New Near-Infrared Dye Enables Prolonged Ureter Visualization During Surgery

Ureteral injury is a serious complication of abdominopelvic surgery that can lead to infection, renal impairment, and reoperation. However, consistent intraoperative identification of the ureters remains difficult because existing fluorescent agents may bind nonspecifically or clear through nonrenal routes. Surgeons need bright, kidney-excreted signals that remain visible throughout complex procedures. To help address this challenge, researchers have developed a super-inert near-infrared dye that keeps the ureters visible for hours while being eliminated unchanged by the kidneys.

A cross-disciplinary team at the University of Hong Kong in Shenzhen (HKU MILES-Shenzhen) created SID-788, a near-infrared (NIR) fluorescent dye designed for surgical navigation of the urinary tract. In a porcine model, SID-788 enabled clear ureter visualization for four to five hours using clinical NIR laparoscopes and robotic surgical systems. This imaging window aligns with the duration of most abdominopelvic procedures, suggesting potential utility for maintaining ureter visibility throughout complex surgeries.

SID-788 is a near-neutral cyanine dye threaded through an alpha-cyclodextrin ring in a rotaxane configuration. This design provides high aqueous solubility of approximately 29 mg/mL and “super-inertness,” with negligible binding to serum proteins, organs, and tissues. The dye remains chemically and photochemically stable under physiological conditions and is completely excreted by the kidneys in its original form within hours of administration.

Preclinical testing demonstrated high-performance ureter imaging in mice and pigs using wide-field NIR-II systems, as well as clinically approved NIR-I laparoscopes and robotic platforms. The approach addresses a long-standing need for urinary-tract-specific fluorescence that minimizes background signal during surgical navigation. Clear visualization is particularly important for avoiding injury and for managing ureteral stenosis or obstruction intraoperatively.

The work involved the University of Hong Kong–Shenzhen Hospital and Peking University First Hospital and was published in Nature Photonics on June 12, 2026. In mouse studies, SID-788 was well tolerated at doses up to 500 times the standard imaging dose of 0.5 mg/kg, supporting continued translation of the platform.

“Wrapping a molecule with a human-compatible cyclodextrin ring is exciting in the NIR dye field. The development of SID-788 serves as a compelling example of integrating fundamental innovation with translational research,” said Hongjie Dai, director of the Materials Institute of Life Sciences and Energy at the University of Hong Kong in Shenzhen.

“Through its novel molecular design, SID-788 possesses properties long pursued by the NIR fluorescent dye field, solving some of the long-standing problems in this field. More importantly, we have successfully accomplished gram-scale synthesis in our laboratory and are currently partnering with a CRO to advance toward kilogram-scale production for clinical translation,” added Dai.

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