Engineered Probiotics with Pb-Binding Enhanced Curli Nanofibers for Oral Lead Elimination

Lead poisoning remains a persistent global health challenge. Current small-molecule chelation therapies for lead poisoning cause systemic side effects due to non-specific metal depletion. Here, we propose an "affinity-selectivity-safety" strategy using a living biointerface in which the probiotic is programmed to overexpress customized curli nanofibers. The high-affinity Pb-binding protein PbrR was anchored onto the cell surface of Escherichia coli Nissle 1917 (EcN) via fusion to the curli nanofiber subunit CsgA and presented within the extracellular self-assembled curli network. After induction, EcNC-P overexpresses the C-P fusion protein, which self-assembles into a dense and stable network of PbrR-functionalized curli nanofibers on the bacterial surface, without impairing bacterial viability, intestinal transit properties, or intrinsic probiotic functions. The engineered probiotics exhibited an exceptional Pb2+ binding capacity of up to 70 mg·g-1 biomass and preferential Pb selectivity over essential metals under competitive conditions. The curli-displayed PbrR provides an array of multidentate Pb2+-chelating sites, endowing the living material with an ultrahigh lead adsorption capacity. Orally ingested EcNC-P was completely excreted within 12 h, ensuring biosafety. In an acute oral Pb exposure mouse model, EcNC-P-based living materials achieved better efficacy than orally administered DTPA under the same dosing condition, reducing blood Pb levels by ∼30% and increasing fecal Pb excretion by ∼1.2-fold. Therapeutic supplementation of the probiotics promoted fecal lead excretion and markedly decreased tissue lead burdens and was associated with alleviated intestinal inflammation and altered gut microbiota composition. No systemic toxicity or adverse effects were observed with single high-dose use. This surface-anchored customized curli nanofiber probiotic integrates high-affinity lead chelation with the bioactivities of a living biointerface, offering a safe, oral, and programmable platform for the holistic management of lead poisoning.