GB2543648A - Vascular graft - Google Patents

Vascular graft Download PDF

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Publication number
GB2543648A
GB2543648A GB1616064.0A GB201616064A GB2543648A GB 2543648 A GB2543648 A GB 2543648A GB 201616064 A GB201616064 A GB 201616064A GB 2543648 A GB2543648 A GB 2543648A
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United Kingdom
Prior art keywords
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vascular graft
lateral
graft
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GB1616064.0A
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GB201616064D0 (en
GB2543648B (en
Inventor
Miraftab Mohsen
Sanami Mohammad
Bipinchandra Parikh Vijay
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Of Bolton, University of
University of Bolton
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Of Bolton, University of
University of Bolton
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Application filed by Of Bolton, University of, University of Bolton filed Critical Of Bolton, University of
Publication of GB201616064D0 publication Critical patent/GB201616064D0/en
Publication of GB2543648A publication Critical patent/GB2543648A/en
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Classifications

    • AHUMAN NECESSITIES
    • A61MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61FFILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
    • A61F2/00Filters implantable into blood vessels; Prostheses, i.e. artificial substitutes or replacements for parts of the body; Appliances for connecting them with the body; Devices providing patency to, or preventing collapsing of, tubular structures of the body, e.g. stents
    • A61F2/02Prostheses implantable into the body
    • A61F2/04Hollow or tubular parts of organs, e.g. bladders, tracheae, bronchi or bile ducts
    • A61F2/06Blood vessels
    • AHUMAN NECESSITIES
    • A61MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61LMETHODS OR APPARATUS FOR STERILISING MATERIALS OR OBJECTS IN GENERAL; DISINFECTION, STERILISATION, OR DEODORISATION OF AIR; CHEMICAL ASPECTS OF BANDAGES, DRESSINGS, ABSORBENT PADS, OR SURGICAL ARTICLES; MATERIALS FOR BANDAGES, DRESSINGS, ABSORBENT PADS, OR SURGICAL ARTICLES
    • A61L27/00Materials for grafts or prostheses or for coating grafts or prostheses
    • A61L27/14Macromolecular materials
    • A61L27/16Macromolecular materials obtained by reactions only involving carbon-to-carbon unsaturated bonds
    • AHUMAN NECESSITIES
    • A61MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61LMETHODS OR APPARATUS FOR STERILISING MATERIALS OR OBJECTS IN GENERAL; DISINFECTION, STERILISATION, OR DEODORISATION OF AIR; CHEMICAL ASPECTS OF BANDAGES, DRESSINGS, ABSORBENT PADS, OR SURGICAL ARTICLES; MATERIALS FOR BANDAGES, DRESSINGS, ABSORBENT PADS, OR SURGICAL ARTICLES
    • A61L27/00Materials for grafts or prostheses or for coating grafts or prostheses
    • A61L27/14Macromolecular materials
    • A61L27/26Mixtures of macromolecular compounds
    • AHUMAN NECESSITIES
    • A61MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61LMETHODS OR APPARATUS FOR STERILISING MATERIALS OR OBJECTS IN GENERAL; DISINFECTION, STERILISATION, OR DEODORISATION OF AIR; CHEMICAL ASPECTS OF BANDAGES, DRESSINGS, ABSORBENT PADS, OR SURGICAL ARTICLES; MATERIALS FOR BANDAGES, DRESSINGS, ABSORBENT PADS, OR SURGICAL ARTICLES
    • A61L27/00Materials for grafts or prostheses or for coating grafts or prostheses
    • A61L27/28Materials for coating prostheses
    • A61L27/34Macromolecular materials
    • AHUMAN NECESSITIES
    • A61MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61LMETHODS OR APPARATUS FOR STERILISING MATERIALS OR OBJECTS IN GENERAL; DISINFECTION, STERILISATION, OR DEODORISATION OF AIR; CHEMICAL ASPECTS OF BANDAGES, DRESSINGS, ABSORBENT PADS, OR SURGICAL ARTICLES; MATERIALS FOR BANDAGES, DRESSINGS, ABSORBENT PADS, OR SURGICAL ARTICLES
    • A61L27/00Materials for grafts or prostheses or for coating grafts or prostheses
    • A61L27/50Materials characterised by their function or physical properties, e.g. injectable or lubricating compositions, shape-memory materials, surface modified materials
    • A61L27/507Materials characterised by their function or physical properties, e.g. injectable or lubricating compositions, shape-memory materials, surface modified materials for artificial blood vessels
    • AHUMAN NECESSITIES
    • A61MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61FFILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
    • A61F2/00Filters implantable into blood vessels; Prostheses, i.e. artificial substitutes or replacements for parts of the body; Appliances for connecting them with the body; Devices providing patency to, or preventing collapsing of, tubular structures of the body, e.g. stents
    • A61F2/02Prostheses implantable into the body
    • A61F2/04Hollow or tubular parts of organs, e.g. bladders, tracheae, bronchi or bile ducts
    • A61F2/06Blood vessels
    • A61F2002/068Modifying the blood flow model, e.g. by diffuser or deflector
    • AHUMAN NECESSITIES
    • A61MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61FFILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
    • A61F2230/00Geometry of prostheses classified in groups A61F2/00 - A61F2/26 or A61F2/82 or A61F9/00 or A61F11/00 or subgroups thereof
    • A61F2230/0063Three-dimensional shapes
    • A61F2230/0091Three-dimensional shapes helically-coiled or spirally-coiled, i.e. having a 2-D spiral cross-section
    • AHUMAN NECESSITIES
    • A61MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61FFILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
    • A61F2240/00Manufacturing or designing of prostheses classified in groups A61F2/00 - A61F2/26 or A61F2/82 or A61F9/00 or A61F11/00 or subgroups thereof
    • A61F2240/001Designing or manufacturing processes
    • AHUMAN NECESSITIES
    • A61MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61FFILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
    • A61F2250/00Special features of prostheses classified in groups A61F2/00 - A61F2/26 or A61F2/82 or A61F9/00 or A61F11/00 or subgroups thereof
    • A61F2250/0058Additional features; Implant or prostheses properties not otherwise provided for
    • A61F2250/0067Means for introducing or releasing pharmaceutical products into the body
    • AHUMAN NECESSITIES
    • A61MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61FFILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
    • A61F2310/00Prostheses classified in A61F2/28 or A61F2/30 - A61F2/44 being constructed from or coated with a particular material
    • A61F2310/00389The prosthesis being coated or covered with a particular material

Abstract

A vascular graft comprising a three dimensional helical shape on an internal surface of the graft. The helical shape extends for at least half the graft length. The helical shape may be formed by a pair of equidistant ridges for the entire length of the ridges. The graft diameter may be less than 6mm. The graft may be formed through depositing a polymer fibre by electrospinning on an outer surface of a device. Helical shape helix angle may be between 30 to 60 degrees. A device 1 for producing the vascular graft comprising: a main shaft 2; a tubular member 4 having an outer surface 4a; a rotational end plate 5; and a series of hinges and cams within tubular member 4. The device may be a mandrel. Outer surface 4a may have a pair of continuous grooves 11 with depth of between 0.10 mm and 0.40 mm. The pair of grooves 11 may wind around the outer surface 4a forming a helical pattern. A compression device for compressing the polymer fibre on the device. The compression device may comprise a plurality of curved blades with ridges corresponding with the device grooves 11. A method for producing a vascular graft.

Description

Vascular Graft
Technical Field of the Invention
The present invention relates to small diameter vascular grafts which can successfully replicate natural blood flow, and to a device for the production of these grafts.
Background to the Invention
Cardiovascular diseases are one of the leading causes of mortality and morbidity worldwide. Each year, cardiovascular diseases cause over 4.3 million deaths in Europe, and nearly 250,000 open surgical revascularizations are performed in the USA for diseased peripheral and coronary arteries. Failure or malfunction of the heart is caused due to a number of factors, including ischemic heart disease (IHD), cardiomyopathy, high blood pressure, diseases of the heart valves, diseases of the pericardium, arrhythmias, and various non-heart conditions that can affect the function of this vital organ. IHD, otherwise called coronary heart disease or atherosclerotic heart disease, is the main cause of heart failure or heart problem in the developed world. In most cases IHD is characterized by hardening and blockage of the arteries due to formation and deposition of plaque along the inner walls of arteries leading to the heart. A number of responsible factors have been identified for such depositions, including dietary habits, higher cholesterol level, lifestyle, side effects of various drugs, genetic malfunction and very recently, hemodynamic factors which deal with blood flow properties.
Alternatively, when oral medication and other treatment options are no longer viable or effective, the most effective treatment of atherosclerosis is bypass vascular grafting whereby obstructed blood flow is rerouted through a newly substituted vascular graft to normalise blood flow.
The best arterial substitute is probably the patient’s own artery or autologous vein, principally the saphenous vein, but because of their limited availability, due to various reasons, it is not always possible to use these autologous vessels. Furthermore, vein grafts in coronary bypass grafts occlude over time due to accelerated atherosclerotic changes with an average 10-year patency of 50%, and, in 15 to 30% of the cases, it cannot be used due to gross abnormalities or because of removal by a previous operation. Moreover, autogenous veins are vulnerable to late complications such as aneurysmal degeneration, fibrosis, and intimal hyperplasia. Additionally, the number of veins which can be transferred without causing circulatory (i.e. venous) disturbances is limited.
To overcome this hurdle, in recent years there has been a huge surge in development and enhancements of artificial or synthetic vascular grafts. To ensure conformity and close proximity to natural veins, an ideal synthetic vascular graft would need to possess a number of crucial characteristics, including good mechanical strength and compliance to resist long-term hemodynamic stresses; non-toxicity; non-immunogenicity; biocompatibility; “off-the-shelf’ availability in various sizes, operative suitability and simplicity of surgical handling; resistance to in vivo thrombosis; ability to endure infection; complete integration with host tissues with satisfactory graft healing and, last but not least, reasonable manufacturing costs.
Large diameter (i.e. greater than 6 mm) synthetic polymer prostheses with long-term patency have been successfully used and have become routine operational practice. However, most blood vessels within the peripheral, cerebral and cardiac vasculature have diameters of less than 6 mm.
When finer prosthetic grafts, i.e. those having a diameter less than 6 mm, are required, current available options have not proved to be effective. In fact, current options have consistently displayed rapid thrombus formation (fibrous tissue build up) and intimal hyperplasia (exuberant muscle growth at the interface between artery and graft) subsequent to bypass surgery, severely limiting their utilisation. Thus, designing and manufacturing small diameter bypass grafts has become a major focus of attention.
Small-diameter vascular grafts are in great demand for coronary and peripheral bypass procedures, but unlike their large counterparts they still fail in long term clinical applications. The failure of small diameter grafts is primarily due to the early formation of thrombosis and intimal hyperplasia.
Established research studies has shown that blood in native arteries flows in a spiral or helical manner; if this notion could be replicated in prosthetic grafts, the collated cholesterol and minerals could literally be “washed away” by the swirling motion of the blood and hence prevent formation of thrombosis and its fatal consequences.
Underperformance or malfunction of small diameter grafts is often associated to the following: a) Hemodynamics or the effect associated to the variations in blood flow in localised area of the blood vessels and their associated effects on surrounding environments; and b) Lack of functional endothelial cell coverage on the graft surface due to surface mismatch and difference in mechanical properties of the synthetic graft and host artery.
Hemodynamics is mainly represented in terms of impedance to flow, wall shear stress, velocity profile of blood, and flow separation. The local flow behaviour of blood is implicated in the formation of atherosclerotic plaques, thrombogenesis and atherogenesis, thus hemodynamics plays an imperative part in the design of small calibre grafts. Thrombosis can be prevented by blood spiralling which results in the “washing away” of collated cholesterol and minerals.
The endothelium is the thin layer of simple squamous cells that lines the interior surface of blood vessels and lymphatic vessels, forming an interface between circulating blood and the rest of the vessel wall. The cells that form the endothelium are called endothelial cells. Active functioning endothelium plays a critical role to maintain non-thrombogenic properties of the blood vessels as it contain heparin sulphate, one of the cofactors for the activation of antithrombin. Graft endothelialization, both in vitro and in vivo, has been shown to enhance the patency of the vascular graft. Yet, confluent endotheliazation has not been achieved very satisfactorily in the case of small and medium diameter vascular grafts.
Moreover, until recently both these factors were studied independently, but recent research has been directed towards a very well established correlation between them. The difference in the surface and mechanical properties between the synthetic graft and natural artery will result in disturbance of blood flow regardless of the diameter of the graft; however, in the case of larger diameter grafts, the effect of the impedance is largely suppressed by higher blood flow rate, which helps to absorb the greater energy of the disturbance compared to the smaller diameter counterparts. Therefore, this turbulence in the blood flow leads to uneven pressure distribution in the small diameter grafts and hence variation in the shear stress inside the graft.
The change in shear stress induces divergent flow associated with low shear stresses resulting in flow separation, rarefaction and increased oscillatory shears. In the presence of higher laminar shear stress, ECs tend to become elongated, aligned and produce antithrombogenic and atheroprotective mediators. In contrast, in the presence of lower, oscillatory shear stress the ECs become randomly oriented, susceptible to inflammation and produce atherogenic responses.
Numerous researchers have acknowledged the advantages provided by swirling flow in the management of blood flow hemodynamics and its resemblance to the natural blood flow pattern in the last couple of decades. Building on the physical theory, a number of researchers have attempted to design and even manufacture small diameter prosthetic grafts based on the helical or the spiral theory' and test these products.
Helical grafts are known in the art, such as that disclosed in US 2012/0296353 Al. US 2012/0296353 discloses a graft device capable of having a variety of coverings wrapped around the device circumference, one covering being a helical covering. A polymer matrix is then deposited on the device by electrospinning. Disadvantageously, the helical covering is not integrally formed as part of the graft device and has to be applied to the graft device prior to a deposition of a polymer matrix onto the graft device.
However, clinical trial results to date are either non-existent or at best are very limited. Most of the grafts manufactured for this purpose contain a swirl flow inducer in the initial length of the graft, i.e. either not covering the entire length of the graft, or they are physically twisted from the outside, such that they resemble a twisted hosepipe. However, during clinical trials they have been accompanied by several lacunas either due to their design or due to their manufacturing techniques. The lacunas observed were reduction of helical geometry as a function of time and renders them similar to the conventional grafts after a certain time interval. The vortex in these bypass grafts were found to consist of low-velocity recirculation flow which has not been sufficient to provide the “wash away” effect.
Moreover, according to FEA (Finite Element Analysis) analyses carried out on these designs, helical grafts increase the helicity of blood flow only up to 11% and thus their effectiveness mainly relies upon the rate of blood flow in localised areas. Hence, the design needs to be improved to enhance the helicity of blood flow and achieve maximum advantages of the swirling flow. Furthermore, these grafts only manage to reduce the areas of shear stress variation by 40% compared to conventional grafts; hence the remaining 60% may experience a higher magnitude of shear stress variation which may affect the function of the graft in the long term. In addition, FEA analysis has also proved that physical twisting of the graft might lead to a pressure drop or uneven pressure distribution within the graft. This uneven pressure can lead to uneven velocity distribution within the graft, which may result in the failure of the graft in long term use. Hence, certain improvements are required in these grafts to maximise benefits associated to helical flow. Moreover, most of these grafts, at best, have performed better at higher flow rates but have not provided adequate swirling flow for lower flow rates.
From the evidence available, it is apparent that none of the current available alternatives have a similar structure to a natural blood vessel or behave mechanically and hemodynamically as it is observed in natural arteries and veins of living subjects.
The geometry of arteries influences their blood flow motion and hence their biology and susceptibility to disease. It is recognized that the geometry of natural blood vessels is far more complicated than that of model vessels and the local flow pattern depends on this local geometry and the velocity distribution Native arterial geometry is three-dimensional, causing blood spiralling which provides relatively uniform wall shear stress and inhibits flow stagnation. However, bypass grafts are essentially two-dimensional and hence do not provide the necessary blood spiralling that assists in the “washing away” of collated cholesterol and minerals.
The fault therefore is very much as a result of poor design and manufacturing method inadequacy. Unless a three-dimensional graft with built-in “wash away” mechanism, good porosity and architectural intercity is produced, the existing fine diameter grafts that are available will not alleviate the problem.
It is therefore an object of the present invention to provide a vascular graft with a helical structure on the inner surface of the graft that has a similar structure to a natural blood vessel, or behave mechanically and hemodynamically as it is observed in natural arteries and veins of living subjects, such that it can provide the necessary blood spiralling and, therefore, a substantial “wash away” effect.
Summary of the Invention
According to a first aspect of the present invention, there is provided a vascular graft comprising a3-dimensional helical shape on an internal surface of the graft, wherein the helical shape extends for at least about 50% of the length of the graft.
Preferably, the 3-dimensional internal helical shape extends for at least about 75% of the length of the graft, most preferably the 3-dimensional helical graft extends for substantially 100% of the length of the graft. Beneficially, the helical pattern extends for the entire length of the graft. This provides an advantage over the grafts in the prior art. The grafts in the prior art often comprise a swirl flow inducer or are formed as a helical shape for only a part of the length of the graft, resulting in undesirably low levels of blood spiralling. The low levels of blood spiralling produced are insufficient to provide the necessary desired “wash away” effect.
Typically, the helical shape is formed from a pair of ridges that are at an equal distance from each other for the entire length of the ridges.
Preferably, the graft has a diameter of less than about 15 mm, more preferably less than about 12 mm, even more preferably less than about 8 mm, and most preferably less than about 6 mm.
Advantageously, a graft with diameter of less than about 6 mm and a helical ridge pattern on the internal surface allows the graft to be used in procedures concerning small diameter blood vessels, such as peripheral, cerebral and cardiac vasculature. Grafts for this type of blood vessel, or similar, which are known in the prior art do not produce the necessary blood swirling effect.
Preferably, the vascular graft of the invention is formed by depositing a polymer fibre on the outer surface of a device by electrospinning. Beneficially, electrospinning allows fabrication of precision-based nano structured vascular scaffolds with a defined internal shape and complex porous architecture. Moreover, the mechanical and biological properties of a nanofiber produced by electrospinning can be easily tuned by varying a starting mixture composition and the electrospinning machine variables.
Preferably, the polymer fibre has a diameter of between about 50 nm and about 700 nm, more preferably between about 125 nm and about 600 nm, even more preferably about 200 nm and about 500 nm, and most preferably about 250 nm and about 450 nm.
Advantageously, the polymer fibre is formed from a polymer solution.
Preferably, the polymer fibre is formed from a polymer solution comprising a polyol.
Preferably, the polymer fibre is formed from a polymer solution comprising a polyol and gelatin.
Preferably, the polyol in the polymer solution is polyvinyl alcohol. Other suitable compounds that may be used include polymers such as; polyurethanes, polycapronolactones, biocompatible silks, or a mixture of any of these polymers with hyaluronic acid, chitosan or gelatine.
Typically, the polymer solution is produced by a method comprising the steps of: a. Stirring a solution comprising a polyol, preferably polyvinyl alcohol, at a temperature between about 60°C and about 100°C, preferably about 80°C, for between about 120 and about 240 minutes, preferably about 180 minutes; b. Cooling the solution formed in step (a) to between about 16°C and about 28°C, typically about room temperature; c. Stirring a mixture of an organic acid, preferably glacial acetic acid, and water, in a ratio between 1:1 and 10:1 (acid:water), preferably about 8:2, at a temperature between about 16°C and about 28°C, typically about room temperature, for between about 30 and about 90 minutes, preferably about 60 minutes; and d. Combining the solutions formed in steps (b) and (c) in a ratio between 1:1 and 10:1, preferably about 8:2, and stirring the combined solutions at a temperature between about 16°C and about 28°C, typically about room temperature, for between about 30 and about 90 minutes, preferably about 60 minutes.
Beneficially, the vascular graft can be coated with a pharmaceutical drug. Also advantageously, the vascular graft can be coated with a polymer solution comprising a drug dispersion. This affords a vascular graft with a dual purpose of providing a vascular graft capable of acting as a drug carrier for controlled release of a pharmaceutical to help with the treatment of disease and, in a longer term, provide blood flow advantages as mentioned previously.
Preferably, the graft has a wall thickness of between about 75 pm and about 800 pm, more preferably between about 150 pm and about 700 pm, even more preferably between about 250 pm and about 550 pm, and most preferably about 400 pm.
Typically, the helical shape has a helix angle of between about 30° and about 60°, more typically between about 35° and about 55°, even more typically between about 40° and about 50°, and most typically about 45°. A helical angle of about 45° is optimal for generating swirling blood flow. A vascular graft of this form closely mimics native blood vessels and provides the advantageous blood swirling required to produce a “wash away” effect.
According to a second aspect of the invention, there is provided a device for producing vascular grafts, comprising a main shaft affixed to a tubular member comprising an outer surface, a rotational end plate distal from the main shaft, and a series of hinge mechanisms and a series of cam mechanisms located within the tubular member.
The main shaft and tubular member are typically substantially cylindrical in shape. The main shaft has a slightly smaller diameter than the tubular member. The main shaft and tubular member are joined by a narrow shoulder portion of greater diameter than the tubular member. The shoulder portion comprises a circular plate which is affixed internally to the shoulder portion at several points of the circumference of the circular plate. The circular plate defines the intersection between the main shaft and the tubular member. At the centre of the circular plate is a receiving means for receiving a rod.
Advantageously, the outer surface of the device comprises a plurality of curved bars that extend for a substantial length thereof. The curved bars preferably extend from the rotational end plate to the shoulder portion. The curved bars exhibit a curvature so when positioned on the outer surface of the tubular member they form a complete cross-sectional circle.
Preferably, the plurality of curved bars comprise a top bar, a bottom bar, two lateral left bars and two lateral right bars. The top bar and bottom bar are located opposite one another and the two lateral left bars and two lateral right bars are located opposite one another.
The two lateral left bars comprise an upper lateral left bar and a lower lateral left bar. The two lateral right bars comprise of an upper lateral right bar and a lower lateral right bar. The two lateral left bars cover a substantial portion of the left side of the tubular member and the two lateral right bars cover a substantial portion of the right side of the tubular member. The upper lateral left bar and upper lateral right bar are abutted by the top bar. The lower lateral left bar and lower lateral right bar are abutted by the bottom bar.
Advantageously, the tubular member comprises an outer surface with a pair of continuous grooves with a depth of between about 0.10 mm and about 0.40 mm, preferably between about 0.15 mm and about 0.35 mm, more preferably between about 0.20 mm and about 0.30 mm, and most preferably about 0.25 mm.
Preferably, the pair of grooves wind around the outer surface of the device to form a helical pattern. Typically, the grooves are an equal distance from each other on the surface of the tubular member.
Advantageously, a helix angle formed by the grooves is measured as between about 30° and about 60°, more advantageously between about 35° and about 55°, even more advantageously between about 40° and about 50°, most advantageously about 45° to the axis of the device. The helical pattern formed by the grooves advantageously provides a device from which a vascular graft can be formed on the surface of the device and thus comprise a helical ridge on the interior surface of the vascular graft.
Typically, the top bar and the bottom bar each comprise a protrusion extending the length of the curved bar and which protrudes towards the centre of the device. A cross section of the tubular member shows the top bar and the bottom bar forming a substantial “T-shape” with the base of the “T” forming the triangular shaped protrusion. The length of the protrusion is equal to the length of the top or bottom curved bar, where the top bar and the bottom bar are of equal length.
Preferably, the point at which the left lateral bars join and the right lateral bars join comprises a protrusion extending the length of the curved bars and which protrudes towards the centre of the device. The protrusion formed at the join of the left lateral bars and the right lateral bars is substantially similar to the protrusion formed from the top bar and the protrusion formed from the bottom bar and, like with the top bar and bottom bar protrusions, extend for the entire length of the lateral left bars and lateral right bars.
Preferably, two pairs of springs are located within the tubular member, one pair of springs located between a first cam mechanism and the main shaft and the second pair of springs located between a second cam mechanism and the rotational end plate, each pair of springs being attached to the protrusion emanating from the join of the left lateral bars and the protrusion emanating from the join of the right lateral bars. The springs act as a cushioned support for when the curved bars are collapsed towards the centre of the device.
Preferably, the rotational end plate comprises a rotational knob.
Advantageously, the rotational knob is fixed to a central rod which extends through the centre of the device for the entire length of the device.
Beneficially, the rod provides support for a series of hinge mechanisms and a series of cam mechanisms. The rod is cylindrical and extends from the rotational knob through the centre of the tubular member and is attached to the circular plate positioned at the shoulder portion of the device.
Advantageously, the series of hinge mechanisms comprises two hinge mechanisms positioned on the central rod opposite one another; each hinge mechanism comprising two links wherein one link is attached to the protrusion of the bottom bar and a second link is attached to the protrusion of the top bar. The hinge mechanisms are located on the rod in a substantially central position with respect to the length of the tubular member. The two hinge mechanisms are separated by a distance of approximately 5 mm. The hinge mechanisms allow for the collapse of the top bar and the bottom bar towards the centre of device.
Preferably, a first rotation of the rotational knob permits an opposing axial movement of the hinge mechanisms. The first rotation of the rotational knob causes the hinge mechanisms to move apart; the first hinge mechanism axially moves along the central rod towards the main shaft and the second hinge mechanism axially moves along the central rod towards the rotational end plate.
Favourably, the axial movement of the hinge mechanisms permits the top bar and the bottom bar to move towards the central rod. Advantageously, the inward collapse of the top bar and bottom bar assists the user in removing a vascular graft from the device once the graft is formed.
Preferably, the series of cam mechanisms comprises two cam mechanisms positioned on the central rod opposite one another; each cam mechanism being attached to the protrusion emanating from the join of the left lateral bars and the protrusion emanating from the join of the right lateral bars; the first cam mechanism being positioned between a pair of springs and the first hinge mechanism and the second cam mechanism being positioned between a pair of springs and the second hinge mechanism.
Preferably, a second rotation of the rotational knob permits opposing lateral movement of the cam mechanisms. The second rotation of the rotational knob causes the cam mechanisms to move apart; the first cam mechanism laterally moves along the central rod towards the main shaft and the second cam mechanism laterally moves along the central rod towards the rotational end plate.
Advantageously, the lateral movement of the cam mechanisms permits the left lateral bars and the right lateral bars to move towards the central rod. Beneficially, the first rotation of the rotational knob causes an inward movement of the top bar and bottom bar; this creates an opening for the subsequent inward movement of the left lateral bars and right lateral bars as a result of the second rotation of the rotational knob.
The two rotations of the rotational knob advantageously cause an inward movement of the top bar, the bottom bar, the left lateral bars and the right lateral bars, permitting the curved bars to collapse towards the centre of the device. The inward collapse of the outer surface of the tubular member decreases the diameter of the tubular member by approximately 1 mm. The collapse of the outer surface of the tubular member allows for easy removal of a vascular graft from the device.
Beneficially, this makes removal of the graft much simpler for the user and vastly reduces the chance of damaging the graft when it is being removed. Moreover, the helical ridges formed on the internal surface of the graft remain largely intact due to the ease of graft removal. This is beneficial as the intact helical ridges on the graft’s interior surface result in the graft still being capable of producing a blood swirling effect, thus providing a substantial “wash away” effect.
Preferably, the device is between about 40 mm and about 100 mm, more preferably between about 50 mm and about 90 mm, even more preferably between about 60 mm and about 80 mm, and most preferably about 70 mm, in length.
Preferably, the device is between about 4 mm and about 0.1 mm, more preferably between about 5 mm and about 9 mm, even more preferably between about 6 mm and about 8 mm, and most preferably about 7 mm, in diameter.
Also envisaged within the scope of the invention is that the device may be manufactured using 3D printing techniques. The present invention therefore also provides a method of manufacturing a device as defined herein via 3D printing.
Preferably, electrospinning can be used to deposit a polymer fibre on the device.
Advantageously, the device can be used to design a vascular graft to be used in cardiovascular and non-cardiovascular applications.
The device of the second aspect of the invention may be a mandrel.
In a third aspect of the present invention, there is provided a method for producing a vascular graft using the device of the second aspect of the invention, comprising the steps of: a. Depositing a polymer fibre onto the device by electrospinning, in order to achieve an initial desired wall thickness of the vascular graft; b. Stopping deposition of the polymer fibre onto the device once the initial desired wall thickness has been achieved; c. Applying pressure to the fibres to ensure the fibres have entered the grooves on the outer surface of the device; d. Carrying out a second step of electrospinning wherein the polymer fibre is deposited onto the device until a second desired wall thickness has been achieved; e. Making a first rotation of the rotational knob to create axial movement of the hinge mechanisms causing the top bar and bottom bar to collapse towards the centre of the device; f. Making a second rotation of the rotational knob to create lateral movement of the cam mechanisms causing the left lateral bar and the right lateral bar to collapse towards the centre of the device; and g. Removing the vascular graft from the device.
Preferably, the initial desired wall thickness is between about 50 pm and about 400 pm, more preferably between about 150 pm and about 300 pm, and most preferably about 200 pm.
Preferably, the second desired wall thickness is between about 75 pm and about 800 pm, more preferably between about 200 pm and about 600 pm, even more preferably between about 300 pm and about 500 pm, and most preferably about 400 pm.
Advantageously, step (c) allows for the deposited polymer fibre to substantially enter the grooves on the outer surface of the tubular member. This results in the beneficial effect of the vascular graft having helical ridges on the graft’s inner surface. It is these helical ridges that promote blood swirling and therefore the desired “wash away” effect. Beneficially, the vascular graft is formed readily comprising helical ridges on its inner surface, thus removing the need for a swirl inducing mechanism to be added to the graft, or the production of a graft in a helical shape, in order to provide a blood swirling effect. Further, the blood swirling effect resulting from the helical ridges on the inner surface of the graft prevents the formation of stagnant regions of blood flow and thus prolongs the function of the graft.
According to one embodiment of the invention, electrospinning of the polymer solution can be carried out by a set-up comprising a syringe (20 ml), a needle (3 cm long, 18 gauges, and flat tip), a ground electrode and a high voltage supply (such as a Spellman High Voltage DC Supply). The polymer solution is electrospun at a voltage of 16 kV and at a tip-to-collector distance of about 15 cm with a feeding rate of about 1 ml/hr at room temperature and at about 1000 rpm.
Also provided within the present invention is a compression device for use in conjunction with the mandrel. The compression device acts to compress the electrospun polymer fibre on the mandrel, ensuring that the fibres are fully compacted within the grooves. This ensures uniformity of the helical ridges within the resultant formed vascular grafts.
The compression device is typically employed after the first electrospinning deposition of the polymer fibre onto the device once the initial desired wall thickness of the vascular graft has been achieved, i.e. step (a) defined above.
Once the compression has been completed, the device is removed from the mandrel and the electrospinning can be resumed.
The compression device typically comprises five parts: a mechanism for opening and closing the compression device; three blades which extend along the length of the tubular member of the mandrel; and an end portion, which is sited on the main shaft portion of the mandrel. The opening and closing mechanism is sited adjacent the end portion.
It is the blades which apply the compression to the electrospun fibre, by neing tightened thereon. The blades each have a curvature which enables them to form a circle when they are in their closed configuration, and each comprise helical ridges which correspond to the helical grooves on the mandrel, in order that the ridges can be inserted into the grooves and fully compress the electrospun fibre into the grooves.
When the compression device is applied to the mandrel, the opening and closing mechanism is rotated either clockwise or anticlockwise to either open or close the blades. The compression device is typically applied to the mandrel with the blades in the open configuration, and an anticlockwise rotation of the opening and closing mechanism closes the blades around the mandrel to apply the pressure. Conversely, the blades are opened to relieve the pressure by a clockwise rotation of the mechanism, and once the compression is complete, the compression device can then be removed.
Therefore, the step (c) of the method for producing a vascular graft as defined above, involving applying pressure to the fibres, may be carried using a compression device as defined herein.
In order that the invention may be more clearly understood, an embodiment thereof will now be described, by way of example only, with reference to the accompanying drawings, of which:
Figure 1 is a side view of a mandrel for producing vascular grafts;
Figure 2 is a perspective view of the mandrel with the left lateral bars removed to display the hinge mechanisms within the tubular member;
Figure 3 is a perspective view of the mandrel with the top bar, upper left bar and upper right bar removed to display the cam mechanism within the tubular member;
Figure 4 is a cross-sectional view of the tubular member towards the main shaft, centrally bisecting the length of the tubular member; and
Figure 5 is the cross-sectional view of figure 4 with the hinge and cam mechanisms contracted.
Figure 6 shows an exploded view of the compression device of the invention.
Figure 7 is a side view of the compression device with the blades in their closed configuration.
Figure 8 is a lateral view of the compression device with the blades in their closed configuration.
Figures 9(a)-(c) are end-on views of the compression device, showing the rotation of the compression device enabling the opening and closing of the blades towards and away from the mandrel.
Figure 10 is a side view of the compression device with the blades in their open configuration.
Figures ll(a)-(b) are lateral view of the compression device with the blades in both their closed and open configurations.
The above embodiment is described by way of example only. Many variations are possible without departing from the scope of the invention, as defined in the appended claims.
Figure 1 shows a mandrel 1 comprising a main shaft 2, a shoulder 3, a tubular member 4, a rotational end plate 5 and a rotational knob 6. The tubular member 4 comprises six curved bars described as an upper left lateral bar 7a, a lower left lateral bar 7b, an upper right lateral bar 8a, a lower right lateral bar 8b, a top bar 9 and a bottom bar 10. The six curved bars form an outer surface 4a of the tubular member 4. The outer surface 4a comprises a series of grooves 11 positioned so as to form a helix on the outer surface 4a of the tubular member 4. The helix formed by the grooves 11 is at a 45° angle to the axis of the mandrel 1. The helix formed extends from the shoulder 3 to the rotational end plate 5.
Figure 2 shows the mandrel 1 with the upper left lateral bar 7a and the lower left lateral bar 7b removed. A circular plate 16 defines the intersection between the main shaft 2 and the tubular member 4. At the centre of the circular plate is a receiving means 16a capable of receiving a screw 12. Starting at the receiving means 16a is the screw 12 which extends throughout the centre of the tubular member 4 to the rotational end plate 5 where the screw 12 is connected to the rotational knob 6. A first spring pair 15a is positioned within the tubular member 4 perpendicular to the length of the screw 12. The first spring pair 15a is attached to a left lateral bar protrusion 17c and a right lateral bar protrusion 17d. A second spring pair 15b is positioned within the tubular member 4 perpendicular to the length of the screw 12. The second spring pair 15b is attached to the left lateral bar protrusion 17c and the right lateral bar protrusion 17d. A first hinge mechanism 13a is supported by the central screw 12. The first hinge mechanism 13a comprises a link 13al to a top bar protrusion 17a. The first hinge mechanism 13a also comprises a link 13a2 to a bottom bar protrusion 17b. The screw 12 is threaded through the first hinge mechanism 13a.
Similarly, a second hinge mechanism 13b is also supported by the central screw 12. The second hinge mechanism 13b comprises a link 13b 1 to the top bar protrusion 17a. The second hinge mechanism 13b comprises a link 13b2 to the bottom bar protrusion 17b. The screw 12 is threaded through the second hinge mechanism 13b.
The hinge mechanisms 13a and 13b are separated by a portion of the rod and are positioned approximately 5 mm apart.
Looking now at Figure 3, a first cam mechanism 14a is supported by the central screw 12 between the first spring pair 15a and the first hinge mechanism 13a. The first cam mechanism 14a is attached to the left lateral bar protrusion 17c and the right lateral bar protrusion 17d. A second cam mechanism 14b is supported by the central screw 12 between the second spring pair 15b and the second hinge mechanism 13b. The second cam mechanism 14b is attached to the left lateral bar protrusion 17c and the right lateral bar protrusion 17d.
Turning to Figure 4, the top bar protrusion 17a is attached to the first hinge mechanism 13a by the link 13al and the bottom bar protrusion 17b is attached to the first hinge mechanism 13a by the link 13a2.
The first cam mechanism 14a is attached to the left lateral bar protrusion 17c and to the right lateral bar protrusion 17d. Also visible are the upper left lateral bar 7a, lower left lateral bar 7b, upper right lateral bar 8a, lower right lateral bar 8b, top bar 9 and bottom bar 10. Figure 4 shows the mandrel 1 after the deposition of a polymer fibre (not shown) by an electrospinning method to form a vascular graft 20.
Figure 5 shows a contracted first hinge mechanism 18a and contracted first cam mechanism 19a as a result of two rotations of the rotational knob 6. The top bar 9 and bottom bar 10 have moved inward toward the screw 12 as a result of the rotation of the screw 12, which moves the first and second hinge mechanisms 13a, 13b inwards. The upper left lateral bar 7a, lower left lateral bar 7b, upper right lateral bar 8a and lower right lateral bar 8b have moved inward toward the central rod 12 as a result of contraction of the first and second cam mechanisms 14a, 14b, and also of the contraction force applied by the springs The inward collapse of the outer surface 4a of the tubular member 4 decreases the diameter of the tubular member 4 by approximately 1 mm.
The inward collapse of the outer surface 4a allows for easy removal of the newly formed vascular graft from around the mandrel 1.
Figure 6 shows an exploded view of the compression device 22 of the invention. The end portion 24 is located at one end of the compression device 22, and is sited over the main shaft 2 of the device of the invention. There are three separate blades 26, which are each typically identical, and which possess helical ridges 28 thereon which are configured to correspond with the helical grooves 11 in the mandrel 1. Upon compression, the helical ridges 28 force the polymer fibre fully into the grooves 11. The blades 26 also comprise protrusions 30, one on each blade, which enable the movement thereof.
The opening and closing mechanism 32, when in use, is located adjacent the end portion 24 (as shown in Figure 7), and comprises three openings 34, which the three protrusions 30 on the blades 26 engage with. With the protrusions 30 engaged with the openings 34, rotation of the mechanism 32 therefore ensures the opening and closing of the blades 26. A clockwise rotation causes the blades 26 to open, while an anticlockwise rotation causes the blades 26 to close together.
Figure 7 shows a side view of the compression device 22, with the blades 26 in their closed configuration. It can be seen that the end portion 24 and opening and closing mechanism 32 are positioned adjacent each other when the compression device 22 is in operation.
Figure 8 shows a lateral view of the compression device 22, again with the blades in their closed configuration, with the protrusions 30 engaged with the openings 34.
Figures 9(a)-(c) are end-on views of the compression device, showing the rotation of the compression device 22 enabling the opening and closing of the blades towards and away from the mandrel.
Figure 9(a) shows the compression device 22 with the three blades 26 in their closed configuration, with their three protrusions 30 engaged with the openings 34 in the the mechanism 32.
Figure 9(b) shows the compression device 22 after some clockwise rotation, which opens up the blades 26; and Figure 9(c) shows the compression device 22 after further clockwise rotation, with the blades 26 opened up even more.
Conversely, the equivalent anticlockwise rotation results in the closing of the blades 26 from their open configuration.
Figure 10 is a corresponding side view of the compression device 22, with the blades 26 in their open configuration.
Figure 11(a) shows a lateral view of the compression device 22, with the blades 26 in their closed configuration and the protrusions 30 engaged with the openings 34, while Figure 11(b) shows a corresponding lateral view of the compression device 22 with the blades 26 in their open configuration.
The techniques disclosed above are by no means meant to be taken as limiting for the production of the present invention.

Claims (50)

1. A vascular graft, comprising a 3-dimensional helical shape on an internal surface of the graft, wherein the helical shape extends for at least 50% of the length of the graft.
2. A vascular graft according to claim 1, wherein the 3-dimensional helical shape extends for substantially 100% of the length of the graft.
3. A vascular graft according to claim 1 or claim 2, wherein the helical shape is formed from a pair of ridges that are at an equal distance from each other for the entire length of the ridges.
4. A vascular graft according to any preceding claim, wherein the graft has a diameter of less than about 15 mm.
5. A vascular graft according to claim 4, wherein the graft has a diameter of less than about 6 mm.
6. A vascular graft according to any preceding claim, wherein the graft is formed by depositing a polymer fibre on the outer surface of the device by electrospinning.
7. A vascular graft according to claim 6, wherein the polymer fibre has a diameter of between about 50 nm and about 700 nm.
8. A vascular graft according to claim 6 or claim 7, wherein the polymer fibre is formed from a polymer solution.
9. A vascular graft according to any of claims 6-8, wherein the polymer fibre is formed from a polymer solution comprising a polyol.
10. A vascular graft according to claim 9, wherein the polymer fibre is formed from a polymer solution comprising a polyol and gelatin.
11. A vascular graft according to claim 9 or claim 10, wherein the polyol is a polyvinyl alcohol.
12. A vascular graft according to any preceding claim, wherein the vascular graft is coated with a pharmaceutical drug.
13. A vascular graft according to any preceding claim, wherein the vascular graft is coated with a polymer solution comprising a drug dispersion.
14. A vascular graft according to any preceding claim, wherein the vascular graft has a wall thickness of between about 75 pm and about 800 pm.
15. A vascular graft according to any preceding claim, wherein the helical shape has a helix angle of between about 30° and about 60°.
16. A device for producing the vascular graft of any preceding claim, comprising a main shaft affixed to a tubular member comprising an outer surface, a rotational end plate and a series of hinge mechanisms and a series of cam mechanisms located within the tubular member.
17. A device according to claim 16, wherein the outer surface comprises a plurality of curved bars that extend for a substantial length of the device.
18. A device according to claim 17 wherein the plurality of curved bars comprise a top bar, a bottom bar, two lateral left bars and two lateral right bars.
19. A device according to claim 18, wherein the top bar and bottom bar are located opposite one another and the two lateral left bars and two lateral right bars are located opposite one another.
20. A device according to any of claims 16 to 19, wherein the tubular member comprises an outer surface with a pair of continuous grooves with a depth of between 0.10 mm and 0.40 mm.
21. A device according to claim 20, wherein the pair of grooves wind around the outer surface of the device to form a helical pattern.
22. A device according to claims 20 to 21, wherein the pair of grooves are at an equal distance from each other on the surface of the tubular member.
23. A device according to claims 20 to 22, wherein the helical grooves have a helix angle of between 30° and 60°.
24. A device according to claim 18 or claim 19, wherein the top bar and the bottom bar each comprise a protrusion extending the length of the curved bar and which protrudes towards the centre of the device.
25. A device according to claim 18 or claim 19, wherein the point at which the left lateral bars join and the right lateral bars join comprises a protrusion extending the length of the curved bars and which protrudes towards the centre of the device.
26. A device according to claim 25, wherein two pairs of springs are located within the tubular member, one pair of springs located between a first cam mechanism and the main shaft and the second pair of springs located between a second cam mechanism and the rotational end plate, each pair of springs are attached to the protrusion emanating from the join of the left lateral bars and the protrusion emanating from the join of the right lateral bars.
27. A device according to any of claims 16 to 26, wherein the rotational end plate comprises a rotational knob.
28. A device according to claim 27, wherein the rotational knob is fixed to a central rod which extends through the centre of the device for the entire length of the device.
29. A device according to claim 28, wherein the rod provides support for the series of hinge mechanisms and the series of cam mechanisms.
30. A device according to any of claims 16 to 29, wherein the series of hinge mechanisms comprises two hinge mechanisms positioned on the central rod opposite one another; each hinge mechanism comprising two links wherein one link is attached to the protrusion of the bottom bar and a second link is attached to the protrusion of the top bar.
31. A device according to claim 27, 28 or 30, wherein a first rotation of the rotational knob permits an opposing axial movement of the hinge mechanisms.
32. A device according to claim 31, wherein the axial movement of the hinge mechanisms permits the top bar and the bottom bar to move towards the central rod.
33. A device according to any of claims 16 to 32, wherein the series of cam mechanisms comprises two cam mechanisms positioned on the central rod opposite one another; each cam mechanism being attached to the protrusion emanating from the join of the left lateral bars and the protrusion emanating from the join of the right lateral bars; the first cam mechanism being positioned between a pair of springs and the first hinge mechanism and the second cam mechanism being positioned between a pair of springs and the second hinge mechanism.
34. A device according to claims 27, 28, 29, 31 or 33, wherein a second rotation of the rotational knob permits opposing lateral movement of the cam mechanisms.
35. A device according to claim 34, wherein the lateral movement of the cam mechanisms permits the left lateral bars and the right lateral bars to move towards the central rod.
36. A device according to any of claims 18 to 35, wherein an inward movement of the top bar, the bottom bar, the left lateral bar and the right lateral bar permit the curved bars to collapse towards the centre of the device.
37. A device according to any of claims 16 to 36, wherein the device is between about 40 mm and about 100 mm in length.
38. A device according to any of claims 16 to 37, wherein the device is between about 4 mm and about 10 mm in diameter.
39. A device according to any of claims 16 to 38, wherein electrospinning can be used to deposit a polymer fibre on the device.
40. A device according to any of claims 16 to 39, wherein the device can be used to design a vascular graft to be used in cardiovascular and non-cardiovascular applications.
41. A device according to any of claims 16 to 40, wherein the device is a mandrel.
42. A compression device for compressing the polymer fibre on the device according to any of claims 16 to 41.
43. A compression device according to claim 42, wherein the compression device comprises a plurality of curved blades, each blade comprising one or more ridges which are configured to correspond with the grooves on the device according to any of claims 20 to 41.
44. A compression device according to claim 42 or claim 43, further comprising a rotating mechanism for opening and closing the compression device.
45. A method for producing a vascular graft using the device of any of claims 16-41, comprising the steps of: a. Depositing a polymer fibre onto the device by electrospinning, in order to achieve an initial desired wall thickness of the vascular graft; b. Stopping deposition of polymer fibre onto the device once the initial desired wall thickness has been achieved; c. Applying pressure to the fibres to ensure the fibres have entered the grooves on the outer surface of the device; d. Carrying out a second step of electrospinning wherein the polymer fibre is deposited onto the device until a second desired wall thickness has been achieved; e. Making an first rotation of the rotational knob to create axial movement of the hinge mechanisms causing the top bar and bottom bar to collapse towards the centre of the device; f. Making a second rotation of the rotational knob to create lateral movement of the cam mechanisms causing the left lateral bar and the right lateral bar to collapse towards the centre of the device; and g. Removing the vascular graft from the device.
46. A method according to claim 45, wherein the initial desired wall thickness is between about 50 pm and about 400 pm.
47. A method according to claim 45 or claim 46, wherein the second desired wall thickness is between about 75 pm and about 800 pm.
48. A method according to any of claims 45-47, wherein the step (c) of applying pressure to the fibres is carried out using a compression device according to any of claims 42-44.
49. A method for manufacturing a device of any of claims 16-41, comprising employing a 3D printing technique.
50. A vascular graft, device or method to produce a vascular graft as described herein in the description and drawings.
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