Endoscopic ultrasonography-guided poly (lactic acid-co-glycolic acid)-poly (ethylene glycol)-poly (lactic acid-co-glycolic acid) thermogel tunnel creation for natural orifice transluminal endoscopic surgery in porcine model

Background: Natural orifice transluminal endoscopic surgery (NOTES) is a minimal invasive treatment. However, tissue dissection under endoscopy is still challenging due to the flexibility of endoscopy body and there is still no effective method for establishing a tunnel towards the targeted area. We previously showed that a new kind of thermogel could be submucosallly injected and served as a cushion for endoscopic dissection. Thus, in this study we investigated the feasibility and safety of tunnel creation using poly (lactic acid-co-glycolic acid)-poly (ethylene glycol)-poly (lactic acid-co-glycolic acid) (PLGA-PEG-PLGA) thermogel for NOTES in a porcine model. Methods: We prepared an injectable thermogel composed of PLGA-PEG-PLGA triblock copolymers which exhibited a low-viscous sol at room temperature and spontaneously transformed into a no-flowing gel at body temperature. This thermogel was used in NOTES in pigs. The success rate and adverse events were observed. Results: The PLGA-PEG-PLGA thermogels were successfully injected to the targeted areas under the guide of endoscopic ultrasonography and the tunnels were created by sucking the gel during NOTES as the endoscopy went forwards in all the three animals. The necropsy of the pigs showed no evidence of iatrogenic injury. No serious bleeding and perforation was observed. The results demonstrated that thermogel injection and tunnel creation by suction during NOTES were feasible, which simplified the procedure of tissue dissection and developed a new method of identifying the targeted area for surgical interventions without causing severe tissue damage. Conclusion: The application of thermogel for tunnel creation in NOTES could optimize current procedures and may have a promising prospect in clinical application.