Au@Pt Nanozyme‐Coated Bacterial Hybrids for Exosome‐Propelled Early Tumor Screening and Treatment Monitoring

Abstract As a pivotal liquid biopsy biomarker, tumor cells‐derived exosomes (TDEs) offer significant advantages for early diagnosis of tumors and the monitoring of treatment effects. However, the lack of reliable universal biomarkers and low concentration in the early stages hinder its clinical application. In this study, nucleolin‐positive exosomes, which have been proven to have tumor screening value in previous work is selected, as the detection object, and used nucleolin aptamer‐functionalized Au@Pt nanozyme‐coated bacteria (ap _AS ‐E.coli‐Au@Pt) as signal amplifier, which enabled a simple and rapid colorimetric aptasensor. By leveraging the large surface area and microbial synthesis properties of bacteria, the in situ synthesized Au@Pt nanozyme demonstrated exceptional catalytic activity and remarkable stability, effectively enhancing the sensitivity and accuracy of this aptasensor. The analysis of serum exosomes using ap _AS ‐E.coli‐Au@Pt successfully monitored tumor progression and the treatment effects of photothermal therapy (PTT) and chemotherapy in a mouse model. Furthermore, this analysis effectively distinguished tumor patients at different stages from those with inflammation and healthy donors, where offered 100% accuracy for both positive and negative samples. These results underscore the potential of this aptasensor for early tumor screening through ultra‐sensitive detection of exosomes (LOD is 40 particles mL ⁻¹ ), as well as for monitoring tumor progression and treatment effects.