In Situ Diagnosis and Therapy Monitoring of Radiation‐Induced Enteritis via Ratiometric NIR‐II Fluorescence Imaging

Abstract Radiation‐induced enteritis (RIE) remains a critical clinical challenge, demanding advanced strategies for diagnostic and therapeutic monitoring. Conventional assessment methods are often time‐consuming and primarily detect anatomic changes at moderate or late stages, limiting timely intervention. Here, DSNP@786s@EM, an innovative biomimetic nanoprobe based on NaYbF 4 :2%Er,2%Ce@NaYF 4 :30%Nd downshifting nanoparticles (DSNP) is presented for real‐time, in situ monitoring of RIE via ratiometric near‐infrared II (NIR‐II) fluorescence imaging. This system integrates downshifting core‐shell nanoparticles with strong NIR‐II emission under dual‐wavelength excitation (808 and 980 nm), and a reactive oxygen species (ROS)‐responsive IR786s dye, enabling absorption competition‐induced emission (ACIE)‐based dynamic ratiometric sensing. Additionally, the probiotic Escherichia coli Nissle 1917 (EcN) membrane (EM) camouflage of the nanoprobe enhances its intestinal retention and colon‐specific targeting, leading to superior diagnostic performance. Comprehensive in vitro and in vivo studies validate DSNP@786s@EM as a highly sensitive and reliable tool for real‐time, quantitative ROS monitoring in an RIE mouse model. Furthermore, ratiometric NIR‐II fluorescence imaging effectively tracks therapeutic responses to dexamethasone, demonstrating its potential for monitoring treatment efficacy. These findings highlight the translational value of DSNP@786s@EM in advancing RIE diagnosis and management, with broader applicability to oxidative stress‐related disorders and precision medicine.