“…[1][2][3][4] During various kinds of BRS, braided stents and laser-cutting stents have been investigated by extensive researches. 2 For the braided stents, the radial strength and flexibility are always considered to be the two dominant indexes 5 for evaluation which are mainly determined by the braiding parameters 6,7 and also affected by the mechanical properties of the weaving monofilament. 8 For the braided stents, the process of shaping the stent by annealing can also affect the mechanical properties of stents.…”
Mechanical properties of poly(L-lactic acid) (PLLA) braided stents are closely related to the performance of the weaving monofilaments. In this study, the PLLA monofilaments were prepared via solid-state drawing (SSD) method and annealed with different constraint methods. Experimental results show that mechanical properties of fabricated monofilaments have been greatly improved by SSD method. With the constrained annealing method, mechanical properties can be further improved while negative effect is shown with unconstrained annealing method. The physicochemical properties of PLLA monofilaments were further characterized, and it is found that the draw ratio of SSD and annealing method can affect the crystallinity and crystallite size, which can directly influence the mechanical properties of the monofilaments.This work tells that it is necessary to consider collectively the effects of SSD method and annealing method of the monofilaments in order to obtain optimized mechanical properties of the braided stents.
“…[1][2][3][4] During various kinds of BRS, braided stents and laser-cutting stents have been investigated by extensive researches. 2 For the braided stents, the radial strength and flexibility are always considered to be the two dominant indexes 5 for evaluation which are mainly determined by the braiding parameters 6,7 and also affected by the mechanical properties of the weaving monofilament. 8 For the braided stents, the process of shaping the stent by annealing can also affect the mechanical properties of stents.…”
Mechanical properties of poly(L-lactic acid) (PLLA) braided stents are closely related to the performance of the weaving monofilaments. In this study, the PLLA monofilaments were prepared via solid-state drawing (SSD) method and annealed with different constraint methods. Experimental results show that mechanical properties of fabricated monofilaments have been greatly improved by SSD method. With the constrained annealing method, mechanical properties can be further improved while negative effect is shown with unconstrained annealing method. The physicochemical properties of PLLA monofilaments were further characterized, and it is found that the draw ratio of SSD and annealing method can affect the crystallinity and crystallite size, which can directly influence the mechanical properties of the monofilaments.This work tells that it is necessary to consider collectively the effects of SSD method and annealing method of the monofilaments in order to obtain optimized mechanical properties of the braided stents.
“…When compressed to 50% of the initial height (outer diameter), the stress of the RHVG reached 152.88 kPa, which was 9.5 times that of the HVG, indicating that the braided stent played a critical role in improving the radial support. 45 Figure 10.(a) Compressive strain–stress curves of the braided stent, the hydrogel vascular graft (HVG) and the reinforced hydrogel vascular graft (RHVG). (b) Compressive elastic recovery rates of the braided stent, the HVG and the RHVG (* P < 0.05).…”
Section: Resultsmentioning
confidence: 99%
“…When compressed to 50% of the initial height (outer diameter), the stress of the RHVG reached 152.88 kPa, which was 9.5 times that of the HVG, indicating that the braided stent played a critical role in improving the radial support. 45 The compression elastic recovery rates of the braided stent, the HVG and the RHVG are shown in Figure 10(b). All three samples showed high elastic recovery rates.…”
A PVA/PAAm (polyvinyl alcohol/polyacrylamide) hydrogel vascular graft reinforced by a braided fiber stent was prepared in the present work, and a series of characterizations were carried out for evaluating the comprehensive performance of the reinforced hydrogel vascular graft (RHVG), including the morphology, the mechanical properties and the biocompatibility. The results show that hydrogel with a mass ratio of 5:8 (PVA:PAAm) is the best candidate for developing an implantation-oriented vascular graft, whose overall performance is the closest to the requirements of clinical applications. The surface of the PVA/PAAm hydrogel is smooth, and the porous structure is uniform and stable. When the longitudinal strain of the RHVG was 50%, the tensile strength reached 905.6 ± 63.1 kPa, much higher than that of a swine common carotid artery (185 kPa). Moreover, the circumferential tensile strength was significantly enhanced by the integration of the stent, and the circumferential compression recovery reached 93.4 ± 6.7%, showing satisfactory structural stability. Furthermore, the suture retention force approached (9.89 ± 0.64 N), higher than that of a canine femoral artery (7.90 ± 0.36 N). More importantly, the radial dynamic compliance reached 3.11 ± 0.09% under testing pressure of 80–120 mmHg, which is 6.9 times that of a commercial expanded polytetrafluoroethylene vascular graft. Lastly, the RHVG has satisfying cytocompatibility and a low hemolysis rate. In summary, the present work may pave the way for developing a novel small-diameter vascular graft for clinical implantation.
“…Peripheral vascular stenosis and digestive tract obstruction are common clinical diseases. Over the years, braided stents with self‐expanding property have shown great potential in treating these diseases due to good elasticity 1–4 . Recently, biodegradable braided stents (BBS) have been proved to have unique advantages over traditional metallic braided stents (MBS).…”
In this paper, the effects of annealing temperature on both radial supporting performance and axial flexibility of poly(L‐lactic acid) (PLLA) braided stents are studied. Stents are annealed at a series of temperatures ranging from 80 to 160°C for 1 h, then indicators of shaping effect, radial supporting performance, and axial flexibility are compared. Stents not annealed and annealed at 80°C cannot be completely shaped. In contrast, stents annealed at 100 to 160°C are well shaped showing radial shrinkage rate of 1.0 ± 0.2% and almost no axial elongation. The radial compressive force and axial force are gradually increased by 51.2% and 89.2%, respectively with the annealing temperature gradually increasing from 80 to 160°C, indicating that the radial supporting performance is improved but axial flexibility is weakened by a higher annealing temperature. Taken together, PLLA braided stents can be annealed at 100 to 120°C to obtain sufficient radial force and lower axial force simultaneously for clinical applications. Moreover, tensile test, X‐ray diffraction, and differential scanning calorimetry are performed for monofilaments annealed at different temperatures to further explore the effect mechanism of annealing temperature on the mechanical properties of stents. This study may provide helpful suggestions for the manufacture of biodegradable braided stents.
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