Photostable NIR Dye Sustains Intraoperative Imaging in Cancer Surgery

Photobleaching of current dyes forces surgeons to work with diminishing contrast over time. Stable intraoperative imaging is essential for identifying critical structures and margins. To help address this challenge, researchers have developed a more photostable NIR dye designed to sustain fluorescence during extended procedures.

Scientists at the Korea Research Institute of Chemical Technology (KRICT), working with the Georgia Institute of Technology, created KR-NIR-P, a polymerized version of indocyanine green (ICG). NIR light penetrates tissue more effectively than visible light, and ICG is the only U.S. Food and Drug Administration (FDA)-approved NIR dye, in clinical use since 1959 for applications such as sentinel lymph node mapping, liver surgery, and biliary tract visualization. With more than 750,000 laparoscopic cholecystectomies performed annually in the United States, dye reliability directly affects surgical visualization.

KR-NIR-P is engineered by chemically linking ICG molecules into a polymer backbone. This architecture partially shields the heptamethine chromophore from molecular oxygen generated during laser irradiation, which is a key driver of photobleaching. Hydrophobic interactions within the polymer stabilize the chromophore and reduce uncontrolled aggregation, allowing fluorescence to persist under continuous illumination.

In bench testing with a 785-nanometer NIR laser, conventional ICG fluorescence dropped to about 40% of its initial intensity within 50 seconds. KR-NIR-P retained approximately 66% of its initial fluorescence even after 200 seconds, reflecting more than a fourfold improvement in photostability under the stated conditions. The polymer also showed excellent biocompatibility, with cell viability exceeding 90% at concentrations up to 20 micromolar in both cancer and normal cells, and apoptosis-related biomarkers comparable to conventional ICG.

Functional validation extended to three-dimensional tumor spheroids, where KR-NIR-P penetrated uniformly into deeper regions. In mouse studies, fluorescence appeared in the sentinel lymph node two hours after footpad injection and intensified at 24 hours, indicating potential utility for real-time lymphatic imaging and surgical oncology. The team plans comprehensive preclinical evaluations, including toxicity and pharmacokinetic studies, to further define safety and performance.

The work was published in Small in 2026 under the title “Indocyanine Green–Inspired Polymeric Chromophores With Intrinsic Photostability for Near-Infrared Imaging”.

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