WO2009050627A1

WO2009050627A1 - Delivery device, particularly for wound dressing

Info

Publication number: WO2009050627A1
Application number: PCT/IB2008/054189
Authority: WO
Inventors: Sima Asvadi; Margreet De Kok; Liesbeth Van Pieterson
Original assignee: Koninklijke Philips Electronics N.V.
Priority date: 2007-10-15
Filing date: 2008-10-13
Publication date: 2009-04-23

Abstract

The invention relates to the delivery device for the controlled delivery of a substance, particularly a device in the form of a wound dressing (100) by which a medicine can be applied to a wound. The delivery device (100) comprises a reservoir element (120) with voids that can be filled with the substance to be delivered, and a squeezing system (110) that can controlledly deform the reservoir system such that the volume of the voids decreases. In a particular embodiment, the reservoir element may be realized by a hollow tube (120) attached along a non-straight course to an elastic carrier (110) such that the substance within the tube is squeezed out when the elastic carrier is stretched.

Description

Delivery device, particularly for wound dressing

FIELD OF THE INVENTION

The invention relates to a delivery device for the dosed delivery of a substance, particularly in the form of a wound dressing.

BACKGROUND OF THE INVENTION

The US 2007/0059496 Al discloses a non-woven multilayer fabric comprising two layers that are connected by an intermediate layer of filaments, wherein said intermediate layer comprises voids of for example tubular shape. In a particular application of the fabric as a wound dressing, medicaments are disposed in the voids such that they can be delivered from there by compression of the multilayer fabric.

SUMMARY OF THE INVENTION

Based on this situation it was an object of the present invention to provide means for delivering a substance, particularly as a wound dressing, which allow the dosed delivery of a substance in a controllable way.

This object is achieved by a delivery device according to claim 1. Preferred embodiments are disclosed in the dependent claims.

The delivery device according to the present invention serves for the dosed delivery of a substance, for example a liquid, a gel, a cream, or a powder, that has some desired physical or (bio-)chemical effect. The delivery device can particularly be a wound dressing that is applied to a wound during the healing process; in this case it will have typical additional features known to a person skilled in the art, for example sterility, biocompatibility and the like. The delivery device comprises the following components: a) A flexible "reservoir element" with voids that can be filled with the substance to be delivered. "Flexibility" of the reservoir element means that it can be deformed by moderate forces and energies, particularly forces/energies that can be generated manually. The flexibility may be completely plastic (i.e. the deformations remain after the removal of the forces), completely elastic (i.e. the original shape is reassumed after the removal of the forces), or have a composition of plastic and elastic components. In the extreme case, the reservoir element may substantially consist of an empty cavity with a jacket around it. b) A "squeezing system" that can controllably deform the reservoir element such that the volume of the voids is decreased. If the voids are initially completely filled with the substance to be delivered, this substance will be squeezed out the voids during the deformation of the reservoir element.

The described delivery device has the advantage to allow a well-controlled delivery of a substance by providing a squeezing system that can controllably deform the reservoir element. This is particularly advantageous in case of a wound dressing in which the correct dosage of medicaments is crucial for the healing process.

The substance to be supplied by the delivery device may particularly be a medicament, for example an antibacterial (e.g. a silver based cream or gel) and/or an antibiotic formulation, a pain relief medicine or gel (e.g. for joint and/or muscle pain), an anti-inflammatory medicine, a specific medication for dermatological disorders (e.g. rash, eczema, or acne), a substance applied for cosmetic purposes (e.g. wrinkle reduction, rejuvenation and/or moisturing effects), and/or a deodorant or perfume. A cream can for example contain hydrophilic or hydrophobic particles for moisture regulation of the affected area. Such materials can also be in liquid form and be encapsulated in a shell that can release its content by thermal, electrical or other types of stimulation. The squeezing system can be realized in many different ways. A first realization proposed by the invention comprises a stretchable (tensile), preferably elastic carrier, for example an elastic rubber plate, a woven, knitted, non-woven, or a spacer fabric, or a single elastic filament yarn. This embodiment has the advantage that actuation of the squeezing system simply comprises the application of oppositely directed forces at opposite ends of the elastic carrier; no access to intermediate positions on the carrier is required. In case of a wound dressing, actuation of the squeezing system can therefore be done without touching the sensitive region of the wound. Moreover, stretching of the elastic carrier is a process that can very well be controlled, thus allowing a well-dosed delivery of the substance. In a further development of the aforementioned embodiment, the elastic carrier comprises a surface pattern that indicates the level of stretch of the carrier (which in turn corresponds to the volume of the applied medicine). If the carrier is for example an elastic fabric, (inelastic) yarns may be woven into the visible surface of the fabric along a curved line that progressively straightens as the fabric is stretched. Using a plurality of (e.g. colored) yarns with different curvatures can thus for example allow to clearly and easily distinguish between different degrees of stretching.

The reservoir element may also be realized in many different ways. In one embodiment, the reservoir element may for example be realized by a textile structure that comprises voids between its filaments which can be filled with the substance to be delivered. Stretching the textile structure will then squeeze out the substance. In another embodiment, the reservoir element may comprise a hollow tube that is permeable for the substance to be delivered. Filling the initially cylindrical voids with the substance will then allow to deliver the substance through the permeable mantle of the tube by changing the shape of the tube. The aforementioned reservoir element in the form of a tube may particularly be combined with a stretchable, elastic carrier as a squeezing system. The hollow tube may in this case be attached along a curved (e.g. zigzag, meander, or spiral) course to the elastic carrier. Stretching the carrier will deform the hollow tube, for example straighten out its turns in the direction of the stretch, thus introducing a reduction of its interior volume and a corresponding expulsion of the substance stored in this volume.

In another realization of the squeezing system, two conductive layers are disposed on opposite sides of the reservoir element. Furthermore, a voltage supply is provided that is coupled to the conductive layers. Different electrical potentials can then be applied to the two conductive layers, thus creating an attractive force between these layers that exerts a pressure on the reservoir element between the layers. A substance contained in the voids of the reservoir element can thus be squeezed out in a well-controllable way. It should be noted that the reservoir element may in this embodiment just be the empty space between the conductive layers (filled e.g. with a substance of a stable form); alternatively, the conductive layers (or at least a part thereof) may conceptually be considered as components of the reservoir element in this case.

There is a variety of possibilities to realize the conductive layers in the aforementioned embodiment. One possibility is to realize them by conductive plates, for example from a thin metal sheet, or from a polymer material (e.g. conductive polymers only or a mixture of conductive and nonconductive polymers). Moreover, the conductive layers may be realized by a fabric of conductive yarns, which favorably provide a highly flexible and permeable structure. The yarns may for example comprises usual natural or synthetic yarns (e.g. polyamide or polyester) that contain conductive particles such as silver and/or that have a conductive coating by materials such as silver, copper or stainless steel. In another embodiment of the invention, the squeezing system may comprise shape memory materials that change their three-dimensional form when being heated beyond a characteristic temperature, wherein said change of shape may exert a pressure on the reservoir element that squeezes out the substance to be delivered. In a particular embodiment, the reservoir itself can be made out of a shape memory alloy or polymer. If the memorized shape of the material is straight but it is mechanically deformed to form a curved, zigzag, meander, etc. shape, upon application of heat it will go back to its memorized shape (in this case straight), hence releasing the medicine. Alternatively, the system can contain shape memory filaments, ribbons, plates, etc. that can act as the squeezing element; in this case a shape change of these elements will induce a change in the form of the reservoir (e.g. straightening).

Furthermore, the delivery device may be completed by components like a temperature controller for controlling the temperature within or at the delivery device (e.g. via controlled heating or cooling), a sensor unit for sensing some parameter of interest (e.g. temperature, humidity, color, bacterial growth or other parameters related to the progress of wound healing), and/or a light therapy unit for combining the effect of medicaments with light therapy.

BRIEF DESCRIPTIONOF THE DRAWINGS These and other aspects of the invention will be apparent from and elucidated with reference to the embodiment(s) described hereinafter. These embodiments will be described by way of example with the help of the accompanying drawings in which:

Fig. 1 shows a perspective view of a wound dressing comprising a hollow tube that is attached to an elastic substrate; Fig. 2 shows a section in x-direction through the device of Fig. 1 in (a) a resting state and (b) a stretched state;

Fig. 3 shows a side view of a hollow tube wrapped around an elastic yarn; Fig. 4 shows a side view of a fabric with voids storing a medicament that is attached to a stretchable fabric; Fig. 5 shows a wound dressing with a layer containing a medicament disposed between two conductive layers. DETAILED DESCRIPTION OF THE EMBODIMENT

Like reference numbers or numbers differing by integer multiples of 100 refer in the Figures to identical or similar components.

The invention will in the following be described with respect to medical applications, particularly wound healing, though the disclosed delivery devices are not restricted to this particular purpose.

The healing process of wounds as well as recovery from skin disorder is essentially an internal process (i.e. through mechanisms led by regenerative systems from within the human or animal body). This process can however be accelerated by the application of suitable medicine, light therapy, or a combination of both (photodynamic therapy). The medicine is normally a topical one in cream, lotion or gel form that is applied by the patient or a medical practitioner (in the case of wounds and dermato logical disorder) or that is taken orally (in the case of photodynamic therapy).

Important topical medicine examples are antibacterial and antibiotic formulations. In principle the outermost layer of skin (stratum corneum) forms a barrier between the internal organs and the environment. This is related to existence of lipids and their complex structural arrangements. Several factors control the absorption of chemical compounds through stratum corneum. These factors include molecular weight, hydrophilicity, lipophilicity, and pH of the chemicals as well as parameters such as concentration of the drug plus surface area, frequency and time of exposure.

Optimal dosing and the duration of treatment by a specific medicine (e.g. antibiotic cream) depends on the type of wound or skin disorder and the phase of the healing process. It is therefore important to control the dosing according to the specific requirements of each case. Wounds can be from different categories including the ones resulting from a surgery or accident (cut, burn, etc.) or more chronic wounds such as decubitis or ulcers in diabetes. The treatment and care process for chronic wounds is labor-intensive and prolongs the patient's hospitalization period in most cases. Especially in the case of infection certain (often costly and elaborate) infrastructure is needed and extra care must be taken by the medical staff.

In view of this, it was an object of the present invention to provide means for a better treatment of dermato logical disorders such as eczema and acne or wound healing processes after an accident, surgery or burn, which include protecting the skin by a bandage and upon need a specific dose of topical medicine to ensure hygienic conditions plus preventing and/or treating infection. To this end systems are proposed that incorporate the dosing of medicine in a wound dressing. This can be combined with a light therapy unit dedicated for wound healing or used as such. It can also be combined with sensing units to monitor the progress of wound healing or be used on its own with input from a person. A number of options for dosing systems for controlled transdermal drug delivery of topical creams, gels or lotions in a partially or completely automated manner through flexible means will be described below. These can be executed in a feedback loop or manually controlled by a physician or nurse supervising the wound healing process or the condition of the skin.

Fig. 1 shows a first embodiment of a wound dressing 100 that comprises the following two main components:

A "squeezing system" in the form of a stretchable, elastic (e.g. textile) layer or substrate 110. - A "reservoir element" in the form of a hollow tube 120 filled with medicine that shall be administered to the affected area. The tube 120 can be made out of a porous material or contain holes. One or more of such tubes are placed on the flexible substrate 110, preferably in a zigzag, wave, spiral, meander or other curved shape. The tube(s) can also be straight if their material is elastic and recovers sufficiently enough from tensile deformation. Attachment of the tube(s) to the substrate 110 can for example be done by gluing or embroidery.

Fig. 2 comprises sections through the hollow tube 120 in x-direction of Fig. 1. Fig. 2 a) shows the system in the initial resting state in which no forces and no stress are applied to the elastic substrate 110. The hollow tube 120 takes its resting form with an approximately circular cross section. The internal void 121 of the tube, that is filled with the medicine to be administered, assumes its maximal volume.

Fig. 2 b) shows a state in which forces tearing in opposite x-directions are applied to the axial ends of the elastic substrate 110, resulting in an axial extension Δx of the substrate. As the tube 120 is fixed to the elastic substrate 110, the stretching also deforms the hollow tube 120. This results in compression and hence a reduction of its diameter which in turn causes the medicine to be squeezed out of the drug delivery tube 120. The parameters of the special shape that the tube 120 has taken (such as curvature, pitch etc.) as well as its diameter can serve as dosing system because they uniquely determine the volume reduction in case of stretching. Hence the volume of the medicine applied to a specific area of skin in dependence on the level of the applied stretch Δx can be calculated.

Fig. 3 shows an alternative realization of a wound dressing 200, in which a hollow tube 220 comprising the medicine to be administered is wrapped in a spiral shape around an elastic textile yarn 210. When the textile yarn 210 is stretched in a definite way, this results in deformation of the hollow tube 220 and, consequently, an expulsion of the medicine it comprises.

Fig. 4 shows a further embodiment of a wound dressing 300. This wound dressing comprises an elastic layer 310 to which a reservoir layer 320 with yarns of a certain construction (e.g. twist turns/cm, bulkiness determined by general density and packing) is attached. Thus a multilayer textile structure is woven or knitted for wound dressing purposes. The reservoir layer 320 that will be in contact with the intended area of skin is impregnated in a medicines meant for topical use (i.e. in the form of cream, gel or lotion) in order to treat a wound, scratch or even as pain relief option for cases like arthritis. The cream or lotion is squeezed out of the voids 321 in the reservoir layer 320 when the elastic layer 310 (and thus also the reservoir layer 320) is stretched at the time of application to the affected area. The level of twist and density of the fabric in the reservoir layer 320 determines the dose of the medicine that results from a certain level of tension or stretch Δx in the elastic layer 310. In the described embodiments with an elastic layer that is stretched, the appropriate level of tension, up to which the medicine containing layer should be stretched, can be indicated by woven lines in the (visible) top layer. These lines may for example have a curved course in their resting state and may become increasingly straight with increasing stretch (like the tube 120 in Fig. 1). Moreover, layers can be connected to each other by several methods such as simple stitching, textile adhesives, embroidery or sonic welding. Fig. 5 shows an alternative embodiment of the wound dressing 400 that comprises a squeezing system 410 consisting of two parallel, electrically conductive sheets or layers 410a and 410b that are disposed on opposite sides of an intermediate fabric layer 420 with voids that are filled with a medicine. The two conductive layers 410a, 410b are coupled to a controllable (DC or AC) voltage supply 421. Thus a voltage can be applied to the conductive layers which induces an attraction between them that exerts a pressure on the intermediate fabric 420. The medicine can thus be squeezed out of the fabric 420 in a well- dosed way. In case a medicine with a form that is stable in itself is used, the fabric in the reservoir element 420 may be omitted and the medicine may fill the space between the conductive layers 410a, 410b by its own.

The conductive layers 410a, 410b may be produced out of multifilament synthetic yarns (e.g. polyamide or polyester) that contain conductive particles such as silver. If a multi- layered wound dressing fabric is made out of such yarns and a layer of medicine in the form of a cream or lotion is laid between two such wound dressing conductive fabric layers 410a, 410b (either as a layer by itself or embedded in a separate porous or open material), these layers will try to make contact upon applying a voltage to them and hence squeeze the medicine out. This can perhaps be combined with a light therapy option.

Another option for making conductive layers is to coat polymeric textile yarns both from natural or synthetic yarns with a conductive polymer or other materials such as silver and then construct a wound dressing fabric of the kind described above from those coated yarns. Silver coated fabrics can further be used as antibacterial materials in sheeting and underwear.

In the aforementioned embodiments, one or more of the conductive fabric layers could be replaced by a conductive plate constructed from one or more polymer types (e.g. conductive polymer only or a mixture of conductive and non-conductive polymers) or metal foils or sheets. Moreover, shape memory materials (SMM), e.g. alloys or polymers, can also be used to induce a stretch in a wound dressing fabric, which can in turn result in the application of a medicinal cream or lotion. This option can also be combined with heat therapy if the applied temperature range of the SMM is tuned properly.

According to a further embodiment of the invention, a voltage can be applied to conductive layers (e.g. metal layers or metallic coated yarns) in order to produce heat for a temperature control. If a wound dressing fabric has been impregnated with encapsulated medicine or a layer of such encapsulated medicine has been placed between fabric layers intended for wound dressing, the heat may melt the encapsulation material of the medicine and cause its application to an affected area. The aforementioned option can be linked to a temperature monitoring/measuring wound dressing material. If the temperature of skin rises above a certain value that can indicate the onset of an infection, the medicine is applied. Skin temperature is around 32° C and in the case of infection it rises to 37° C. A feedback from temperature measurement can therefore activate the drug delivery if the temperature rise is above 5-6° C.

Finally it is pointed out that in the present application the term "comprising" does not exclude other elements or steps, that "a" or "an" does not exclude a plurality, and that a single processor or other unit may fulfill the functions of several means. The invention resides in each and every novel characteristic feature and each and every combination of characteristic features. Moreover, reference signs in the claims shall not be construed as limiting their scope.

Claims

CLAIMS:

1. A delivery device (100-400), particularly a wound dressing, for the dosed delivery of a substance, comprising a) a flexible reservoir element (120-420) with voids (212, 321) that can be filled with the substance; b) a squeezing system (110-410) that can controllab Iy deform the reservoir element such that the volume of the voids decreases.

2. The delivery device (100-400) according to claim 1, characterized in that the substance to be delivered comprises a medicament, particularly an antibacterial and/or an antibiotic formulation, a pain relief medicine or gel, an antiinflammatory medicine, a medication for dermatological disorders, a substance applied for cosmetic purposes, and/or a deodorant or perfume.

3. The delivery device (100-300) according to claim 1, characterized in that the squeezing system comprises a stretchable, preferably elastic carrier (110-310).

4. The delivery device (100-300) according to claim 3, characterized in that the elastic carrier (110-310) comprises a surface pattern indicating the level of stretch.

5. The delivery device (100-300) according to claim 1, characterized in that the reservoir element comprises a textile structure (320) and/or a hollow, permeable tube (120, 220).

6. The delivery device (100-200) according to claims 3 and 5, characterized in that the hollow tube (120, 220) is attached along a non-straight course to the elastic carrier (110, 210).

7. The delivery device (400) according to claim 1, characterized in that the squeezing system (410) comprises two conductive layers (410a, 410b) disposed on opposite sides of the reservoir element (420), and a voltage supply (421) that is coupled to these conductive layers.

8. The delivery device (400) according to claim 7, characterized in that the conductive layers comprise a conductive plate, particularly from a polymer material, and/or a fabric (410a, 410b) of conductive yarns, particularly yarns comprising conductive particles and/or yarns with a conductive coating.

9. The delivery device (100-400) according to claim 1, characterized in that the squeezing system comprises a shape memory material.

10. The delivery device (100-400) according to claim 1, characterized in that it further comprises a temperature controller, a light therapy unit and/or a sensor unit.