Development of Sodium Polyacrylate-Based High-Performance Submucosal Injection Material with Pseudoplastic Fluid Characteristics

The development of high-performance submucosal injection materials (SIMs) has significantly contributed to the advancement of rapid and safe endoscopic submucosal dissection (ESD). A previous study authored by us described that pseudoplastic fluid was more suitable for high-performance SIMs than Newtonian fluid. Herein, a novel high-performance SIM is developed, which is primarily composed of sodium polyacrylate (SPA) and exhibits pseudoplastic fluid characteristics. As a representative of current high-performance SIMs with Newtonian fluid characteristics, 0.4% sodium hyaluronate (HA) was selected as the target for comparison. Further, viscoelasticity, submucosal elevation height (SEH), and injection pressure (IP) of HA and SPA were evaluated. The results obtained by ESD were compared using HA or SPA in an ex vivo model. According to the measured viscoelasticity, the concentration of SPA was adjusted to 0.07%; this was aimed at obtaining the IP of SPA, which is equal to that of 0.4% HA. Moreover, no significant difference was observed between the IP values (31.6 ± 1.7 vs 31.4 ± 3.1 psi). SEHs of 0.07% SPA were higher than those of 0.4% HA at all postinjection times (P < 0.001). The duration of the ESD procedure using 0.07% SPA was significantly shorter than that obtained using 0.4% HA (16.6 ± 3.7 vs 22.2 ± 2.9 min, P = 0.0276); further, the total volume of the injected 0.07% SPA was significantly less than that of 0.4% HA (9.0 ± 3.1 vs 15.7 ± 3.9 mL, P = 0.0165). Based on rheological analysis, a high-performance SIM (0.07% SPA) with pseudoplastic fluid characteristics was theoretically developed. It was observed that the SIM performance of 0.07% SPA was higher than that of 0.4% HA.