(355g) Next Generation Multi Modal Endoscopic Tattoo Inks for Precise Marking of Gastrointestinal (GI)-Lesions

Colorectal cancer (CRC) is the second leading cause of cancer related deaths in United States. In 2023, about 153,020 people will be diagnosed with (CRC) and 52,550 will die from the disease. As a result, early detection, and monitoring of suspicious lesions, including polyps, is critical to improving surgical outcomes and survival in patients. Colorectal lesions or polyps are marked using a tattoo ink to facilitate open abdominal or laparoscopic intervention to remove disease tissue or for long-term follow-up. However, the only currently available FDA-approved ink has significant drawbacks of which is loss of spatial retention, which is critical to the performance of the ink. Moreover, the ink suffers from fibrotic inflammation and peritonitis. Finally, a significant limitation is that these inks are not amenable to multimodal imaging, and therefore always require endoscopic intervention during longitudinal monitoring. There is a critical need for new tattoo inks that can improve surgical outcomes in colorectal endoscopy. Cationic chitosan derivative was used to encapsulate a library of anionic iron-oxide nanoparticles (IO based) and an anionic dual dye (indocyanine green (ICG) and rose bengal (RB)) (DD based) mixture to generate Tissue-Adhesive Tattoos generation-2 (TAT2) inks. These inks will stay with no diffusion to create a precise marking visualized under endoscopic white light (IO based and DD based) and laparoscopic near infrared light (NIR) (DD based).

The TAT2 inks were characterized using dynamic light scattering (DLS), transmission electronic microscopy (TEM), scanning electron microscopy (SEM), and viscosity to determine their size, morphology, shelf-life stability and injectability. The pro-inflammatory potential of both TAT2 library was assessed using the J774-DUAL mouse macrophage reporter cell line in vitro. IO based and DD based TAT2 candidates that demonstrated low inflammatory activity and high colloidal stability were evaluated ex vivo in porcine intestinal tissues and demonstrated excellent tight localization and similar contrast to Spot Ex (FDA approved), In addition, the NIR fluorescent potentials of DD based TAT2 were quantified using IVIS imaging of porcine colon tissue used for ex vivo. In vivo biocompatibility and performance of IO based TAT2 was evaluated by subcutaneous implantation in BALB/c mice, followed for 28-days replicated similar performance as observed in ex vivo and no adverse cell reactions. Endoscopic submucosal injection of four lead IO based inks were carried out in the colon of Yorkshire porcine and the efficacy and clinical toxicity were evaluated after 14-days. The in vivo performance of DD based TAT2 is under evaluation.

Both in vivo studies (mice and pigs) of lead IO based TAT2 candidates demonstrated superior spot localization performance while maintaining equivalent contrast to the commercial ink. Blood chemistry and histopathology of key organs of all the pigs used in the study indicated no toxicity of the TAT2 inks. The inks also demonstrated magnetic resonance contrast in post-mortem mice. All four novel inks outperformed the commercial inks when comparing spot localization with equivalent contrast performance in mice and pigs with variable tissue interactions.

We have developed an advanced set of next-generation endoscopic TAT2 inks that outperform existing options. These inks show improved precision in spot localization, exceptional contrast, minimal inflammatory effects, and the ability to be used for multimodal imaging. This innovative approach to clinical imaging holds promises for enhancing clinical outcomes in patients with gastrointestinal diseases.