Coated eptfe suture

Abstract

A method for coating expanded polytetrafluoroethylene (ePTFE) sutures, the method comprising: applying a chemical etchant to a surface of the ePTFE suture, the chemical etchant comprising a base etchant to remove fluorine from the surface of the ePTFE suture to produce an etched ePTFE suture; and applying a coating to the etched ePTFE suture to produce a coated ePTFE suture, the coating comprising a cross-linkable silicone polymer, the coating comprising an antimicrobial agent selected from the group comprising triclosan, chlorhexidine, polyhexamethylene biguanide (PHMB), octenidine, and silver.

Description

[0001] Priority Statement

[0002] This disclosure claims priority to U.S. Provisional Patent Application Serial No. 63 / 792,613, filed April 22, 2025, the disclosure of which is incorporated herein by reference. Background Technology

[0003] Surgical sutures are used to close wounds and surgical incisions, and to repair damaged or severed muscles, blood vessels, and tissues. Typically, the suture is attached to a needle at one end, and the needle is pulled through the tissue to form one or more loops that hold the tissue together. The suture is then tightened using one or more knots, allowing the tissue to remain pulled together. Sutures can be applied manually (i.e., by the surgeon's hand) or by a suturing device (e.g., via an endoscope).

[0004] Sutures can be made from a variety of natural and synthetic materials, including polytetrafluoroethylene (PTFE) and expanded PTFE (ePTFE). PTFE sutures are widely used due to their strength and biocompatibility. ePTFE sutures are very strong, soft, and smooth, making them ideal for many surgical procedures, including bone grafts, implant surgeries, and spinal cord replacements, where soft monofilament sutures are desired. These properties also make ePTFE sutures easy to knot. However, due to the slippage nature of ePTFE, there is a risk of knots unraveling. Additionally, the porous nature of ePTFE can promote the growth of bacteria and / or other pathogenic microorganisms. Summary of the Invention

[0005] This disclosure relates to a method for coating expanded polytetrafluoroethylene (ePTFE) sutures, the method comprising: applying a chemical etchant to the surface of the ePTFE suture, the chemical etchant comprising a base etchant to remove fluorine from the surface of the ePTFE suture, thereby producing an etched ePTFE suture; and applying a coating to the etched ePTFE suture to produce a coated ePTFE suture, the coating comprising a crosslinkable silicone polymer, the coating comprising an antimicrobial agent selected from the group consisting of triclosan, chlorhexidine, polyhexamethylene biguanide (PHMB), oteninidine, and silver.

[0006] In one embodiment, applying the chemical etchant includes immersing the PTFE suture in a container containing an alkaline etchant at a set temperature for a set duration until the surface of the PTFE suture changes from dark blue to transparent light brown.

[0007] In one embodiment, the duration is set to two minutes and the temperature is set to 50°C, wherein applying the chemical etchant also includes periodically shaking the container.

[0008] In one embodiment, applying the coating includes: immersing the etched ePTFE suture into a container including the coating; or brushing, rolling, or spraying the coating onto the surface of the etched ePTFE suture.

[0009] In one embodiment, the method further includes: curing the coating by a convection oven, wherein the curing parameters include a set duration at a set temperature; or flash curing the coating.

[0010] In one embodiment, the first curing parameter includes 5 seconds at 150°C, and the second curing parameter includes 120 seconds at 90°C.

[0011] In one embodiment, removing fluorine from the surface of the ePTFE suture reduces the lubricity of the etched ePTFE suture relative to the ePTFE suture, wherein the lubricity of the coated ePTFE suture is reduced relative to the ePTFE suture.

[0012] In one embodiment, the coated ePTFE suture includes the controlled release of an antimicrobial agent over a period of at least 3 days.

[0013] In one embodiment, the base etchant comprises sodium naphthalene or sodium amino.

[0014] In one embodiment, curing the coating produces a cross-linked silicone matrix carrying an antimicrobial agent.

[0015] Furthermore, this disclosure relates to a coated expanded polytetrafluoroethylene (ePTFE) suture comprising: a base ePTFE suture including a surface on which a chemical etchant is applied, the chemical etchant including a base etchant to remove fluorine from the surface of the base ePTFE suture; and a coating applied to the base ePTFE suture, the coating comprising a crosslinkable silicone polymer, the coating comprising an antimicrobial agent selected from the group consisting of triclosan, chlorhexidine, polyhexamethylene biguanide (PHMB), oteninidine, and silver.

[0016] In one embodiment, the chemical etchant is applied by immersing the base PTFE suture in a container containing an alkaline etchant at a set temperature for a set duration until the surface of the ePTFE suture changes from dark blue to transparent light brown.

[0017] In one embodiment, the duration is set to two minutes and the temperature is set to 50°C, wherein applying the chemical etchant also includes periodically shaking the container.

[0018] In one embodiment, the coating is applied by: immersing the base ePTFE suture in a container containing the coating; or by brushing, rolling, or spraying the coating onto the surface of the base ePTFE suture.

[0019] In one embodiment, the coating is cured by a convection oven, wherein the curing parameters include a set duration at a set temperature, or the coating is cured by flash curing.

[0020] In one embodiment, the first curing parameter includes 5 seconds at 150°C, and the second curing parameter includes 120 seconds at 90°C.

[0021] In one implementation, removing fluoride from the surface of the base ePTFE suture reduces the lubricity of the base ePTFE suture.

[0022] In one implementation, the antimicrobial agent is released over a period of at least 3 days.

[0023] In one embodiment, the base etchant comprises sodium naphthalene or sodium amino.

[0024] In one embodiment, curing the coating produces a cross-linked silicone matrix carrying an antimicrobial agent. Attached Figure Description

[0025] Figure 1 Methods for manufacturing coated ePTFE sutures according to various exemplary embodiments are shown.

[0026] Figure 2 A table illustrating the antimicrobial stability of coated ePTFE sutures is shown, based on an example. Detailed Implementation

[0027] The exemplary embodiments can be further understood with reference to the following description and accompanying drawings, wherein the same reference numerals refer to the same elements. The exemplary embodiments relate to expanded polytetrafluoroethylene (ePTFE) sutures comprising an antimicrobial coating and a method for producing coated ePTFE sutures by a chemical etching process and a coating process.

[0028] Sutures can be formed from ePTFE into monofilaments, i.e., a single strand of ePTFE. Sutures formed from ePTFE are bioinert, non-absorbable, strong, extremely soft, and smooth, making them ideal for many surgical procedures, including bone grafts and implant surgeries, where soft monofilament sutures are desirable. ePTFE sutures also show excellent results for notochord replacement. ePTFE sutures are also easy to knot. However, due to the slippage properties of the ePTFE material, there is a risk of knot unraveling in ePTFE sutures. Postoperative knot failure can have serious consequences, requiring a repeat cardiopulmonary bypass. Some surgeons mitigate this risk by securing the knot in more complex ways, such as using multiple additional knots or by using clips.

[0029] Another potential problem with ePTFE sutures is the porous nature of the material, which could allow bacteria and other pathogens to attach to and penetrate the suture body, thereby exacerbating infection.

[0030] Therefore, due to the slippage properties of this type of material, it is necessary to improve the knot strength of ePTFE sutures. More complex knots can present challenges when performing surgery endoscopically. Additionally, the antimicrobial properties of ePTFE sutures need to be improved. Therefore, a solution is needed to address these two key challenges of ePTFE sutures.

[0031] Coatings have been applied to sutures to improve suture performance by, for example, reducing friction, increasing knot strength, reducing tissue reactivity, and / or providing antimicrobial properties. Commonly used polymer coatings include polyglactin, polycaprolactone, and polybutyrate to improve handling and reduce friction. Antimicrobial protective ingredients (APIs) can be introduced into coatings to prevent bacterial colonization and reduce the risk of infection. Some common APIs include triclosan, chlorhexidine, polyhexamethylene biguanide (PHMB), oteninidine, and silver.

[0032] Coatings can be applied to stitches using techniques including dipping, brushing, rolling, or spraying. Vapor deposition is a coating technique in which a solid / liquid coating material evaporates at a set temperature (e.g., at high temperatures) and is deposited as a vapor phase onto a surface under controlled temperature / pressure conditions, causing the vapor to condense and solidify onto the surface.

[0033] ePTFE sutures are difficult to coat, making it challenging to incorporate triclosan into them. Vapor deposition can be used to deposit APIs (e.g., triclosan) onto the suture surface, but controlled release of the API from the suture remains technically challenging. The loose binding of triclosan molecules on the ePTFE surface leads to rapid release of the molecule. Antimicrobial sutures are preferably designed with controlled release, allowing their antimicrobial function to be maintained for a certain period, such as 3 days.

[0034] A silicone-based suture coating has been developed comprising a crosslinkable silicone polymer, a silicone crosslinking agent, and an antimicrobial agent, such as, for example, triclosan, as described in commonly assigned U.S. Patent No. 11,464,889, the disclosure of which is incorporated herein by reference. The crosslinking process for the silicone polymer includes mild curing conditions, such that the antimicrobial component remains within the crosslinked silicone matrix and does not decompose or evaporate. The antimicrobial agent can be uniformly distributed throughout the silicone matrix. This silicone-based antimicrobial coating has shown improved knotting performance in PET sutures.

[0035] According to various exemplary embodiments, methods for improving the knotting performance of ePTFE sutures while incorporating antimicrobial properties therein over an extended duration are described. Exemplary embodiments typically include a chemical etching process and a coating process. Typically, chemical etching is applied to the surface of the ePTFE suture to prepare the suture for coating with a coating agent (such as, for example, the silicone-based coating described above). In the various embodiments described below, specific types of etchants (i.e., etching agents) and coatings are described in conjunction with specific parameters of the etching and coating processes. Those skilled in the art will understand that the exemplary embodiments are not limited thereto, and different coatings may be used according to embodiments of the invention, which may influence the selection of different etchants and related modifications to the etching and coating processes described below.

[0036] In various embodiments, ePTFE sutures include monofilament sutures. Those skilled in the art will understand that exemplary embodiments are not limited to monofilament sutures, and that different types of ePTFE sutures, such as braided sutures, barbed sutures, etc., can be coated according to embodiments of the invention. Furthermore, ePTFE sutures can have different closure styles, such as standard (a closure without pre-formed knots for the thread), loop knots (a single loop knot at the end of the thread), tie knots (a pre-formed knot at the end of the thread that can be tightened), etc. It should be understood that ePTFE sutures according to embodiments of the invention exhibit improved knot strength properties, making it possible to use simpler closure styles without the risk of knot unraveling.

[0037] In some implementations, chemical etching is applied to the surface of the ePTFE suture. Since the lubricity of ePTFE is a result of its chemical structure—a fluorosheath covering carbon atom chains—this chemical structure needs to be altered to achieve true adhesion and a strong bond between the coating and the suture. Exemplary chemical etching processes achieve this by immersing the ePTFE suture in a tank or by applying an etchant to the surface of the suture, bringing the ePTFE suture into contact with the etchant (e.g., sodium naphthalene or sodium amide) used to alter the fluorosheath.

[0038] Because these etchants are derived from sodium (an alkali metal), they react chemically with ePTFE, thereby removing fluorine atoms from the ePTFE molecule. Those skilled in the art will understand that alternative types of etchants can be applied to modify the fluorine sheath of the ePTFE suture. Since the fluorine sheath is responsible for the lubrication of PTFE, removing most of the fluorine from the surface essentially removes this property, allowing the surface to adhere to virtually any substrate, including silicone-based materials.

[0039] In some embodiments, a coating is applied to the surface of an etched ePTFE suture. The controlled release properties of silicone make it attractive as a candidate carrier for ePTFE sutures. In some embodiments, the coating comprises a silicone coating solution containing an antimicrobial agent (e.g., triclosan). Those skilled in the art will understand that alternative coating solutions may be suitable for coating etched ePTFE sutures.

[0040] Compared to uncoated ePTFE sutures, coated ePTFE sutures produced by the disclosed chemical etching and coating techniques offer superior knot strength and extended antimicrobial efficacy. Prototypes of the coated ePTFE sutures underwent knot strength and zone of inhibition (ZOI) tests to demonstrate their superior performance relative to uncoated ePTFE, which will be described in more detail below.

[0041] Figure 1 A method 100 for manufacturing coated ePTFE sutures according to various exemplary embodiments is shown. Method 100 generally includes a chemical etching process 110 in which a chemical etch is applied to the ePTFE suture, and a coating process 120 in which a coating is applied to the etched suture. In some exemplary examples, the coating comprises a silicone-based coating, and the chemical etchant comprises sodium naphthalene, as described in substeps 111-115 of the chemical etching process 110 and substeps 121-123 of the coating process 120 below.

[0042] Method 100 relates to ePTFE sutures. In one embodiment, the ePTFE suture comprises Aeos™ USP 3, Zeus, Orangeburg, SC, with a length of 40 inches. Those skilled in the art will understand that any type of ePTFE suture (currently commercially available or to be developed in the future) can be etched and coated according to the described embodiment. According to the technology of the present invention, any number of ePTFE sutures can be chemically etched and coated, depending on the capacity of the equipment used for these processes.

[0043] In step 110, the suture is immersed in an etching solution (i.e., etchant) in a container. In one embodiment, the etching solution contains 40 g of FluroEtch™ fluoropolymer pre-bonded etchant (Acton Technology, Pittston, PA). As described above, in other embodiments, other etchants suitable for fluoropolymers may be used to remove the fluorine layer from the suture. The suture may be immersed for a specific duration, and in some cases, the container may be shaken.

[0044] In one example implementation, in step 111, the sutures are immersed in the etchant at a set temperature for a set duration. In one example, 10 ePTFE sutures are fully immersed in the etching solution at 50°C for 1 minute. In step 112, the etching solution is agitated, for example, for 10 seconds. In step 113, the sutures remain immersed in the etching solution for another duration. In one example, the ePTFE sutures are fully immersed in the etching solution at 50°C for another minute. In step 114, the etching solution is agitated, for example, for 10 seconds. The deep blue of the etching solution turns into a very light yellow. As a result of this process, the white ePTFE sutures turn into a dark brown. In step 115, the etched sutures are rinsed with isopropanol and water. The etched sutures are then dried, for example, under ambient conditions.

[0045] Chemical etching process 110 removes fluorine from the surface of the ePTFE suture to reduce its lubricity. The resulting surface of the etched ePTFE suture is suitable for coating application.

[0046] In step 120, the etched suture is coated. In some embodiments, the coating is applied by dip-dip coating. In other embodiments, the coating is applied by other conventional coating techniques, such as brush coating, roller coating, or spray coating. In some embodiments, the coating is a silicone-based coating containing triclosan, for example, as described above with respect to U.S. Patent No. 11,464,889.

[0047] In one example implementation, in step 121, a silicone-based coating solution is applied to the surface of an etched ePTFE suture by a dip coating tank. In step 122, the suture is conveyed to an inline convection oven. In step 123, the coating is cured in the oven at a set temperature for a set duration. In one example, the curing time may be 5 seconds at 150°C. In another example, the curing time may be 120 seconds at 90°C. The curing time / temperature is set to complete the vinyl silylation addition crosslinking reaction of the silicone coating solution. Flash curing can also be used. The active antimicrobial component triclosan remains in the coating after the curing process due to its relatively low temperature and short processing time.

[0048] In other implementations, different types of coatings may be used, such as other silicone-based coatings or other polymer-based coatings. In these cases, different coating application and curing parameters / techniques may be used.

[0049] The resulting coated suture exhibits enhanced knot strength due to reduced lubricity caused by the reaction of the etchant with the fluoride sheath of the original ePTFE suture. Although the addition of a silicone-based coating increases the lubricity of the coated ePTFE suture relative to the etched ePTFE suture, the lubricity of the coating is reduced relative to the original ePTFE suture, allowing the suture to remain sufficiently rough so that simple knots can maintain their intended duration without slippage.

[0050] Knot strength tests were performed to evaluate knot behavior under suture tension. The tests were conducted in a tension testing machine with constant displacement. Ten samples were tested for each group of sutures. The sutures were immersed in a sodium chloride solution for 24 hours and tested while wet. For each sample, a knot was tied around a plastic mandrel, with four knots tied for each suture sample. The failure mode—unraveling or breakage—was recorded for each sample. Knot performance was rated as strong (no slippage), slippage and breakage, or slippage (no breakage).

[0051] The results of the knot strength test showed that all knots from the prototype sample (an etched ePTFE sample coated with silicone containing triclosan) were strong, while all knots from the uncoated ePTFE suture slipped.

[0052] Testing for antimicrobial properties can include the zone of inhibition (ZOI) test. The ZOI test is a routine method for evaluating the inhibitory effect of antimicrobial agents on specific bacterial strains of interest. ZOI determination can be used to test diffusing agents. As the agent diffuses from the disc, the concentration decreases logarithmically. The sensitivity of an organism to the agent is determined by the appearance and size of the area where no growth occurs (i.e., the zone of inhibition). Typically, a ZOI value of 3 mm is considered an effective zone for inhibiting infection.

[0053] This inhibition zone test was used to evaluate the antimicrobial properties of the prototype test article. The test article was aseptically placed in individual sterile Petri dishes and challenged with 100 μL of Staphylococcus aureus or Escherichia coli containing 10 colony-forming units (CFU). Trypsin-soy agar (TSA) was poured into each dish and allowed to solidify. These plates were incubated at 37°C for 48 hours. After incubation, the plates were examined using a dark-field colony counter, and the inhibition zone was measured.

[0054] ZOI (in millimeters) was measured at three points along the suture: each cut end of the suture and the center. To assess the ability of the suture to inhibit colonization over time, the suture was removed daily using sterile forceps and transferred to freshly inoculated plates (to aseptically remove any residual TSA from the suture). These plates were incubated overnight, and ZOI was measured. This daily transfer continued until the third day, and the results are summarized below.

[0055] The control sutures included ePTFE sutures coated with triclosan prepared by conventional vapor deposition. Figure 2 Table 200 shows the antimicrobial stability of coated ePTFE sutures according to an example. As shown, the control sample maintained a ZOI of 5.3 mm after day 1 and showed no antimicrobial activity by day 2. The prototype sample maintained a ZOI of 9.7 mm after day 1, 7.7 mm after day 2, and 6.1 mm after day 3.

[0056] Therefore, silicone-coated ePTFE sutures containing triclosan exhibit antimicrobial activity against *Escherichia coli* in vitro. The activity lasts for several days and is stable after sterilization. In contrast, triclosan-coated ePTFE sutures prepared using conventional vapor deposition techniques exhibit activity lasting only one day. The additional antimicrobial properties of the described embodiment would be a valuable adjunct to reduce the risk of SSIs and patient-related morbidity, as well as the financial impact on the healthcare system.

[0057] It will be apparent to those skilled in the art that various modifications may be made to this disclosure without departing from its scope. Furthermore, those skilled in the art will understand that features of any embodiment in the various implementations may be combined in any manner inconsistent with the description and / or functionality of those embodiments.

Claims

1. A method for coating expanded polytetrafluoroethylene (ePTFE) sutures, comprising: A chemical etchant, comprising a base etchant, is applied to the surface of the ePTFE suture to remove fluorine from the surface of the ePTFE suture, thereby producing an etched ePTFE suture. as well as A coating is applied to the etched ePTFE suture to produce a coated ePTFE suture, the coating comprising a crosslinkable silicone polymer and an antimicrobial agent selected from the group consisting of triclosan, chlorhexidine, polyhexamethylene biguanide (PHMB), oteninidine, and silver.

2. The method according to claim 1, wherein, Applying the chemical etchant includes: The PTFE suture is immersed in a container containing the alkaline etchant at a set temperature for a set duration until the surface of the PTFE suture changes from dark blue to transparent light brown.

3. The method according to claim 2, wherein, The set duration includes two minutes, and the set temperature includes 50°C, wherein applying the chemical etchant further includes periodically shaking the container.

4. The method according to claim 1, wherein, Applying the coating includes: The etched ePTFE suture is immersed in a container containing the coating; or The coating is applied by brushing, rolling, or spraying onto the surface of the etched ePTFE suture.

5. The method according to claim 1, further comprising: The coating is cured by a convection oven, wherein the curing parameters include a set duration at a set temperature, or The coating is rapidly cured.

6. The method according to claim 5, wherein, The first curing parameter includes 5 seconds at 150°C, and the second curing parameter includes 120 seconds at 90°C.

7. The method according to claim 1, wherein, Removing fluorine from the surface of the ePTFE suture reduces the lubricity of the etched ePTFE suture relative to the ePTFE suture, wherein the lubricity of the coated ePTFE suture is reduced relative to the ePTFE suture.

8. The method according to claim 1, wherein, The coated ePTFE suture includes controlled release of the antimicrobial agent over a period of at least 3 days.

9. The method according to claim 1, wherein, The basic etchant contains sodium naphthalene or sodium amino.

10. The method according to claim 1, wherein, Curing the coating produces a cross-linked silicone matrix carrying the antimicrobial agent.

11. A coated expanded polytetrafluoroethylene (ePTFE) suture, comprising: A base ePTFE suture, the base ePTFE suture including a surface on which a chemical etchant is applied, the chemical etchant including a base etchant to remove fluorine from the surface of the base ePTFE suture; and A coating, which is applied to the base ePTFE suture, comprises a crosslinkable silicone polymer and an antimicrobial agent selected from the group consisting of triclosan, chlorhexidine, polyhexamethylene biguanide (PHMB), oteninidine, and silver.

12. The coated ePTFE suture according to claim 11, wherein, The chemical etchant is applied by immersing the base PTFE suture in a container containing the base etchant at a set temperature for a set duration until the surface of the ePTFE suture changes from dark blue to transparent light brown.

13. The coated ePTFE suture according to claim 12, wherein, The set duration includes two minutes, and the set temperature includes 50°C, wherein applying the chemical etchant further includes periodically shaking the container.

14. The coated ePTFE suture according to claim 11, wherein, The coating is applied by immersing the base ePTFE suture in a container containing the coating, or by brushing, rolling, or spraying the coating onto the surface of the base ePTFE suture.

15. The coated ePTFE suture according to claim 11, wherein, The coating is cured by a convection oven, wherein the curing parameters include a set duration at a set temperature, or the coating is cured by flash curing.

16. The coated ePTFE suture according to claim 15, wherein, The first curing parameter includes 5 seconds at 150°C, and the second curing parameter includes 120 seconds at 90°C.

17. The coated ePTFE suture according to claim 11, wherein, Removing fluorine from the surface of the base ePTFE suture reduces the lubricity of the base ePTFE suture.

18. The coated ePTFE suture according to claim 11, wherein, The antimicrobial agent is released over a period of at least 3 days.

19. The coated ePTFE suture according to claim 11, wherein, The basic etchant contains sodium naphthalene or sodium amino.

20. The coated ePTFE suture according to claim 11, wherein, Curing the coating produces a cross-linked silicone matrix carrying the antimicrobial agent.

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