Medical dressing comprising a carrier and a composite material

Abstract

Disclosed is a medical dressing having a carrier material and a composite material. The composite material includes oil droplets dispersed in a matrix. The matrix includes one or more cellulose derivatives and nanocellulose.

Claims

1. A medical dressing having a first side adapted to face a wound or tissue site when in use and a second side, opposite to said first side, said medical dressing comprises a carrier material and a composite material, wherein said composite material comprises oil droplets dispersed in a matrix, said matrix comprises one or more cellulose derivative(s) and nanocellulose.

2. The medical dressing according to claim 1, wherein said carrier material comprises a net, a foam, a fibrous structure, a film, a gel, a silicone based adhesive or an acrylic adhesive, or any combinations thereof.

3. The medical dressing according to claim 1, wherein said composite material is incorporated into said carrier material and said carrier material is provided on said first side of said medical dressing thus forming a wound or tissue contacting layer.

4. The medical dressing according to claim 3, wherein said carrier material has a first side, adapted to face a wound or tissue site when in use and a second side, opposite to said first side, and wherein said composite material is provided in a higher amount, based on weight, proximate to said first side of said carrier material than proximate to said second side of said carrier material.

5. The medical dressing according to claim 3, wherein said medical dressing further comprises a support layer and wherein said wound or tissue contacting layer has a no load thickness of from 0.1 mm to 10 mm.

6. The medical dressing according to claim 5, wherein said carrier material is silicone based adhesive.

7. The medical dressing according to claim 1, wherein said composite material forms a, continuous or discontinuous, layer on said carrier material and wherein said composite material is provided on said first side of said medical dressing thus forming a wound or tissue contacting layer.

8. The medical dressing according to claim 1, wherein said medical dressing comprises a cover layer, provided at a second side of said medical dressing.

9. The medical dressing according to claim 1, wherein said medical dressing comprises said composite material in an amount ranging from 0.01 to 600 g/m.sup.2 of said carrier material.

10. The medical dressing according to claim 1, wherein said nanocellulose is nanocrystalline cellulose.

11. The medical dressing according to claim 1, wherein said one or more cellulose derivative(s) is/are cellulose ether derivative(s).

12. A medical dressing having a first side, adapted to face a wound or tissue site during use, and a second side, opposite to said first side, said medical dressing comprises a carrier material in the form of a gel, said gel comprises an oil-in-water emulsion comprising oil droplets dispersed in an aqueous phase comprising a matrix, said matrix comprises one or more cellulose derivatives and nanocellulose.

13. The medical dressing according to claim 12, wherein said carrier material has a first side, adapted to face a wound or tissue site when in use and a second side, opposite to said first side, and wherein said oil-in-water emulsion is provided in a higher concentration, based on weight, proximate to said first side than proximate to said second side of said carrier material.

14. A method of producing a combined carrier material and composite material for use as a component in the medical dressing according to claim 1, comprising the steps of; a) providing an oil-in water emulsion comprising or consisting of oil droplets dispersed in an aqueous phase comprising one or more cellulose derivatives and nanocellulose; b) contacting a carrier material with said oil-in-water emulsion; and c) drying said oil-in-water emulsion until 50-100% by weight of the water comprised in said oil-in-water emulsion has evaporated, before or after step b).

15. The method of producing a combined carrier material composite material according to claim 14, wherein said carrier material comprises a net, a foam, a fibrous structure, a film, a gel, a silicone based adhesive or an acrylic adhesive, or any combinations thereof.

16. A method of producing a medical dressing comprising the steps of: a) producing a combined carrier material and composite material according to claim 14; and b) incorporating said combined carrier material and composite material into a medical dressing.

17. A method of producing a carrier material in the form of a gel comprising an oil-in-water emulsion for use as component in the medical dressing according to claim 12, comprising the steps of; a) providing an oil-in water emulsion comprising or consisting of oil droplets dispersed in an aqueous phase comprising one or more cellulose derivatives and nanocellulose; and b) contacting a gel with said oil-in-water emulsion.

18. A method of producing a medical dressing comprising the steps of: a) producing a gel comprising an oil-in water emulsion according to claim 17; and b) incorporating said gel comprising said oil-in-water emulsion into a medical dressing.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1a illustrates a schematic perspective view a medical dressing according the the present disclosure;

(2) FIG. 1b illustrates an enlarged view of the composite material as disclosed herein, taken from FIG. 1a;

(3) FIG. 2 illustrates the rate of solvent casting from emulsions made with three different cellulose derivatives;

(4) FIG. 3 illustrates the redispersion of the composite material;

(5) FIG. 4 illustrates mass loss due to oil leakage upon compression of the composite material;

(6) FIG. 5 illustrates a graph of the compressive stress vs strain relation of composite materials;

(7) FIG. 6 illustrates a silicone based adhesive coated with the composite material;

(8) FIG. 7 illustrates a micrograph of a polyurethane foam coated with the composite material;

(9) FIG. 8 illustrates the magnitude of the initial backscattered light of given emulsions;

(10) FIG. 9 illustrates a micrograph of a stable Pickering emulsion prior to drying;

DETAILED DESCRIPTION

(11) The present disclosure thus relates to a medical dressing comprising a carrier material and a composite material. The composite material comprises oil droplets dispersed in a matrix. The matrix comprises one or more cellulose derivatives and nanocellulose.

(12) The carrier material according to the present invention may be a foam structure, such as for example, an open-cell foam or a closed-cell foam that comprises through-holes. Non-limiting examples of suitable polymer foams include polyurethane foams, polyvinyl alcohol foams, silicone foams, polyolefin foams, alginate foams, and combinations thereof. In some embodiments, the polymer foam comprises a polyurethane foam. Non-limiting examples of suitable polyurethane foams include polyester-based and polyether-based foams. As a non-limiting example, AVANCE™ Foam sold by MöInlycke Health Care is made of a hydrophobic reticulated polyurethane foam with a large open cell structure.

(13) The carrier material may also be a net structure, such as a low-adhering net made by e.g. a woven or a knitted fabric comprising for example polyamides, polyesters, polyolefins, cellulose-based polymers and polyurethans. Also a fibrous structure such as a nonwoven material, e.g. spunbond, meltblown, carded, hydroentangled, wetlaid nonwovens etc. may be used. Suitable nonwoven materials can be composed of natural fibres, such as wood pulp or cotton fibres, manmade fibres, such as polyester, polyethylene, polypropylene, viscose etc., or from a mixture of natural and syntethic fibres. A film such as a polymeric film, e.g. a polyurethane, polyolefin, polyester or polyamide film may also act as a carrier material according to the present disclosure.

(14) FIG. 1a illustrates an embodiment of a medical dressing 4 as disclosed herein, wherein the carrier is a vapour permeable film carrier 1 coated with a continuous layer of the composite material 2. In FIG. 1b, which is an enlarged view of the composite material 2 taken from FIG. 1a, the composite material 2 comprises oil droplets 5 dispersed in a matrix 3 thereby forming an interface 6 between each of the oil droplets 5 and the matrix 3. The matrix 3 comprises one or more cellulose derivative(s) and nanocellulose. In the embodiment as disclosed in FIG. 1b, the matrix 3 is enriched by nanocellulose at the interface 6 (i.e. at the surface of the oil droplets). The medical dressing 4 disclosed herein further comprises an adhesive border 7 to adhere the medical dressing 4 to a dermal surface.

(15) The composite material or o/w emulsion may also be included in a gel, such as a hydrogel or a hydrofiber, acting as a carrier material, or other substantially dilute systems, and be used as a medical dressing. Suitable polymers which may form hydrogels are alginates, polyacrylic acid (PAA), poly(N-isopropyl acrylamide), chitosan, hyaluronic acid, polyvinyl alcohol (PVA), or proteins, such as collagen. The o/w emulsion may be added pre or post crosslinking of the hydrogel. The crosslinking of the hydrogel is either performed by adding a crosslinker for chemical crosslinking or for the creation of junction zones.

(16) If the emulsion is added pre crosslinking of the hydrogel, 0.1-30 wt. % emulsion (wet) may be added to the solution. In the case of alginates, the divalent calcium ion in CaCl.sub.2 will contribute to the creation of junction zones and create calcium alginate gels with droplets of emulsion between these junctions.

(17) When adding the emulsion post crosslinking of the hydrogel, the hydrogel will absorb the emulsion. This procedure is comparable to impregnating the material, where the droplets of emulsion are distributed homogenously in the hydrogel. The amount of added emulsion may thus be 0.1-10 wt. % of the hydrogel. However, if a more rigid hydrogel, i.e. with a higher degree of cross-linking is needed, the emulsion may be used a softener and be added in amounts of from about 10-30 wt. % of the hydrogel.

(18) The composite material may also be included in, such as dispersed in or coated on to, a silicone based or acrylic adhesive acting as the carrier and suitable for use in medical dressings, non-limiting examples on suitable adhesives are two-component RTV systems such as Q72218 (Dow Corning) and SilGel 612 (Wacker Chemie AG). The composite material may for example be added in powdered form on the silicone based or acrylic adhesive and/or dispersed within the silicone based or acrylic adhesive or may also be mixed with the adhesive as an emulsion. The emulsion may for example be added either to component A or B in the two-component adhesive before curing. The suitable amount of composite material in such a silicone based or acrylic adhesive is from 5-30 wt %.

(19) Many known wound dressings include a self-adhering adhesive, also known as pressure-sensitive adhesive (PSA), which purpose is to adhere to the wound and/or to the skin surrounding the wound and thus to fixate the dressing in a desirable position. Various adhesives are being used for affixing medical products on the skin, some of the most common being encompassed by the terms acrylic adhesives and silicone based adhesives, among others. Such adhesives may also be suitable to use in or on a carrier as disclosed herein.

(20) The composite material may be coated or deposited onto an acrylic or silicone based adhesive. A coating of the composite material, for example in powder form, on an adhesive material as disclosed herein needs to be high enough in concentration to give effect (on skin, wound or infection) but low enough to still retain the adhesive properties, if such is desired. Hence, a suitable thickness of the layer provided by coating/deposition may be within the range from 1 to 500 μm, optionally from 10 to 100 μm. The concentration of composite material per area of carrier material may be within the range from 0.05 to 3 g/m.sup.2, optionally within the range from 0.15 to 0.80 g/m.sup.2. The adhesive is in contact with the skin or the wound and should therefore be a silicone based or acrylic adhesive suitable for application in a medical dressing. Such adhesives forms often part of secondary carrier materials in medical dressings, such as a foam carrier, nonwoven carrier, a net carrier, superabsorbents, hydrogel, a film carrier, a wound dressing or prevention dressing, such as the dressings sold under the trademarks Mepilex® Border, Mepilex® Border Ag, Mepilex®, Mepilex® Ag, Mepitel®, Mepore® by MöInlycke Healthcare AB.

(21) When the carrier material for the composite material is a gel, such as a hydrogel or a hydrofiber, an organogel or a silicone gel, the gel may be further applied to an additional carrier material structure such as foam, net, nonwoven material or film to provide a medical dressing. The gel may be applied as a layer, such as by coating, on the foam, net, nonwoven material or film to provide for a medical dressing.

(22) The medical dressing as disclosed herein may be prepared by incorporating the composite material into the carrier material or applied to a surface thereof. The carrier material may be coated either by redissolving the composite material, such as by adding water, or prior to drying the o/w emulsion. The o/w emulsion may for example be coated onto a carrier material by means of spray coating, extrusion, dipping, impregnation and/or spreading. The composite material may also be incorporated into the carrier material, such as for example when the carrier material is an adhesive, a gel, such as a hydrogel, a hydrofiber, or during preparation of the foam or such as during extrusion of a film, fibers or net.

(23) The carrier material coated/treated with the o/w emulsion is subsequently dried, such as by means of heating. In a production line the carrier material may be carried by means of a conveyer belt in a manufacturing process, and heat may be applied to the conveyer belt. The coated carrier material may also be dried in a separate drying step post-coating, such as in an oven.

(24) The oil-in-water emulsion may also be spray dried to provide a dry composite material powder, which may be powder coated onto the carrier material.

(25) Preparation of the Composite Material

(26) Materials Used in the Preparations of the Composite Material

(27) Materials used were; Microcrystalline cellulose (MCC), Avicel PH101. Carboxymethyl cellulose sodium salt (Sigma Aldrich) Mw=90000; d=1.59. HPMC 60SH-50 50cP type 2910 (Shiu ETSU Chemical). HPMC 90SH-100 100cP type 2208 (Shiu ETSU Chemical). HPC-SSL Mw=40000 (Nisso Chemical) HEC 250 G PHARM Natrosol sample. HEC 250 HHX PHARM Natrosol. EHEC Bermocoll E230 FQ (Akzo Nobel). MC Methocel A4M Premium (Dow Chemicals). Dodecane Reagentplus >99% (Sigma Aldrich). Hexadecane Reagentplus >99% (Sigma Aldrich). Ion exchange resin, Dowex Marathon C-Hydrogen (Sigma Aldrich). Fluorescein isothiocyanate isomer I (Sigma Aldrich).

(28) Isolation of Crystalline Nanocellulose

(29) The CNCs used were isolated from microcrystalline cellulose by first adding 40 g of MCC to a 2 liter Erlenmeyer flask containing 400 ml milli-Q water (resistivity 18.2 MΩ) under constant stirring. 389 ml of sulphuric acid (95-97%) was then added drop wise to the flask over a period of 30 minutes whilst the flask simultaneously was being surrounded by an ice slurry to ensure that hydrolysis did not occur until all the acid has been added. The flask containing the acid and the MCC-suspension was then heated to 45° C. The reaction was continued at 45° C. for two hours after which the slurry was poured into a 5 liter Erlenmeyer flask containing 4 liters of deionized water upon which the reaction was quenched.

(30) The slurry containing CNCs, amorphous remnants from the MCC and sulphuric acid was portionally centrifuged (Heraens Megaforce 40, Thermo scientific) at 3900 rpm for 15 minutes upon which the supernatant was discarded and replaced with additional slurry whilst shaking vigorously to disperse solid content at the bottom of the vessel. This process was later repeated twice by replacing supernatant with deionized water to ensure that amorphous, water-soluble by-products had been separated from the CNCs. The centrifuged CNCs were transferred into a dialysis membrane (Spectrapor Dialysis membrane tubing, MWCO: 12:14.000) and placed in a tank containing deionized water where it was left for approximately two weeks. The water in the tank was changed twice a day to ensure elimination of as many free ions as possible.

(31) The CNCs were after dialysis dispersed in deionized water and sonicated (Ultrasonic Processor model VC505, Sonics Vibra-cell) for 14 minutes at an amplitude of 4% to ensure that the individual nanocrystals were separated from a potential aggregated state. The vessels containing the suspension during sonication were furthermore surrounded by ice to prevent overheating from the excess input of energy. 10-15 lab spoons of ethanol cleaned ion exchange beads (Dowex Marathon C-hydrogen) were added to the newly sonicated suspension of CNC to eliminate the remaining free ions. The suspension was left for two days under stirring after which the suspension was titrated with 0.1M sodium hydroxide to minimize the conductivity. The dilute suspension of CNCs was rotary evaporated (Büch rotavapor R-200) to a final concentration of no more than 4% to ensure colloidal stability and manageable viscosity of the CNC-suspension.

(32) CNCs with a length and width of at least 234±66 nm and 30±7 nm respectively were isolated from MCC. The dimensions are dependent on the degree of hydrolysis reached during isolation which can be varied by choice of acid, concentration of acid and stirring mechanism during hydrolysis. The dimensions are furthermore not only differing from batch to batch, various degrees of polydispersity as a result of inhomogeneous distribution of acid throughout the bulk of the microfibrils can also be identified.

(33) As understood by the skilled person in the art, the crystalline nanocellulose may of course be isolated according to other known methods.

(34) Cellulose Derivatives

(35) Cellulose derivatives were chosen based on their performances as additives in emulsion formulations with CNCs. A summary of studied CDs can be seen in table 1 below. Performances were based on visual observation where an unstable or unsuitable emulsion simply was referred to as “−”. Some emulsions were seemingly stable in the wet state but not during drying and was therefore also referred to as “−” or “+” in the dry emulsion column. A stable o/w emulsion is an emulsion which may hold the oil dispersed. If the emulsion is unstable, an oil layer will accumulate on the surface which will be seen visually. If the oil droplets ends up very large, such as for example 500 μm, if the droplets coalescence or if the oil-in-water emulsion does not dry to a composite material these are also signs of unstable and unsuitable emulsions.

(36) TABLE-US-00001 TABLE 1 Available CDs which were tested as components in emulsions and solid emulsions. Dry emulsion/ Viscosity composite CD (mPas (2%)) Emulsion material Methyl Cellulose 4000 [30]  + − Hydroxypropyl  50 [33] + + Methyl Cellulose Hydroxypropyl 100 [33] + + Methyl Cellulose Hydroxyethyl 4500* [31]  − − Cellulose HHX Hydroxyethyl 250-400 [31]   + + Cellulose G Carboxymethyl 50-200** [32]    + + Cellulose Ethyl Hydroxyethyl >400 + + Cellulose Hydroxypropyl <50 [34] + − Cellulose Grade SSL “+” indicates success and “−” indicates failure. Viscosity of CDs also apparent. *viscosity measured for a 1% solution. **viscosity measured for a 4% solution.

(37) Preparation of the Oil-In-Water Emulsion

(38) The cellulose derivative(s) as disclosed herein and above were diluted in Milli-Q (18.2 MΩ) to manageable viscosities that wouldn't hinder emulsification, usually corresponding to a solution of 4-7 wt. %, depending on the type of CD chosen. The actual concentration of the CDs was measured gravimetrically.

(39) Emulsions were prepared by adding CD solution to a plastic vial (50 ml) containing the CNC-suspension. Calcium chloride 0.1M solution was then added together with additional Milli-Q to meet the requirements on the appropriate oil/water ratio.

(40) The oil phase was added on top of the water phase, after which emulsification and homogenization was performed using diax 900 homogenizer (Heidolph Instruments) at a speed of 22000-23000 rpm. The mixture of oil and water phase was homogenized for 5 minutes.

(41) Composite Material/Dry Emulsion Preparation

(42) Composite material according to the present disclosure were derived from polymer pickering emulsions prepared according to the above under “Preparation of the o/w emulsion”, by pouring the emulsions into petri dishes and allowing them to dry. The amount of time required for an emulsion to dry was tracked gravimetrically where a steady state occurred, according to FIG. 2, when all of the water had been assumed to have left the emulsion since the mass ratio did not change as a function of time.

(43) The rate of solvent casting from emulsions made with three different cellulose derivatives in petri dishes is shown in FIG. 2. Dry emulsions assumed to be ready for characterization when the mass ratio in the petri dish did not change as a function of time. The mass of the individual emulsions were between 20 and 23 grams.

(44) Redispersion of the Composite Material

(45) The amount of water evaporated from emulsions during transformation to solid emulsions may be tracked gravimetrically if redispersion is to be done. Redispersion of a stable composite material may be done by adding the same amount of water that have evaporated to a plastic vial containing the composite (broken up in pieces). The vial may be left for a day to make sure redispersion of the solid emulsion to an emulsion is fully complete and not influenced by energy input which would create new interfaces rather than maintaining the original ones. The emulsion was after complete redispersion (determined visually) poured into a petri dish and left to dry. See FIG. 3, wherein the first step, the water evaporates, in a second step water is added and the composite material is redispersed and in a final and third step it may be seen that by evaporating the water the composite material may again be produced.

(46) As may be seen, the composite material as disclosed herein is a highly flexible composite material which may be produced and dried and in a later and separate step, be applied to a carrier material to produce a medical dressing as disclosed herein.

(47) Characterization of the Materials

(48) Atomic Force Microscope (AFM)—Characterization of CNC

(49) Pieces of mica were cut and freshly cleaved using double-sided tape. A few drops of 0.1 wt. % cationic polyethylenimine (PEI, Mw=40000 g/mole) were added to the mica plate prior to the addition of CNC to ensure adhesion of the negatively charged specimens to the plate. The mica plate containing PEI was dried with nitrogen after which a few drops of a 0.05 wt. % CNC-suspension was added and dried with nitrogen in a similar manner. The PEI and CNC-suspension were let to rest only one minute before drying with nitrogen to ensure no aggregation would occur, that if present would make sizing difficult. AFM was performed (NT-MDT Atomic Force Microscope) using silicone cantilevers with a golden reflective side and a force constant of 1.45-15.1 N/m in a semi-contact mode. Micrographs were analyzed to determine the dimensions of the isolated nanocrystals.

(50) Light Microscopy—Characterization of Emulsions

(51) Light microscopy was performed by adding a few drops of fresh emulsion into a plastic vial, after which the emulsion was diluted with appropriate amount of distilled water. The amount of water used was determined visually based on the turbidity so that the emulsion droplets would be distinguishable whilst still showing a statistically relevant amount of droplets.

(52) The size of the emulsion droplets was determined by optical microscopy.

(53) Multiple Light Scattering (MLS)

(54) Emulsions were analyzed within 10 minutes of production by pouring fresh polymer pickering emulsions in customized tubes that were then inserted in a Turbiscan MA2000. The magnitude of backscattered light, both initial and time dependant, was collected over a specific length interval in the tube. The length interval was chosen to make sure variations in light intensity were meaned over a suitable set of data points. Initial magnitude of backscattered light was collected to get information regarding the average relative droplet size in the emulsions, whereas time dependent (over 24 hours) were means to assess the relative stability of the emulsions.

(55) Composite Material/Dry Emulsion Compression Tests

(56) Initial experiments were made and suggest that the following examples would be suitable for application in a medical dressing as disclosed herein.

(57) Composite material Ex.1: 2% CMC 0.5% CNC 20% Paraffin oil

(58) Composite material Ex.2: 2% HPMC 0.5% CNC 20% Paraffin oil

(59) Composite material Ex.3: 2% HPMC 0.5% CNC 20% Silicone oil

(60) Composite material Ex.4: 1.52% HEC 0.48% HPMC 0.5% CNC 20% Silicone oil

(61) These four emulsions were dried to composite materials and punched into 15 mm diameter discs, with a thickness ranging between 0.7-1.5 mm, and compressed at a rate of 0.5%/s to various strains between 20-99%. Results that were obtained from the testing was i) Stress-strain relationship for the four solid emulsions and ii) mass loss (i.e. oil release) as a function of strain rate. The results are described in respective figure below.

(62) FIG. 4 is an illustration of mass loss due to oil leakage upon compression of the composite materials. The oil release was rather linear after 20% strain as shown by R.sup.2-values. The relatively low amount of oil release at, and prior to 20% strain can be explained by the stiffness of the material, which still is prominent at low strain percentages for each of the composite materials. There is a shift in stress-strain behavior around 20% strain for each sample, which corresponds to when a linear oil release behavior starts to become apparent. The discs lost around 70% mass when compressed fully, which indicates very good encapsulation of the oil, considering some oil was lost on the surface of the samples and during sample preparation (punching of the discs).

(63) FIG. 5 illustrates a stress vs strain curve for the composite materials Ex. 1-4. It is noted that the HPMC-HEC-CNC emulsion is significantly softer than the rest, even despite containing equal amounts of oil with similar release trend. The curves were obtained from a mean value of eight different compression tests for each specimen.

(64) For venous leg ulcers and other chronic wounds it is conventional to apply rather low pressures, such as around 40 mm Hg on the medical dressing, which is less than 0.01 MPa. For patients with a risk of pressure ulcers, the force may be somewhat higher than 0.01 MPa. This means that the pressure exerted to the composite material in the medical dressin is relatively low. However, the strain at low level still induces a release of oil of approximately 5-10 wt % as a burst release.

(65) This mechanism is of importance for regulation of the controlled and sustained release for both wound and tissue (such as antimicrobial substances/oils for wounds or nurturing oils/vitamins for pressure ulcer prevention). Sustained release is necessary for the tissue site not to contain an exaggerated amount of oil, since this may affect the adhesion of the adhesive for maintaining the medical dressing correctly positioned.

(66) Additionally, the release of substances, such as antimicrobial substances or antimicrobial oils needs to be controlled after the initial burst release of actives, in order to maintain a low toxicity for mammalian cells. Consequently, the dressing material will, after a pressure has been applied, act as a reservoir, which either will dissolve in a sustained manner when in contact with sweat (slowly) and/or wound exudate (faster).

(67) As the patient moves the pressure will change over the dressing material, allowing for release in a new area of the dressing and a continuous release of active substance(s) for as long as it is needed.

EXAMPLES

(68) The following examples illustrate medical dressing prepared according to the present disclosure without limiting the same.

Example 1

(69) Oil-in-water emulsions were prepared in accordance with the method described above, i.e. cellulose derivative(s) (CD) was dissolved in a 0.1 M CaCl.sub.2 aqueous solution in an amount providing a concentration within the range of from 1 to 3 wt. % of the resulting emulsion. Nanocrystalline cellulose (CNC) was dissolved in the same solution in an amount providing a concentration within the range of from 0.3 to 1.0 wt. %, based on the total weight of the o/w emulsion. Alternatively, the CNC may be dissolved in 0.1 M CaCl.sub.2 solution before mixing the CNC solution with the solution comprising the CD solution. An oil phase was then provided by adding the oil to the aqueous solution, all oil at once or to pipette the oil into the solution while the homogenizer is on and stirring of the solution in the homogenizer to create the emulsion, 22 000-24 000 rpm for 5 minutes with an ULTRA-TURRAX® T25.

(70) In these examples the cellulose derivative used was HPMC, Metolose from Shiu Etsu, 50 cps, and CNC, produced according to the method above, was used to provide the encapsulation of the oil droplets.

(71) Four different oils were used in the examples;

(72) Oil 1: Ondina oil (paraffin oil), Ondina X430 from Shell

(73) Oil 2: Corn oil, Sigma Aldrish

(74) Oil 3: Canola oil, Sigma Aldrish

(75) Oil 4: Silicone oil, Belsil DM350 deom Wacker Chemie

(76) TABLE-US-00002 TABLE 5 Weight % Weight % Weight % Weight % water (before Ex. Oil HPMC CNC oil drying) 1 Oil 1 2.00% 1.00% 20.00% 77.00% 2 Oil 1 2.06% 0.34% 20.60% 77.00% 3 Oil 1 1.07% 0.53% 21.40% 77.00% 4 Oil 1 1.09% 0.18% 21.73% 77.00% 5 Oil 2 2.00% 1.00% 20.00% 77.00% 6 Oil 2 2.06% 0.34% 20.60% 77.00% 7 Oil 2 1.07% 0.53% 21.40% 77.00% 8 Oil 2 1.09% 0.18% 21.73% 77.00% 9 Oil 3 2.00% 1.00% 20.00% 77.00% 10 Oil 3 2.06% 0.34% 20.60% 77.00% 11 Oil 3 1.07% 0.53% 21.40% 77.00% 12 Oil 3 1.09% 0.18% 21.73% 77.00% 13 Oil 4 2.00% 1.00% 20.00% 77.00% 14 Oil 4 2.06% 0.34% 20.60% 77.00% 15 Oil 4 1.07% 0.53% 21.40% 77.00% 16 Oil 4 1.09% 0.18% 21.73% 77.00% 17 Oil 1 1.42% 0.35% 21.23% 77.00% 18 Oil 1 1.42% 0.35% 21.23% 77.00% 19 Oil 1 1.42% 0.35% 21.23% 77.00%

(77) The examples 1-6, 9-10, 13-14 and 17-19 were successfully provided as composite materials with desired mechanical properties, such as a relatively high to high mechanical strength and resistance to mechanical deformation.

(78) Silicone Based Adhesive Coated Onto a Polyurethane Film

(79) In this example a polyurethane film was coated with a silicone based adhesive comprising 5 wt. % composite material. The silicone based adhesive was a typical two-component silicone addition-curing polysiloxane system, comprising vinyl-functional polysiloxanes in both components (A and B), a platinum catalyst in one of the components (A) and hydride-containing polysiloxanes in the other component (B).

(80) 18 g of component (A) of the polysiloxane system described above was mixed with 2 g of composite material, Ondina Oil, 0.5 wt % CNC and 2 wt % HPMC, and the mixture was homogenized for 30 s at 13 500 rpm using an Ultra-Turrax T25. 10 g of the resulting mixture was mixed with 9 g of component (B) using a speedmixer for 2 min at 2 000 rpm. The final mixture was coated onto a 20 μm polyurethane film and cured on a hot plate at 120° C. for 2 min. The result is illustrated in FIG. 6.

(81) Polyurethane Foam Coated with Composite Material

(82) A 5 mm thick polyurethane foam provided on a conveyor belt was spray coated with an emulsion according to example 1 and 9 in an in-line process using an ultrasonic nozzle, while heating the conveyor belt to enable drying of the foam structure. The resulting coated polyurethane foam is illustrated in FIG. 7.

(83) The water in the emulsion may also be evaporated until it is a thicker slurry, before spray coating it on the polyurethane foam. The emulsion may additionally be added to the polyurethane foam by means of a roll-to-roll process, immersion/dipping, or slot dye process, a further option is to spraydry the material, hence creating a dry powder of the emulsion, which can be powder coated onto the polyurethane foam.

(84) Nonwoven Material Coated with Composite Material

(85) A spunlace nonwoven material (30% viscose and 70% polyester) provided on a conveyor belt was spray coated with an emulsion according to example 1 and 9 in an in-line process using an ultrasonic nozzle, while heating the conveyor belt to enable drying of the nonwoven material.

(86) The water in the emulsion may also be evaporated until it is a thicker slurry before spray coating it on the nonwoven material. The emulsion may additionally be added to the nonwoven material by means of a roll-to-roll process, immersion/dipping, or a slot dye process. A further option is to spraydry the material, hence creating a dry powder of the emulsion, which can be powder coated onto the nonwoven material.

(87) A coating on a non-adhesive material, such as a polyurethane foam, nonwoven, hydrofibre, etc., can be thicker than on an adhesive. This type of coating will be more similar to an impregnation of the material. The limiting factor is the conformability of the material after the impregnation, since medical dressings need to be soft against the skin. If the material stiffens, it needs to be softened in the post process impregnation, or include a softening agent during impregnation. Impregnation may be performed on the side of the material closest to the tissue or wound, or on both sides. The concentration of the composite material may be between from 0.1 to 50 grams/m.sup.2 on one side, or from 0.1 to 100 grams/m.sup.2 if both sides are impregnated. The material may also be entirely soaked in the emulsion, with a concentration between 1-250 grams/m.sup.2.

(88) Hydrogel or High Water Content Material

(89) The hydrogel was prepared by dissolving 3% alginate (Sigma Aldrich) in MilliQ water in a beaker while stirring at 90° C., the alginate being of medium chain length. The solution was cooled down before adding equal amounts of the pickering oil-in-water emulsion in a 0.1M CaCl.sub.2/CaCO.sub.3 buffer (ratio 1:1) using a blender or homogenizer followed by a short sonication. GDL (glucono-delta-lactone) was added using a blender for release of calcium ions from CaO.sub.3 to promote crosslinking. The resulting hydrogel is an alginate hydrogel comprising 1.5% alginate.

(90) According to this example, the oil-in-water emulsion is soaked or mixed into the hydrogel. However, the emulsion may also be applied by dipping or with an in-line spreading/smearing of the emulsion onto the hydrogel. The material may withstand a small increase in temperature for water removal, if needed.

(91) The composite material may also be added as a dry powder and coated on top of the hydrogel.

Example 2

(92) An assessment of the emulsion stability and mechanical testing of the composite material as disclosed herein was also made to confirm the emulsion stability and to verify that desired mechanical properties, such as a relatively high to high mechanical strength and resistance to mechanical deformation, were obtained for the composite materials.

(93) All emulsions presented in this section contains 2.5% solid content, either 2.0% CDs+0.5% CNCs or 2.5% CDs. This specific concentration was based on the choice of CDs where it was found that appropriate CDs were not too viscous during emulsification whilst still estimated to be able to provide the composite material with sufficient amount of solid content.

(94) Assessment of Emulsion Stability Using MLS

(95) FIG. 8 shows the magnitude of the initial backscattered light of emulsions with given composition of CDs and CNCs with a dodecane content of 25% wt. Also shown is the backscattered light of a redispersed CMC/CNC emulsion. Data was collected less than 10 minutes after emulsification.

(96) The results from MLS in FIG. 8 reveal significant differences in initial oil droplet size amongst the emulsions with varying type of CDs. Emulsions produced with EHEC and HPMC exhibited smaller droplet sizes compared to those with HEC and CMC whereas EHEC and HPMC relative to each other were quite similar (68-70% BS). These emulsions only showed minor oil droplet size change (decline) with the addition of CNCs; indicating that the polymers played a major role in characteristic oil droplet size. For emulsions with HEC and CMC the trend was the opposite, though minor in the case of CMC; indicating that the CNCs were to a greater extent involved in the oil droplet character.

(97) In order to characterize the relative stability of emulsions with varying CDs with and without CNCs, MLS was performed over 24 hours. Stability in this section refers to small amount of coalescence as indicated by small decrease in intensity of backscattered light over time. The relative stability of emulsions solely made with CDs ranked in the following order, as may be seen in see table 2 below, from the most stable to the least; CMC(1.1%)>EHEC(2.8%)>HPMC(4.1%)>HEC(46.3%). Emulsions with HEC showed phase separation after 24 hours; an observation which was not found in any of the other emulsions. The phase separation of emulsions solely stabilized with HEC in relation to the stability of the ones with HEC+CNCs shows interesting contrasts, which points on the role of the CNCs; to be active at the oil/water interface.

(98) With the addition of CNCs (keeping the solid content constant) the stability ranking changed to CMC(0.6%)>HEC(1.9%)>EHEC(2.9%)>HPMC(5.6%). The stability of CMC and HEC emulsions were found to be enhanced by the addition of CNCs, though the relative enhancement of CMC emulsions was insignificant in comparison to HEC emulsions. HEC went from being completely unstable (46% decrease in BS) to one of the most stable (2% decrease in BS) with the addition of CNCs. The stability of EHEC was unaffected by the addition of CNCs with its minor change of 0.1% BS, whereas the one with HPMC decreased as indicated by the increase in difference from 4.1% to 5.6%.

(99) The most stable emulsions were produced with CMC, and although CMC on its own produced extremely stable emulsions (2nd in stability rankings) it was shown that CNCs could enhance the stability even further (from 1.1% BS to 0.6% BS). FIG. 9 is a micrograph of a stable emulsion according to the present disclosure comprising Ondina oil, CMC and CNC.

(100) TABLE-US-00003 TABLE 2 Difference in BS light over a time period of 24 hours for emulsions with given composition of CDs and CNCs. All emulsions were made with 25% dodecane. A large value in difference in BS over measured time period corresponds to a relatively unstable emulsion. Emulsion Composition ΔBS 2.5% CMC 1.07 ± 0.25 2% CMC 0.5% CNC 2.82 ± 0.23 2.5% EHEC 0.57 ± 0.14 2% EHEC 0.5% CNC 2.92 ± 0.46 2.5% HEC 46.3 ± 0.25 2% HEC 0.5% CNC 1.87 ± 0.74 2.5% HPMC 4.08 ± 0.19 2% HPMC 0.5% CNC 5.57 ± 0.30

(101) It should be noted that all emulsions were enhanced by the presence of CNC, either through decreased coalescence or an increase in viscosity of original emulsions. The nature of Pickering emulsions coupled with the high aspect ratio of CNCs is believed to be the biggest factor for stability in both emulsions and solid emulsions.