Patent Description:
In general, a stent is a conduit configured to be placed in a body to create or maintain a passageway within the body. Varieties of stents exist for different purposes, from expandable coronary, vascular, and biliary stents, to simple plastic stents used to allow urine to flow between a kidney and a bladder.

In the context of a prosthetic heart valve, a stent serves as a structural component that can anchor the prosthetic heart valve to the tissue of a heart valve annulus. Such a stent can have varying shapes or diameters. A stent is typically formed of a biocompatible metal frame, such as stainless steel, cobalt-chrome alloy, or nitinol. In some prosthetic heart-valve applications, the stent is made from laser-cut tubing of a plastically expandable metal, which may subsequently be treated to be self-expanding. Other stents that can be used with a prosthetic heart valve include rigid rings, spirally wound tubes, and other tubes that fit within a heart valve annulus and that define an orifice therethrough for the passage of blood.

Some stents used with prosthetic heart valves are self-expanding, while other stents used with prosthetic heart valves are mechanically expandable, for example, balloon-expandable. A self-expanding stent may be crimped or otherwise compressed into a small tube and may possess sufficient elasticity to spring outward by itself when a restraint such as an outer sheath is removed. In contrast, a balloon-expanding stent may be made of a material that is less elastic and that capable of plastic expansion from the inside out when converting the stent from a contracted diameter to an expanded diameter. The plastic expansion may be accomplished with a balloon or other device, for example, a device with mechanical fingers. With such a balloon-expanding stent, the stent material plastically deforms after the application of a deformation force, such as an inflating balloon or expanding mechanical fingers.

<CIT> describes a medical appliance or prosthesis comprising one or more layers of electrospun nanofibers, including electrospun polymers. The electrospun material may comprise layers including layers of polytetrafluoroethylene (PTFE). Electrospun nanofiber mats of certain porosities may permit tissue ingrowth into or attachment to the prosthesis. In one example described in <CIT>, an inner layer is spun onto a mandrel. The inner layer is peeled off the mandrel. The inner layer is reapplied to the mandrel and a wire scaffolding is formed over the mandrel and the inner layer. An outer layer of material is then electrospun onto the scaffold and the inner layer.

A self-expanding stent or balloon-expanding stent may be used as part of a prosthetic heart valve having a single-stage implantation in which a surgeon secures a hybrid heart valve having an anchoring skirt and valve member to a heart valve annulus as one unit or piece. One solution especially for aortic valve replacement is provided by the Edwards Intuity® valve system available from Edwards Lifesciences of Irvine, California. Aspects of the Edwards Intuity valve system are disclosed, for example, in <CIT>. The Edwards Intuity valve is a hybrid of a surgical heart valve and an expandable stent that helps to secure the valve in place. Embodiments of an implantation process use only three sutures, replacing the time-consuming process of placing a dozen or more sutures and tying knots on each. An exemplary delivery system advances the Edwards Intuity valve with the stent at the leading or distal end until it is located within the valve annulus and/or left ventricular outflow tract, at which point a balloon inflates to expand the stent against the aortic annulus and/or ventricular tissue.

<FIG> show an exemplary hybrid prosthetic heart valve <NUM> assembled on a valve holder <NUM> as taught in the prior art, while <FIG> show the valve holder <NUM> separated from the heart valve <NUM>. The prosthetic heart valve <NUM> includes a valve member <NUM> having an anchoring skirt <NUM> attached to an inflow end thereof. The valve member <NUM> is non-collapsible and non-expandable, while the anchoring skirt <NUM> may expand from the contracted state shown in <FIG> into an expanded state. The valve member <NUM> may comprise a surgical valve similar to a Carpentier-Edwards PERIMOUNT Magna® Aortic Heart Valve available from Edwards Lifesciences of Irvine, California. The anchoring skirt <NUM> includes an inner plastically-expandable stent covered with a fabric, for example, a polymeric fabric.

<FIG> show the assembly of a cloth-covered anchoring skirt <NUM> as taught in the prior art. The size of the anchoring skirt <NUM> will vary depending upon the overall size of the heart valve <NUM>. The anchoring skirt <NUM> comprises an inner stent frame <NUM>, a fabric covering <NUM>, and a band-like lower sealing flange <NUM>. The inner stent frame <NUM> may comprise a tubular plastically-expandable member having an undulating or scalloped upper end <NUM> that matches the contours of an inflow portion of the heart valve <NUM>.

In the prior art, the fabric <NUM> was sewn to the stent frame <NUM>. A tubular section of fabric <NUM> was drawn taut around the stent frame, inside and out, and sewn thereto to form an intermediate, cloth-covered frame <NUM>. A particular sequence for attaching the tubular section of fabric <NUM> around the stent frame <NUM> included providing longitudinal suture markers at <NUM>-degree locations around the fabric to enable registration with similarly circumferentially-spaced commissure features on the stent frame. After surrounding the stent frame <NUM> with the fabric <NUM>, a series of longitudinal sutures at each of the three <NUM>-degree locations secured the two components together. Furthermore, a series of stitches were provided along the undulating upper end <NUM> of the stent frame <NUM> to complete the fabric enclosure.

The polymer cloth attached to the bare metal stent serves to reduce friction between the stent and the body orifice, to secure the prosthetic heart valve in the orifice location, to fill gaps through which fluid could pass through, and to provide a location for tissue in-growth. Applying and sewing the cloth, however, is a time-consuming and laborious process. There is thus a need for an alternative method of applying a fabric or fabric-like material to both the inner and outer surfaces of a stent in a way that reduces labor time and production costs. Embodiments disclosed herein satisfy this need and other needs.

The claimed invention is defined in independent claim <NUM> and relates to a prosthetic heart valve comprising a stent body, wherein the stent body comprises an inner surface defining a cavity and an outer surface opposing the inner surface and wherein the stent body has a length between first and second ends of the stent body, and a coat sheet formed from an electrospun material, wherein the coating sheet comprises a first portion that covers at least a portion of the stent body outer surface and a second inverted portion extending inside the cavity of the stent body, wherein the second inverted portion has a diameter that is tapered from a diameter of the first portion, wherein at least one of the first and second ends of the stent body is covered by the coating sheet.

Preferred configurations of the claimed invention are defined in dependent claims <NUM> to <NUM>. In so far as any of the embodiments or examples described herein are not encompassed by the scope of the claims, they are considered to be as supplementary background information and do not constitute a definition of the claimed invention per se.

According to various embodiments of the disclosed technology, there is disclosed a method that is part of an overall process for applying polymeric material to a stent. This may be accomplished using electrospinning techniques coupled with iterative steps and equipment to cover both the inner surface and the outer surface of a stent.

By way of illustration, electrospun polymeric material may be applied to a metal stent while the stent and a supporting mandrel are rotated by a rotary tool. Over time, the electrospinning process produces a layer of polymeric threads or fibers covering the outside of the metal stent. While the polymeric threads are being applied to the stent, the threads also layer over the mandrel that supports the stent. If the mandrel has a diameter less than the diameter of the stent, then a tapered layer of polymeric material is produced, forming a cone or frustum of polymeric material that extends from the surface of the mandrel to the stent. This cone of polymeric material can then be used as an inner layer of material for the stent by placing the material inside the stent.

The placement of the cone of polymeric material inside the stent may be accomplished by moving the mandrel with respect to the stent, which inverts the cone of polymeric material and wraps it in toward the inner surface of the stent. In this way, both the inner surface and the outer surface of the stent may be fully encased with polymeric material without the need for applying and sewing a pre-made polymeric cloth.

In accordance with a particular embodiment, there is disclosed a method of applying an electrospun material to an inner surface of a stent. The method comprises coupling a mandrel to a stent body. The stent body comprises an inner surface defining a cavity and an outer surface opposing the internal surface. The stent body also has a length along an axis defined by the mandrel between a first end of the stent body and a second end of the stent body. An electrospun material is applied to at least a portion of the stent external surface and to at least a portion of the mandrel to form a coating sheet. A portion of the coating sheet extends from at least one of the first end or second end of the stent to the mandrel. One or both of the stent and the mandrel are moved to apply at least some of the portion of the coating sheet onto the internal surface of the stent body.

In one embodiment, the step of coupling the mandrel to the stent body comprises the steps of attaching the stent body to a valve holder and threading the valve holder onto the mandrel. The step of attaching the stent body to the valve holder comprises the step of suturing the stent body to the valve holder. The stent body comprises a plurality of commissure ends. The valve holder comprises a plurality of stabilizing legs. Each of the plurality of commissure ends is attached to one of the plurality of stabilizing legs. The valve holder may be adhered to the mandrel.

In another embodiment, the mandrel comprises a secondary frame portion. The portion of the coating sheet extends from at least one of the first end or second end of the stent to the secondary frame portion of the mandrel.

A further embodiment comprises the step of attaching the mandrel to a rotary tool and the step of orienting a spinneret so that the spinneret is directed substantially toward the stent body and substantially perpendicular to the axis defined by the mandrel. A voltage is placed between the spinneret and the mandrel. Both the mandrel and the stent body are rotated about the axis defined by the mandrel. Both the mandrel and the stent body are also oscillated along the axis defined by the mandrel.

In a further embodiment, the step of moving one or both of the stent and the mandrel produces an inverted portion of the coating sheet extending inside the cavity of the stent.

In yet a further embodiment, the portion of the coating sheet comprises an excess portion that is not applied onto the inner surface of the stent body. The method further comprises the step of applying at least some of the excess portion onto the outer surface of the stent body.

Each feature, concept, or step is independent, but can be combined with any other feature, concept, or step disclosed in this application.

In accordance with another particular embodiment there is disclosed a method of applying an electrospun material to an inner surface of a stent. The method comprises the step of coupling a mandrel to a stent body. The stent body comprises an inner surface defining a cavity and an outer surface opposing the inner surface. The stent body has a length along an axis defined by the mandrel between a first end of the stent body and a second end of the stent body. A secondary frame is coupled to the mandrel. An electrospun material is applied to at least a portion of the stent outer surface and to at least a portion of the secondary frame to form a coating sheet. A portion of the coating sheet extends from at least one of the first end or second end of the stent to the secondary frame. One or both of the stent and the secondary frame are moved to apply at least some of the portion of the coating sheet onto the inner surface of the stent body.

In one embodiment, the stent has a stent diameter. The secondary frame has a secondary frame diameter. The stent diameter is greater than the secondary frame diameter.

Another embodiment comprises the step of positioning the stent body so that the stent body is between the secondary frame and the valve holder. An alternative embodiment comprises the step of positioning the stent body so that the secondary frame extends within the cavity of the stent body.

In another embodiment, the step of applying the electrospun material further comprises the step of concurrently rotating both the stent body and the secondary frame about the axis defined by the mandrel and oscillating both the stent body and the secondary frame along the axis defined by the mandrel. The step of moving one or both of the stent and the secondary frame produces an inverted portion of the coating sheet extending inside the cavity of the stent.

In accordance with another particular embodiment there is disclosed a method of applying an electrospun material to an inner surface of a stent. The method comprises providing a stent defining an axis and having an inner surface, an outer surface, a first end, a second end, and a central cavity. A mandrel is extended axially within the central cavity of the stent. The stent and the mandrel are rotated along the axis. An electrospun material is applied to at least a portion of the outer surface of the stent, and to at least a portion of the mandrel, while the stent and the mandrel are rotating along or around the axis, so that a sheet of the electrospun material is formed, tapering from at least one of the first end or the second end of the stent to the mandrel. Either or both of the stent and the mandrel are moved along the axis so that at least a portion of the sheet of the electrospun material is inverted within the central cavity of the stent. At least a portion of the inner surface of the stent is covered with the portion of the sheet of the electrospun material.

Other features and aspects of the disclosed technology will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, which illustrate, by way of example, the features in accordance with embodiments of the disclosed technology. The summary is not intended to limit the scope of any inventions described herein, which are defined solely by the claims attached hereto.

The technology disclosed herein, in accordance with one or more various embodiments, is described in detail with reference to the following figures. The drawings are provided for purposes of illustration only and merely depict typical or example embodiments of the disclosed technology. These drawings are provided to facilitate the reader's understanding of the disclosed technology and should not be considered limiting of the breadth, scope, or applicability thereof. For clarity and ease of illustration, these drawings are not necessarily made to scale.

The figures are not intended to be exhaustive or to limit the invention to the precise form disclosed. The invention can be practiced with modification and alteration, and the disclosed technology is limited only by the claims and the equivalents thereof.

Embodiments of the technology disclosed herein are directed toward methods for applying material to a stent. More particularly, various embodiments of the technology disclosed herein relate to methods for applying an electrospun material to the inner and outer surfaces of a stent.

Referring to <FIG> of the illustrative drawings, there is shown a system <NUM> for applying an electrospinning material <NUM> to a stent <NUM>. The system <NUM> comprises a source of electrospinning material <NUM>, a collector <NUM>, and a controller <NUM>. The source of electrospinning material is any suitable device, for example, a device comprising a spinneret electrically coupled to a voltage source. As discussed below, embodiments of the source include at least one syringe pump, at least one syringe mounted on the at least one syringe pump, and at least one syringe needle fluidly coupled to the at least one syringe, where the at least one syringe needle is a spinneret. In some embodiments, the voltage source is electrically coupled to the at least one syringe needle. As used herein, the term "syringe pump" may include the combination of a syringe pump, syringe, and syringe needle, as will be apparent by context.

In one embodiment, the electrospinning material <NUM> is a solution of polyethylene terephthalate (PET). The PET solution may be created by mixing PET, for example, at about <NUM>% to <NUM>% by weight, with a suitable solvent or mixture of solvents, such as hexafluoroisopropanol (HFIP) at about <NUM>% to <NUM>% by weight, and permitting the PET to dissolve fully. In a particular embedment, the PET solution is created by mixing PET at about <NUM>% to <NUM>% by weight with a solvent such as HFIP at about <NUM>% to <NUM>% by weight. Instead of or in addition to PET, another polymer may be used, either alone or in combination, such as a polymer selected from the group consisting of polytetrafluoroethylene (PTFE), polycaprolactone (PCL), polydioxanone (PDO), polyglycolic acid (PGA), and polyurethane (PU). Additionally, one or more drugs and/or biologically active ingredients may be added to the solution. Similarly, other solvents or mixtures thereof are used in other embodiments.

In one embodiment, the stent <NUM> is a stent for use as part of a prosthetic heart valve, such as the Edwards Intuity® valve system disclosed in <CIT> or the Edwards SAPIEN® Transcatheter Heart Valve. The stent <NUM> may be an expandable stainless-steel stent. The material, however, is not limited to stainless steel, and other materials such as cobalt-chrome alloys and nitinol may be used. A first end <NUM> of the stent (see <FIG>) follows a generally circular, undulating path having alternating arcuate troughs and pointed peaks that generally correspond to the undulating contour of the underside of a sewing ring (not shown) for use as part of a prosthetic heart valve. A second end <NUM> of the stent substantially describes a circle without the undulations. A mid-section of the stent has three rows of expandable struts <NUM> extending circumferentially in a sawtooth or chevron pattern between axially-extending struts <NUM>. The first end <NUM> of the stent comprises a continuous, relatively thicker reinforcing ring having a substantially constant diameter interrupted by eyelets <NUM>. The stent frame <NUM> comprises an inner surface <NUM> defining a cavity <NUM> and an outer surface <NUM> opposing the inner surface.

The syringe pump <NUM> serves as the source of the electrospinning material <NUM> to be applied to the stent <NUM>. Some embodiments include a plurality of syringe pumps. In general, electrospinning uses an electrical charge to draw very fine (typically on the micro- or nanometer scale) fibers from a liquid, such as a polymer solution or a polymer melt. In one electrospinning method, the polymer is discharged through a charged orifice toward a target, wherein the orifice and the target have opposing electrical charges. A voltage source is provided that creates a first charge at the charged orifice and an opposing charge at the target. The polymer is electrostatically charged by contact with the charged orifice. The electrostatically charged polymer is then collected at the target. Electrospinning PTFE is described in <CIT>.

An embodiment of a syringe pump <NUM> is shown in <FIG>. In this embodiment, the syringe pump <NUM> is a KDS100 syringe pump made by KD Scientific Inc. of Holliston, Massachusetts, although other syringe pumps, pressure sources, and/or solution reservoir/dispensers may alternatively be used. In a particular embodiment, the syringe pump <NUM> is configured for a flow rate of about <NUM> milliliters per hour.

The syringe pump <NUM> is used with a syringe <NUM>, as shown in <FIG>. In one embodiment, the syringe <NUM> is a <NUM>-mL plastic syringe, although other syringes may alternatively be used. The syringe <NUM> comprises a cylindrical body <NUM> defining a reservoir <NUM>, into which an amount of the electrospinning material <NUM> is placed. After the reservoir <NUM> is filled, the syringe <NUM> is placed horizontally on the syringe holder block <NUM> of the syringe pump <NUM> and is fixed in place using a syringe clamp <NUM>. In other embodiments, the syringe is fixed in another orientation, for example, vertically, or at a different angle.

Once the syringe pump <NUM> is fitted with a loaded syringe <NUM>, the orifice <NUM> of the syringe may be connected to a plastic tube that leads to a spinneret <NUM> having a spinneret tip <NUM>. In one embodiment, the spinneret <NUM> is a stainless-steel needle having an inner diameter of approximately <NUM> millimeters, although other spinnerets may alternatively be used. The electrospinning material <NUM> is electrostatically drawn from the spinneret tip <NUM> by placing or applying a high voltage or potential difference between the spinneret tip and the collector <NUM> using a high-voltage power supply <NUM> connected by wires <NUM> to the spinneret and the collector. In one embodiment, the high-voltage power supply <NUM> is an about <NUM> kV to <NUM> kV direct-current power supply. In a particular embodiment, the high-voltage power supply <NUM> is configured to apply a voltage of approximately <NUM> kV. Other potentials are applied in other embodiments, for example, where the electrospinning parameters include one of a polymer other than PET and/or a solvent other than HFIP.

An embodiment of a collector <NUM> is shown in <FIG>. The collector <NUM> comprises a base <NUM> configured to hold a rotary tool <NUM> at a first end <NUM> and a rotary holder <NUM> at a second end <NUM>. The rotary tool <NUM> comprises a rotor motor configured to rotate a first collet <NUM> and a slide motor configured to slide the first collet back and forth with respect to the rotatory holder <NUM> in an oscillating fashion. The rotary holder <NUM> has a corresponding second collet <NUM>. A mandrel <NUM> (see <FIG>) may be placed in the collector <NUM> by placing a first end <NUM> of the mandrel in the first collet <NUM> and a second end <NUM> of the mandrel in the second collet <NUM>. The rotary tool <NUM> is coupled via a cable <NUM> to the controller <NUM> for controlling the rotor and slide motors.

An embodiment of a controller <NUM> is shown in <FIG>. The controller <NUM> shown in <FIG> includes a DC motor controller comprising a rotor switch <NUM> for turning the rotor motor on and off, a slide switch <NUM> for turning the slide motor on and off, a rotor speed dial <NUM> for controlling the rotational speed of the rotor motor, and a slide speed dial <NUM> for controlling the oscillation speed of the slide motor. Other types of controllers are used in other embodiments.

Referring to <FIG> of the illustrative drawings, there is shown an embodiment of a mandrel <NUM> for use in the system <NUM>, the mandrel holding a stent holder or valve holder <NUM>, which in turn holds a stent <NUM>. The mandrel <NUM> may be an approximately <NUM>-millimeter stainless-steel rod, although mandrels of different diameters and materials may alternatively be used. In one embodiment, the mandrel <NUM> has a diameter that is less than the diameter of the stent <NUM>.

The valve holder <NUM> is used to hold the stent <NUM>. In one embodiment, the stent holder <NUM> may be a valve holder <NUM> as shown in <FIG>. The stent holder <NUM>, as seen in <FIG>, includes a central tubular hub portion <NUM> and a plurality of stabilizing legs <NUM> projecting axially and radially outward therefrom. In the embodiment shown, the stent holder <NUM> has three stabilizing legs <NUM>, although a stent holder having greater or fewer stabilizing legs may be used. The central tubular hub portion <NUM> has an internal bore <NUM>. The stent holder <NUM> may be formed of a rigid polymer such as acetal (DELRIN®, DuPont), nylon, or polypropylene. The stent <NUM> is directly secured to the stabilizing legs <NUM> of the stent holder <NUM> using sutures <NUM> at the commissure ends <NUM> of the stent <NUM> in the illustrated embodiment, although stent holder and stent are secured using other methods in other embodiments, for example, using pins, clips, clamps, or frictionally.

The stent holder <NUM> is threaded onto the mandrel <NUM> via the stent holder's internal bore <NUM>. In one embodiment, the stent holder <NUM> (and stent <NUM>) may be left free to translate along an axis <NUM> defined by the mandrel <NUM>. In another embodiment, the stent holder <NUM> may be secured to the mandrel <NUM>, for example, mechanically or adhesively using an adhesive or adhering means <NUM> that is non-permanent. Examples of suitable adhesive or adhering means include epoxy and adhesive tape.

In one embodiment, a secondary frame <NUM> may be additionally threaded onto the mandrel <NUM> so that the stent <NUM> is positioned between the secondary frame <NUM> and the stent holder <NUM>. In the embodiment shown in <FIG>, the secondary frame <NUM> comprises a plurality of support elements, which in the illustrated embodiment comprise outer loops <NUM> connected together by a plurality of connecting wires <NUM>. Each of the plurality of outer loops <NUM> is connected via a plurality of spokes <NUM> to one of a plurality of inner loops <NUM>, which are sized and arranged to form an internal bore <NUM> through which the mandrel <NUM> may be threaded. Other embodiments use fewer or more support elements, and/or support elements with different diameters, structures (for example, disks), and/or shapes (for example, non-circular). In another embodiment (see, for example, <FIG>), the secondary frame <NUM> is a piece of metal or other suitable material, such as stainless steel, ceramic, or polymer, having an internal bore through which the mandrel <NUM> may be threaded. In one embodiment, the secondary frame <NUM> has a diameter that is less or smaller than the diameter or inner diameter of the stent <NUM>. In a particular embodiment, the secondary frame <NUM> extends at least partially within the cavity <NUM> of the stent <NUM>.

Referring to <FIG> of the illustrative drawings, there is shown a method <NUM> of applying an electrospun material to a stent.

The method comprises a step <NUM> of coupling a mandrel to a stent body. The stent may be a stent <NUM> and the mandrel may be a mandrel <NUM>, as described above.

In one embodiment, the step <NUM> comprises the step <NUM> of attaching the stent <NUM> to the stabilizing legs of a stent or valve holder (such as the stent holder <NUM>), for example, as described above using an attaching means, such as sutures at the commissure ends <NUM> of the stent <NUM>. The step <NUM> may also comprise the step <NUM> of placing the stent holder <NUM> onto the mandrel <NUM> so that the mandrel extends axially within the stent holder's internal bore <NUM>. In a particular embodiment, the step <NUM> precedes the step <NUM>, while in another embodiment, the step <NUM> precedes the step <NUM>.

As described above, the stent holder <NUM> (and stent <NUM>) may be left free to translate along the axis <NUM> defined by the mandrel <NUM>. In one embodiment, however, the step <NUM> further comprises the step <NUM> of securing the stent holder <NUM> to the mandrel <NUM>, for example, mechanically or using an adhesive or adhering means <NUM> that is non-permanent, such as epoxy or adhesive tape, to the mandrel.

In step <NUM>, a secondary frame is coupled to the mandrel <NUM> so that the stent <NUM> is positioned between the secondary frame and the stent holder <NUM>. In one embodiment, the secondary frame is the secondary frame <NUM> shown in <FIG>. In another embodiment, as shown in <FIG>, the secondary frame is a piece of metal or other suitable material <NUM>, such as stainless steel, ceramic, or polymer, having an internal bore through which the mandrel <NUM> may be threaded. At least a portion of the metal piece <NUM> has a diameter that is less than the diameter or inner diameter of the stent <NUM> but greater than the diameter of the mandrel <NUM>. In the particular embodiment shown in <FIG>, the metal piece <NUM> is positioned with respect to the stent <NUM> so that a portion of the metal piece extends within the cavity <NUM> of the stent <NUM>.

In step <NUM>, the mandrel <NUM> is placed on a collector (such as the collector <NUM>). In one embodiment, the placement of the mandrel <NUM> on the collector is accomplished by placing the first end <NUM> of the mandrel in the first collet <NUM> and the second end <NUM> of the mandrel in the second collet <NUM>. <FIG> shows a collector <NUM> holding a mandrel <NUM>, a stent holder <NUM>, and a stent <NUM>.

In step <NUM>, the stent <NUM> and the mandrel <NUM> are concurrently rotated about and oscillated along the axis <NUM> defined by the mandrel <NUM>. As described above, the collector <NUM> may comprise a rotary tool <NUM> having a rotor motor configured to rotate a collet and a slide motor configured to slide the collet back and forth in an oscillating fashion, with the collet holding an end of the mandrel. The operational parameters of the rotary tool <NUM> may be controlled by the controller <NUM>.

In step <NUM>, a syringe pump (such as the syringe pump <NUM>) is fitted with a syringe (such as the syringe <NUM>) containing an amount of an electrospinning material (such as the electrospinning material <NUM>). The electrospinning material <NUM> may be placed in the reservoir <NUM> of the syringe <NUM>. The syringe <NUM> may be placed on the syringe holder block <NUM> of the syringe pump <NUM> and fixed in place using the syringe clamp <NUM>.

In step <NUM>, the orifice <NUM> of the syringe <NUM> is connected via a tube to a spinneret (such as the spinneret <NUM>), with the spinneret positioned and oriented so that the spinneret tip <NUM> is directed toward the stent <NUM>. In an alternative embodiment, the spinneret <NUM> is connected directly to the orifice <NUM> of the syringe <NUM>. The spinneret <NUM> may be oriented so that it is approximately perpendicular to the axis defined by the mandrel <NUM>.

In step <NUM>, a voltage or potential is placed or applied between the spinneret tip <NUM> and the collector <NUM>. In one embodiment, the voltage may be applied by connecting the high-voltage power supply <NUM> by the wires <NUM> to the spinneret <NUM> and the collector <NUM>. As part of step <NUM>, the high-voltage power supply <NUM> may be configured to apply a voltage of about <NUM> kV to <NUM> kV. In a particular embodiment, the high-voltage power supply <NUM> may be configured to apply a voltage of about <NUM> kV.

In step <NUM>, the electrospinning material <NUM> is applied to at least a portion of the outer surface <NUM> of the stent <NUM> and to at least a portion of the mandrel <NUM> to form a coating sheet <NUM>. The application of the electrospinning material <NUM> produces a first cone portion <NUM> of the coating sheet <NUM> extending from the second end <NUM> of the stent <NUM> to the mandrel <NUM>. <FIG> shows such a coating sheet <NUM> formed on the mandrel <NUM>, the stent holder <NUM>, and the outer surface <NUM> of the stent <NUM>. The first cone portion <NUM> of the coating sheet <NUM> extends from the second end <NUM> of the stent <NUM> to the mandrel <NUM>. A second cone portion <NUM> of the coating sheet <NUM> extends from the first end <NUM> of the stent <NUM> to the central tubular hub portion <NUM> of the stent holder <NUM>.

In step <NUM>, the mandrel <NUM> (along with the coated stent <NUM> and stent holder <NUM>) is removed from the collector <NUM>.

In step <NUM>, one of the stent <NUM> and the mandrel <NUM> are moved axially with respect to the other of the stent <NUM> and the mandrel <NUM>. Alternatively, in step <NUM>, both of the stent <NUM> and the mandrel <NUM> may be moved axially with respect to each other. The movement produces an inverted portion <NUM> of the coating sheet <NUM> extending inside the cavity <NUM> of the stent <NUM> from one of the first end <NUM> or the second end <NUM> of the stent. The inverted portion <NUM> may be formed from the first cone portion <NUM> or the second cone portion <NUM> of the coating sheet <NUM>. <FIG> shows a coating sheet <NUM> formed on the mandrel <NUM>, the stent holder <NUM>, and the outer surface <NUM> of the stent <NUM>. An inverted portion <NUM> of the coating sheet <NUM> extends from the second end <NUM> of the stent <NUM> to the mandrel <NUM>.

In one embodiment, prior to or after performing the step <NUM>, a step <NUM> may be performed of removing at least some of the second cone portion <NUM> of the coating sheet <NUM>. The removal of the second cone portion <NUM> of the coating sheet <NUM> may be accomplished by cutting the second cone portion where it meets the first end <NUM> of the stent <NUM>. The coating sheet on the outer surface <NUM> of the stent <NUM> is left undisturbed. <FIG> shows a coating sheet <NUM> formed on the mandrel <NUM> and the outer surface <NUM> of the stent <NUM>. The second cone portion <NUM> of the coating sheet <NUM> has been removed. An inverted portion <NUM> of the coating sheet <NUM> extends from the second end <NUM> of the stent <NUM> to the mandrel <NUM>.

Once the step <NUM> is performed, a step <NUM> may be performed of removing the stent holder <NUM> from the stent <NUM>. The removal of the stent holder <NUM> from the stent <NUM> may be accomplished by disengaging the members securing the two together, for example, by cutting the sutures <NUM> at the commissure ends <NUM> of the stent <NUM>.

In step <NUM>, at least some of the inverted portion <NUM> of the coating sheet <NUM> is applied onto the inner surface <NUM> of the stent <NUM>. In one embodiment, this application is accomplished simply by the movement in step <NUM> of moving the stent <NUM> with respect to the mandrel <NUM> and allowing the inverted portion <NUM> of the coating sheet <NUM> to adhere to the inner surface <NUM> of the stent. In another embodiment, this application is accomplished by a user (for example, manually using fingers) or a tool applying sufficient force to the inverted portion <NUM> of the coating sheet <NUM> so that the inverted portion adheres and/or extends along at least a portion of the inner surface <NUM> of the stent <NUM>. <FIG> shows a coating sheet <NUM> applied to both the inner surface <NUM> and the outer surface <NUM> of the stent <NUM>, producing a covered stent <NUM>.

In one embodiment, the method <NUM> may be repeated to produce a thicker encapsulation of the stent. In another embodiment, the inverted portion <NUM> of the coating sheet <NUM> extends beyond the inner surface <NUM> of the stent <NUM>, forming an excess portion. In this embodiment, the method <NUM> may further comprise a step <NUM> of folding the excess portion of the inverted portion <NUM> back onto the outer surface <NUM> of the stent <NUM>, producing a second layer of material on the outer surface of the stent and completely encapsulating the stent.

The method <NUM> thus produces a covered stent <NUM> that has a consistent inner and outer covering. The method <NUM> desirably results in less handling of the stent, reduced labor time, and reduced material costs as compared to sewing a pre-made polymeric cloth onto the stent.

Additionally, the method <NUM> can provide control over the properties of the electrospun material in a way that is not possible with the sewing method. For example, the flowrate of the electrospinning material <NUM> can be controlled by adjusting the flowrate of the syringe pump <NUM>. The voltage between the spinneret tip <NUM> and the collector <NUM> can be controlled by adjusting the voltage applied by the high-voltage power supply <NUM>. The rotational speed of the rotor motor and the oscillation speed of the slide motor in the rotary tool <NUM> can be controlled by adjusting the rotor speed dial <NUM> and the slide speed dial <NUM> on the controller <NUM>.

By controlling the equipment settings and electrospinning time, an operator can produce select for different material properties at localized points, a more streamlined construction that permits increased laminar flow through the stent, and/or a pore size in the coating sheet that permits appropriate tissue ingrowth. In one embodiment, the equipment settings and electrospinning time are adjusted to produce a coating sheet <NUM> with at least a portion thereof having some combination of: a thickness in the range of from about <NUM> to about <NUM> millimeters, inter-nodular distances in the range of from about <NUM> to about <NUM> microns, a tensile strength in the range of from about <NUM> MPa to about <NUM> MPa (from about <NUM> to about <NUM> pounds per square inch), and an average density of from about <NUM> to about <NUM> grams per milliliter.

In one embodiment, instead of using the stent holder <NUM>, an inner holder is used to hold the stent <NUM>. Referring to <FIG> of the illustrative drawings, there is shown an embodiment of an inner holder <NUM> for holding the stent <NUM>. The inner holder <NUM>, as seen in <FIG>, includes a central tubular hub portion <NUM> and a plurality of stabilizing legs <NUM> projecting outward therefrom. In the embodiment shown, the inner holder <NUM> has three stabilizing legs <NUM>, although an inner holder having greater or fewer stabilizing legs may be used. The central tubular hub portion <NUM> has an internal bore <NUM>. The inner holder <NUM> may be formed of metal or a rigid polymer, such as acetal (DELRIN®, DuPont), nylon, or polypropylene. The stent <NUM> is held by the stabilizing legs <NUM> of the inner holder <NUM> by positioning the inner holder in the cavity <NUM> of the stent and contracting the stent and/or expanding the holder so that at least a portion of the inner surface <NUM> of the stent contacts an outer surface <NUM> of the stabilizing legs (see <FIG>). In other embodiments, the inner holder includes another structure, for example, an expanding mandrel or a balloon.

In one embodiment, each of the plurality of stabilizing legs <NUM> of the inner holder <NUM> comprises a radial portion <NUM> extending in a generally radial direction outward from an outer surface <NUM> of the central tubular hub portion <NUM> and an angular portion <NUM> extending in a generally angular direction about an axis <NUM> defined by the central tubular hub portion. The outer surface <NUM> is on the angular portion <NUM> of the inner holder <NUM>.

The inner holder <NUM> allows the stent <NUM> to be placed on the mandrel <NUM> without the use of sutures and lessens interference during the electrospinning steps. Referring to <FIG> of the illustrative drawings, the inner holder <NUM> is threaded onto the mandrel <NUM> via the inner holder's internal bore <NUM>. In one embodiment, the inner holder <NUM> (and stent <NUM>) may be left free to translate along the axis <NUM> defined by the mandrel <NUM>. In another embodiment, the inner holder <NUM> may be secured to the mandrel <NUM> mechanically or adhesively, for example, using the adhering means <NUM>. In a further embodiment, the inner holder <NUM> may be kept in position on the mandrel <NUM> using a stop or collar, for example, by threading an elastomer tube <NUM> onto the mandrel (see <FIG>).

In one embodiment, a secondary frame <NUM> may be additionally threaded onto the mandrel <NUM>. As shown in <FIG>, the secondary frame <NUM> may be threaded onto the mandrel <NUM> so that the secondary frame is facing the undulating or scalloped first end <NUM> of the stent <NUM>. In an alternative embodiment, the secondary frame <NUM> may be threaded onto the mandrel <NUM> so that the secondary frame is facing the second end <NUM> of the stent <NUM>. In the embodiment shown in <FIG>, the secondary frame <NUM> comprises a suitable material, for example, a piece of metal, such as stainless steel, ceramic, or polymer having an internal bore <NUM> through which the mandrel <NUM> may be threaded. In an alternative embodiment, the secondary frame <NUM> includes a 3D-printed polymer fixture or a balloon. In the embodiment shown in <FIG>, the secondary frame <NUM> has a diameter that is less or smaller than the diameter or inner diameter of the stent <NUM>.

In one embodiment, the secondary frame <NUM> comprises a cylindrical portion <NUM> and a conical portion <NUM>. The diameter of the cylindrical portion <NUM> is greater than the diameter of the mandrel <NUM> and slightly less than the outermost diameter of the inner holder <NUM>. In a particular embodiment, the diameter of the cylindrical portion <NUM> is approximately <NUM> millimeters to approximately <NUM> millimeters less than the outermost diameter of the inner holder <NUM>. When used with a coating sheet <NUM> having a thickness in the range of from about <NUM> to about <NUM> millimeters, such a cylindrical portion diameter permits the axial movement of one or both of the stent <NUM> and the secondary frame <NUM> so that at least some of the coating sheet can be applied onto the inner surface <NUM> of the stent.

In one embodiment, the cylindrical portion <NUM> of the secondary frame <NUM> has a length <NUM> equal to or greater than a length <NUM> of the stent <NUM>, measured from an eyelet <NUM> of the first end <NUM> of the stent to the second end <NUM> of the stent. In a particular embodiment, the length <NUM> is equal to or greater than twice the length <NUM> of the stent <NUM>. Such a cylindrical portion length permits the inverted portion <NUM> of the coating sheet <NUM> (originally electrospun onto an outer surface <NUM> of the secondary frame <NUM>) to extend beyond the inner surface <NUM> of the stent <NUM> by an amount sufficient to allow the excess portion to be folded back onto the outer surface <NUM> of the stent, producing a second layer of material covering the outer surface of the stent when implemented as described below.

Similar to the method <NUM>, the method <NUM> comprises a step <NUM> of coupling a mandrel to a stent body. The stent may be a stent <NUM> and the mandrel may be a mandrel <NUM>, as described above.

In one embodiment, the step <NUM> comprises the step <NUM> of positioning an inner holder (such as the inner holder <NUM>) in the cavity of the stent <NUM> and the step <NUM> of contracting the stent so that at least a portion of the inner surface <NUM> of the stent contacts the outer surface <NUM> of the stabilizing legs <NUM> of the inner holder <NUM> (see <FIG>). The step <NUM> may also comprise the step <NUM> of placing the inner holder <NUM> onto the mandrel <NUM> so that the mandrel extends axially within the inner holder's internal bore <NUM>. In a particular embodiment, the steps <NUM> and <NUM> precede the step <NUM>, while in another embodiment, the step <NUM> precedes the steps <NUM> and <NUM>.

As described above, the inner holder <NUM> (and stent <NUM>) may be left free to translate along the axis <NUM> defined by the mandrel <NUM>. In one embodiment, however, the step <NUM> further comprises the step <NUM> of securing the inner holder <NUM> to the mandrel <NUM> mechanically or adhesively, for example, by adding an adhering means <NUM> that is non-permanent, such as epoxy or adhesive tape, to the mandrel.

In step <NUM>, a secondary frame is coupled to the mandrel <NUM> so that the secondary frame is facing the undulating or scalloped first end <NUM> of the stent <NUM>. In an alternative embodiment, the secondary frame may be threaded onto the mandrel <NUM> so that the secondary frame is facing the second end <NUM> of the stent <NUM>. In one embodiment, the secondary frame is the secondary frame <NUM> shown in <FIG>.

In step <NUM>, the secondary frame <NUM> moved with respect to the stent <NUM> so that the secondary frame <NUM> extends at least partially within the cavity <NUM> of the stent <NUM>. <FIG> shows a mandrel <NUM> on which an inner holder <NUM>, a stent <NUM>, and a secondary frame <NUM> have been threaded so that the secondary frame extends at least partially within the cavity <NUM> of the stent. An stop or collar, for example, an elastomer ring <NUM>, may additionally be threaded onto the mandrel <NUM> and positioned adjacent an apex <NUM> of the conical portion <NUM> of the secondary frame <NUM> to keep the secondary frame in position on the mandrel.

In step <NUM>, similar to the step <NUM>, the mandrel <NUM> is placed on a collector (such as the collector <NUM>). In one embodiment, the placement of the mandrel <NUM> on the collector is accomplished by placing the first end <NUM> of the mandrel in the first collet <NUM> and the second end <NUM> of the mandrel in the second collet <NUM>.

In step <NUM>, similar to the step <NUM>, the stent <NUM> and the mandrel <NUM> are concurrently rotated about and oscillated along the axis <NUM> defined by the mandrel <NUM>. As described above, the collector <NUM> may comprise a rotary tool <NUM> having a rotor motor configured to rotate a collet and a slide motor configured to slide the collet back and forth in an oscillating fashion, with the collet holding an end of the mandrel. The rotary tool <NUM> may be controlled by the controller <NUM>.

In step <NUM>, similar to the step <NUM>, a syringe pump (such as the syringe pump <NUM>) is fitted with a syringe (such as the syringe <NUM>) containing an amount of an electrospinning material (such as the electrospinning material <NUM>). The electrospinning material <NUM> may be placed in the reservoir <NUM> of the syringe <NUM>. The syringe <NUM> may be placed horizontally on the syringe holder block <NUM> of the syringe pump <NUM> and fixed in place using the syringe clamp <NUM>.

In step <NUM>, similar to the step <NUM>, the orifice <NUM> of the syringe <NUM> is connected via a tube to a spinneret (such as the spinneret <NUM>), with the spinneret positioned and oriented so that the spinneret tip <NUM> is directed toward the stent <NUM>. In an alternative embodiment, the spinneret <NUM> is connected directly to the orifice <NUM> of the syringe <NUM>. The spinneret <NUM> may be oriented so that it is approximately perpendicular to the axis defined by the mandrel <NUM>.

In step <NUM>, similar to the step <NUM>, a voltage is placed or applied between the spinneret tip <NUM> and the collector <NUM>. In one embodiment, the voltage may be placed by connecting the high-voltage power supply <NUM> by the wires <NUM> to the spinneret <NUM> and the collector <NUM>. As part of step <NUM>, the high-voltage power supply <NUM> may be configured to apply a voltage of about <NUM> kV to <NUM> kV. In a particular embodiment, the high-voltage power supply <NUM> may be configured to apply a voltage of about <NUM> kV.

In step <NUM>, the electrospinning material <NUM> is applied to at least a portion of the outer surface <NUM> of the stent <NUM> and to at least a portion of the secondary frame <NUM> to form a coating sheet <NUM>. The application of the electrospinning material <NUM> produces a first portion <NUM> of the coating sheet <NUM> on the outer surface <NUM> of the stent <NUM> and a second portion <NUM> of the coating sheet on the outer surface <NUM> of the secondary frame <NUM>. <FIG> shows such a coating sheet <NUM> formed on the mandrel <NUM>, the outer surface <NUM> of the secondary frame <NUM>, and the outer surface <NUM> of the stent <NUM>. A cone portion <NUM> of the coating sheet <NUM> extends from the second end <NUM> of the stent <NUM> to the mandrel <NUM>.

In step <NUM>, the mandrel <NUM> (along with the coated stent <NUM>, the inner holder <NUM> and the coated secondary frame <NUM>) is removed from the collector <NUM>.

In step <NUM>, the cone portion <NUM> and other surplus portions of the coating sheet <NUM> beyond the first portion <NUM> and the second portion <NUM> are removed. The removal of the surplus portions of the coating sheet <NUM> may be accomplished, for example, by cutting the coating sheet at the apex <NUM> of the conical portion <NUM> of the secondary frame <NUM>, and at the second end <NUM> of the stent <NUM>. The first portion <NUM> and the second portion <NUM> are left undisturbed. <FIG> show a coating sheet <NUM> formed on the mandrel <NUM>, the outer surface <NUM> of the secondary frame <NUM>, and the outer surface <NUM> of the stent <NUM>. The cone portion <NUM> and other surplus portions of the coating sheet <NUM> beyond the first portion <NUM> and the second portion <NUM> have been removed.

In step <NUM>, the inner holder <NUM> is removed from the cavity <NUM> of the stent <NUM>.

In step <NUM>, one of the stent <NUM> and the secondary frame <NUM> are moved axially with respect to the other of the stent <NUM> and the secondary frame <NUM>. Alternatively, in step <NUM>, both of the stent <NUM> and the secondary frame <NUM> may be moved axially with respect to each other. The movement produces an inverted portion <NUM> of the coating sheet <NUM> extending inside the cavity <NUM> of the stent <NUM> from the first end <NUM> of the stent. The inverted portion <NUM> may be formed from the second portion <NUM> of the coating sheet <NUM>. In one embodiment, steps <NUM> and <NUM> are combined, with the secondary frame <NUM> pushing the inner holder <NUM> out of the cavity <NUM> of the stent <NUM> as the secondary frame is moved.

In step <NUM>, similar to the step <NUM>, at least some of the inverted portion <NUM> of the coating sheet <NUM> is applied onto the inner surface <NUM> of the stent <NUM>. In one embodiment, this application is accomplished simply by the movement in step <NUM> of moving the stent <NUM> with respect to the secondary frame <NUM> and allowing the inverted portion <NUM> of the coating sheet <NUM> to adhere to the inner surface <NUM> of the stent. In another embodiment, this application is accomplished by a user (for example, manually using fingers) or a tool applying a sufficient force to the inverted portion <NUM> of the coating sheet <NUM> so that the inverted portion extends along and/or adheres to at least a portion of the inner surface <NUM> of the stent <NUM>. <FIG> shows a coating sheet <NUM> applied to both the inner surface <NUM> and the outer surface <NUM> of the stent <NUM>, producing a covered stent having an excess portion <NUM> of the coating sheet <NUM> extending beyond the second end <NUM> of the stent.

In step <NUM>, the excess portion <NUM> of the coating sheet <NUM> is folded back onto or over the outer surface <NUM> of the stent <NUM>, producing a second layer of material on the outer surface of the stent and completely encapsulating the stent. The method <NUM> may be repeated to produce a thicker encapsulation of the stent.

Referring to <FIG> of the illustrative drawings, there is shown an embodiment of an inner holder <NUM> for holding the stent <NUM>. The inner holder <NUM> may be an alternative embodiment of the inner holder <NUM>, as shown in <FIG>. The inner holder <NUM>, as seen in <FIG>, includes a central tubular hub portion <NUM> and a plurality of stabilizing legs <NUM> projecting outward therefrom. In the embodiment shown, the inner holder <NUM> has three stabilizing legs <NUM>, although an inner holder having greater or fewer stabilizing legs may be used. The central tubular hub portion <NUM> has an internal bore <NUM>. The inner holder <NUM> may be formed of metal or a rigid polymer, such as acetal (DELRIN®, DuPont), nylon, or polypropylene. The stent <NUM> is held by the stabilizing legs <NUM> of the inner holder <NUM> by positioning the inner holder in the cavity <NUM> of the stent <NUM> and contracting the stent <NUM> and/or expanding the holder <NUM> so that at least a portion of the inner surface <NUM> of the stent <NUM> contacts an outer surface <NUM> of the stabilizing legs <NUM> (see <FIG>). In other embodiments, the inner holder includes another structure, for example, an expanding mandrel or a balloon.

In one embodiment, each of the plurality of stabilizing legs <NUM> of the inner holder <NUM> comprises a radial portion <NUM> extending in a generally radial direction outward from an outer surface <NUM> of the central tubular hub portion <NUM> and an angular portion <NUM> extending in a generally angular direction about an axis <NUM> defined by the central tubular hub portion <NUM>. The outer surface <NUM> is on the angular portion <NUM> of the inner holder <NUM>.

In one embodiment, each of the plurality of stabilizing legs <NUM> comprises a chamfered edge <NUM> extending along each angular portion <NUM>, facing one side of the inner holder <NUM>. In one embodiment, the chamfered edge <NUM> aligns an inner edge of each angular portion <NUM>, extending from the radial portion <NUM> all the way to the tip of the angular portion <NUM>, as seen in <FIG>. In one embodiment, the width of the angular portion <NUM> with the chamfered edge <NUM> is equal to or less than the width of the radial portion <NUM>. In one embodiment, the chamfered edge <NUM> may have a constant width along its length, or the width may vary. In other embodiments, the chamfered edge <NUM> may be segmented, or may have other shapes, sizes, and/or locations.

The inner holder <NUM> allows the stent <NUM> to be placed on the mandrel <NUM> without the use of sutures and lessens interference during the electrospinning steps. Referring to <FIG> of the illustrative drawings, the inner holder <NUM> is threaded onto the mandrel <NUM> via the inner holder's internal bore <NUM>. In one embodiment, the inner holder <NUM> (and stent <NUM>) may be left free to translate along the axis <NUM> defined by the mandrel <NUM>. In another embodiment, the inner holder <NUM> may be secured to the mandrel <NUM> mechanically or adhesively, for example, using the adhering means <NUM>. In a further embodiment, the inner holder <NUM> may be kept in position on the mandrel <NUM> using a stop or collar, for example, by threading an elastomer ring <NUM> onto the mandrel <NUM> (see <FIG>).

<FIG> also demonstrates an embodiment of an auxiliary frame <NUM> for assisting the cutting of the coating sheet. In one embodiment, the auxiliary frame <NUM> is threaded onto the mandrel <NUM> before threading the inner holder <NUM> onto the mandrel <NUM>, so that the auxiliary frame <NUM> is facing the second end <NUM> of the stent <NUM>. In one embodiment, the auxiliary frame <NUM> comprises a suitable material, for example, a piece of metal, such as stainless steel, ceramic, or polymer having an internal bore through which the mandrel <NUM> may be threaded. A stop or collar, for example, an elastomer ring <NUM>, may be threaded onto the mandrel <NUM> and positioned on either or both sides of the auxiliary frame <NUM> to keep the auxiliary frame <NUM> in position on the mandrel <NUM>. In one embodiment, the inner holder <NUM> and the auxiliary frame <NUM> may be spaced on the mandrel <NUM> by one or more elastomer rings <NUM> (see <FIG>). In one embodiment, the diameter of the auxiliary frame <NUM> is greater than the diameter of the mandrel <NUM> and approximately equal to or slightly more than the outermost diameter of the inner holder <NUM>. The auxiliary frame <NUM> has an outer surface <NUM> that may or may not be in contact with the stent <NUM>. As shown in <FIG>, the outer surface <NUM> is spaced from the stent <NUM> to assist with the cutting of the coating sheet between the auxiliary frame <NUM> and the stent <NUM>.

As shown in <FIG> of the illustrative drawings, an embodiment of a secondary frame <NUM> is threaded onto the mandrel <NUM> so that the secondary frame <NUM> is facing the undulating or scalloped first end <NUM> of the stent <NUM>. In an alternative embodiment, the secondary frame <NUM> may be threaded onto the mandrel <NUM> so that the secondary frame <NUM> is facing the second end <NUM> of the stent <NUM>. In the embodiment shown in <FIG>, the secondary frame <NUM> comprises a suitable material, for example, a piece of metal, such as stainless steel, ceramic, or polymer having an internal bore through which the mandrel <NUM> may be threaded. In an alternative embodiment, the secondary frame <NUM> includes a 3D-printed polymer fixture or a balloon. In the embodiment shown in <FIG>, the secondary frame <NUM> has a diameter that is less or smaller than the diameter or inner diameter of the stent <NUM>.

In one embodiment, the secondary frame <NUM> comprises a cylindrical portion <NUM>. In one embodiment, the secondary frame <NUM> is similar to the secondary frame <NUM> as shown in <FIG>, except that the secondary frame <NUM> at an end does not comprise a conical portion. The diameter of the cylindrical portion <NUM> is greater than the diameter of the mandrel <NUM> and slightly less than the outermost diameter of the inner holder <NUM>. In a particular embodiment, the diameter of the cylindrical portion <NUM> is approximately <NUM> millimeters to approximately <NUM> millimeters less than the outermost diameter of the inner holder <NUM>. When used with a coating sheet <NUM> having a thickness in the range of from about <NUM> to about <NUM> millimeters, such a cylindrical portion diameter permits the axial movement of one or both of the stent <NUM> and the secondary frame <NUM> so that at least some of the coating sheet can be applied onto the inner surface <NUM> of the stent <NUM>.

In one embodiment, the cylindrical portion <NUM> of the secondary frame <NUM> has a length <NUM> equal to or greater than a length <NUM> of the stent <NUM>, measured from an eyelet <NUM> of the first end <NUM> of the stent to the second end <NUM> of the stent. In a particular embodiment, the length <NUM> is equal to or greater than twice the length <NUM> of the stent <NUM>. Such a cylindrical portion length permits an inverted portion (such as the inverted portion <NUM>) of the coating sheet <NUM> (originally electrospun onto an outer surface of the secondary frame <NUM>) to extend beyond the inner surface <NUM> of the stent <NUM> by an amount sufficient to allow the excess portion to be folded back onto the outer surface <NUM> of the stent, producing a second layer of material covering the outer surface <NUM> of the stent when implemented as described below. A stop or collar, for example, an elastomer ring <NUM>, may additionally be threaded onto the mandrel <NUM> and positioned adjacent an end of the secondary frame <NUM> to keep the secondary frame <NUM> in position on the mandrel <NUM>.

<FIG> shows that a coating sheet <NUM> is formed on the mandrel <NUM>, the outer surface <NUM> of the secondary frame <NUM>, the outer surface <NUM> of the stent <NUM>, and the outer surface <NUM> of the auxiliary frame <NUM>. Cone portions <NUM> and <NUM> of the coating sheet <NUM> extend from the end of the auxiliary frame <NUM> and the end of the secondary frame <NUM> to the mandrel <NUM>, respectively.

<FIG> shows that the cone portion <NUM> and other surplus portions of the coating sheet <NUM> beyond the second end <NUM> of the stent are removed. In one embodiment, the removal of the surplus portions of the coating sheet <NUM> beyond the second end <NUM> of the stent may be accomplished by cutting the coating sheet <NUM> on the auxiliary frame <NUM> where it meets the first end <NUM> of the stent <NUM>. Alternatively, the cutting of the coating sheet <NUM> is at the space between the auxiliary frame <NUM> and the inner holder <NUM> or the second end <NUM> of the stent. The coating sheet <NUM> on the outer surface <NUM> of the stent <NUM> is left undisturbed. In one embodiment, before removing the surplus portions of the coating sheet <NUM>, the mandrel <NUM> (along with the coated stent <NUM>, the inner holder <NUM>, the coated secondary frame <NUM>, and the coated auxiliary frame <NUM>) is removed from the collector <NUM>.

As shown in <FIG>, the cone portion <NUM> and other surplus portions of the coating sheet <NUM> beyond the end of the cylindrical portion <NUM> of the secondary frame are also removed. In one embodiment, the removal of the surplus portions of the coating sheet <NUM> beyond the end of the cylindrical portion <NUM> may be accomplished by cutting the cone portion <NUM> where it meets the cylindrical portion <NUM>.

In one embodiment, after the cone portions <NUM> and <NUM> and other surplus portions of the coating sheet <NUM> are removed, the mandrel <NUM> and the auxiliary frame <NUM> are removed, and the inner holder <NUM> is removed from the cavity <NUM> of the stent <NUM>. In one embodiment, one of the stent <NUM> and the secondary frame <NUM> are moved axially with respect to the other of the stent <NUM> and the secondary frame <NUM>. Alternatively, both of the stent <NUM> and the secondary frame <NUM> may be moved axially with respect to each other. The movement produces an inverted portion (such as the inverted portion <NUM> ) of the coating sheet <NUM> extending inside the cavity <NUM> of the stent <NUM> from the first end <NUM> of the stent. The inverted portion may be formed from the second portion <NUM> of the coating sheet <NUM>. In one embodiment, the secondary frame <NUM> pushes the inner holder <NUM> out of the cavity <NUM> of the stent <NUM> as the secondary frame <NUM> is moved.

In one embodiment, similar to <FIG>, at least some of the inverted portion of the coating sheet <NUM> is applied onto the inner surface <NUM> of the stent <NUM>. In one embodiment, this application is accomplished simply by the movement of the stent <NUM> with respect to the secondary frame <NUM> and allowing the inverted portion of the coating sheet <NUM> to adhere to the inner surface <NUM> of the stent. In another embodiment, this application is accomplished by a user (for example, manually using fingers) or a tool applying a sufficient force to the inverted portion of the coating sheet <NUM> so that the inverted portion extends along and/or adheres to at least a portion of the inner surface <NUM> of the stent <NUM>. In one embodiment, the coating sheet <NUM> is applied to both the inner surface <NUM> and the outer surface <NUM> of the stent <NUM>, producing a covered stent <NUM> having an excess portion (such as the excess portion <NUM>) of the coating sheet <NUM> extending beyond the second end <NUM> of the stent. In one embodiment, the excess portion of the coating sheet <NUM> is folded back onto or over the outer surface <NUM> of the stent <NUM>, producing a second layer of material on the outer surface of the stent <NUM> and completely encapsulating the stent <NUM>. An embodiment of a completely encapsulated stent <NUM> on the second frame <NUM> is shown in <FIG>, with the edge <NUM> of the folded second layer of material on the outer surface of the stent <NUM>.

Referring to <FIG> of the illustrative drawings, there is shown an embodiment of a filter device <NUM> that comprises a filter <NUM> held by a filter base <NUM>. In one embodiment, the filter <NUM> comprises a solid rectangular sheet, although other shapes may alternatively be used. In one embodiment, the filter <NUM> comprises a suitable material, for example, a piece of glass or plastic. In one embodiment, the filter <NUM> is fitted into one of a plurality of grooves on the top surface of the filter base <NUM>, while each groove serves to stabilize the filter <NUM> and to keep the filter <NUM> perpendicular to the top surface of the filter base <NUM>. In one embodiment, the filter base <NUM> includes an extension portion <NUM> extending from the middle on one side of the base <NUM>, in the same plane as the base <NUM>. The grooves extend radially from the middle of the edge of the extension portion <NUM> toward the sides of the base <NUM> (see <FIG>). When fitted in one of the grooves, one edge <NUM> of the filter <NUM> is adjacent to and perpendicular to the edge of the extension portion <NUM>. An axis A of the base <NUM> is defined as the direction perpendicular to the edge of the extension portion <NUM> from which the grooves extend. An angle Φ of the filter <NUM> fitted in a groove is defined by the angle of the direction B of the groove from the axis A. The angle of the filter <NUM> is thus adjustable via fitting the filter <NUM> in a selected groove. <FIG> shows six grooves symmetrically located on either side of the axis A, although other numbers of grooves, symmetrically or non-symmetrically arranged, may alternatively be used. In one embodiment, the angles Φ of the filter <NUM> may be selected from, for example, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, or <NUM> degrees. In another embodiment, another structure may be used to hold the filter <NUM> at different angles, for example, a hinged structure that permits the filter to be positioned at a desired angle.

<FIG> shows that, in a system similar to that of <FIG>, the filter <NUM> with the base <NUM> is positioned between the spinneret <NUM> and the collector having a mandrel <NUM>, a secondary frame <NUM>, and an encapsulated stent <NUM> thereon. The edge <NUM> of the filter <NUM> is positioned adjacent to the stent <NUM>, with a portion on one side of the filter <NUM> and the other portion on the other side. In one embodiment, one portion of the stent <NUM> is on the same side of the filter <NUM> as the spinneret <NUM>, and thus is exposed to the spinneret <NUM> and can be electrospun. The other portion of the stent <NUM> on the other side of the filter <NUM> is covered/blocked by the filter <NUM>, and thus cannot be electrospun.

As shown in <FIG>, the mandrel <NUM>, on which the secondary frame <NUM> with encapsulated stent <NUM> thereon is threaded, is connected to the collector. The filter <NUM> is positioned so that the edge <NUM> is between the first end <NUM> and second end <NUM> of the stent <NUM>. The edge <NUM> of the folded second layer of the excess portion (such as the excess portion <NUM>) on the outer surface of the encapsulated stent <NUM> is on the exposed side of the filter <NUM>. In one embodiment, the angle Φ of the filter <NUM> is about <NUM> degrees, although other angles may be alternatively used.

<FIG> shows a coating sheet <NUM> formed on the mandrel <NUM>, a portion of the outer surface <NUM> of the secondary frame <NUM>, and the exposed portion of the encapsulated stent <NUM>. In one embodiment, as shown in <FIG>, the coating sheet <NUM> covers the edge <NUM> of the folded second layer of the excess portion. A cone portion <NUM> of the coating sheet <NUM> extends from the end of the secondary frame <NUM> to the mandrel <NUM>. The cone portion <NUM> and other surplus portions of the layer of coating sheet <NUM> beyond the second end <NUM> of the stent <NUM> are removed, as shown in <FIG>. The removal of the cone portion <NUM> and surplus portions of the coating sheet <NUM> may be accomplished, for example, by cutting the coating sheet <NUM> at the second end <NUM> of the stent <NUM>. The layer of coating sheet <NUM> that covers the exposed portion of the encapsulated stent <NUM> is left undisturbed. In one embodiment, the mandrel <NUM> is removed from the collector before removal of the cone portion <NUM> and surplus portions of the coating sheet <NUM>.

Referring to <FIG> of the illustrative drawings, there is shown a method <NUM> of applying an extra layer of electrospun material to the encapsulated stent <NUM>. In one embodiment, the extra layer of material may cover the edge (such as the edge <NUM>) of the folded second layer of the excess portion (such as the excess portion <NUM>) on the outer surface of the encapsulated stent <NUM>.

In step <NUM>, the mandrel <NUM> that has the secondary frame <NUM> and the encapsulated stent <NUM> thereon is placed on a collector (such as the collector <NUM>). In one embodiment, the placement of the mandrel <NUM> on the collector is accomplished in a similar manner as described in the step <NUM>.

In step <NUM>, the filter <NUM> is placed between the spinneret (such as the spinneret <NUM>) and the collector, while the edge <NUM> of the filter <NUM> is adjacent to the encapsulated stent <NUM> and perpendicular to the axis <NUM> defined by the mandrel <NUM>. In one embodiment, the filter <NUM> held by the base <NUM> is positioned at an angle Φ (see <FIG>), while the spinneret <NUM> is at one side of the filter <NUM>, referred to as the "exposed side".

In step <NUM>, the position of the edge <NUM> of the filter is adjusted such that a portion of the encapsulated stent <NUM> that comprises the edge <NUM> of the folded portion is at the exposed side of the filter <NUM>.

Steps <NUM>, <NUM>, <NUM>, and <NUM> are similar to the steps <NUM>, <NUM>, <NUM>, and <NUM>, respectively. In step <NUM>, the stent <NUM> and the mandrel <NUM> are concurrently rotated about and oscillated along the axis <NUM> defined by the mandrel <NUM>. In step <NUM>, a syringe pump (such as the syringe pump <NUM>) is fitted with a syringe (such as the syringe <NUM>) containing an amount of an electrospinning material (such as the electrospinning material <NUM>). In step <NUM>, the syringe <NUM> is connected to a spinneret (such as the spinneret <NUM>), with the spinneret positioned and oriented so that the spinneret tip <NUM> is directed toward the exposed portion of the encapsulated stent. In step <NUM>, a voltage is placed or applied between the spinneret tip <NUM> and the collector <NUM>.

In step <NUM>, the electrospinning material <NUM> is applied to the exposed portion of the encapsulated stent <NUM> and to at least a portion of the secondary frame <NUM> and the mandrel <NUM> to form an extra layer of coating sheet (such as the coating sheet <NUM>). The extra layer of coating sheet covers the exposed portion of the encapsulated stent <NUM> including the edge of the folded second layer of the excess portion on the outer surface of the stent <NUM>. <FIG> shows such a coating sheet <NUM> formed on the mandrel <NUM>, a portion of the outer surface <NUM> of the secondary frame <NUM>, and the exposed portion of the encapsulated stent <NUM>. A cone portion <NUM> of the coating sheet <NUM> extends from the second end <NUM> of the stent <NUM> to the mandrel <NUM>.

In step <NUM>, the mandrel <NUM> (along with the encapsulated stent <NUM> with the extra layer of coating sheet, and the secondary frame <NUM>) is removed from the collector.

In step <NUM>, similar to step <NUM>, the cone portion <NUM> and other surplus portions of the extra layer of coating sheet beyond the second end <NUM> of the stent <NUM> are removed. The removal of the surplus portions of the coating sheet <NUM> may be accomplished, for example, by cutting the coating sheet <NUM> at the second end <NUM> of the stent <NUM>. The extra layer of coating sheet <NUM> that covers the exposed portion of the encapsulated stent <NUM> is left undisturbed, as seen in <FIG>.

In step <NUM>, the secondary frame <NUM> is removed from the mandrel <NUM>.

Claim 1:
A prosthetic heart valve comprising:
a stent body (<NUM>);
wherein the stent body (<NUM>) comprises an inner surface (<NUM>) defining a cavity (<NUM>) and an outer surface (<NUM>) opposing the inner surface (<NUM>), and
wherein the stent body (<NUM>) has a length between first (<NUM>) and second (<NUM>) ends of the stent body (<NUM>); and
a coating sheet (<NUM>) formed from an electrospun material (<NUM>);
wherein the coating sheet (<NUM>) comprises a first portion that covers at least a portion of the stent body outer surface (<NUM>) and a second inverted portion (<NUM>) extending inside the cavity (<NUM>) of the stent body (<NUM>) and covering at least a portion of the inner surface (<NUM>) of the stent body (<NUM>);
wherein the second inverted portion (<NUM>) has a diameter that is tapered from a diameter of the first portion;
wherein at least one of the first (<NUM>) and second (<NUM>) ends of the stent body (<NUM>) is covered by the coating sheet (<NUM>).