A redox-responsive NIR fluorescent nanoprobe for tumor microenvironment-activated surgical navigation with submillimeter precision†

Surgical precision in tumor resection critically relies on real-time intraoperative imaging, yet conventional probes face limitations in specificity and spatiotemporal control. Here, we present a tumor microenvironment (TME)-activated near-infrared (NIR) fluorescent nanoprobe (DNS–DYE/PEG–NI) that integrates dual responsiveness to hypoxia and glutathione (GSH) for submillimeter-level surgical navigation. The system comprises a GSH-activatable NIR fluorophore (λ_ex/em = 679/730 nm) quenched by 2,4-dinitrobenzenesulfonyl (DNS) moieties and hypoxia-sensitive amphiphilic PEG–NI micelles. Upon tumor accumulation via the enhanced permeability and retention (EPR) effect, a hypoxic TME triggers micelle disassembly through nitroimidazole (NI) reduction, releasing DNS–DYE. Subsequent GSH cleavage restores fluorescence via intramolecular charge transfer (ICT) recovery, achieving a 12.3-fold tumor-to-normal tissue signal ratio and >90% reduction in off-target activation compared to non-responsive controls. Systematic validation demonstrates: (1) dose-dependent fluorescence recovery (35-fold intensity increase at 10 mM GSH); (2) hypoxia-driven micelle destabilization (800% hydrodynamic diameter expansion); (3) sustained colloidal stability (12.9% size variation over 15 days); and (4) low cytotoxicity (cell viability >90% at 125 μg mL⁻¹). In vivo studies reveal precise tumor delineation within 12 h post-injection, enabling real-time resection of submillimeter lesions. By coupling TME-specific activation with prolonged tumor retention, this dual-responsive nanoprobe advances fluorescence-guided surgery toward precision oncology, reducing positive margin rates from 70% to <5% in preclinical models.