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

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 NaYbF₄:2%Er,2%Ce@NaYF₄:30%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.