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

Abstract

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 outerdiameter 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 AE 0.6 mN mm −2 ) was significantly higher than that of a conventional metallic stent (4.4 AE 0.3 mN mm −2 ), suggesting that PVA hydrogels were applicable as self-expandable stents.

Fabrication of tough, anisotropic, chemical-crosslinker-free poly(vinyl alcohol) nanofibrous cryogels via electrospinning

“…For instance, nanobers with conduit shapes can be potentially utilized as base polymers of biliary stents because of its anisotropic structure, which would lead to anisotropic swelling and mechanical properties. 21 Hollow bers also can be fabricated in conjunction with the core-shell nanober fabrication method, 44,45 which is applicable for use in uid removal or membrane plasmapheresis. Furthermore, PVA hydrogels with antibacterial property can be fabricated while maintaining the suppressed release of antibacterial reagents; 23 these hydrogels may be used in gauze and surgical suture.…”

“…[14][15][16] Furthermore, anisotropic hydrogels are also desirable for medical devices, e.g., wound dressing, 17 vascular applications, 18,19 self-inating tissue expanders, 20 and self-expandable biliary stents. 21 However, the hydrogels fabricated usually have isotropic structures, which would negatively impact their applicability to these devices. Therefore, a fabrication method for constructing anisotropic hydrogels with excellent biocompatibility is highly required.…”

“…Poly(vinyl alcohol) (PVA), due to its biocompatibility, has numerous biomedical applications, including wound dressing, 22,23 contact lenses, 24 and implants for various tissues and organs such as cartilage, 25 vascular access, 26 stent for biliary drainage, 21 ligament, 27 and tissue engineering applications. 28 The fabrication of PVA hydrogels with anisotropic structures using electrospinning has been investigated due to its small ber diameter, high surface-to-volume ratio, and controllable porous structure and shape.…”

Characterization and preliminaryin vivoevaluation of a self-expandable hydrogel stent with anisotropic swelling behavior and endoscopic deliverability for use in biliary drainage

“…Tube-shaped hydrogel specimens were dried at 60 1C in an oven to various extension ratios, as described in our previous report. 25 Both ends of the hydrogels were penetrated with silk strings. The hydrogels were placed vertically in a drying chamber (600 mm  500 mm  500 mm) at 60 1C under tension: one end of the hydrogel was anchored to the ceiling of the chamber with the silk string and the other end was attached to weights to achieve length extension ratios of 1.5, 2.0, and 2.5.…”

“…We previously designed a novel self-expandable stent composed of poly(vinyl alcohol) (PVA) hydrogel, exploiting the swelling property of PVA hydrogel as a self-expanding property. 25 PVA is being investigated as a self-expandable material because it has excellent mechanical properties and long-term dimensional stability and can be easily prepared through simple physical crosslinking. [26][27][28] Furthermore, PVA is eligible for use as an implant material and has already been used in numerous biomedical applications, 29,30 including wound dressings, 31,32 contact lenses, 33 and implants for various tissues and organs, such as cartilage, 34 vascular access, 35 ligaments, 36 and bone tissue engineering applications.…”