Yarn and corresponding material with reduced physical additives for use in implantable devices and methods of making the same

Abstract

A material for use in medical devices that are implantable into a patient is provided herein. The material comprises little to no physical additives and beneficial properties for forming yarn that is biocompatible while exhibiting improved degradation resistance, abrasion resistance, and / or tensile strength (among other beneficial properties). In particular, the yarn may be substantially free of titanium dioxide. The yam may form fabric that is usable as or in a medical device for implantation within a patient. Some such medical devices include braided stents, surgical grafts, endovascular grafts, surgical repair mesh, fabric covered sewing rings, sutures, or other implantable medical devices.

Description

YARN AND CORRESPONDING MATERIAL WITH REDUCED PHYSICAL ADDITIVES FOR USE IN IMPLANTABLE DEVICES AND METHODS OF MAKING THE SAMECROSS-REFERENCE TO RELATED APPLICATION(S)

[0001] This application claims priority to U.S. Provisional Application No. 63 / 654,236, entitled “YARN AND CORRESPONDING MATERIAL WITH REDUCED PHYSICAL ADDITIVES FOR USE IN IMPLANTABLE DEVICES AND METHODS OF MAKING THE SAME”, filed May 31, 2024, which is incorporated by reference herein in its entirety.FIELD OF THE INVENTION

[0002] Embodiments of the present invention relate generally to polyester compositions, and more specifically to degradation resistant biocompatible polyester compositions used in medical yarns, where such yams (and corresponding medical devices) are beneficial for use for implantation into a patient - particularly for long-term implantation use.BACKGROUND OF THE INVENTION

[0003] Yarns (e.g., textile yams) arc formed from one or more filaments, and corresponding fabric may be produced from such yarn through weaving, knitting, felting, braiding or other similar techniques.

[0004] Many fabrics used in medical settings are formed using yams and resins which were adapted from the clothing textile industry, and were not designed specifically or intended for medical purposes. In this regard, although the yarn may be biocompatible, the yarn may not be optimal when used in the body or used with other medical device components.

[0005] Medical yams may be used for medical devices, such as by being formed into a fabric used as or for the medical device. Some such example medical devices include implantable devices, such as braided stents, surgical grafts, endovascular grafts, surgical mesh, fabric covered sewing rings, sutures, and other implantable components or devices. Notably, however, yarns and resulting fabric may degrade over time based on various factors, some of which may be accelerated by being within the patient’s body (e.g., through movement, rubbing, exposure to bodily fluids, enzymes, tissues, and other environmental conditions, among other things) and / or by being utilized with or next to other structures, such as may be part of the same medical device (e.g., the fabric may interact with a metal structure, such as a stent or frame). The degradation of the yarn may be detrimental to its function and / or performance (and that of the overall medical device), such as may cause reduced performance and / or failure of the yarn and / or medical device. Thus, there exists a need for a material which is biocompatible and has reduced degradation when exposed to such conditions, so as to improve implantable medical devices and other medical yams made from the material.BRIEF SUMMARY OF THE INVENTION

[0006] Yams and corresponding filament(s) may be formed from polymer compositions (e.g., resins) including, for example, polyester, such as polyethylene terephthalate (PET) or polyolefins. For example, in various embodiments, a polymer matrix including the polyester is formed into one or more filaments that form the yam.

[0007] Historically, the first textile based medical devices were manufactured using readily available yams, such as primarily Dacron® from DuPont® that were used in apparel and home textiles. These yarns used physical additives for various reasons that related to a desiredappearance of the fabric and / or ease of manufacturing. For example, such historical yams included titanium dioxide (TiCh) as a delustering agent to improve visual appeal of the yam and the resulting clothing. Notably, TiCh also aided in extrusion of the polymer composition when being formed into filament(s) and the resulting yarn as it improves heat resistance.

[0008] However, it has been determined that such physical additives create potential issues with the polymer compositions forming the filament(s) / yarns. In this regard, it has been determined that the physical additives exposed on the external surfaces of the filament(s) / yams are abrasive when interacting with adjacent structures. Such interaction may compromise the integrity and lead to issues in the medical device and / or the adjacent structure - leading to failure of either or both.

[0009] Notably, the first medical devices used larger yams with higher denier (80 to 160 g / denier as an example), and were typically used as stand-alone (without support structures) medical devices, like knitted and woven surgical grafts. In such sized yarns, it is thought that the physical additives did not affect the resulting performance of the yam / fabric / medical device - as the yarns exceeded the coverage, mass, and / or strength required clinically and were not as vulnerable to the exposed metal structures in early devices.

[0010] However, with the miniaturization of implantable medical devices and the components used to make them to support minimally invasive surgeries, the deniers of yam being used became smaller and the denier per filament also decreased. Accordingly, it has been determined that even the relatively small size of physical additives, such as TKb (e.g., around 0.3 pm), is enough to cause performance issues, such as increased degradation of the yam / fabric / medical device. For example, having smaller yarns with the same size TiCF means that such additives account for a higher ratio of particle size to the filament diameter (whichmakes filaments more abrasive). For example, an 18 pm filament in larger yarns used in early devices may now be 10 pm in diameter in lower profile medical fabrics. Along similar lines, some medical devices forced more yarns and filament(s) into smaller volumes compared to prior medical devices - which increased the loading forces filaments were exposed to - particularly for the physical additives. room Moreover, implantable medical fabrics transitioned from a stand-alone medical device, like a surgical graft, to endovascular grafts where they became components of the devices and were combined with stents and sutures, and also used as valve skirts and support structures, such as on heart valves, to provide attachment mechanisms and prevent leakage. Accordingly, the exposure of the filament! s) / yarns to adjacent structures increased drastically, leading to more opportunities for interaction of the physical additives with the surrounding structure - leading to corresponding degradation issues.

[0012] With the advent of the next generation of thinner polyester fabrics made from smaller yarns being used in combination medical devices, the potential impact of degradation and also the dynamics of the fabric interaction with the rest of the components of the medical device have become potential failure modes for these medical devices. Specifically, the physical additives higher percentage distribution of the particles in a filament and the overall smaller diameter of the yam and filaments enable the degradation process to impact the medical device sooner in the patient’s body particularly compared to the larger yarns and thicker fabrics used previously. In addition, many next generation fabrics are combined with metal stent structures, the movements of the fabrics against these metal structures creates potential abrasion points (particularly relative to the physical additives positioned near the external surfaces of the filament(s) / yam).

[0013] Said differently, to explain, the physical additives (like TiCE) on the external surface of the filament and internal in the filament act like sandpaper on adjacent surfaces (such as other components / structures) - which can in turn lead to the weakening of the component and also changing the surface characteristics of the yarn. This cycle leads to even worsening conditions that more aggressively abrade the yarn, leading to the fabric component being damaged to the point of failure. Of course, the other side of this is true too, as the yarn (and the physical additives therein) may wear down the other components / structures (e.g., adjacent yarns, structures, etc.) - thereby leading to corresponding failures. Since these failures may take a long time to show up in the patient’s body, and usually do not appear with the standard pulsatile testing and other long term bench testing, these issues have just started coming to light in recent years.

[0014] One approach to address these issues is to use nanoparticles for the TiO2, which may decrease the degradation and abrasion effect. However, there are potential concerns with using nanoparticles in long term implants and, thus, although such an approach may be technically feasible, it may not be suitable for the end application (e.g., long-term implantation within a patient’s body).

[0015] Embodiments of the present invention are thus directed towards a biocompatible material (e.g., polymer composition(s)) formed from polyester, for example, polyethylene terephthalate (PET), that is free or substantially free (e.g., includes less than 0.2% by weight, or preferably less than 0. 15% by weight or 0. 1 % by weight) of a physical additive, such as TiCE. The material is used to form one or more filaments to create a yam that may be woven, knitted, felted, braided, or similar into a fabric, which is then used for and / or as a medical devices and / or one or more components of a medical device, such as for braided stents, surgical grafts,endovascular grafts, surgical mesh, fabric covered sewing rings, heart valves, sutures, and other implantable components or devices. The material is degradation resistant and / or abrasion resistant, and thus, extends the lifespan of the medical devices formed from the yarn, and reduces failures of the medical devices.

[0016] Notably, however, it has been observed that manufacturing custom polyester yams and fibers with no TiCh in small denier filaments is a challenge to obtain all of the best properties for the end use. Thus, various embodiments of the present invention have found ways to manufacture and form the desired polymer compositions and the resulting filament(s) / yarns in such a manner, including without TiCh, such that the corresponding formed yam provides for improved degradation resistance, abrasion resistance, and / or tensile strength (among other beneficial properties) in a desired state, such as a relaxed state and / or an extended state. The end result is a yam that's filaments have uniform smooth external surfaces without the surface impurities created by the physical additives (like TiCh). This greatly reduces the abrasion effect between this new fabric and adjacent fabric or stmctures. The interior of the filaments also do not have micro imperfections in the polymer matrix created by the physical additives (like TiCh) which leads to much greater structural integrity to resist degradation of the yarn and the overall medical device (and adjacent structures). Along similar lines, the filament(s) / yam may also have greater tensile strength due to the polymer matrix not being filled by the physical additives (like TiO2).

[0017] In some embodiments, the material contains a reduced amount of physical additives, such as less than 2% by weight, less than 1% by weight, less 0.5% by weight, less than 0.3% by weight, or even less than 0.1% by weight. Notably, some such embodiments may accomplish this by being free of any TiO2and / or being free or having a reduced amount of otheradditives, such as colorants, such as TiO?, etc. In some embodiments, the material contains a reduced amount of physical additives or impurities, such as less than 2% by weight, less than 1% by weight, less than 0.5% by weight, less than 0.2% by weight, or specifically less than 0.1% by weight. Notably, some such embodiments may accomplish this by being free of or having a reduced amount of any physical additives or impurities, with some example impurities being fillers or elements, such as antimony, manganese, or aluminum. In some embodiments, the physical additives and / or impurities may not be present in the polymer composition forming the filament(s) / yam. Additionally or alternatively, the physical additives and / or impurities may be removed or cleaned, such as separately and / or in one or more stages of the manufacturing process (e.g., before, after, or during the yarn manufacturing and / or any downstream component or medical device manufacturing).

[0018] In this regard, in addition to being free or substantially free of TiCb and / or free or near free of any physical additives, the resulting yam may be designed to have particular properties that have long been difficult to produce. Notably, such material provides unexpected results for their given size that solve a long-felt need for providing smaller biocompatible medical components for long-term implantation (e.g., the medical devices having increased degradation resistance while exhibiting other beneficial properties, such as reduced sizing, abrasion resistance, tensile strength, among others - leading to less medical device failures, correspondingly less life-threatening procedures, and a better overall patient experience among many other benefits).

[0019] In an example embodiment, a yarn for use in a medical device for implantation into a patient is provided. The yarn comprises one or more filaments formed from a polymer composition that is substantially free of titanium dioxide (TiCh), wherein the yam defines adensity of 100 denier or less, wherein the yam is biocompatible, and wherein the yarn is substantially free of titanium dioxide (TiCh).

[0020] In some embodiments, the yam is formed into a fabric that is substantially free of titanium dioxide.

[0021] In some embodiments, the polymer composition comprises polyester, wherein the polyester is polyethylene terephthalate.

[0022] In some embodiments, the yam does not comprise nanoparticles.

[0023] In some embodiments, the yam defines a tensile strength of at least 3 g / denier.

[0024] In some embodiments, the yam defines a tensile strength of at least 7 g / denier.

[0025] In some embodiments, the yam defines a tensile strength between 3 g / denier - 35 g / denier.

[0026] In some embodiments, the yam defines a density of 50 denier or less.

[0027] In some embodiments, the yam defines a density of 40 denier or less.

[0028] In some embodiments, the yam defines a density of 20 denier or less.

[0029] In some embodiments, the yam defines a density of 10 denier or less.

[0030] In some embodiments, the yam is abrasion resistant.

[0031] In some embodiments, the polymer composition passes a chemical characterization test such that the polymer composition has less than 2% by weight of physical additives or impurities, wherein the polymer composition comprises less than or equal to 0.2% titanium dioxide included in the physical additives or impurities.

[0032] In some embodiments, the yam is biostable.

[0033] In another example embodiment a medical device comprising the yarn is provided, where the yam comprises one or more filaments formed from a polymer compositionthat is substantially free of titanium dioxide (TiCh), wherein the yam defines a density of 100 denier or less, wherein the yarn is biocompatible, and wherein the yarn is substantially free of titanium dioxide (TiCh).

[0034] In another example embodiment, an implantable graft comprising the yarn is provided, where the yam comprises one or more filaments formed from a polymer composition that is substantially free of titanium dioxide (TiCh), wherein the yam defines a density of 100 denier or less, wherein the yarn is biocompatible, and wherein the yarn is substantially free of titanium dioxide (TiCh).

[0035] In some embodiments, the implantable graft comprises a metal structure.

[0036] In another example embodiment, an implantable suture comprising the yarn is provided, where the yam comprises one or more filaments formed from a polymer composition that is substantially free of titanium dioxide (TiCh), wherein the yam defines a density of 100 denier or less, wherein the yarn is biocompatible, and wherein the yarn is substantially free of titanium dioxide (TiCh).

[0037] In another example embodiment, a medical mesh comprising the yam is provided, where the yam comprises one or more filaments formed from a polymer composition that is substantially free of titanium dioxide (TiCh). wherein the yam defines a density of 100 denier or less, wherein the yam is biocompatible, and wherein the yam is substantially free of titanium dioxide (TiCh).

[0038] In another example embodiment, a yam for use in a medical device for implantation into a patient is provided. The yam comprises one or more filaments formed from a polymer composition that comprises less than 2% by weight of physical additives, wherein the yam defines a density of 100 denier or less, wherein the yarn is biocompatible, wherein the yarncomprises less than 2% by weight of physical additives, and wherein the one or more filaments comprise less than or equal to 0.2% titanium dioxide included in the physical additives.

[0039] In some embodiments, the yam is formed into a fabric that is substantially free of titanium dioxide.

[0040] In some embodiments, the polymer composition comprises polyester, wherein the polyester is polyethylene terephthalate.

[0041] In some embodiments, the yam does not comprise nanoparticles.

[0042] In some embodiments, the yam defines a tensile strength of at least 3 g / denier.

[0043] In some embodiments, the yam defines a tensile strength of at least 7 g / denier.

[0044] In some embodiments, the yam defines a tensile strength between 3 g / denier - 35 g / denier.

[0045] In some embodiments, the yam defines a density of 50 denier or less.

[0046] In some embodiments, the yam defines a density of 40 denier or less.

[0047] In some embodiments, the yam defines a density of 20 denier or less.

[0048] In some embodiments, the yam defines a density of 10 denier or less.

[0049] In some embodiments, the yam is abrasion resistant.

[0050] In some embodiments, the polymer composition passes a chemical characterization test such that the polymer composition has less than 2% by weight of physical additives or impurities.

[0051] In some embodiments, the yam is biostable.

[0052] In another example embodiment, a medical device comprising the yam is provided. The yarn comprises one or more filaments formed from a polymer composition that comprises less than 2% by weight of physical additives, wherein the yarn defines a density of100 denier or less, wherein the yarn is biocompatible, and wherein the yarn comprises less than2% by weight of physical additives.

[0053] In another example embodiment, an implantable graft comprising the yarn is provided. The yarn comprises one or more filaments formed from a polymer composition that comprises less than 2% by weight of physical additives, wherein the yarn defines a density of 100 denier or less, wherein the yarn is biocompatible, and wherein the yarn comprises less than 2% by weight of physical additives.

[0054] In some embodiments, the implantable graft further comprises a metal structure.

[0055] In another example embodiment, an implantable suture comprising the yarn is provided. The yarn comprises one or more filaments formed from a polymer composition that comprises less than 2% by weight of physical additives, wherein the yarn defines a density of 100 denier or less, wherein the yarn is biocompatible, and wherein the yarn comprises less than 2% by weight of physical additives.

[0056] In another example embodiment, a medical mesh comprising the yam is provided. The yam comprises one or more filaments formed from a polymer composition that comprises less than 2% by weight of physical additives, wherein the yam defines a density of 100 denier or less, wherein the yam is biocompatible, and wherein the yam comprises less than 2% by weight of physical additives.

[0057] In another example embodiment, a method of forming a yam for a medical device for implantation into a patient is provided. The method comprises crystalizing a polyester resin pellet such that the crystalized polyester resin pellet exhibits desired properties, wherein the polyester resin pellet is formed of material substantially free of titanium dioxide (TiCh). The method further comprising melting the crystalized polyester resin pellet formed of meltedpolyester resin; extruding the melted polyester resin into one or more filaments; and weaving the polymer resin filaments into the yarn, wherein the yarn defines a density of 100 denier or less.

[0058] In some embodiments, the material of the polyester resin pellet comprises polyethylene terephthalate.

[0059] In some embodiments, the method further comprises performing a chemical characterization test on the material of the polyester resin pellet to confirm that the material has less than 2% by weight of physical additives or impurities, wherein the physical additives or impurities includes at least titanium dioxide.

[0060] In some embodiments, the method further comprises cleaning the material of the polyester resin pellet to remove one or more physical additives or impurities.

[0061] In some embodiments, the method further comprises forming a fabric using the yam. In some embodiments, the method further comprises forming a medical device or a portion thereof from the fabric.

[0062] In another example embodiment, a method of forming a yam for a medical device for implantation into a patient is provided. The method comprises crystalizing a polyester resin pellet such that the crystalized polyester resin pellet exhibits desired properties, wherein the polyester resin pellet is formed of material that has less than 2% by weight of physical additives or impurities. The method further comprises melting the crystalized polyester resin pellet formed of melted polyester resin; extruding the melted polyester resin into one or more filaments; and weaving the polymer resin filaments into the yarn, wherein the yam defines a density of 100 denier or less.

[0063] In some embodiments, the material of the polyester resin pellet comprises polyethylene terephthalate.

[0064] In some embodiments, the material is substantially free of titanium dioxide (TiO2).

[0065] In some embodiments, the method further comprises cleaning the material of the polyester resin pellet to remove one or more physical additives or impurities.

[0066] In some embodiments, the method further comprises forming a fabric using the yam. In some embodiments, the method further comprises forming a medical device or a portion thereof from the fabric.BRIEF DESCRIPTION OF THE DRAWINGS

[0067] Having thus described the invention in general terms, reference will now be made to the accompanying drawings, which are not necessarily drawn to scale, and wherein;

[0068] FIG. 1 illustrates an example spool of yarn, such as may be formed of one or more filaments produced from various material described herein, in accordance with some embodiments discussed herein;

[0069] FIG. 2A illustrates a schematic close-up view of a portion of an example filament comprising physical additives such as titanium dioxide, in accordance with some examples discussed herein;

[0070] FIG. 2B illustrates a schematic close-up view of the portion of the example filament of FIG. 2A after being exposed to one or more conditions, such as an extended time within the patient and / or a structure of a medical device, such as a metal structure of a stent, in accordance with some examples discussed herein;

[0071] FIG. 3 shows a close-up view of a portion of a yarn formed of filaments, in accordance with some example embodiments discussed herein;

[0072] FIG. 4 illustrates a schematic close-up view of a portion of an example filament comprising no physical additives, in accordance with some example embodiments discussed herein;

[0073] FIGs. 5A-E show example medical devices formed from example yarn described herein, in accordance with some embodiments discussed herein;

[0074] FIG. 6 shows an example method of manufacturing a medical device, in accordance with some embodiments discussed herein;

[0075] FIG. 7 illustrates a flowchart showing a testing protocol that replicates aging for example yarns;

[0076] FIG. 8 shows an example testing set up for each yarn being tested in accordance with the testing protocol;

[0077] FIG. 9 shows scanning electron microscopy (SEM) images of the tested yarns in accordance with the testing protocol, wherein the SEM images were taken at magnitude of lOOOOx; and

[0078] FIG. 10 illustrates determined positioning of TiOi in an example tested yam, where the positioning of the TiO2 correlates to a crevice being formed.DETAILED DESCRIPTION OF THE INVENTION

[0079] Some example embodiments now will be described more fully hereinafter with reference to the accompanying drawings, in which some, but not all example embodiments are shown. Indeed, the examples described and pictured herein should not be construed as being limiting as to the scope, applicability or configuration of the present disclosure. Rather, theseexample embodiments are provided so that this disclosure will satisfy applicable legal requirements.

[0080] FIG. 1 illustrates an example spool 100 of yam formed of polyester for use within yams, such as used in the medical industry. Since historically yams used in the medical industry were formed from yam used in the clothing industry, many of the filament materials forming the yam contain various additives to provide properties to the yams. For example, yarns in the clothing industry typically included desired colorants (e.g., titanium dioxide (TiCh)) to form, for example, semi-dull yarn, although additional physical additives were also used to form desirable features of the resulting clothing. Notably, the TiCh also provided for aiding in extrusion, making the manufacturing process easier.

[0081] TiOr is a white particle, which is added into a polyester resin (e.g., polymer composition) that is used in the material to form the filaments / yam in order to achieve a desired luster of the yam. In this regard, when referring to TiCh as a colorant, it is appreciated that using different amounts of TiCb in the polymer composition for the filament(s) / yarn causes adjustment in the luster of the yam, which can lead to a designed perception / brightness of the color of the resulting yarn / fabric (e.g., thus, references / description regarding TiCh adjusting the color or having a lack of TiCF being colorless are considered accordingly). The TiO particles are distributed throughout the resin, yielding a color throughout the resin and any resulting filaments / yam formed therefrom. The weight percent of TiCh added to the polyester resin helps defines the color of the resin (notably, the relative distribution of the TiCh may also have a corresponding effect on the perceived color (particularly from different viewpoints) in addition to the amount of TiCF by weight used). For example, a polyester containing 0.1% TiOr by weight may be super bright, polyester containing 0.2%-0.5% TiCF by weight may be semi-dull,dull polyester may contain about 0.4%-l .0% TiO2by weight, and full dull or Dacron® polyester may contain about 2.5% TiO2by weight or, in some cases, up to 3.0% TiO2by weight (although relativity terms may vary - for example - as used herein, a polymer composition with be termed dull when compared with another that is termed semi-dull due to a relative increased amount of TiO2).[00821 In some cases, other physical additives were used in the polyester resin to impart other desirable properties, such as heat resistance, stabilizers, performance enhancers or other features, such as may be beneficial to resulting yams and fabrics (e.g., often for other industries besides the medical industry). Some such example other physical additives include colorants or dyes, flame retardants, and antimicrobials.

[0083] However, it has been determined that some such physical additives cause undesirable flaws that result in medical device failure, particularly when the medical device (with the corresponding yarn) has been implanted in a patient. In this regard, as noted herein, the physical additives mixed in the polymer composition formed abrasion issues that, due to, for example, interaction, resulted in degradation and potential failure of the fabric and / or medical device (or adjacent structure) after implantation. Notably, forming desirable sized yarn and fabric for medical devices (e.g., with yarn having less than 80 denier) leads to increased percentages of physical additives on the external surfaces of the filaments / yam (relative to prior medical devices). Further, the desire to utilize the fabric with other structures and / or the increased usage of filaments / yams adjacent to each other leads to further exposure and physical contact or interaction. Moreover, the presence of physical additives leads to different properties of the yam, such as potential reduced tensile strength.

[0084] In this regard, when such yarns / fabric is included in implantable medical devices, such as braided stents, surgical grafts, endovascular grafts, surgical mesh, fabric covered sewing rings, sutures, heart valves, and other implantable components or devices - there can be resulting failure of the medical device. Notably, medical device failures may lead to lifethreatening situations, causing, for example, intervention, increased surgical procedures and detriment to the overall patient experience.

[0085] FIGs. 2A-B illustrate an example filament including TiCh particles contained therein and the resulting effects of facing such adverse conditions as noted herein. FIG. 2A illustrates an example filament 200 comprising TiCh particles 225 within a polyester composition 220, for example polyethylene terephthalate. The illustrated filament 200 of FIG. 2A defines an outer surface 200a which is smooth. The TiO particles 225 are distributed throughout the filament 200 both along a length L of the filament 200 and throughout a width W of the filament 200.

[0086] FIG. 2B illustrates potential degradation of the filament 200’ when exposed to various conditions, such as due to movement with a portion of the medical device or other structure, etc. In this regard, FIG. 2B illustrates the filament 200’ where indentations or pits 200b formed on the surface of the filament 200’ in locations of the TiCh particles 225. For example, the TiOi particles may move, dislodge, decompose, or otherwise interact with the rest of the polyester composition 220 of the filament 200’ - causing degradation of the smooth surface, loss of tensile strength, and / or reduction in other properties of the filament / yam - leading to pitting (or other failures). As an example, as the filament around the TiOi particle degrades, the pitting expands and may expand into other pitted areas - forming larger ruptures, etc., leading to reduce performance and / or failure. As another example, the fluctuation in diameter of the filament along the length of the filament creates weak points (e.g., affecting thestructural integrity of the filament). The weak points may fail when exposed to stress, causing the filament(s) to break - leading to failure of the yam and / or resulting medical device. Notably, though pitting is shown in FIG. 2B, it is noted that other failures may occur, such as a reduction in properties of the yarn leading to other failures (such as with the remainder of the medical device) and / or to adjacent structures, such as other yarn, other structures (such as stents, etc.), etc. - such as described herein. For example, regarding adjacent structures, degradation of the yam may lead to exposure of more TiCh particles to rub against an adjacent stmcture, such as a stent - which may ultimately cause performance issues with the stent, such as buckling, degradation, etc. Along similar’ lines, if the yam that is keeping the stent attached to the remainder of the fabric is degraded and fails, the stent may not be held in the desired implanted position - potentially causing reduced performance, failure, or other issues.

[0087] Thus, to improve the longevity of medical yarns, filament material and corresponding yam and medical devices and corresponding methods of manufacturing for improved tensile strength, durability, and a reduced degradation rate, and abrasion are provided herein. In this regard, various embodiments of the present invention are thus directed towards a biocompatible material (e.g., polymer composition(s)) formed from polyester, for example, polyethylene terephthalate (PET), that is free or substantially free (e.g., includes less than 0.2% by weight, or preferably less than 0.15% by weight or 0.1% by weight) of physical additives such as TiCh. An example yarn with filaments 191 formed of PET is shown in FIG. 3. A schematic view of an example according to various embodiments described herein is illustrated by the filament 400 shown in FIG. 4. Such filament(s) / yam provide for improved degradation resistance, abrasion resistance, and / or tensile strength (among other beneficial properties) in both a relaxed state and an extended state. Notably, as used herein, embodiments of the present invention are designed tobe non-absorbable or aromatic polyesters and, thus, not aliphatic polyesters. In this regard, maintaining stability, structural integrity, and strength (and resistance to degradation) is important.

[0088] Notably, however, it has been observed that manufacturing custom polyester yarns with no or nearly no physical additives (like TiO ) in small denier filaments is a challenge to obtain all of the best properties for the end use. Thus, various embodiments of the present invention have found ways to manufacture and form the desired polymer compositions and the resulting filament(s) / yarns in such a manner, including without TiCh, such that the corresponding formed yarn provides for improved degradation resistance, abrasion resistance, and / or tensile strength (among other beneficial properties) in both a relaxed state and an extended state. The end result is a yarn that has filaments with uniform smooth external surfaces without the surface imperfections created by the physical additives (like TiCT). This greatly reduces the abrasion effect between this new fabric and adjacent fabric or structures. The interior of the filaments also do not have micro imperfections in the polymer matrix created by the physical additives (like TiCh) which leads to much greater structural integrity to resist degradation of the yarn and the overall medical device (and adjacent structures). Along similar lines, the filament(s) / yam also has greater tensile strength due to the polymer matrix not being filled by the physical additives (like TiCk).

[0089] In some embodiments, the material contains a reduced amount of physical additives, such as less than 2% by weight, less than 1 % by weight, less than 0.5% by weight, less than 0.2% by weight, or specifically less than 0.1% by weight. In various embodiments, the material does not contain any nanoparticles.

[0090] In some embodiments, the filament material may be a polyester material, for example polyethylene terephthalate, though other polymers are considered. The filament material may be TiCh free and / or contain a reduced amount of physical additives, such as less than 2% by weight, less than 1% by weight, less than 0.5% by weight, less than 0.2% by weight, or specifically less than 0.1% by weight. The polymer or plastic material may be formed into a resin pellet to be crystalized and later formed into one or more filaments. Notably, it has been discovered that crystalization of the resin pellet may be specific to cause the resultant filament(s) to exhibit desirable properties (e.g., tensile strength, abrasion resistance, among other properties). In this regard, some embodiments of the present invention perform specific crystallization processes that were developed for filament material without TiCh and / or other physical additives previously present in filament material.

[0091] It has also been noted that the filament material may be colorless as a composition in an amorphous state, however it has been found that the filament material may define some color or opacity when formed into filament(s) / yam such as may be due to the interweaving of the filaments and / or light reflectance thereon.

[0092] Once the polymer material is crystallized in a desired state, the crystalized pellet is melted and extruded into one or more filaments that are formed into yarn. The yam then is prepared through texturing, twisting, winding and / or warping for weaving, knitting, felting, braiding or other similar techniques, and formed into fabric that may form or be used in or with various medical devices.

[0093] In some embodiments, the yam may define a linear density of less than 300 denier. In some embodiments, the yam may define a linear density of less than 100 denier. In some embodiments, the yam may define a linear density of less than 90 denier. In some embodiments,the yarn may define a linear density of 85 denier or less. In some embodiments, the yarn may define a linear density of less than 50 denier. In some embodiments, the yarn may define a linear density of 40 denier or less. In some embodiments, the yam may define a linear density of less than 20 denier. In some embodiments, the yarn may define a linear density of 10 denier or less.

[0094] In some embodiments, the resultant yarn may have a tensile strength of at least 3 g / denier. In some embodiments, the yam may have a tensile strength of at least 7 g / denier. In some embodiments, the yam may have a tensile strength of at least 10 g / denier. In some embodiments, the yam may have a tensile strength of at least 35 g / denier. In some embodiments, the yarn may have a tensile strength between 3 - 35 g / denier. In some embodiments, the yam may have a tensile strength between 4 - 5 g / denier. In some embodiments, the yam may have a tensile strength between 5 - 6 g / denier.

[0095] In an example experiment, yams comprising different weight percentages of TiOi were compared. It was found that decreasing the TiCh present in a yarn by 30% led to a 10% increase in tensile strength. Thus, decreasing the TiCT within the filament material created a stronger and less abrasive yarn. Further, the yam with a lower weight percent of TiCh degraded slower than the yam with a higher TiCF weight percent when exposed to the same conditions. Additionally, the yarn with a lower TiO weight percent was a less abrasive material when compared to the yarn with a higher TiCh weight percent. Accordingly, use of such yarn with no TiOz and / or reduced additives provides increased degradation resistance and increased abrasion resistance, making such type yam more beneficial for use as or with medical devices, particularly, for example, for stents where a metal stmcture may be prone to mb against the yam / fabric.

[0096] In some embodiments, one or more cleaning operations may be performed at various stages of the manufacturing process, such as to remove various physical additives or impurities. For example, various scanning electron microscopy testing has shown that varying levels of aluminum, antimony, or iron. In various embodiments, it may be desirable to remove some or all such additives or impurities, such as by not adding them and / or through cleaning operations.

[0097] In some embodiments, filament material used to create yarns for use in medical devices must pass a chemical characterization test. Chemical characterization tests, such as International Standard (ISO) 10993 tests, are used to provide information about the safety, efficacy, and quality of the medical device. The test may identify the chemical composition of the material, identify contaminates in the material, analyze biocompatibility of the material, and / or determine compliance with regulatory standards for the function of the device.

[0098] Some of the chemical characterization tests include extractable and leachable studies, which determine what substances can migrate from the medical device into the surrounding area (e.g., into the body). Additionally or alternatively, the chemical characterization test may involve biocompatibility testing to evaluate the biological response of medical device materials when in contact with living tissue or fluids. Some biocompatibility testing may provide cytotoxicity assays, genotoxicity assays, and hemocompatibility tests to assess potential adverse effects of the materials on cells, tissue, blood, and other internal components. Additionally, degradation studies may assess the chemical stability and long term performance of the materials under various environmental conditions. Material identification may be conducted to determine the identity and purity of the materials used in medical devices. Sterilization validation may be used to evaluate the effectiveness of sterilization and cleaning processes to remove residualchemicals. In some embodiments, the filament material described herein may pass a chemical characterization test for implantable devices.

[0099] In this regard, in addition to being free of TiCh and / or free or near free of any physical additives or impurities, the resulting yam may be designed to have particular’ properties that have long been difficult to produce. Notably, such material provides unexpected results that solve a long-felt need for providing biocompatible medical devices for long-term implantation (e.g., the medical devices have increased degradation resistance while exhibiting other beneficial properties, such as reduced sizing, abrasion resistance, tensile strength, among others - leading to less medical device failures).

[0100] As noted herein, the yam and corresponding fabric contemplated herein may be used to form medical devices and / or components for medical devices, such as medical devices used for implantation within a patient. FIGs. 5A-E illustrate example medical devices that such yam / fabric may be used in. Notably, however, any medical devices are contemplated. FIG. 5A illustrates two example stents 120 used, for example, for treating vascular disease, such as to keep a blood vessel open. In some embodiments, such as with reference to FIG. 5B, an example medical device 130 may comprise a woven fabric 132 with a metal structure 131 (e.g., stent, such as may be formed, at least partially, of nitinol, stainless steel, or other alloy) attached to the fabric, such as via a suture 133. FIG. 5C illustrates an example graft 107 formed of the fabric, where the graft 107 may be used, for example, for treating or bypassing a damaged blood vessel or similar structure within the body. FIG. 5D illustrates an example medical mesh 110 formed of various yarns described herein. In some embodiments, the medical mesh 110 may be used, for example, for wound treatment or as part of a medical device. FIG. 5E illustrates an example braided yarn 140 used with a metal buckle 141 as another example medical device.

[0101] FIG. 6 shows an example flowchart illustrating an example method 300 of manufacturing a medical device (and / or the underlying yam / fabric), such as in accordance with various embodiments described herein. Operation 302 includes crystalizing a polyester resin pellet, such as to form a crystalized polyester chip that exhibits desirable properties once formed into a yam / fabric. At operation 304, the crystalized polyester chip is then processed by melting and extrusion. Then, at operation 306, the extruded polymer composition is drawn and, if appropriate, bundled (when forming a multifilament) to formed the yarn. At operation 308, the yam is formed as or into one or more medical devices, such as described herein. Notably, various additional method steps or operations can be performed at various stages of the method 300, such as various cleaning operations and / or testing (e.g., chemical and / or physical testing).

[0102] In order to illustrate some of the above noted benefits of yam that is free or substantially free of TiCh, a testing protocol was developed to illustrate how prolonged exposure during implantation effects such yams. When forming the testing protocol, to replicate aging in the prolonged environment, different temperatures were utilized, such as using an Arrhenius based polymer aging equation that is well accepted to replicate aging during medical device testing. See e.g., Hukins, D.W.L., Mahomed, A., & Kukureka, S.N.. (2008) Accelerated aging for testing polymeric biomaterials and medical devices. Medical engineering & physics, 30(10), 1270-1274. In short, the aging equation utilizes an empirical observation of a “10-degree rule” that notices that increasing the temperature by about 10° roughly doubles the rate of many polymer reactions. See e.g., Hemmerich, K.J. (1998) General aging theory and simplified protocol for accelerated aging of medical devices. Medical Plastics and Biomaterials, 5, 16-23. With reference to FIG. 7, the testing protocol 400 exposed testing samples of yam at different temperatures. The control batch 402c was kept at 37°C (equivalent to an internal bodytemperature of 98.7 °F) and underwent ~60 revolutions per minute during exposure to simulate implantation, which after 2 months was considered to equate to implantation for 2 months. In order to replicate aging, a second batch 402b was kept at 67°C and underwent ~60 revolutions per minute during exposure to simulate implantation, which after 2 months was considered to equate to implantation for 1.3 years. Along similar lines, a third batch 402a was kept at 80°C and underwent ~60 revolutions per minute during exposure to simulate implantation, which after 2 months was considered to equate to implantation for 3.3 years.

[0103] For the testing protocol, each batch comprised of 3 different yam compositions, yarn formed of 0.0% TiCh (noted herein as “clear”), yarn formed of 0.2% TiCh (noted herein as “semi” - short for semi-dull), and yam formed of 0.4% TiCh (noted herein as “dull”). With reference to FIG. 8, for each yam composition, the test yarn 505 of 2 m was wrapped around a sanded glass pipet 502 and that was inserted into a 15 mL Falcon Tube 510 that contained 13 mL of phosphate buffered saline (PBS) at a pH of 7.4.

[0104] After 2 months of exposure, the tested yam was removed and scanning electron microscopy imagery was taken at varying magnitudes. Notably, as illustrated at 10,000x magnitude in FIG. 9, significantly less surface deformities, such as cracks and crevices, were found at all temperatures in the “clear-” 0.0% TiO test yarn versus the “semi” 0.2% TiO test yam and the “dull” 0.4% TiCh test yam. What’s more, with reference to FIG. 10, a point spectrum analysis was performed on an example “dull” 0.4% TiCL test yam that was exposed for 2 months at 80°C, and the smooth surface shows no presence of TiCL (illustrated in Graph 601), but the crevice formed in the surface clearly shows the presence of TiCh (illustrated in Graph 602) - further lending support to the theory that the additive of TiCh likely increases the surface friction during exposure and leads to surface degradation at an increased rate.Based on the testing, it was also observed that for the “clear” 0.0% TiCh test yam, less cracks formed in the contact surface area (e.g., where the filament contacts the glass pipet, which simulates the surface area contacting, for example, a stent or other medical device). Likewise, it has been observed that the “clear” 0.0% TiCL test yarn over aging conditions results in less mass loss and less loss of tensile strength. Additionally, the “clear” 0.0% TiO test yarn exhibits greater extension / elongation with reduced stiffness so as to enable undergoing greater deformation before breakage. Further, the “clear” 0.0% TiCh test yam exhibits an overall reduced negative impact relative to the other test yarns when the test yarns are in contact with a surface, such as a stent or metal alloy.Conclusion

[0105] Many modifications and other embodiments of the inventions set forth herein will come to mind to one skilled in the art to which these inventions pertain having the benefit of the teaching presented in the foregoing description and the associated drawings. Therefore, it is to be understood that the embodiments of the invention are not to be limited to the specific embodiments disclosed and that the modification and other embodiments are intended to be included within the scope of the invention. Moreover, although the foregoing descriptions and the associated drawings describe example embodiments in the context of certain example combinations of elements and / or functions may be provided by alternative embodiments without departing from the scope of invention. In this regard, for example, different combinations of elements and / or functions than those explicitly described above are also contemplated within the scope of the invention. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.

Claims

THAT WHICH IS CLAIMED:

1. A yarn for use in a medical device for implantation into a patient, wherein the yarn comprises: one or more filaments formed from a polymer composition that is substantially free of titanium dioxide (TiCL), wherein the yam defines a density of 100 denier or less, wherein the yam is biocompatible, and wherein the yam is substantially free of titanium dioxide (TiCh).

2. The yam of claim 1, wherein the yam is formed into a fabric that is substantially free of titanium dioxide.

3. The yam of any of claims 1-2 wherein the polymer composition comprises polyester, wherein the polyester is polyethylene terephthalate.

4. The yam of any of claims 1-3, wherein the yam does not comprise nanoparticles.

5. The yam of any of claims 1-4, wherein the yam defines a tensile strength of at least 3 g / denier.

6. The yam of any of claims 1-4, wherein the yam defines a tensile strength of at least 7 g / denier.

7. The yam of any of claims 1-4, wherein the yam defines a tensile strength between 3 g / denier - 35 g / denier.

8. The yam of any of claims 1 -4, wherein the yam defines a density of 50 denier or less.

9. The yam of any of claims 1-4, wherein the yam defines a density of 40 denier or less.

10. The yam of any of claims 1-4, wherein the yam defines a density of 20 denier or less.

11. The yam of any of claims 1-4, wherein the yam defines a density of 10 denier or less.

12. The yam of any of claims 1-11, wherein the yam is abrasion resistant.

13. The yam of any of claims 1-12, wherein the polymer composition passes a chemical characterization test such that the polymer composition has less than 2% by weight of physical additives or impurities, wherein the polymer composition comprises less than or equal to 0.2% titanium dioxide included in the physical additives or impurities.

14. The yam of any of claims 1-13, wherein the yam is biostable.

15. A medical device comprising the yarn of any of claims 1-14.

16. An implantable graft formed from the yam of any of claims 1-14.

17. The implantable graft of claim 16, further comprising a metal structure.

18. An implantable suture formed from the yam of any of claims 1-14.

19. A medical mesh formed from the yarn of any of claims 1-14.

20. A yarn for use in a medical device for implantation into a patient, wherein the yarn comprises: one or more filaments formed from a polymer composition that comprises less than 2% by weight of physical additives, wherein the one or more filaments comprise less than or equal to 0.2% titanium dioxide included in the physical additives, wherein the yam defines a density of 100 denier or less, wherein the yam is biocompatible, and wherein the yam comprises less than 2% by weight of physical additives.

21. The yam of claim 20, wherein the yarn is formed into a fabric that is substantially free of titanium dioxide.

22. The yam of any of claims 20-21 wherein the polymer composition comprises polyester, wherein the polyester is polyethylene terephthalate.

23. The yam of any of claims 20-22, wherein the yam does not comprise nanoparticles.

24. The yam of any of claims 20-23, wherein the yam defines a tensile strength of at least 3 g / denier.

25. The yam of any of claims 20-23, wherein the yam defines a tensile strength of at least 7 g / denier.

26. The yam of any of claims 20-23, wherein the yam defines a tensile strength between 3 g / denier - 35 g / denier.

27. The yam of any of claims 20-23, wherein the yam defines a density of 50 denier or less.

28. The yam of any of claims 20-23, wherein the yam defines a density of 40 denier or less.

29. The yam of any of claims 20-23, wherein the yam defines a density of 20 denier or less.

30. The yam of any of claims 20-23, wherein the yam defines a density of 10 denier or less.

31. The yam of any of claims 20-30, wherein the yam is abrasion resistant.

32. The yam of any of claims 20-31, wherein the polymer composition passes a chemical characterization test such that the polymer composition has less than 2% by weight of physical additives or impurities.

33. The yam of any of claims 20-32, wherein the yam is biostable.

34. A medical device comprising the yarn of any of claims 20-33.

35. An implantable graft formed from the yarn of any of claims 20-33.

36. The implantable graft of claim 35, further comprising a metal structure.

37. An implantable suture formed from the yam of any of claims 20-33.

38. A medical mesh formed from the yarn of any of claims 20-33.

39. A method of forming a yarn for a medical device for implantation into a patient, the method comprising: crystalizing a polyester resin pellet such that the crystalized polyester resin pellet exhibits desired properties, wherein the polyester resin pellet is formed of material substantially free of titanium dioxide (TiCh); melting the crystalized polyester resin pellet formed of melted polyester resin; extruding the melted polyester resin into one or more filaments; and weaving the polymer resin filaments into the yam, wherein the yam defines a density of 100 denier or less.

40. The method of claim 39, wherein the material of the polyester resin pellet comprises polyethylene terephthalate.

41. The method of claim 39, further comprising performing a chemical characterization test on the material of the polyester resin pellet to confirm that the material has less than 2% by weight of physical additives or impurities, wherein the physical additives or impurities includes at least titanium dioxide.

42. The method of claim 39, further comprising cleaning the material of the polyester resin pellet to remove one or more physical additives or impurities.

43. The method of claim 39, further comprising forming a fabric using the yam.

44. The method of claim 43, further comprising forming a medical device or a portion thereof from the fabric.

45. A method of forming a yarn for a medical device for implantation into a patient, the method comprising:crystalizing a polyester resin pellet such that the crystalized polyester resin pellet exhibits desired properties, wherein the polyester resin pellet is formed of material that has less than 2% by weight of physical additives or impurities; melting the crystalized polyester resin pellet formed of melted polyester resin; extruding the melted polyester resin into one or more filaments; and weaving the polymer resin filaments into the yam, wherein the yam defines a density of 100 denier or less.

46. The method of claim 45, wherein the material of the polyester resin pellet comprises polyethylene terephthalate.

47. The method of claim 45, wherein the material is substantially free of titanium dioxide (TiO2).

48. The method of claim 45, further comprising cleaning the material of the polyester resin pellet to remove one or more physical additives or impurities.

49. The method of claim 45, further comprising forming a fabric using the yam.

50. The method of claim 49, further comprising forming a medical device or a portion thereof from the fabric.

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