damage. Furthermore, the administration of EcN-Tyr (A/C)₁ increased the abundance of beneficial bacteria, such as Akkermansia and Ligilactobacillus, while reducing the abundance of harmful bacteria, such as Escherichia-Shigella, clearly indicating the positive effects on the balance of gut microbiota. In summary, EcN-Tyr (A/C)₁, as a novel probiotic carrier, shows great potential in the treatment of RE, and pioneers new avenues for leveraging natural biomaterials to treat RE.