Designed and fabrication of triple-layered vascular scaffold with microchannels.

Currently, one of the best preparation strategies for the triple-layered vascular scaffold is to imitate the three-layer structure of natural blood vessels to achieve the biofunctional characteristics of vascular transplantation. Here, we developed a combinatorial method to fabricate triple-layered vascular scaffold (TVS) by using electrospinning and coaxial 3 D printing. First, Polycaprolactone-collagen (PCL-Col) was applied to prepared the inner layer of TVS by electrospinning. Second, egg white/sodium alginate (EW/SA) blend hydrogel was extruded to form hollow filaments by coaxial 3 D printing and crosslinking mechanism, which enwound around the surface of the inner layer in a circumferential direction as the intermediate layer of TVS. Finally, electrospun PCL-Col nanofibers were wrapped on the surface of hydrogel layer as the outer layer of TVS. The morphological characterization and mechanical strength of the fabricated TVS were measured. Compared with natural blood vessels, results shown that ultimate tensile stress (UTS), strain to failure (STF), the estimated burst strength and the suture retention strength (SRS) of TVS were superior. Also, the fabricated TVS exhibits good hydrophilicity and excellent flexibility. Moreover, the biocompatibility of TVS was investigated through human umbilical vein endothelial cells (HUVECs), the results demonstrated that cells can successfully attach the surface of graft and maintain high viability. In summary, all of results demonstrated that this method could fabricate a novel triple-layered vascular scaffold, possessing appropriate mechanical properties and good biological properties, which has the potential to be used in tissue engineered vascular grafts applications.

Treatment of type I endoleak after endovascular repair of infrarenal abdominal aortic aneurysm: success of fibrin glue sac embolization.

PURPOSE: To analyze a single-center experience of fibrin glue sac embolization to eliminate type I endoleaks after endovascular aneurysm repair (EVAR), assessing the feasibility and effectiveness of the technique in long-term follow-up. METHODS: A retrospective study was conducted involving 783 EVAR patients treated between August 2002 and February 2009. Under a standardized protocol, 42 (5.4%) patients (37 men; mean age 73 ± 8 years) underwent intraoperative transcatheter fibrin glue sac embolization to resolve type I endoleak persisting after initial intraoperative maneuvers to close the leak or in necks too short or angulated for cuff placement. Intrasac pressure was measured before and after glue injection. Computed tomographic angiography was performed to assess the outcome after 3, 6, and 12 months and annually thereafter. RESULTS: In this type I endoleak cohort, 16 (38.1%) patients had proximal necks <10 mm long, and 5 (11.9%) patients had proximal neck angulation >60°; 22 additional devices (8 stents, 14 cuffs) had been placed in the initial attempts to resolve the endoleaks. After fibrin glue injection, 41 (97.6%) of the 42 endoleaks were resolved using a mean 15 ± 10 mL of glue. Intrasac pressure decreased significantly in successfully treated cases. The patient who failed embolotherapy was converted to open surgery (2.4%); he died 2 months later from multiorgan failure. Two (4.8%) patients died in the perioperative period from myocardial infarction. One (2.4%) patient developed right lower extremity ischemia unrelated to the fibrin glue treatment. There were no allergic reactions. Over a median follow-up of 39.9 months (range 10-88), 3 (7.1%) patients died (1 aneurysm-related). Cumulative survival was 90.5% at 1 year, 87.0% at 3 years, and 82.6% at 5 years. The mean maximal aneurysm diameter fell from the baseline 59.5 ± 14.7 mm to 49.0 ± 11.6 mm (p<0.001). Of the 4 patients with increased aneurysm diameter during follow-up, 1 was converted, 2 are being observed due to advanced age, and 1 died of renal failure. No recurrent type I endoleak or glue-related complications were observed in follow-up. CONCLUSION: Fibrin glue sac embolization to eliminate type I endoleak after EVAR yielded excellent results in our experience, effectively and durably resolving the leaks. Balloon occlusion of the proximal aorta must be done during glue injection to block proximal flow and facilitate formation of a structured fibrin clot.

Fabrication of multilayer tubular scaffolds with aligned nanofibers to guide the growth of endothelial cells.

Aligned electrospun fibers used for the fabrication of tubular scaffolds possess the ability to regulate cellular alignment and relevant functional expression, with applications in tissue engineering. Despite significant progress in the fabrication of small-diameter vascular grafts (SDVGs) over the past decade, several challenges remain; one of the most problematic of these is the fabrication of aligned nanofibers for multilayer SDVGs. Furthermore, delamination between each layer is difficult to avoid during the fabrication of multilayer structures. This study introduces a new fabrication method for minute delamination four-layer tubular scaffolds (FLTSs) that consist of an interior layer with highly longitudinal aligned nanofibers, two middle layers composed of electrospun sloped and circumferentially aligned fibers, and an exterior layer comprising random fibers. These FLTSs are used to simulate the structures and functions of native blood vessels. Here, thermoplastic polyurethane (TPU)/polycaprolactone (PCL)/polyethylene glycol (PEG) were electrospun to fabricate FLTSs or tubular scaffolds with completely random fibers layer (RLTSs). The surface wettability of the TPU/PCL/PEG tubular scaffold was tested by water contact angle analysis. In particular, compared with RLTSs, FLTSs showed excellent mechanical properties, with higher circumferential and longitudinal tensile properties. Furthermore, the high viability of the human umbilical vein endothelial cells (HUVECs) on the FLTSs indicated the biocompatibility of the tubular scaffolds comparing to RLTSs. The aligned and random composite structure of the FLTSs are conducive to promoting the growth of HUVECs, and the cell adhesion and proliferation on these scaffolds was found to be superior to that on RLTSs. These results demonstrate that the fabricated FLTSs have the potential for application in vascular tissue regeneration and clinical arterial replacements.