EP4237019A1

EP4237019A1 - Method for producing wound dressings on the basis of phospholipid-containing nanodispersions

Info

Publication number: EP4237019A1
Application number: EP21814676.9A
Authority: EP
Inventors: Rolf Daniels
Original assignee: Prof4skin GmbH
Current assignee: Nsc Pharma & Co KG GmbH
Priority date: 2020-10-30
Filing date: 2021-11-01
Publication date: 2023-09-06
Also published as: US20230405176A1; WO2022089680A1; CN116390778A; DE102020006675A1; CA3196830A1

Abstract

The present invention relates to a method for the production of a wound dressing on the basis of phospholipid nanodispersions.

Description

Process for the production of wound dressings from phopholipid-containing nanodispersions

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The present invention relates to a method for producing a wound dressing from phospholipid-containing nanodispersions.

It is known to cover wounds in the skin of humans or animals with wound dressings. These are designed to absorb blood and wound exudate and prevent foreign bodies from penetrating. Depending on the design, wound dressings can ensure a moist wound environment or reduce pain through the substances they contain, promote wound healing or have an antimicrobial effect. A simple and widely used wound dressing made of cotton fabric and adhesive tape is known as a band-aid. Newer wound dressings contain, for example, alginates, hydrogels or hydrocolloids. Such wound dressings generally have to be fixed to the uninjured skin, for example by means of films which are themselves coated with acrylate adhesives.

Despite all the developments in the field of wound dressings, there is still a need for wound dressings with improved properties.

WO 2019/243988 A1 describes nanodispersions of phospholipids that are brought into fiber form using electrospinning, which can be used to produce wound dressings. The present invention describes alternative production methods for producing wound dressings from the nanodispersions shown in principle in WO 2019/243988 A1.

Further prior art is formed by the following documents:

• Choudhury et al., Recent Update on Nanoemulgel as Topical Drug Delivery System, Journal of Pharmaceutical Sciences, Vol. 06, 7, July 2017, pp. 1736-1751 describes trans-dermal drug delivery systems based on nanoemulgels. • WO2016/198238 A1 describes a material containing a hydrogel and nanoparticles with adjustable porosity for the formation of cell cultures.

• Hajialyani et al., Natural product-based nanomedicines for wound healing purposes, Internat. Journal of Nanomedicine 2018,13, pp.5023-5043 describes various hydrogel-based nanoparticulate systems for wound healing.

The present invention relates to a method for producing wound dressings from a phospholipid-containing nanodispersion with the following method steps: a) mixing at least one phospholipid with at least one pharmaceutically acceptable oil and water, b) carrying out emulsification by rotor-stator or ultrasonic emulsification or by high pressure -homogenization of the mixture to obtain a dispersion, wherein at least 90% of the particle droplets have a diameter of less than 10 pm (preferably <1 pm), c) mixing the dispersion from step b) with the aqueous solution of a pharmaceutically acceptable polymer, d) layered application of the resulting polymer solution with dispersed particles to a carrier e) drying at elevated temperature, reduced pressure and/or freeze drying f) optional mechanical division of the layer and/or separation from the carrier, according to claim 1.

Further advantageous configurations of the invention are the subject matter of the dependent claims.

According to process step a), at least one phospholipid is first mixed with at least one pharmaceutically acceptable oil and water. In principle, all known phospholipids can be used as the phospholipid. Preferred phospholipids are phosphatidylcholine, phosphatidylethanolamine, phosphatidylinositol, phosphatidylserine, or mixtures thereof. Particularly preferred phospholipids are hydrogenated phospholipones, such as are available under the name "Phospholipon® 90H" or "Phospholipon 80H". This is mainly hydrogenated phosphatidylcholine. Other commercially available products made from phospholipids for pharmaceutical purposes, in particular from hydrogenated phospholipids, can also be used successfully. In principle, the pharmaceutically acceptable oil can be selected from the large number of known vegetable oils. Castor oil, corn oil, coconut oil, linseed oil, olive oil, peanut oil or mixtures thereof have proven particularly useful.

The mixture from process step a) usually contains: approx. 1-15% phospholipid, preferably 2.5-9% approx. 1-10% pharmaceutically acceptable oil, preferably 1-5%

water to 100%.

Optionally, the aqueous mixture can also contain 0.05 to 5 percent by weight of birch extract. For this purpose, birch extract is particularly preferred, which contains the following components (data in percent by weight (wt.%)):

betulin 74-85 wt.%,

Lupeol 1.0-4.0 wt%.

Betulinic acid 3.0-5.0 wt.%

Erythrodiol 0.3-2.8 wt.% and optionally other birch extract components, in particular oleanolic acid,

Betulinic acid, betulinic acid methyl ester 2-13 wt.%

An advantage of the nanodispersion containing birch extract is that the pharmaceutically active components of the birch bark extract are distributed in the finest particles or droplets, which leads to improved bioavailability. Such a nanodispersion can be applied directly to wounds or infected skin, for example by spraying it onto the affected area of the body. The nanodispersion of the present invention is superior in handling properties compared to an oleogel. It is a liquid that can even be sprayed or spread on infected areas of skin.

The initially described aqueous mixture of phospholipid and pharmaceutically acceptable oil and optional birch extract is mixed using a suitable mixer-homogenizer and a predispersion is produced in this way. This pre-dispersion is then further treated to reduce the desired particle size of the individual droplet particles from an average droplet particle size of <10 µm, optionally to a submicron size of about <1 µm and preferably below 400 nm. This can be done by intensive shearing using rotor-stator homogenizers or ultrasonic emulsification, which are very efficient in reducing droplet size. Alternatively, high-pressure homogenization can be used, eg a piston-gap-type high-pressure homogenizer, to produce nanoemulsions with extremely small particle sizes down to a few nanometers. The application of ultrasound and microfluidization are other well-known and well-described methods for the production of nanoemulsions.

It is well known that such dispersions are subject to a size distribution of the particles. Depending on the circumstances of the manufacturing process, the size distribution of the particles (particularly the median and the range) may vary.

For the present method, it has been found that the median value of the particle sizes should be in the nanometer range, i.e. less than 1000 nm, preferably less than 800 nm, particularly preferably less than 800 nm. In individual cases, however, a dispersion with a median value of the size distribution of 5,000 nm (5 pm) must be stable enough to achieve the desired result. In any case, at least 90% of the particles should have a size of less than 10,000 nm (10 μm), preferably 90% of the particles should have a size of less than 5,000 nm (5 μm), particularly preferably 90% of the particles should have a size of smaller than 1,000 nm (1 pm). All dispersions defined above are referred to as nanodispersions in this document. The methods mentioned above for producing dispersions with the above properties, in particular for achieving the desired particle size distributions, are known in principle and therefore do not require a detailed explanation at this point. Reference is made, for example, to the work Emulgiertechnik, B. Behr's Verlag, 3rd edition 2012, ISBN 978-3-89947-869-3, in particular Chapter VII. 5.

The pre-emulsion is converted into a nanodispersion in step b) of the process. The particle droplets contained in this nanodispersion have a size distribution in the lower micron range. At least 90% of the particle droplets must be less than 10 microns in diameter.

Various methods from the prior art are available for converting the pre-emulsion produced in step a) into a nanodispersion, for example the use of a rotor-stator homogenizer with high shearing (eg toothed ring disperser or colloid mill) by application by ultrasound, by high-pressure homogenization or by microfluidization. All of these methods are adequately described in the prior art so that no further explanations are necessary at this point. According to the invention, the nanodispersion formed is then mixed with an aqueous polymer solution. In this way, extremely small droplets of the nanodispersion are dispersed within the carrier polymer. The disperse particles of the birch bark extract are finely distributed in the polymer matrix, whereby an ultra-homogenization step can also be helpful.

The polymers useful for the preferred embodiment must be pharmaceutically acceptable. Such polymers can be selected from polyethylene oxide, polyvinyl alcohol, polyvinyl acetate, polyvinylpyrrolidone, hyaluronic acid, alginates, carrageenan, xanthan, cellulose derivatives such as carboxymethyl cellulose, sodium methyl cellulose, ethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, hydroxypropylmethyl cellulose, hydroxypropylmethyl cellulose phthalate, cellulose acetate phthalate, starch derivatives such as hydroxyethyl starch, sodium starch glycolate, chitosan and derivatives , albumin, gelatin, collagen, polyacrylates and their derivatives. Particularly preferred are those polymers that are readily soluble on a wound without undesirable properties. Polyvinyl alcohol or poly(lactide-co-glycolide) are particularly preferred. Most preferably, the hydrophilic polymer polyvinyl alcohol (PVA) is used, which has already been approved for human use by the FDA. PVA polymers have unique properties such as good chemical resistance, thermal stability, biodegradability, biocompatibility and non-toxicity that make them suitable for wound dressings.

Typically, an aqueous solution of the polymer is prepared. The solution contains about 5-20% by weight of the polymer, preferably about 10%. The aqueous polymer solution is mixed with the nanodispersion from process step b) in a weight ratio of 25:75 to 75:25. A preferred mixing ratio is 60-70% of the polymer solution to 40-30% of the nanodispersion.

In step d) of the process, the polymer-dissolved nanodispersion produced in this way is applied in layers to a carrier. Suitable carriers are, for example, aluminum foil, plastic foils, glass, cotton fabrics or nonwovens or polymer fabrics or nonwovens. Optionally, the layer is smoothed out mechanically and at the same time excess dispersion is removed, e.g. by using a squeegee.

The nanodispersion can also be applied to the carrier by first foaming the nanodispersion by introducing gases (eg introducing propane/butane; N2O or dimethyl ether under pressure) and then applying the foam evenly to the carrier. In step e) of the method, the nanodispersion layer is dried. This drying can be carried out at elevated temperature and/or at reduced pressure. The temperature should not exceed 60 degrees Celsius. Typical pressure ranges for drying are 10 to 100 mbar, with lower pressures being entirely possible.

Alternatively, the drying can also be carried out by freeze drying.

The dried nanodispersion should have a layer thickness of 0.05 to 5 mm.

After drying, the layer produced is typically mechanically cut or stamped into pieces. Each piece may vary in size and shape. Typical sizes are 1 to 100 square centimeters and of various shapes (e.g. round, oval or rectangular). Depending on requirements, however, larger pieces can also be produced. These can optionally be adapted to the geometry of the wounds.

The dividing into pieces can be done with or without a carrier. For example, the layer can be detached from the carrier and then cut. Alternatively, the layer can be cut with a carrier film and the film as carrier can then be detached immediately before use.

Sterilization can of course also be carried out as part of the process, for example by heating, sterile filtration and/or irradiation of the aqueous mixture produced in step 1. Alternatively or additionally, the wound dressing produced at the end of the method can also be sterilized thermally or by radiation.

The dried nanodispersion produced according to the method is suitable as a wound dressing. Since the layer itself has only low adhesive properties, it is usually fixed to the wound or the edges of the wound by means of another film with adhesive properties (adhesive layer) or a suitable adhesive.

examples

The examples below show further details of the process according to the invention, without intending to have a limiting effect. A person skilled in the art can, based on the information presented here, make further developments without having to use the invention. Example 1 Base mixtures for the production of nanodispersions la) Phospholipon 90 H 2.5%

sunflower oil 1.0 %

Birch extract 0.5%

Water 96.0% lb) Phospholipon 90 H 2.5%

sunflower oil 1.0 %

Water 96.5% lc) Phospholipon 90 H 8.0%

sunflower oil 10.0 %

Birch Extract 5.0%

Water 77.0% ld) Phospholipon 90 H 8.0%

sunflower oil 10.0 %

Water 82.0% le) Phospholipon 80 H 2.5%

sunflower oil 1.0 %

Birch extract 0.5%

Water 96.0% lf) Phospholipon 80 H 2.5%

sunflower oil 1.0 %

Water 96.5% lg) Phospholipon 80 H 8.0%

sunflower oil 10.0 %

Birch Extract 5.0%

Water 77.0% lh) Phospholipon 80 H 8.0%

sunflower oil 10.0 %

Water 82.0% 1i) Phospholipon 90 H 2.5%

Corn Oil 1.0%

Birch extract 0.5%

Water 96.0%

1 j) Phospholipon 90 H 2.5%

Coconut Oil 1.0%

Water 96.5% lk) Phospholipon 80 H 8.0%

Olive oil 10.0%

Birch Extract 5.0%

Water 77.0% l l) Phospholipon 80 H 8.0%

Flaxseed Oil 10.0%

Water 82.0%

example 2

The mixture prepared according to Example 1 is first converted into a nanodispersion as follows:

The mixture of phospholipid and pharmaceutically acceptable oil and optional birch extract from process step a) is mixed in a mixer-homogenizer and a predispersion is produced in this way. This pre-emulsion is then further treated (at least 3, preferably 8 cycles at 100 MPa, 70° C.) by means of high-pressure homogenization (Emulsiflex C-3, Avestin, Mannheim, Germany) to reduce the particle size of the individual droplet particles from an average droplet particle size of >10 μm to a submicron size of about <1 pm and preferably below 400 nm.

The nanodispersion is then intensively mixed with a polymer solution (10% PVA solution) (e.g. Bekomix or Frymacoruma mixer-homogenizer) and further processed as follows: Version 1)

The polymer-dissolved nanodispersion is applied (preferably sprayed) to a carrier layer, e.g. a textile fabric or fleece, and then dried at elevated temperature, e.g. 60 °C, with or without applying a vacuum.

This results, for example, in an adhesive bandage with an active layer.

Variant 2)

The polymer-dissolved nanodispersion is applied (poured or sprayed) onto a suitable substrate, e.g. carrier film, and then dried at elevated temperature, e.g. 60 °C, with or without applying a vacuum.

The film that forms (film thickness approx. 0.1 - 0.2mm) is separated from the base, if necessary cut to a suitable size and can now be used on its own as a wound dressing or in combination with other materials used for wound dressings are used, and/or are combined with an adherent layer to form composite wound dressings.

Variant 3)

The polymer-dissolved nanodispersion is converted into a foam by introducing air or another suitable gas via nozzles or by mechanically incorporating air or another suitable gas. This foam is applied (brushed, poured or sprayed on) to a suitable substrate, e.g. carrier film, and then dried at elevated temperature, e.g. 60 °C, with or without applying a vacuum.

The porous film that forms is separated from the base, if necessary cut to a suitable size, and can now be isolated as a wound dressing or combined with other materials used for wound dressings and/or an adhering layer to form composites -Wound dressings are joined together.

Variant 4)

The polymer-dissolved nanodispersion is frozen in a suitable layer thickness in a conventional freeze-drying process at a temperature of < -20 °C and then freeze-dried. The porous, spongy layer that forms is separated from the substrate, e.g. carrier foil, if necessary cut to a suitable size and can then be isolated on its own as a wound dressing or in combination with other materials that are used for wound dressings and/or or an adhering layer to form composite wound dressings.

Example 2a

As an alternative to example 2, a nanodispersion can be produced as follows:

Phosphatidylcholine and birch bark extract are dispersed in water at 70°C and stirred under vacuum for 30 min. This is followed by a 10-minute homogenization (rotor-stator > 10m/s). Sunflower oil is added with further stirring and under reduced pressure and the mixture is homogenized for a further 30 minutes (rotor-stator>10 m/s). The phase is cooled to 40°C. The polymer solution (10% PVA solution) is added and mixed intensively (e.g. Bekomix or Frymacoruma mixer-homogenizer). The polymer-dissolved nanodispersion can be further processed as described in example 2 (variants 1-4).

Example 3

In order to demonstrate the activity of the wound dressings according to the invention, an ex vivo wound healing test for pigs can be carried out. Dau pig ears from a slaughterhouse (for human consumption) are delivered to the laboratory immediately after slaughter, cleaned and disinfected. Then 6 mm punch biopsies are taken from the earlobes and fat and subcutaneous fat are removed. As a result, wounds were created by removing the epidermis and the upper dermis in a central area of 7.1 mm ² . Then the ex vivo wound healing model thus formed is placed in culture dishes dermis-bottom on gauze and incubated with Dulbecco's modified Eagle's medium supplemented with hydrocortisone, 2% fetal calf serum, penicillin and streptomycin at the air-liquid interface. 4 cm ² of the wound dressing is applied immediately after the wound and the models are incubated for 48 hours at 37° C. and 5% CO 2 . Further steps included shock freezing, cryostat sections of the central parts of the wound healing models are identified with a ruler in the microscope and - by checking the total length of the wound during the evaluation - stained with hematoxylin and eosin. The wound healing process (re-epithelialization) is assessed by measuring the distance between the wound edge and the top of the regenerated epidermis with a microscope. In the example, the wound was not treated at all as a control. An oleogel was used as a comparison with the prior art. A slight improvement was observed. Furthermore, a polyvinyl alcohol mat without birch bark extract (PVA mat) was used. It shows that the healing properties are better than the control and even better than with oleogel.

Figure 1 shows the results of the tests carried out:

Column 1 (far left) shows the untreated control.

Column 2 shows the treatment with Oleogel (corresponding to the approved finished drug Episalvan) Column 3 shows the treatment with an electrospun wound dressing with birch extract according to WO 2019/243988 A1.

Column 4 shows treatment with an electrospun placebo dressing. Column 5 shows the treatment with the TE-containing film from Figure 1.

Claims

Expectations:

1. A process for the production of wound dressings from a phospholipid-containing nanodispersion with the following process steps: a) mixing at least one phospholipid with at least one pharmaceutically acceptable oil and water, b) carrying out emulsification by rotor-stator or ultrasonic emulsification or by high-pressure homogenization of the Mixture to obtain a dispersion, wherein at least 90% of the particle droplets have a diameter of less than 10 μm, c) mixing the dispersion with the aqueous solution of a pharmaceutically acceptable polymer, d) layer-like application of the resulting polymer solution with dispersed nanoparticles onto a carrier e) drying at elevated temperature, reduced pressure and/or freeze drying f) optionally mechanical division of the layer and/or separation from the support.

2. The method according to claim 1, characterized in that the phospholipid is selected from phosphatidylcholine, phosphatidylethanolamine, phosphatidylinositol, phosphatidylserine, hydrogenated phospholipids (especially hydrogenated phosphatidylcholine) or mixtures thereof.

3. The method according to claim 1 or 2, characterized in that at least one pharmaceutically acceptable oil is selected from sunflower oil, castor oil, corn oil, coconut oil, linseed oil, olive oil, peanut oil or mixtures thereof.

4. The method according to claim 1, 2 or 3, characterized in that the mixture of phospholipid with oil and water contains 0.05 to 5 percent by weight of birch extract.

5. The method according to claim 4, characterized in that the birch extract comprises the following components, calculated as a percentage by weight:

Betulin 74-85 wt.%, Lupeol 1.0-4.0 wt.%,

betulinic acid 3.0-5.0 wt.%,

Erythrodiol 0.3-2.8% by weight and optionally other birch extract components, in particular oleanolic acid, betulinic acid, betulinic acid methyl ester 2-13% by weight.

6. The method according to at least one of claims 1 to 5, characterized in that the nanodispersion is produced by using a mixer with high shearing, by using ultrasound, by high-pressure homogenization or by microfluidization.

7. The method according to at least one of claims 1 to 6, characterized in that the pharmaceutically acceptable polymer is selected from polyethylene oxide, polyvinyl alcohol, polyvinyl acetate, polyvinylpyrrolidone, hyaluronic acid, alginates, carrageenan, xanthan, cellulose derivatives, sodium methyl cellulose, ethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, hydroxypropylmethyl cellulose , hydroxypropylmethylcellulose phthalate, cellulose acetate phthalate, starch derivatives, sodium starch glycolate, chitosan and derivatives, albumin, gelatin, collagen, polyacrylates and their derivatives, polyvinyl alcohol or poly(lactide-co-glycolide).

8. The method according to at least one of claims 1 to 7, characterized in that the nanodispersion dispersed in the polymer is applied to a carrier, the carrier being selected from aluminum foil, plastic foil, glass, cotton fabric or fleece or polymer fabric or fleece.

- 14 - . Method according to at least one of Claims 1 to 7, characterized in that the nanodispersion dispersed in the polymer is applied to a carrier with foaming, the carrier being selected from aluminum foil, plastic foil, glass, cotton fabric or fleece or polymer fabric or fleece.

10. The method according to at least one of claims 1 to 9, characterized in that the drying of the nanodispersion dispersed in the polymer is carried out at elevated temperature and/or at reduced pressure.

11. The method according to at least one of claims 1 to 9, characterized in that the drying of the nanodispersion dispersed in the polymer is carried out by freeze drying.

12. The method according to at least one of claims 1 to 11, characterized in that the dried layer of nanodispersion dispersed in the polymer has a layer thickness of 0.1 to 5 mm.

13. The method according to at least one of claims 1 to 12, characterized in that after the drying, a mechanical comminution of the dried layer into 1-100 cm ² large parts is carried out.

14. The method according to at least one of claims 1 to 13, characterized in that the carrier is separated off after drying.

15. Wound dressing produced by the method according to at least one of claims 1 to 14.

16. Use of the dried nanodispersion dispersed in the polymer, produced by the method according to at least one of claims 1 to 14, as a wound dressing.