Ex vivo Burst Pressure Assay for Hydrogel Sealants

Further, to study the sealing effect of hydrogels, an ex vivo burst pressure experiment [46 ] was conducted. The experimental set up was assembled by referring to a previously published [47 (link)] method with few modifications. A piece of esophageal mucosa of diameter 5 cm was cut out from pig esophagus obtained from Tokyo Shibaura Organ Co., Ltd., then placed tightly over the custom-made sealing device (Figure 2). The device was assembled such that a circular gap of diameter 2 cm exposed the mucosal tissue. A 2 mm diameter incision was made on top of the tissue using a biopsy punch. A total of 1 ml each of 1% w/v CGG-BA at pH 5, 7.4, and 10 were placed in the gap over the mucosa, covering the incision. Fibrin glue was also tested as a control material. The thickness of the hydrogels applied was roughly 4 mm. All the samples were incubated at 37°C for 30 min before measurement. The resistive pressure that the hydrogel can withstand when phosphate-buffered saline (PBS) was ejected at a flow rate of 10 ml min⁻¹. The flow was controlled by a syringe connected to a syringe pump (ELCM2WF 10K-AP, Oriental Motor, Tokyo, Japan) [48 ]. The pressure drop resisted by the hydrogel over the tissue was measured using a pressure gauge (AP-12s, Keyence Corporation, Osaka, Japan). The pressure-drop corresponding to the failure of the gel was noted as the burst pressure.
Figure 2.

(a) Schematic of the burst pressure measurement, (b) Image of the experimental setup.