Generating theranostic bacteria by depositing a protective visual therapeutic nanocoating via in situ sequential mineralization

Oral bacteriotherapy is increasingly exploited but faces challenges in simultaneously monitoring treatment process and achieving desirable efficacy. Here, we develop theranostic bacteria by depositing a protective visual therapeutic nanocoating via in situ sequential mineralization. Using two-step metal ion adsorption and nucleation, bacterial surface is successively mineralized with an inner manganese dioxide/ferric oxide nanoparticle layer and an outer calcium carbonate layer. Upon ingestion, the outer layer neutralizes gastric acid through double-decomposition reaction, protecting bacterial viability and the inner layer. During intestinal passage, the inner layer enables T1/T2 dual-mode magnetic resonance imaging for real-time tracking, whereas the lesion-triggered release of manganese ions allows T1 single-mode pathological detection. The inner layer also exhibits superoxide dismutase and catalase activities, synergizing therapeutic effects with bacteria. Further supported by satisfactory performances in two murine models of <i>Salmonella</i>-induced colitis and apolipoprotein E-deficient atherosclerosis, this work provides a platform to generate innovative theranostic agents for advanced bacteriotherapy.