Self-expandable hydrogel biliary stent design utilizing the swelling property of poly(vinyl alcohol) hydrogel

We have developed a novel self-expandable biliary stent comprising poly(vinyl alcohol) (PVA). The swelling ratio of the dried PVA hydrogels decreased from 6.7 to 2.6 as the saponification degree increased from 95 to 99.9, whereas the storage modulus and tear strength increased from 17 to 400 kPa and from 0.5 to 10 N mm(-1), respectively. The dimensional ratios of the inner- and outer-diameter and the length of the dried tube-shaped hydrogels (saponification degree of 98.5) prepared by simple air drying isotropically increased 1.4-1.5 times in physiological saline. Meanwhile, the dimensional ratios of the dried hydrogels prepared by drying under extension increased by twice, whereas the length decreased slightly, indicating anisotropic swelling. The radial force of the reswollen tube-shaped hydrogels (6.6 +/- 0.6 mN mm(-2)) was significantly higher than that of a conventional metallic stent (4.4 +/- 0.3 mN mm(-2)), suggesting that PVA hydrogels were applicable as self-expandable stents. (c) 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 137, 48851.