Patent Description:
In the medical field, and in the area of wound care particularly, it is well-established that many factors, including the amount of moisture present at a wound site, affects how quickly a wound will heal. Generally speaking, having an excessive amount of moisture present at a wound site, especially when combined with the warm environment provided by the body, leads to undesirable bacteria growth and production of protease enzymes in the wound. Such growth can cause further damage to healthy cells and delay the healing process. However, insufficient moisture at the wound site can cause eschar (scab) formation and scarring and may cause the wound care device, or medical dressing, to adhere to the wound. If the dressing adheres to the wound, subsequent removal of the dressing may cause undue discomfort to the patient as well as disrupt newly granulated tissue. Infection of the wound may also be compounded when a medical dressing is removed, and portions of the dressing remain behind in the wound itself, particularly if the dressing is already colonized with pathogenic microbes. Thus, it is important that the dressing maintains its physical integrity when exposed to stress, such as during removal from the wound, in order to prevent additional complications and delays in healing.

It desirable to have a dressing system that transfer excess moisture as well as does not stick to the wound, is low friction, is hypoallergenic, inert, and optionally create a dressing that is cool to the patient's touch.

US-A_2011/<NUM> discloses a compression dressing of a size of at least <NUM>" x <NUM>",comprising as sequential layers (a) optionally, a skin-contacting layer, (b) at least one layer of moisture transport fabric comprised of elastic fiber, wherein the moisture transport fabric exhibits a sufficient amount of elasticity to apply a compressive force to a body part when applied thereto, (c) at least one absorptive reservoir layer; and (d) optionally, at least one layer of elastic fabric comprising the outermost layer of the compression dressing; which compression dressing provides one-way, active fluid management of fluid away from the skin and into the absorptive reservoir layer.

<CIT> relates to a knitted sock comprising an inner sock layer comprising a reciprocated heel portion, a toe portion and a sole portion and the heel portion, toe portion and sole portion are of the same yarn composition, the inner sock layer having an inner toe end; an outer sock layer having an outer toe end; the inner toe end and the outer toe end being joined to form a single composite toe end; the single composite toe end being closed to provide a substantially flat toe seam.

The present invention provides a sterilized wound dressing (<NUM>) comprising:.

Referring now to <FIG>, there is shown a cross-sectional illustration of one embodiment of the burn wound dressing system <NUM>. The burn wound dressing system <NUM> contains a multi-ply knit fabric <NUM>, a skin graft <NUM>, and the patient's outer portion of the body (typically the skin) <NUM>.

The dressing systems <NUM>, <NUM> are sized so that they cover the area desired to be protected. Preferably, the dressing systems have a length and a width greater than the area of the wound on the patient <NUM> (burn or surgical wound). In one embodiment, the dressing systems have a length and a width at least <NUM>% greater than the area of the wound on the patient <NUM>, more preferably at least <NUM>% greater.

<FIG> shows a cross-sectional illustration of one embodiment of the surgical wound dressing system <NUM>. The surgical wound dressing system <NUM> contains a multi-ply knit fabric <NUM>, an absorption dressing <NUM>, a compression dressing <NUM>, and the patient's outer portion of the body (typically the skin) <NUM>.

The knit fabric <NUM> has an upper surface 10a and a lower surface 10b. When the fabric <NUM> is placed into the system, preferably the lower surface 10b would be facing the patient and upper surface 10a would be facing away from the patient. The knit fabric <NUM> of <FIG> and <FIG> is shown containing <NUM> plies; a first knit ply <NUM> and a second knit ply <NUM>. The knit fabric <NUM> is a unitary material that is formed together in a knitting machine with the two plies separated by a dashed line. The plies <NUM> and <NUM> are not formed as discrete knit layers and then joined together in a later operation. <FIG> is a photomicrograph of a cross-section of one embodiment of the multi-ply knit fabric <NUM>. <FIG> is a photomicrograph of the upper surface (first knit ply) of the multi-ply knit fabric of <FIG> and <FIG> is a photomicrograph of the lower surface (second knit ply) of the multi-ply knit fabric of <FIG>.

The multi-ply knit fabric <NUM> may be made by any suitable knitting method, including both warp knitting and weft (or circular) knitting. Circular knitting is preferred in some embodiments, as it tends to be more cost efficient. The two plies may have the same knit construction or different.

The first knit ply <NUM> comprising a plurality of first yarns and forms the upper surface 10a of the fabric <NUM>. The first yarns in the first knit ply <NUM> may be any suitable yarn. "Yarn", in this application, as used herein includes a monofilament elongated body, a multifilament elongated body, ribbon, strip, yarn, tape, fiber and the like. The first knit ply <NUM> may contain one type of yarn or a plurality of any one or combination of the above. The yarns may be of any suitable form such as spun staple yarn, monofilament, or multifilament, single component, bi-component, or multi-component, and have any suitable cross-section shape such as circular, multi-lobal, square or rectangular (tape), and oval. In one preferred embodiment, the first ply <NUM> contains multifilament polyester yarns as these have been shown to have good performance at low cost.

The first knit ply may have any suitable knit pattern and be formed by any suitable yarns. The yarns in the first ply may be a single plurality or type of yarn (e.g., the fabric can be formed solely from yarns comprising a blend of cellulosic yarns and synthetic yarns, such as polyamide yarns), or the textile can be formed from several pluralities or different types of yarns (e.g., the fabric can be formed from a first plurality of yarns comprising cellulosic yarns and polyamide yarns and a second plurality of yarns comprising an inherent flame resistant yarn). The yarns may be formed of (but are not limited to) cellulosic yarns (such as cotton, rayon, linen, jute, hemp, cellulose acetate, and combinations, mixtures, or blends thereof), polyester yarns (e.g., poly(ethylene terephthalate) yarns, polypropylene terephthalate) (PET) yarns, poly(trimethylene terephthalate) yarns), poly(butylene terephthalate) yarns, and blends thereof), polyamide yarns (e.g., nylon <NUM> yarns, nylon <NUM>,<NUM> yarns, nylon <NUM>,<NUM> yarns, and nylon <NUM> yarns), polyvinyl alcohol yarns, an elastic polyester-polyurethane copolymer (SPANDEX®), flame-resistant meta-aramid (NOMEXO)and combinations, mixtures, or blends thereof.

The second knit ply <NUM> comprising a plurality of polytetrafluoroethylene (PTFE) yarns and forms the lower surface 10b of the fabric <NUM>. Preferably, if the fabric <NUM> is made into a garment, the second knit ply <NUM> faces the wearer and is preferably in direct contact with the wearer's skin. The lower surface 10b of the fabric <NUM> has a surface roughness of < <NUM>, preferably < <NUM>. PTFE yarn could be of any denier or sizes. In one preferred embodiment, <NUM> denier PTFE is used and in another embodiment, <NUM> denier PTFE yarn is used. However, depending on the desired weight (g/m<NUM> (oz/yd<NUM>)) and other properties, the denier of the PTFE yarn could be smaller or larger.

The PTFE yarns have a density of <NUM>-<NUM>/cm<NUM>, preferably <NUM>-<NUM>/cm<NUM>, more preferably <NUM>-<NUM>/cm<NUM>. Typical textile yarns, such polyester, nylon or cotton have densities of < <NUM>/cm<NUM>. The PTFE yarns have a transmission in the IR region of <NUM>-<NUM> of ≥ <NUM>%, more preferably ≥ <NUM>%. In case of polyester, it has C-O stretching frequency from <NUM>-<NUM> (micron) and C-H bending from <NUM>-<NUM>, which leads to reduced transmission, ≤ <NUM>% in the IR region of <NUM>-<NUM>. It has been shown that this ≤ <NUM>% transmission in the IR region of <NUM>-<NUM>µmicrons produces a fabric with less active cooling. The PTFE yarns also have a thermal conductivity of ≥ <NUM> W/(m. K), more preferably ≥ <NUM> W/(m. K), more preferably ≥ <NUM> W/(m. Polyester yarn has much lower thermal conductivity of -<NUM> W/(m. Preferably, the PTFE yarns have a generally rectangular cross-sectional shape.

When measuring aspect ratio, the cross-section of the yarn is measured across the entire width (even if the tape is folded onto itself). In one embodiment, the PTFE yarns have a cross-section aspect ratio across the entire width of (<NUM>:<NUM>)-(<NUM>:<NUM>). Typical flat polyester has the aspect ratio of less than <NUM>:<NUM>. Typical PTFE yarn is used in a folded state, meaning that there are fold lines running along the length of the tape yarns and portions of the yarn lay on other portions of the yarn (sometimes like an accordion) such as can be seen in <FIG>. If the aspect ratio is measured of the folded PTFE yarn, the aspect ratio would be (<NUM>:<NUM>)-(<NUM>:<NUM>).

The first <NUM> and second <NUM> plies are integrated through combined portions, this is preferably done at the time of knitting such that the fabric <NUM> is created as a multi-ply knit fabric, not as two separate knit fabrics that are then joined in a subsequent process step. This integration may be from one of the following methods, or a combination of the methods.

The first method is interlacing first yarns from the first ply among the PTFE yarns of the second knit ply, meaning that a portion of the first yarns from the first ply leave the first ply, travel down into the second ply where they are interlaced with yarns within the second ply, and then travel back up to the first ply.

The second method is interlacing PTFE yarns from the second ply among the first yarns of the first knit ply, meaning that a portion of the PTFE yarns from the second ply leave the second ply, travel up into the first ply where they are interlaced with yarns within the first ply, and then travel back down to the second ply to the first ply.

The third method is interlacing a plurality of third yarns among the first yarns of the first knit ply and the PTFE yarns of the second knit ply. This means that a third yarn (which may be the same or different yarn than the first yarns and/or PTFE) travels between the plies, interlacing with yarns from both plies and in essence, tying them together. Preferably, the third yarns comprise PTFE yarns.

In a preferred embodiment, the second method is used to interlace the first <NUM> and second <NUM> ply together. This method is preferred because of the lower complexity during the knitting process using the circular knitting.

In one embodiment, the multi-ply knit fabric is made using what is referred to as a flat back mesh construction. In this construction, the yarns are evenly spaced on the flat side, while the yarns are not spaced evenly on the mesh side (PTFE side) (open). The knitting diagram for this construction can be seen in <FIG>. Preferably, the second ply is more open than the first ply, meaning that there are gaps in the second ply (so that when looking at the lower surface of the fabric <NUM>, some of the first ply <NUM> can be seen through the gaps in the second ply <NUM>. The mesh allows the moisture from the human skin to transport more efficiently to the environment, while minimizing the materials use. PTFE is preferably used in the mesh side. In the mesh side, the gaps between two yarns could be up to <NUM>-<NUM>.

Thickness of the both faces are almost equally distributed, while contents of different yarns are controlled by changing the gap between the yarns in the mesh side. Tightness of the knitting is also controlled to achieve the total fabric thickness. Typical fabric thickness can be varied from <NUM>-<NUM>.

In one embodiment, the fabric <NUM> contains a third knit layer. Preferably, this third knit layer is on the first ply (on the side opposite to the second ply) or between the first and second plies. When the fabric <NUM> contains a third ply, the second play preferably still forms the lower surface 10b of the fabric <NUM>. The third layer may be knitted from any of the materials (or combinations of materials) disclosed as suitable materials for the first <NUM> or second <NUM> ply and is preferably knit as the same time and integral with the first and second plies.

It is preferred to have the amount of PTFE yarns in the fabric <NUM> (as a whole) be as low as possible due to the cost of the PTFE yarns in relation to the other yarns in the fabric <NUM>. In one embodiment, the fabric <NUM> comprises < <NUM> wt. % PTFE yarns. In another embodiment, the fabric <NUM> comprises < <NUM> wt. % PTFE yarns. In another embodiment, the fabric <NUM> comprises <NUM>-<NUM> wt. % PTFE yarns. It is believed to be most important to concentrate the PTFE yarns on the lower surface 10b of the fabric <NUM> to maximize their cooling effect, the non-stick, and other desired properties. In one embodiment, the second knit ply comprises ≥ <NUM> wt. % PTFE yarns. In another embodiment, the lower surface 10b comprises ≥ <NUM> wt. % PTFE yarns.

The multi-ply knit fabric also contains a composition comprising at least one silver ion-containing compound on at least the upper surface of the multi-ply knit fabric. In another embodiment, the knit fabric is dip coated to the composition so that all of the surfaces of the yarns within the knit fabric are exposed to the composition. Typically, the composition sticks very minimally to almost not at all to the PTFE yarns.

The silver ion-containing compound is preferably selected from the group consisting of silver ion exchange materials (e.g. silver zirconium phosphates, silver calcium phosphates and silver zeolites), silver particles (e.g. silver metal, nanosilver, colloidal silver), silver salts (e.g. AgCl, Ag<NUM>CO<NUM>), silver glass, and mixtures thereof. One preferred silver ion-containing compound is an antimicrobial silver sodium hydrogen zirconium phosphate available from Milliken & Company of Spartanburg, South Carolina, sold under the tradename AlphaSan®. Other potentially preferred silver-containing antimicrobials suitable for use herein-including silver zeolites, such as a silver ion-loaded zeolite available from Sinanen Co. of Tokyo, Japan under the tradename Zeomic®, and silver glass, such as those available from Ishizuka Glass Co. of Japan under the tradename lonpure®-may be utilized either in addition to, or as a substitute for, the preferred species listed above. Other silver ion-containing materials may also be used. Various combinations of these silver-containing materials may be made if adjustments to the silver release rate over time are desired.

Generally, the silver-based compound is added in an amount of <NUM>-<NUM>% by total weight of the particular finish composition; more preferably <NUM>-<NUM>%; and most preferably <NUM>-<NUM>%. The antimicrobial finish itself, including, for example, any desired binders, wetting agents, odor absorbing agents, leveling agents, adherents and thickeners, is added to the substrate in an amount of ≥ <NUM> % of the total device weight.

A binder material has been found useful in preventing the antimicrobial from flaking off the fabric and onto the wound. Preferably, this component is a polyurethane-based binding agent, although a wide variety of cationic, anionic, and non-ionic binders may also be used, either alone or in combination. Preferably, the binding agent is biocompatible such that is does not cause negative reactions in the wound. In essence, such binders provide durability by adhering the antimicrobial to the target substrate, such as fibers or fabrics, without negatively affecting the release of silver ions to the wound.

Total add-on levels of silver to the target substrate may be ≥ <NUM> ppm. More preferably, total add-on levels of silver may be ≥ <NUM> ppm. Although an upper boundary limit of silver add-on levels to the target substrate has not been determined, consideration of the manufacturing economics and the potential to irritate a sensitive wound site suggests avoiding excessive silver levels.

Silver ion-containing compounds (such as AlphaSan®, Zeomic®, or Ionpure®) may be admixed in an aqueous dispersion with a binder to form a bath into which the knit fabric is immersed. Other similar types of compounds that provide silver ions may also be utilized.

When specific polyurethane-based binder materials are utilized, the antimicrobial characteristics of the treated substrate are effective with regard to the amount of surface available silver that is released to kill bacteria, without altering the color of the treated substrate (that is, while substantially maintaining its original appearance). While it currently appears that the use of polyurethane-based binder resins are preferred due to their allowance of silver release and bio-neutral properties, in practice essentially any effective cationic, anionic, or non-ionic binder resin that is not toxic to the wound may be used.

An acceptable method of providing a durable antimicrobial silver-treated fabric surface is the application of a silver ion-containing compound and polyurethane-based binder resin from a bath mixture. This mixture of antimicrobial compound and binder resin may be applied through any technique as is known in the art, including spraying, dipping, padding, foaming, printing, and the like. By using one or more of these application techniques, a fabric may be treated with the antimicrobial compound and binder resin on only one side of the fabric (e.g. the wound contact surface of a wound care device), or it may be treated on both sides of the fabric.

Preferably, the multi-ply knit fabric (as well as all of the other layers within the systems <NUM>, <NUM>) are sterilized. This sterilization can occur to each layer within the systems before assembly or after the systems are assembled together. Any suitable sterilization method may be used that does not harm or otherwise interfere with the desired properties of the systems. For example, heat, irradiation, or chemicals may be used separately or in combination to sterilize the systems <NUM>, <NUM>.

In one embodiment, the multi-ply knot fabric <NUM> and/or the systems <NUM>, <NUM> are non-electrically conductive. "Non-electrically conductive" is defined as having a resistance in ohms per square inch of fabric of > <NUM>,<NUM>Ω, preferably > <NUM>,<NUM>Ω and most preferably > <NUM> × <NUM><NUM> Ω, when measured in accordance with AATCC Test Method <NUM>-<NUM>.

Referring back to <FIG>, the burn wound dressing system <NUM> contains a skin graft <NUM>. Skin grafts are often employed after serious injuries when some of the body's skin is damaged. Surgical removal (excision or debridement) of the damaged skin is followed by skin grafting. The grafting serves two purposes: reduce the course of treatment needed (and time in the hospital) and improve the function and appearance of the area of the body which receives the skin graft.

There are two types of skin grafts, the more common type is where a thin layer is removed from a healthy part of the body (the donor section) like peeling a potato, or a full thickness skin graft, which involves pinching and cutting skin away from the donor section. The graft may be human skin, pig skin, artificial skin, or any other suitable material for the skin graft. Having the lower side 10b of the multi-ply knit fabric <NUM> next to the skin graft <NUM> is advantageous as the low friction and non-stick characteristics of the PTFE yarns protects the skin graft <NUM>. The skin graft is adjacent and located in a touching fashion to the burn wound on the patient's skin <NUM>.

The burn dressing system <NUM> is applied by any suitable method to the patient's skin <NUM>. After the layers <NUM>, <NUM> are placed on the skin <NUM>, additional layers may be added for additional functionality and to hold the dressing system to the skin. Adhesive, compression wraps, stitches, and or staples are some ways to attaching the system <NUM> to the patient.

Referring back to <FIG>, the surgical wound dressing system <NUM> also contains an absorption dressing <NUM> and a compression dressing <NUM>. The absorption.

The absorption dressing <NUM> is any suitable dressing that can absorb and retain an amount of liquid suitable for the wound. Some examples of absorption dressings include cotton batting, gauze, high absorbency, swellable polymers such as used in feminine hygiene products and diapers. The compression dressing <NUM> is any suitable material that holds the layers of the system <NUM> to the patient's skin <NUM> while also preferably providing some compression. Elasticized bandages, such as ACE® bandages are one example of a compression dressing <NUM>.

Weight of the fabric was measured using ASTM D <NUM>. Air permeability was measured using ASTM D <NUM>. MVTR was measured ASTM E <NUM> - <NUM>: Water Vapor Transmission of Materials, modified procedure B; both Open Jar Method and with the Air Flow method. Q-Max is the measurement of the maximum heat loss that can occur when the skin touching objects or other materials. Larger Q-max, cooler the material, in this case fabric, to human touch. The Kawabata thermal tester (Thermolabo) is used to measure the Q-max. Intrinsic thermal resistance, apparent intrinsic evaporative resistance, and total heat loss are measured using a sweating guarded hot plate using ASTM F1868, Part C.

The table below summarizes the <NUM> examples. The PTFE yarn used was either <NUM> den (Lenzing™ Profilen FG02 natural) and <NUM> den (Lenzing™ Profilen FR110 natural). The polyester yarn used was a multi-filament yarns in a <NUM> ply or <NUM> ply <NUM>/<NUM> construction. Examples <NUM>-<NUM> were knitted in flat back mesh construction as shown in <FIG>. Example <NUM> was a <NUM>/<NUM> PTFE (<NUM> den)/polyester interlock knit and example <NUM> was a <NUM>% polyester interlock knit. Examples <NUM>-<NUM> were subjected to navy disperse dyeing process and tentering for testing and evaluation. Example <NUM> was a commercially available fabric from ADIDAS™ called Climachil which is a double knit, bi-ply. The outerply contains typical multifilament round polyester yarn and the inner ply contains multifilament flat polyester yarns.

The examples were tested for air permeability, moisture vapor transmission rate (MVTR) (ASTM E <NUM> - <NUM>: Water Vapor Transmission of Materials, modified procedure B; both Open Jar Method and with the Air Flow) (g/m<NUM>/<NUM> hrs ) and Q-max (W/cm<NUM>) of back (skin side) and face of the fabrics.

As one can see form the table above, examples containing PTFE yarn (Examples <NUM>-<NUM>) has slightly higher MVTR (~<NUM>-<NUM>/m<NUM>/<NUM> hrs) than the polyester examples (Examples <NUM>-<NUM>) (~<NUM>-<NUM>/m<NUM>/<NUM> hrs). Comparing Examples <NUM>, <NUM>, and <NUM> (knitted with the flat back mesh construction as shown in <FIG>) had much higher MVTR values in the military method, where there is airflow at the top of the jar compared to Examples <NUM> and <NUM> (without the PTFE yarns). This indicates the moisture vapor transmission is induced by the airflow.

In terms of cooling effect, the higher the Q-max, cooler the fabric feels to its touch. The Q-max measurement using Kawabata thermal tester (Thermo Labo) showed higher Q-max values on both sides of the fabric of Examples <NUM>-<NUM> compared to Examples <NUM>-<NUM>.

Total heat loss was measured using a large sweating guarded hot plate as per ASTM F1868 part C and data is summarized in the table above. This measurement confirmed that intrinsic thermal resistance of PTFE yarn based knits with flat back mesh construction fabric (Ex. <NUM>-<NUM>) is lower compared to all polyester fabrics (Ex. The evaporative resistance of PTFE containing knits (Ex. <NUM>-<NUM>) are lower compared to the all polyester knit (Ex. Lower thermal resistance along with lower evaporative together yielded fabrics with impressive up to <NUM>% improvement in the total heat loss, comparing Ex. <NUM>-<NUM> with Ex.

In conclusion, excellent Q-max, excellent thermal conductivity (lower resistance), lower evaporative resistance, higher heat loss for PTFE based flat back mesh knits (Examples <NUM>-<NUM>). All these properties are important for active cooling application in textile.

Examples <NUM>-<NUM> compared to Example <NUM> explore peel strength adhesion between a knit fabric and pig skin. To test the examples, a <NUM> x <NUM> (<NUM>" x <NUM>") sample of the knit fabric was placed on the dermis/hypodermis of pig skin with bovine serum and then <NUM> layers of gauze were placed on the knit layer. The samples were then dried for <NUM> hours at <NUM>. Peel strength was then measured.

Claim 1:
A sterilized wound dressing (<NUM>) comprising:
(a) a multi-ply knit fabric comprising:
(i) a first knit ply forming the upper surface of the fabric and comprising a plurality of first yarns;
(ii) a second knit ply forming the lower surface of the fabric and comprising a plurality of polytetrafluoroethylene (PTFE) yarns which have
- a density of <NUM>-<NUM>/cm<NUM>,
- a transmission in the IR range of <NUM>-<NUM> of ≥ <NUM>%, and
- a thermal conductivity of ≥ <NUM> W/(m·K);
wherein the first ply and the second ply are integrated through combined portions formed by at least one of
- interlacing first yarns among the PTFE yarns of the second knit ply,
- interlacing PTFE yarns among the first yarns of the first knit ply, and
- interlacing a plurality of third yarns among the first yarns of the first knit ply and the PTFE yarns of the second knit ply; and
(b) a composition comprising at least one silver ion-containing compound on at least the upper surface of the multi-ply knit fabric.