B7H3-IRDye800CW

**B7H3-IRDye800CW** is a novel targeted fluorescent probe developed for intraoperative guidance during osteosarcoma surgery. This diagnostic agent combines an anti-B7H3 antibody (Omburtamab) with the near-infrared fluorescent dye IRDye800CW, creating a tool that can accurately label osteosarcoma areas after intravenous administration by targeting CD276 (B7-H3), which is highly expressed in osteosarcoma. The probe is synthesized by conjugating IRDye800CW NHS Ester with the antibody. Each antibody is conjugated with approximately 1.77 IRDye800CW molecules. The conjugate has an average diameter of 20 nm and exhibits a maximum emission wavelength at 810 nm with a long near-infrared II (NIR-II) emission tail extending to 1500 nm. Its primary application is to help surgeons identify and resect residual osteosarcoma lesions, including small satellite lesions (less than 2 mm) and lung metastatic lesions, which might be missed during conventional surgery. It can also be used for rapid pathological diagnosis of osteosarcoma specimens through in vitro incubation. The probe has shown good biocompatibility in preclinical studies with lower cytotoxicity than ICG, and its components (Omburtamab and IRDye800CW) have prior clinical safety data.