GB2060381A - Compositions containing microfibres - Google Patents

Abstract

For the treatment of wounds, sores, ulcerations and other exudative affections of the skin, there is used a microfibrous material based on synthetic polymer, and having a high specific superficial area of over 30 m<2>/g, and very small size, the diameter being in the range of from 2 to 10 microns and the length in the range of from 1 to 5 mm. High-density polyethylene is the preferred polymer. The microfibres may be formulated as powders, occulusive pads, ointments or creams and may also contain one or more curative substances.

Description

SPECIFICATION Microfibres for the treatment of wounds, sores, ulcerations and other exudative skin affections This invention relates to microfibres for use in the treatment of wounds, sores and ulcerations of the skin and of other skin affections which produce discharge fluids (exudates).

According to the invention, there is provided, for use in the topical treatment of wounds, sores, ulcerations and other exudative skin affections, microfibres of synthetic polymer(s) which microfibres have a surface area of more than 30 m2/g, a diameter of from 2 to 10 microns and a length of from 1 to 5 mm.

The microfibres may have quite particular a shape, and are suitable for the absorption of exudates from the surfaces treated therewith and for the constant maintenance of a healthy, oxygen-rich and balanced constant humidity environment such as to encourage the occurrence and the persistence of the conditions which are most appropriate for reinstating the physiological skin functions. In addition, the microfibres permit a crust to be formed at a certain distance from the skin, rather than directly on the skin.

Thus, a barrier-layer preventing the exit, from the affection, of dust, bacteria, toxic degradation products, inflammatory agents and so forth is not formed. Therefore, the affection can be much more conveniently cleaned and its healing is thereby accelerated.

The microfibres have a very small size, i.e. their diameter is from 2 to 10 microns and their length is from 1 to 5 mm. In addition they have a very large specific surface area, i.e. over 30 m2/g.

The microfibres are preferably obtained by flash extrusion, i.e. by extrusion, through a nozzle from a pressurised environment to an environment at ambient pressure, the pressure differential between the two environments being at least 30 atmospheres, of solutions of polymers or of homogeneous solutions of mixtures of polymers in appropriate proportions. Such a process is disclosed, for example, in Italian Patent Specification No. 995,549. In flashing, there occurs sudden evaporation of the solvent, with the attendant formation of microfibres having a very small size.

In order that the healing of wounds, sores and ulcerations, especially of the purulent kind, may be achieved, it is essential to remove therefrom the exudated that they discharge, as well as the pollutants which may induce infection, while concurrently maintaining a correct balance of humidity so as to ensure a clean environment and such conditions as to encourage the rapid regeneration of the skin cells.

Above all, it is vital, in such cases, to prevent the formation of crusts, due to the reticulation of fibrin, which adhere too closely to the surface of the wound, sore or ulceration and which impede a regular exchange of moisture between the skin and the atmosphere, thus causing the stagnation of the exudates and the attendant formation of infectious pockets.

There is no concordance of opinion as to the possibility of accelerating the regeneration of skin tissues in the case of wounds, ulcerations and the like.

It is certain, however, that in the case of purulent or exudative affections, the removal of infected materials or or the possibly infectious medium or agent capable of encouraging the formation of thick crusts encourages the regeneration of the cells and thus the healing of the injured surface.

It has been suggested to treat wounds or exudative affections of the skin with powders or dry powdered materials in minute particle form, the powders or powdered materials being of an inorganic or organic nature and possibly being based on polymers. However, little or no success has been achieved.

It has also been suggested, this time with a certain success, to use macromolecular substances containing hydrophilic groups, in the form of a powder consisting of minute, virtually spherical, particles which absorb, presumably in a selective way, the fluids discharged from wounds or other skin alterations.

This is disclosed in British Patent Specification No.

1,454,055.

In accordance with the present invention, it has been found that the local application, in the form of dusting powders, occlusive pads, ointments, creams or other preparations, of microfibres of the kind described above has surprisingly been conducive, both in the form of microfibres as such and in combination with other medicaments, to a quick healing of the damaged skin surfaces. In addition to absorbing and removing the noxious fluids, these microfibres seem to ensure a fully satisfactorytranspira- tion of the underlying skin surface. Furthermore, the microfibres do not pack on the wounds and do not form any hard or adhering crusts, so that they can conveniently be withdrawn during the progress of the medication without causing any additional damage to the affection, contrary to what occurs with conventional wound dressing materials.

In orderthatthe present invention may be better understood, a description will now be given of tests carried out on rabbits on which purulent sores had been artificially induced, with a view to ascertaining the effect of the microfibres on wound healing, in comparison with other commercial products intended for the same purposes. Concurrently, tests were conducted on rabbits having sores of the same kind, without the application of any wound healing product.

The test were conducted on 18 white New Zealand rabbits. On all of the rabbits, a sore was artificially induced. To this end, a skin strip 8 by 8 centimetres was removed surgically from the back, with anaesthesia. The exposed area was infected by spreading thereon an admixture of mouse and rabbit excrements, human pus and physiological solution, the admixture having been carefully homogenized in a mortar, whereafter the wound so infected was covered with the overturned skin strip and with a moistened gauze.

After having maintained the thus treated portion of the skin in a moist and warm environment for four days, the wounds were infected by a mixed bacterial flora, mainly composed of Escherichia Col, Proteus sp., Pseudomonas Aeruginosa, Staphylococcus Aureus and Betahaemolytic Streptococcus.

For each rabbit the size and the exact contour of the wound was recorded on a X-ray plate, as follows.

After four days from the surgical removal of the skin strip and the application of the infectious materials, the skin strip and gauze was removed from all rabbits. All of the loose dirt, crust and pus were removed and the wounds were irrigated with 20 ml of physiological solution. An unexposed X-ray plate was laid on the wound and the wound contour was exactly traced with a pen. An arrow was placed in the direction of the head of the rabbit and the plate was marked with the rabbit's name, so that subsequently the plate could be placed in the same position for each rabbit. Thus the size of the wound was periodically checked on known dates. The marked plates, complete with all the records, served for the determination of the wound healing time.

The wounds were checked for a total time of about 23 days. As a matter of fact, this time is the period in which the maximum wound healing takes place, as had been ascertained on pilot tests on two control rabbits, even though the complete healing was expected to require 4≈weeks.

The eighteen rabbits, whose wounds had been cleaned as described above, were divided into three groups of 6 rabbits each. A first group (Group 1 ) was the control group. The six rabbits of this group were left with their wounds exposed to the air, without any medication at all. No wound dressings were applied in any case since this would promote, especially in rabbits, a too intensive purulence, even under aseptical conditions. The other two groups of six rabbits each received a medication, as follows.

The second group (Group 2) was medicated with a macromolecular substance obtained by crosslinking dextran or carboxymethyldextran with epichlorohydrin in the form of microspherical particles, the use of which for the dressing of exudative wounds is described in British Patent Specification No. 1,454,055 and which is marketed underthetrade mark "Debrisan". The third group (Group 3) was treated with high-density polyethylene microfibres obtained according to the method of Italian Patent Specification No. 995,549 and having, on average, a diameter of from 5 to 10 microns, a length of from 1.4 to 1.6 mm, and a specific surface area of about 40 m2lg.

A layer of the material was placed on the wounds.

Every third day, the wounds were checked, and the debris and the applied material were removed. The wound contour was traced on the respective plates.

Each rabbit then receiving the medication treatment exactly as before.

In order to give a numerical evaluation of the heal ing of the wound, the following method was adopted. On completion of the test period, there were drawn on each plate a set of approximately circular, concentrical circles. On each plate, a cross was drawn in such a position that the intersection of the cross-arms fell approximately at the centre of the circles. The ends of the cross-arms were oriented in the positions of 3 o'clock 6 o'clock,9 o'clock and 12 o'clock. As the baseline, the initial tracing of the wound the time of surgical skin removal was taken. Also, the last reading, that is the one corresponding to the healing of the wound, was recorded.

The distance in millimetres between the baseline and the ultimate tracing was measured along each cross-arm (in the order 3, 6, 9, 12). The sum of these distances, divided by four, gave the average length of the healed wound for each rabbit The rate of wound healing was calculated by dividing the average length of the healed wound by the number of days required in total for the healing of the wounds.

Table 1 gives the values relativetothe healing of the wounds of each animal of each group.

Subsequently, the average of the healing of the wounds was calculated for each group of rabbits, while concurrently evaluating the average testing time for each group by summing the healing rate of the rabbits of each group and dividing this sum by 6.

One of the rabbits which had been treated with "Debrisan" gave an anomalous response to the treatment, i.e. at the end of the period of time by which the wounds of all the other rabbits had healed, it had a pus pocket and its wound did not heal. The values of this second evaluation are tabulated in Table 2.

It is apparent from the mere reading of the Tables that the rabbits of Group 3 exhibit an improved total (i.e. group) and average wound-healing rate (see particularly Table 2).

Moreover, the following observations were made on the behaviour of the wounds treated in different ways in the three groups of rabbits. For the rabbits of Group 1 the formation of a thick crust, rather difficult to clean, was noted. A portion of the crust was so adhered that it could not be removed without damaging the wound and causing pain to the animal. The same problem was noted for the rabbits of Group 2. In this case, furthermore, a few difficulties were experienced in keeping the "Debrisan" on the wound, on account of the exceedingly high freeflowing properties of this product, so that the wound was left partially exposed. For the rabbits of Group 3 the formation of a thick, but light, crust was noted, but the crust was not pasty on the wound surface and could easily be peeled off so that it was easy to clean the wound quickly. In addition, the application of the microfibrous materials to the wounds proved to be convenient since, due to its soft texture, it stayed easily on the wound without pasting.

TABLE 1

RABBITs GROUP No. of LINE 12 LINE 3 LINE 6 LINE 9 AVERAGE HEALING SPEED name " days mm mm mm mm healing mm a day mm FIONA 1 24 33 38 32 30 33.25 1.385 FREDA 1 24 32 30 22 35 29.75 1.239 FOULKES 1 24 20 9 26 22 19.25 0.802 FRED 1 24 9 13 6 9 9.25 0.385 AGNES 1 22 26 33 37 39 33.75 1.534 ANNABEL 1 22 32 30 43 35 35.00 1.590 DEE 2 24 15 2 24 6 13.25 0.550 DELIN 2 24 31 30 38 30 32.25 1.343 DORIS 2 24 30 25 27 22 26.00 1.083 CONDOM 2 22 20 19 11 23 18.25 0.760 CAROLINE 2 22 27 14 23 34 24.5 1.113 DESMOND 2 24 32 27 35 30 31.00 1.291 BEATRICE 3 25 47 37 47 46 44.25 1.770 CONNI 3 22 34 17 28 34 28.25 1.284 COTTI 3 22 39 32 32 22 31.25 1.420 CATHI 3 22 43 23 28 45 34.75 1.579 CAESARI 3 22 10 25 10 30 18.75 0.852 BETTI 3 25 51 32 38 32 38.25 1.530 TABLE 2 GROUP 1 Total Group Healing Rate 6.935 mmlday (6 animals) Average Healing Rate 1.155 mmlday/animal Average number of days 23,35 GROUP2 Total Group Healing Rate 6.140 mmlday (6 animals) Average Healing Rate 1.023 mmldaylanimal Average number of days 23,33 GROUP3 Total Group Healing Rate 8.435 mmlday (6 animals) Average Healing Rate 1.405 mmldaylanimal Average number of days 23,00

Claims (7)

1. For use in topical treatment of wounds, sores, ulcerations and other exudative skin affections, microfibres of synthetic polymer(s) which microfibres have a surface area of more than 30 m21g, a diameter of from 2 to 10 microns and a length of from 1 to 5 mm.

2. Microfibres as claimed in claim 1,the microfibres having been obtained by flashing a solution of said polymer(s), either alone or in admixture with other polymer(s).

3. Microfibres as claimed in claim 1 or 2, in the form of a powder, an occlusive pad, an ointment or a cream.

4. Microfibres as claimed in any of claims 1 to 3, wherein the synthetic polymer is high density polyethylene.

5. Microfibres as claimed in any of claims 1 to 4, in association with one or more curative substances.

6. Microfibres as claimed in claim 1, substantially as hereinbefore described.

7. A method for the treatment of a wound, a sore, an ulceration or other exudative skin affection, which method comprises allowing it to heal in contact with microfibres as claimed in any of claims 1 to 6.