Innovative submucosal injection solution for endoscopic resection with phosphorylated pullulan: a preclinical study

Background and Aims The submucosal injection solution is used to assist in endoscopic surgery. The high viscosity of current solutions makes it difficult to inject. In the present study, we developed an extremely low-viscosity, easy-to-use submucosal injection solution using phosphorylated pullulan (PPL). Methods The PPL solutions were prepared at different concentrations, and their viscosity was measured. The mucosal elevation capacity was evaluated using excised porcine stomachs. Controls included 0.4% sodium hyaluronate (SH), 0.6% sodium alginate (SA), and saline. To evaluate the practicality, the catheter injectability of 0.7% PPL was measured, and endoscopic mucosal resection (EMR) and endoscopic submucosal dissection (ESD) were performed using the stomach and colorectum of live pigs. As controls, 0.4% SH and saline were used. Results The PPL solutions were of extremely low viscosity compared to those of 0.4% SH and 0.6% SA. Nevertheless, the mucosal elevation capacity of PPL solutions for up to 0.7% concentration was similar to that of 0.4% SH, and 0.7% PPL was less resistant to catheter infusion than 0.4% SH and 0.6% SA. In live pig experiments with EMR and ESD, snaring after submucosal injection of 0.7 % PPL was easier than with 0.4% SH, and ESD with 0.7% PPL produced less bubble formation than with 0.4% SH, and the procedure time tended to be shorter with 0.7% PPL than with 0.4% SH because of the shorter injection time. Conclusions The PPL solution is an innovative and easy-to-use submucosal injection solution.