Mechanical properties and degradation process of biliary self‐expandable biodegradable stents

Abstract

Objectives:The clinical outcomes and prevalence of adverse events associated with biliary biodegradable stents (BS) can differ according to degradation process and time. The aim of this study was to observe the degradation process and time of different BS prototypes, and to evaluate sequential changes in their mechanical properties.Methods: Using an in vitro bile flow phantom model, we compared degradation time, radial force changes, and morphologic changes among four different BS prototypes: polydioxanone (PDO) BS, polyglycolide (PGA) BS, polydioxanone/ poly-L-lactic acid (PDO/PLLA) sheath-core BS, and polydioxaone/magnesium (PDO/Mg) sheath-core BS. Using an in vivo swine bile duct dilation model, we performed a direct peroral cholangioscopy (DPOC) examination to observe the biodegradation process and related adverse events at regular intervals. Results:In the bile flow phantom model, the PGA BS and PDO/ Mg BS prototypes showed rapid radial force reduction and morphological changes and complete degradation within six weeks. PDO/PLLA BS maintained high radial force and kept their original shape for longer than the PDO BS, up to 16 weeks. A total of 24 BS were inserted into the dilated bile ducts of 12 swine. In this animal model, DPOC examination revealed that PDO BS and PDO/PLLA BS maintained their original shapes for approximately 12 weeks, but PDO BS showed a greater degree of fragmentation and induced biliary stones and bile duct obstruction. Conclusion:Our results showed that PDO/PLLA BS maintained their original shape and radial force for a relatively long time and minimized adverse events.

Raman Spectroscopy as a Novel Method for the Characterization of Polydioxanone Medical Stents Biodegradation

“…Such stents have been inserted, e.g., into the esophagus [14,15], intestine [16], bronchus [17], trachea [18] or bile duct [19]. PPDX stents have been widely studied in in vivo medical trials [14,16,[19][20][21][22], their mechanical properties have been investigated [23][24][25][26], and their degradation has also been studied to some extent from a physicochemical point of view [25,27]. Stents made of similar materials have also been analyzed in studies [28] (poly(L-lactic acid) endovascular stent) and [29] (intracoronary stent coated with poly(Llactic acid)).…”

Preventive Effect of Biodegradable Stents On Biliary Stricture And Fibrosis After Biliary Anastomosis In A Porcine Model

“…23,24 In addition, if a stent fracture occurs during the indwelling period and is not degraded quickly, fracture-related adverse events will occur. 22 To solve these technical problems, we used a sheath-core technique in which different biodegradable materials were inserted into the center of biodegradable wires (Fig. 1 & Supplementary Fig.…”

“…1) and reported the results of a previous experimental study. 22 Using this novel method, Mg with high elasticity and short degradation time was inserted into the center of an outer PDO polymer. Because the degradation times of the two materials differed, it was possible to control the phenomena caused by biodegradation.…”

“…The PDO/Mg sheath-core mono lament was fabricated using a previously reported technique. 22 PDO as an outer sheath was coated onto a magnesium wire by a melt-coating method. The thickness of the PDO polymer coated onto the magnesium wire was controlled by adjusting the melting ow of the extruder and metering pumps.…”

“…Our previous study reported that the maintenance duration of BS can be adjusted by using different types of wires and sheath-core techniques. 22 In one of our BS prototypes with a polydioxanone/magnesium (PDO/Mg) sheath-core BS, morphological changes occurred at six weeks, and the BS were totally degraded at eight weeks. Therefore, we thought that if the overall thickness of the BS was made as thin as possible, it could be used to prevent biliary stricture and brosis after DD biliary anastomosis.…”