Comparison of the knitted silk vascular grafts coated with fibroin sponges prepared using glycerin, poly(ethylene glycol diglycidyl ether) and poly(ethylene glycol) as porogens

Abstract

Development of a small-diameter artificial vascular graft is urgent because existing materials often occlude within a short time. We have shown that small-diameter vascular graft using Bombyx mori silk fibroin is a potential candidate. Silk fibroin grafts are fabricated by coating silk fibroin on the knit tube prepared from silk fibroin fibers. However, there is a serious problem that the coated silk fibroin portion hardens when alcohol is used for insolubilization of the coated silk fibroin. This hardening prevents the desired biodegradation of the coated silk fibroin. In this study, we improved the silk fibroin coating method of the knit silk fibroin tube. Namely, the silk fibroin sponge coating was performed using glycerin, poly(ethylene glycol diglycidyl ether) or poly(ethylene glycol). In addition, silk fibroin grafts were prepared avoiding dryness during the coating process and were kept in the hydrated state until implantation into the abdominal aorta was complete. After implantation of the hydrated silk fibroin grafts, grafts were taken out at two weeks or three months, and histopathological examination was performed. The grafts coated with three types of silk fibroin sponges had a higher tissue infiltration rate than alcohol-treated grafts and were superior in the formation of smooth muscle cell and vascular endothelial cell remodeling. Biodegradations of the silk fibroin grafts prepared using the three types of silk fibroin sponge coatings and alcohol-treated silk fibroin grafts were also examined with protease XIV in vitro, and the grafts were observed by scanning electron microscopy before and 24 h after biodegradation. Faster biodegradations were observed for grafts coated with the three types of silk fibroin sponges. C solid-state nuclear magnetic resonance studies showed that the conformation of the silk fibroin sponge prepared using porogen was a random coil with high mobility in the hydrated state. We believe that small-diameter silk fibroin vascular grafts coated with quick biodegradable silk fibroin sponges can be developed based on these findings.

Silk fibroin vascular graft: a promising tissue-engineered scaffold material for abdominal venous system replacement

“…The inner diameter of the SF tube was 3 mm. To remove silk sericin, the knitted SF tube was degummed in a mixture of sodium carbonate (0.08% w/v) and Marseille soap (0.12% w/v) solution at 95 °C for 2 h, as previously reported 19,33 . To make the SF sponge, an aqueous solution of SF was prepared.…”

“…The longitudinal suture retention strength, circumferential tensile strength, and circumferential compressive elastic modulus of the SF grafts coated with SF sponges were determined using a tensile testing machine, table-top material tester (EZ Graph , Shimadzu Corp., Kyoto, Japan) according to the previously reported methods 18,19,33,34 . For the longitudinal suture retention test, a sample tube was cut to a length of 20 mm and then the suture was passed through 2 mm from the end., pulled by a clamp (3 mm/min.)…”

“…SF biomaterial has biologic advantages, such as better biocompatibility, high affinity for cells, and susceptibility to proteolytic degradation in vivo without antigenicity 16,17 . Recently, experimental artery replacement using double-raschel knitted SF vascular grafts coated with an SF sponge was reported in animal models 18,19 . Enomoto et al first reported rat aorta replacement using an SF graft with a 1-year patency rate of 85%.…”

Three-Layered Silk Fibroin Tubular Scaffold for the Repair and Regeneration of Small Caliber Blood Vessels: From Design to in vivo Pilot Tests

“…Building a 3D sponge-like layer on one or both sides of the tubular braided/knitted textile core may represent a step forward in approaching more complex scaffold architectures (Aytemiz et al, 2013; Liu et al, 2013, 2018; Ding et al, 2016; Zamani et al, 2017; Tanaka et al, 2018). The manufacturing techniques used by various authors, albeit with minor variations, share common steps: immersion of the tubular textile core in a mold, pouring a polymer solution, freeze-drying, and possible solvent consolidation of the just created layer.…”

“…Crosslinking agents can be added to modulate porosity, strength, elasticity, and degradation rate; functional molecules, most often anti-thrombogenic agents, can also be loaded into the sponge. In vivo implantation up to 1 year in dogs (Aytemiz et al, 2013) and rabbits (Liu et al, 2018), and up to 3 months in rats (Tanaka et al, 2018) resulted in high patency rate, absence of thrombus, aneurysm, or infection, and a physiological level of endothelialization of the internal lumen of the graft with no signs of intimal hyperplasia.…”