Abstract
Recently, Bombyx mori silk fibroin (SF) has been shown to be a suitable material for vascular prostheses for small arteries. In this study, we developed a softer SF graft by coating water-dispersed biodegradable polyurethane (PU) based on polycaprolactone and an SF composite sponge on the knitted SF vascular graft. Three kinds of 13C solid-state nuclear magnetic resonance (NMR), namely carbon-13 (13C) cross-polarization/magic angle spinning (MAS), 13C dipolar decoupled MAS, and 13C refocused insensitive nuclei enhanced by polarization transfer (r-INEPT) NMR, were used to characterize the PU-SF coating sponge. Especially the 13C r-INEPT NMR spectrum of water-dispersed biodegradable PU showed that both main components of the non-crystalline domain of PU and amorphous domain of SF were highly mobile in the hydrated state. Then, the small-diameter SF artificial vascular grafts coated with this sponge were evaluated through implantation experiments with rats. The implanted PU-SF-coated SF grafts showed a high patency rate. It was confirmed that the inside of the SF grafts was covered with vascular endothelial cells 4 weeks after implantation. These results showed that the water-dispersed biodegradable PU-SF-coated SF graft created in this study could be a strong candidate for small-diameter artificial vascular graft.
Highlights
The annual incidence of deaths associated with cardiovascular diseases is predicted to reach 23.3 million worldwide by 2030 [1]
The important characteristic of small-diameter silk fibroin (SF) grafts with a high patency ratio is remodeling, which is never observed for commercially available poly(ethylene terephthalate) (PET) fiber or expanded polytetrafluoroethylene (ePTFE) grafts
The aqueous solution of the SF-PU-Glyc mixture was frozen at −20 ◦C overnight
Summary
The annual incidence of deaths associated with cardiovascular diseases is predicted to reach 23.3 million worldwide by 2030 [1]. The commercially available useful artificial vascular grafts are limited to diameters > 6 mm. The development of a small-diameter artificial vascular graft with high patency has been desired. Bombyx mori silk fiber is a natural protein fiber produced by silkworms It has a long history of use as an excellent textile material [10]. The patency of a 1.5 mm-diameter SF fiber graft coated with SF was significantly higher than that of an expanded polytetrafluoroethylene (ePTFE) graft used as control (85.1% vs 30%, p < 0.01) at 1 year after implantation in rat abdominal aorta. The important characteristic of small-diameter SF grafts with a high patency ratio is remodeling, which is never observed for commercially available poly(ethylene terephthalate) (PET) fiber or ePTFE grafts. The tube of SF fiber grafts coated with SF tends to be rigid; better transplant results by the improvement of thrombus formation and/or compliance mismatch [19,20,21] are expected by using softer SF grafts
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