To explore the targeting of toluidine blue: low molecular dextran-40 to the lymphatic system and its effect assessment.

To investigate the targeting effect of toluidine blue-dextran-40 (TB-Dex-40) on the head and neck lymphatic system. Thirty healthy adult New Zealand white rabbits were randomly divided into two groups: the experimental group (TB-Dex-40 group, n = 15) and the control group (TB group, n = 15). In the experimental group, 1.0% TB-Dex-40 (0.14 mOsm/L) was submucosally injected at the lingual margin (1 cm from the tip of the tongue), while in the control group, 1.0% toluidine blue (32.60 mOsm/L) was administered under the same conditions. The time required for the dye to reach and stain the sentinel lymph node (SLN) was recorded, and the diffusion range of the dyes in the tongue was measured. SLN samples were collected at 30 min and 2 h post-injection for histopathological examination. SLN staining persistence was observed at 1 day, 2 days, and 4 weeks post-injection. Routine blood and biochemical tests were conducted before and 2 weeks after the experiment to evaluate systemic safety. Additionally, in two separate rabbits, the two dyes were injected into the common carotid artery to observe their effects on cervical lymph nodes, submandibular glands, and tongue tissue. A sucrose preference test was performed during animal rearing to assess potential neurotoxicity induced by the dyes. In the experimental group, it took (21.67 ± 0.19) seconds for the dye to reach the SLN and stain lymphatic vessels, which was significantly longer than that in the control group [(3.22 ± 0.34) seconds] (P < 0.01). The SLN stained in the experimental group remained clearly visible even after 4 weeks, whereas the SLN stained in the control group had completely faded by 2 days. The diffusion range of the dye in the tongue was significantly smaller in the experimental group [(10.53 ± 1.09) mm] compared with the control group [(20.04 ± 1.06) mm] (P < 0.01). No abnormalities were detected in the blood parameters of the experimental animals. Neither group exhibited neurological abnormalities. After injection via the common carotid artery, significant staining was observed in the lymph nodes of the TB group but not in the TB-Dex-40 group. TB-Dex-40 demonstrates superior targeting capabilities within the lymphatic system and holds substantial potential for clinical translation.Clinical relevance: TB-Dex-40 exhibits specificity for lymphatic vessels and serves as an effective tracer with significant clinical potential. Its molecular structure provides a robust theoretical foundation for the development of future imaging agents.