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. 2021 Jun;9(6):E918-E924.
doi: 10.1055/a-1396-4236. Epub 2021 May 27.

Development of a gel dedicated to gel immersion endoscopy

Tomonori Yano  1 , Atsushi Ohata  2 , Yuji Hiraki  2 , Makoto Tanaka  2 , Satoshi Shinozaki  1 , Alan Kawarai Lefor  3 , Hironori Yamamoto  1
Affiliations

Development of a gel dedicated to gel immersion endoscopy

Tomonori Yano et al. Endosc Int Open. 2021 Jun.

Abstract

Backgrounds and study aims Gel immersion endoscopy is a novel technique to secure the visual field during endoscopy. The aim of this study was to develop a dedicated gel for this technique. Methods To identify appropriate viscoelasticity and electrical conductivity, various gels were examined. Based on these results, the dedicated gel "OPF-203" was developed. Efficacy and safety of OPF-203 were evaluated in a porcine model. Results In vitro experiments showed that a viscosity of 230 to 1900 mPa·s, loss tangent (tanδ) ≤ 0.6, and hardness of 240 to 540 N/cm 2 were suitable. Ex vivo experiments showed electrical conductivity ≤ 220 μS/cm is appropriate. In vivo experiments using gastrointestinal bleeding showed that OPF-203 provided clear visualization compared to water. After electrocoagulation of gastric mucosa in OPF-203, severe coagulative necrosis was not observed in the muscularis but limited to the mucosa. Conclusions OPF-203 is useful for gel immersion endoscopy.

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Conflict of interest statement

Competing interests Drs. Yano and Ohata hold patents for and are the inventors of the dedicated gel for this method.

Figures

Fig. 1
Fig. 1
a Dean-Stark trap, filled with 1 % Evans Blue. b Injection of pilot gel with optimal viscoelasticity creates a transparent space. c When injecting pilot gel with unsuitable viscoelasticity, it mixes with the pigment immediately.
Fig. 2
Fig. 2
Results of the in vitro experiment for identification of appropriate viscoelasticity. Loss tangent (tanδ) is defined as the ratio between the loss modulus (G’’) and the storage modulus (G’).
Fig. 3
Fig. 3
Results of the ex vivo experiment. In air, distilled water and pilot gel (224 μS/cm or less), the electrocoagulation was effective. In the saline or OS-1 jelly, electrocoagulation was not effective.
Fig. 4
Fig. 4
In vivo experiment in the porcine model of gastrointestinal bleeding. a It was impossible to identify the bleeding point by using the water immersion technique. b The OPF-203 enables clear visualization of the bleeding point.
Fig. 5
Fig. 5
Resected specimen of the stomach in a porcine model to assess electrocoagulation. Effective electrocoagulation by using monopolar hemostatic forceps was observed a in the air and b OPF-203, c not observed in the saline.
Fig. 6
Fig. 6
Histopathological findings of the resected specimen after electrocoagulation. Sufficient coagulative necrosis is observed in both the air and OPF-203 groups up to the submucosal tissue. No coagulative necrosis of the muscularis is observed in all groups (hematoxylin and eosin, × 200).
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