Abstract
Several inflammatory conditions of the bile ducts cause strictures that prevent the drainage of bile into the gastrointestinal tract. Non-pharmacological treatments to re-establish bile flow include plastic or self-expanding metal stents (SEMs) that are inserted in the bile ducts during endoscopic retrograde cholangiopancreatography (ERCP) procedures. The focus of this study was to 3D print an anatomically accurate model of the extrahepatic bile ducts (EHBDs) with tissue-like mechanical properties to improve in vitro testing of stent prototypes. Following generation of an EHBD model via computer aided design (CAD), we tested the ability of Formlabs SLA 3D printers to precisely print the model with polymers selected based on the desired mechanical properties. We found the printers were reliable in printing the dimensionally accurate EHBD model with candidate polymers. Next, we evaluated the mechanical properties of Formlabs Elastic (FE), Flexible (FF), and Durable (FD) resins pre- and post-exposure to water, saline, or bile acid solution at 37 °C for up to one week. FE possessed the most bile duct-like mechanical properties based on its elastic moduli, percent elongations at break, and changes in mass under all liquid exposure conditions. EHBD models printed in FE sustained no functional damage during biliary stent deployment or when tube connectors were inserted, and provided a high level of visualization of deployed stents. These results demonstrate that our 3D printed EHBD model facilitates more realistic pre-clinical in vitro testing of biliary stent prototypes.
Highlights
Bile is produced in the liver and drains through the bile ducts into the small intestine where it aids in digestion (Figure 1A)
Designs were generated with three different wall thicknesses to compensate for the variations
Designs were generated with three different wall thicknesses to compensate for the variations in in achievable printing resolution across the threeresins resinswe wetested
Summary
Bile is produced in the liver and drains through the bile ducts into the small intestine where it aids in digestion (Figure 1A). Cholestasis occurs when the bile ducts are inflamed or blocked, and bile is unable to drain out of the liver. Treatment for acute or chronic cholestasis includes insertion of plastic or self-expanding metal stents (SEMs) into the extrahepatic bile ducts (EHBD) to re-establish bile flow to the intestines (Figure 1B,C). Biomedical devices like biliary stents cannot be in vivo tested in small animal research models; these devices must be tested in porcine, ovine, or non-human primate models. Efficient and accurate in vitro testing of these devices during pre-clinical studies, in lieu of large animal testing, reduces the number of research animals that undergo procedures and/or are sacrificed to obtain the pre-clinical data required for submission to the FDA [4,5,6].
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