Polylactic acid self-expanding aortic stent with programmable structure

Abstract

The invention discloses a structure-programmable polylactic acid self-expanding aortic stent, which is characterized in that an integrated programmable structure design is carried out on a stent skeleton by utilizing a hyperelastic material, and the structure-programmable polylactic acid self-expanding aortic stent comprises an elastic constraint support area, a non-constraint area and a full-elastic constraint area which are sequentially arranged from a near end to a far end; the hyperelastic body and the stent skeleton material are both biodegradable polymer materials; the stent skeleton is formed by weaving high-performance monofilaments, the elastic constraint supporting area of the stent is located in the ascending aorta, the non-constraint area of the stent is located in the aortic arch, and the full-elastic constraint area of the stent is located in the descending aorta. Sufficient radial support can be effectively provided for the damaged area of the aortic dissection, it is ensured that good lumen compliance and sufficient blood supply are achieved in the aortic arch area, and meanwhile good wall attaching capacity can be kept in the descending aorta so as to prevent the aortic dissection from shifting. After the blood vessel is repaired, the stent is gradually degraded, so that a series of complications caused by implantation are eliminated, and treatment conditions are improved for patients.

Description

Technical Field

[0001] The invention belongs to the technical field of medical devices, and in particular relates to a structure-programmable polylactic acid self-expanding aortic stent. Background Art

[0002] Aortic dissection disease refers to the separation of the intima and the media due to damage to the aortic wall, allowing blood to flow between the two, thus forming a new false lumen. This process causes the media of the aortic wall to separate from the still intact adventitia. Among them, acute type A aortic dissection has the highest mortality rate among all types of aortic dissection. Acute type A aortic dissection refers to the dissection that starts from the aortic root and invades the ascending aorta or the aortic arch and even the descending aorta at the same time. This is a disease involving the separation of the intima of the aortic wall, causing blood to flow into the media in the blood vessel wall, forming a false channel between the inner and outer layers of the media. The disease does not respond well to drug treatment, and the only effective method currently is surgical treatment.

[0003] The key to surgical treatment is to target the rupture in the ascending aorta. When plugging the rupture, an intraluminal stent system that conforms to the physiological characteristics of the aorta must be used. The main difficulty lies in the selection of the distal and proximal anchoring areas, and the stent must have sufficient support and lumen flexibility in the short term. The aortic stents currently used are generally made of metal alloys, including mesh stents and metal mesh stents with polyester film coating. This type of metal stent is usually made of medical stainless steel or nickel-titanium alloy materials, which can effectively support the dissection and fix the position in the short term. Three months after the operation, vascular endothelial cells will grow into the stent and gradually cover it, so that the vascular function is basically restored. However, since these metal stents are non-degradable, they will exist in the blood vessels for a long time, which may lead to complications such as restenosis and allergic reactions, requiring patients to take medication for a long time to reduce rejection reactions in the body.

[0004] Therefore, there is an urgent need to develop a biodegradable type A aortic stent to overcome the above-mentioned defects. Summary of the invention

[0005] To solve the above problems, the present invention discloses a structurally programmable polylactic acid self-expanding aortic stent. Through the programmable integrated structural design, it can not only effectively support the rupture of the dissection in the ascending aorta, but also adapt to the curvature of the lumen in the aortic arch and play a fixing role in the descending aorta, thereby enhancing the long-term lumen plasticity effect. After the vascular function is restored, the stent will gradually degrade and eventually disappear completely, thereby eliminating the hidden dangers caused by the long-term existence of the stent.

[0006] To achieve the above object, the technical solution of the present invention is as follows: A structurally programmable polylactic acid self-expanding aortic stent is used to design an integrated programmable structure of the stent skeleton using a superelastic material, including: an elastically constrained support area, a non-constrained area and a fully elastically constrained area are arranged in sequence from the proximal end to the distal end; the stent skeleton is a self-expanding stent woven from high-performance medical polylactic acid monofilaments; wherein the elastically constrained support area is a region where local monofilament intersections are elastically constrained; the non-constrained area is a region where monofilament intersections can move freely; and the fully elastically constrained area is a region where all intersections are elastically constrained.

[0007] Such a configuration enables the integrated design of the aortic stent consisting of three structural areas to have a clear positioning when implanted in the aorta: wherein the elastic constraint support area is located in the ascending aorta, the non-constraint area is located inside the aortic arch, and the fully elastic constraint area is located in the descending aorta segment. Such a design helps to achieve a one-time delivery and implantation of the lesion location, wherein the elastic constraint support area effectively supports the damaged dissection in the ascending aorta to prevent blood from entering the dissection; the non-constraint area can fully adapt to the lumen shape of the aortic arch, thereby reducing the force of the stent on the blood vessel, making the true lumen of the aortic arch well plastic while ensuring smooth blood flow; and the fully elastic constraint area is set in the straight descending aorta section, which can provide sufficient radial support to ensure the fixation effect.

[0008] The basic unit of the stent skeleton is a high-performance medical polylactic acid monofilament, the initial elastic modulus of the polylactic acid monofilament is ≥7 GPa, the breaking strength is ≥400 MPa, and the breaking elongation is ≥20%; the degradation time of the polylactic acid monofilament in a phosphate buffer solution at 37°C is controllable and the mechanical properties are maintained for ≥6 months; the basic feature of the polylactic acid monofilament is a spiral line, and a stent skeleton is formed by a plurality of spiral lines evenly cross-woven clockwise and counterclockwise; the stent skeleton needs to be woven with at least 6 clockwise spiral lines and 6 counterclockwise spiral lines, so as to ensure that the stent has good supporting performance and flexibility and excellent degradation performance.

[0009] A degradable superelastic material is used to elastically constrain the intersection of the monofilaments in the stent skeleton. The superelastic material uses poly (L-lactide-co-ε-caprolactone), PLCL, and hexamethylene diisocyanate (HDI) in different weight ratios, and is dissolved in a tetrahydrofuran solution to form a mixed solution; the mechanical properties of the superelastic body can be regulated by the weight ratio of PLCL and HDI; the mixed solution is quantitatively configured at the intersection of the monofilaments. After the elastic constraint of the intersection of the stent skeleton, the volatilization solution must be dried at room temperature and annealed at high temperature; the room temperature is 25±5℃; the high temperature is 100-125℃; the stent is designed with an integrated molding, which can simplify the stent implantation process, facilitate quick start-up, and reduce the difficulty of shell surgery.

[0010] In summary, the structure is programmable and can constrain the number and distribution of intersections in different regions of the bracket through hyperelasticity. The specific configuration is as follows: The structure of the elastic constraint support area is that the intersection points of the area along the circumferential direction are locally elastically constrained; the specific method of the local constraint can be set according to the degree of fragmentation of the ascending aortic dissection; the elastic constraint support area has sufficient radial support when implanted in the ascending aorta; the sufficient radial support can hold the aortic dissection close to the blood vessel.

[0011] The monofilaments in the non-constrained area can move relative to each other and bend with the aortic arch, thereby ensuring blood circulation in the remaining branches. At the same time, it can reduce the straightening force caused by the support on the greater curvature side of the aortic arch and effectively improve the bending performance on the lesser curvature side of the aortic arch, thereby ensuring that the stent conforms to the shape of the aortic arch and shapes its true lumen well.

[0012] The structure of the fully elastic constraint zone is that the intersection of the zone is fully elastically constrained; when the fully elastic constraint zone is implanted in the descending aorta, it is located in the straight area and has sufficient radial support; the sufficient radial support can ensure that the entire stent does not shift after implantation in the aorta.

[0013] The beneficial effects of the present invention are: The programmable polylactic acid self-expanding aortic stent described in the present invention can not only effectively support the rupture of the dissection in the ascending aorta and prevent blood from entering the dissection, but also adapt to the curvature of the lumen in the aortic arch and play a fixing role in the descending aorta, thereby enhancing the long-term lumen plasticity effect. After the function of the vascular tissue is restored, the stent will gradually degrade and eventually convert into water and carbon dioxide, thereby eliminating the potential hidden dangers caused by the long-term retention of the stent in the ascending aorta, aortic arch and descending aorta, and further simplifying the complexity of the surgical operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 This is a schematic diagram of an application scenario of a structure-programmable polylactic acid self-expanding aortic stent according to an embodiment of the present invention; Figure 2 A schematic diagram of the structure of a programmable polylactic acid self-expandable aortic stent according to an embodiment of the present invention; Figure 3 An initial stress-strain diagram of a structural unit polylactic acid monofilament of a structure-programmable polylactic acid self-expandable aortic stent according to an embodiment of the present invention; Figure 4 A graph showing changes in mechanical properties of a structural unit polylactic acid monofilament of a programmable polylactic acid self-expandable aortic stent as a function of degradation time according to an embodiment of the present invention; Figure 5 A stress-strain diagram of an elastic body with different ratios of PLCL and HDI of a structure-programmable polylactic acid self-expandable aortic stent according to an embodiment of the present invention; Figure 6 A schematic cross-sectional view of a programmable polylactic acid self-expandable aortic stent according to an embodiment of the present invention; Figure 7 Schematic diagram of ascending aortic dissection and the greater and lesser curvatures of the aortic arch.

[0015] Figure ID: 10-Structural programmable polylactic acid self-expanding aortic stent, 11-Stent skeleton, 111-High-performance medical polylactic acid monofilament, 112-Superelastic body, 113-Unelastic monofilament intersection, 114-Elastic monofilament intersection, R1-elastic constraint support area, R2-non-constrained area, R3-full elastic constraint area, 21- ascending aorta, 22- aortic arch, 23- descending aorta, 24- aortic branches, 211-ascending aortic dissection, 212-inner wall of ascending aorta, 221-greater curvature of aortic arch, 222-lesser curvature of aortic arch, A- proximal end, B- distal end. DETAILED DESCRIPTION

[0016] The present invention will be further explained below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the following specific embodiments are only used to illustrate the present invention and are not used to limit the scope of the present invention.

[0017] like Figure 1As shown, this embodiment provides a structurally programmable polylactic acid self-expanding aortic stent 10, which has an integrated programmable structural design with an elastic constraint support area R1, a non-constraint area R2, and a full elastic constraint area R3 from the proximal end to the distal end. The "proximal end" usually refers to the proximal end A in the direction of the aorta, and the "distal end" usually refers to the distal end B in the direction of the aorta.

[0018] The stent skeleton 11 is a self-expanding stent woven from high-performance medical polylactic acid monofilaments 111; Figure 2 As shown, the elastic constraint support area R1 is an area where the local intersection points of the single filaments 111 are constrained by the superelastic body 112; the support non-constrained area R2 is an area where the intersection points of the single filaments 111 can move freely; and the support full elastic constraint area R3 is an area where all intersection points are constrained by the superelastic body 112.

[0019] Such configuration enables the integrated design of the aortic stent 10 consisting of three structural areas to have a clear positioning when implanted in the aorta: wherein the elastic constraint support area R1 is located at the ascending aorta 21, the non-constraint area R2 is located inside the aortic arch 22, and the fully elastic constraint area R3 is located at the descending aorta 23. Such a design helps to achieve a one-time delivery and implantation of the lesion location, wherein the elastic constraint support area R1 effectively supports the damaged dissection in the ascending aorta 21 to prevent blood from entering the dissection; the non-constraint area R2 can fully adapt to the lumen shape of the aortic arch 22, thereby reducing the force on the blood vessel, making the true lumen of the aortic arch well plastic while ensuring smooth blood flow through the aortic branch 24; and the fully elastic constraint area R3 is set in the straight section of the descending aorta 24, which can provide sufficient radial support to ensure the fixation effect.

[0020] In this embodiment, the basic unit of the stent 10 is a high-performance medical polylactic acid monofilament 111. Figure 3 As shown, the initial elastic modulus of the polylactic acid monofilament 111 is ≥7 GPa, the breaking strength is ≥400 MPa, and the breaking elongation is ≥20%. Figure 4 As shown, the degradation time of the polylactic acid monofilament 111 in a phosphate buffer solution at 37°C is controllable and the mechanical properties are maintained for ≥6 months; the basic feature of the polylactic acid monofilament 111 is a spiral line, which is composed of a plurality of spiral lines evenly cross-woven clockwise and counterclockwise to form a stent skeleton 11; the stent skeleton 11 needs to be woven with at least 6 clockwise spiral lines and 6 counterclockwise spiral lines; this makes the stent have good supporting performance and flexibility as well as excellent degradation performance.

[0021] In this embodiment, a degradable superelastic material 112 is used to elastically constrain the intersection of the monofilaments in the stent skeleton 11. The superelastic material 112 is made of poly (L-lactide-co-ε-caprolactone), PLCL, and hexamethylene diisocyanate (HDI) in different weight ratios, and is dissolved in a tetrahydrofuran solution to form a mixed solution; Figure 5 As shown, the mechanical properties of the superelastic body 112 can be adjusted by the weight ratio of PLCL and HDI; the ratios of PLCL and HDI are 15:1, 10:1, 5:1, 10:3 and 5:2, respectively, but not limited to these weight ratios; the mixed solution is quantitatively configured at the monofilament intersection 113. After the monofilament intersection 113 of the stent skeleton 11 is elastically constrained, it is necessary to perform room temperature drying of the volatilized solution and high temperature heat setting annealing treatment; the room temperature is 25±5°C; the high temperature is above 100°C; the stent 10 is designed to be integrated, which can not only enhance the mechanical properties of the stent through elastomers of different weight ratios, but also simplify the stent implantation process, facilitate quick start-up, and reduce the difficulty of shell surgery.

[0022] In summary, the structure is programmable in that the number and distribution of the intersections 113 in different regions of the bracket 11 can be constrained by the superelastic body 112. Figure 6 As shown, the specific configuration is as follows: In this embodiment, at least 6 clockwise spirals and 6 counterclockwise spirals are used to weave the stent skeleton 11. This example is described by taking 6 spirals as an example. The structure of the elastic constraint support area R1 is that the local intersection 113 of the area is constrained by the elastic body 112; the local intersection 113 is set according to the fragmentation of the aortic dissection 211. Figure 7 As shown; the positions of the local intersection points 113 constrained by the elastic body 112 are distributed at intervals along the axial direction; the elastic constraint support area R1 has sufficient radial support when implanted in the ascending aorta 21; the sufficient radial support can make the ascending aortic dissection 211 close to the inner wall 212 of the ascending aorta.

[0023] In this embodiment, the monofilaments 111 in the non-constrained area R2 of the stent can move relative to each other and bend along with the aortic arch 22, thereby ensuring blood circulation in the remaining aortic branches 24. At the same time, the straightening force caused by the support of the greater curvature side 221 of the aortic arch can be reduced, and the bending performance of the lesser curvature side 222 of the aortic arch can be effectively improved, thereby ensuring that the stent 10 conforms to the shape of the aortic arch 22 and shaping its true lumen well.

[0024] In this embodiment, the structure of the fully elastic constraint zone R3 is that the intersection of the zone is fully elastically constrained 114; when the fully elastic constraint zone R3 is implanted in the descending aorta 23, it is located in the straight area and has sufficient radial support; the sufficient radial support can ensure that the overall stent 10 does not shift after implantation in the descending aorta 23.

[0025] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0026] It should be noted that the above content only illustrates the technical idea of ​​the present invention and cannot be used to limit the protection scope of the present invention. For ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications all fall within the protection scope of the claims of the present invention.

Claims

1. A structure-programmable polylactic acid self-expandable aortic stent, characterized in that: The stent skeleton is designed with an integrated programmable structure using a hyperelastic material, including: an elastic constraint support area, a non-constraint area and a full elastic constraint area are sequentially arranged from the proximal end to the distal end; The stent skeleton is a self-expanding stent woven from high-performance medical polylactic acid monofilaments; the stent is in the shape of a bendable hollow cylinder; The elastically constrained support area is a region where local monofilament intersections are elastically constrained; The non-constrained area is a region where the monofilament intersections can move freely; The fully elastically constrained area is an area in which all the monofilament intersections are elastically constrained; The structurally programmable polylactic acid self-expanding aortic stent is configured as follows: the aortic stent is an integrated design, and when implanted in the aorta, the elastic constraint support area of ​​the stent is located in the ascending aorta, the non-constraint area of ​​the stent is located in the aortic arch, and the full elastic constraint area of ​​the stent is located in the descending aorta.

2. A structure-programmable polylactic acid self-expandable aortic stent according to claim 1, characterized in that: The basic unit of the stent skeleton is a high-performance medical polylactic acid monofilament, the initial elastic modulus of the polylactic acid monofilament is ≥7 GPa, the breaking strength is ≥400 MPa, and the breaking elongation is ≥20%; the degradation time of the polylactic acid monofilament in a phosphate buffer solution at 37°C is controllable and the mechanical properties are maintained for ≥6 months; the basic feature of the polylactic acid monofilament is a spiral line, and a stent skeleton is formed by a plurality of spiral lines evenly cross-woven clockwise and counterclockwise; the stent skeleton needs to be woven with at least 6 clockwise spiral lines and 6 counterclockwise spiral lines.

3. The structure-programmable polylactic acid self-expandable aortic stent according to claim 1, characterized in that: A degradable superelastic material is used to elastically constrain the intersection of the monofilaments in the stent skeleton; the superelastic material is selected from poly (L-lactide-caprolactone) and hexamethylene diisocyanate in different weight ratios and dissolved in a tetrahydrofuran solution to form a mixed solution; The mixed solution is quantitatively disposed at the intersection points of the monofilaments.

4. A structure-programmable polylactic acid self-expandable aortic stent according to claims 1-3, characterized in that: After elastically constraining the cross points of the support skeleton, the volatilization solution is dried at room temperature and annealed at high temperature; the room temperature is 25±5°C; the high temperature is 100-125°C; the support is designed to be integrated.

5. The structure-programmable polylactic acid self-expandable aortic stent according to claim 1, characterized in that: The structure of the elastic constraint support area is that the intersection points of the area along the circumferential direction are locally elastically constrained; the specific method of the local constraint is set according to the degree of fragmentation of the ascending aortic dissection; the elastic constraint support area of ​​the stent has sufficient radial support when implanted in the ascending aorta; the sufficient radial support can hold the aortic dissection close to the blood vessel.

6. The structure-programmable polylactic acid self-expandable aortic stent according to claim 1, characterized in that: The non-constrained area is an area in which the monofilament intersections can move freely; the non-constrained area is adaptively curved when implanted in the aortic arch; and a large amount of blood can pass through the non-constrained area of ​​the stent.

7. The structure-programmable polylactic acid self-expandable aortic stent according to claim 1, characterized in that: The structure of the fully elastic constraint zone is that the intersection of the zone is fully elastically constrained; when the fully elastic constraint zone is implanted in the descending aorta, it is located in the straight area and has sufficient radial support; the sufficient radial support ensures that the entire stent does not shift.

8. The structure-programmable polylactic acid self-expandable aortic stent according to claim 1, characterized in that: The structure is programmable by constraining the number and distribution of intersections in different regions of the bracket through the superelastic body; the mechanical properties of the superelastic body are regulated by the ratio of PLCL and HDI.

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