Freeze-casting porous chitosan ureteral stents for improved drainage

Abstract

As a new strategy for improved urinary drainage in parallel to the potential for additional functions such as drug release and self-removal, highly porous chitosan stents are manufactured by radial, bi-directional freeze-casting. Inserting the porous stent in a silicone tube to emulate its placement in the ureter shows that it is shape conforming and remains safely positioned in place, also during flow tests, including those performed in a peristaltic pump. Cyclic compression tests on fullyhydrated porous stents reveal high stent resilience and close to full elastic recovery upon unloading. The drainage performance of the chitosan stent is evaluated, using effective viscosity in addition to volumetric flow and flux; the porous stent's performance is compared to that of the straight portion of a commercial 8 Fr double-J stent which possesses, in its otherwise solid tube wall, regularly spaced holes along its length. Both the porous and the 8 Fr stent show higher effective viscosities when tested in the silicone tube. The performance of the porous stent improves considerably more (47.5%) than that of the 8 Fr stent (30.6%) upon removal from the tube, illustrating the effectiveness of the radially aligned porosity for drainage. We conclude that the newly-developed porous chitosan ureteral stent merits further in vitro and in vivo assessment of its promise as an alternative and complement to currently available medical devices.

Freeze Casting: From Low‐Dimensional Building Blocks to Aligned Porous Structures—A Review of Novel Materials, Methods, and Applications

“…The application of unidirectional freezing, bidirectional freezing, [ 12a,14 ] radial freezing, [ 15 ] radial‐concentric freezing, [ 16 ] freezing under flow, [ 17 ] dynamic freezing, [ 18 ] random freezing, [ 19 ] or freeze−thawing [ 20 ] have been explored as means toward the control of porosity and microstructure for functional freeze cast scaffolds. In the case of conventional unidirectional freezing, the suspension starts freezing under a single temperature gradient, causing the nucleation of ice to occur randomly on the cold finger surface ( Figure A).…”

“…Over the past decade, freeze‐cast scaffolds based on biomacromolecules have been made using cellulose, [ 9b,90,96 ] chitosan, [ 14,91,97 ] pullulan, [ 98 ] chitin, [ 99 ] collagen, [ 100 ] konjac glucomannan, [ 43a ] amyloid fibril, [ 101 ] and silk fibroin [ 15a,30b,102 ] as building blocks, often including subsequent hybridizations [ 103 ] and their derived carbonaceous products. [ 43a,104 ] In freeze‐casting processes, cellulose represents the most widely studied macromolecular building block.…”

“…Because of these properties, chitosan freeze casting has been predominantly studied as a fabrication route for biomaterials such as bone supports and stents with further studies towards mechanical applications in foam form. [ 14,97c ]…”

“…[ 15a ] A notable example in recent years in the freeze casting of chitosan for the fabrication of stents and drug delivery devices. [ 14 ]…”

Redesigned Silk: A New Macroporous Biomaterial Platform for Antimicrobial Dermal Patches with Unique Exudate Wicking Ability

“…Devising new ways to shape biomaterials into controlled macroporous constructs, whose design principles rely often in reproducing the structural building block and composition found in natural materials, holds promise in dictating their functionalities in applications as diverse as drug delivery carriers, biomimetic membranes, and implants [2] . In this context, ice-templating (also known as freeze-casting) has evolved from a ceramics-oriented process devoted to the fabrication of lightweight materials to one of the most promising routes to fabricate aligned macroporous biomaterials from biopolymers [3][4][5][6] . The technique is based on a uniaxial thermal gradient that promotes the segregation of solutes and/or suspended particles induced by a growing ice front.…”