WO1990006501A1

WO1990006501A1 - Diffusion cell for testing ointments and the like

Info

Publication number: WO1990006501A1
Application number: PCT/FI1989/000224
Authority: WO
Inventors: Ari Tuomi
Original assignee: Huhtamäki Oy
Priority date: 1988-12-09
Filing date: 1989-12-05
Publication date: 1990-06-14
Also published as: FI86339C; AU4646789A; FI885709A; FI86339B; FI885709A0

Abstract

Diffusion cell for testing ointments and the like. The cell comprises at least two body members (2 and 3) which define a closed diffusion chamber which is divided with a membrane (7) into two chambers, i.e. an ointment chamber (8) for the ointment to be tested, and a receptor chamber (9) for a receptor medium and provided with an inlet and an outlet for the receptor medium. The ointment chamber is provided with a hole disk (11) to be brought into engagement with the upper surface of the membrane (7) and provided with at least one hole (13, 14) for receiving the ointment to be testted, as well as holding means (16) for cooperation with the hole disk and the inner wall of the ointment chamber so that when the cell is assembled and closed, the holding means lock the hole disk with optionally interleaved skin sample into contact with the membrane.

Description

Diffusion cell for testing ointments and the like

The object of the present invention is a diffusion cell for testing ointments and the like, which cell compri¬ ses at least two body members which define a closed diffusion chamber which is divided with a membrane into two chambers, i.e. an ointment chamber for the ointment to be tested, and a receptor chamber for a receptor me¬ dium and provided with an inlet and an outlet for the receptor medium.

A diffusion cell of this kind is known for example from the DE patent publication 30 09 843, which is used for studying the release of active agents from oint¬ ments. With the cell it is possible to study various diffusion processes in ointments and the penetration of active agents through the membrane into the receptor medium, wherein its concentration may be determined. In the known device the ointment chamber and the ointment contained therein is heated by making the wall of the ointment chamber opposite the membrane into a heat exc¬ hanger, for example by circulating warm water along its outer surface. In the known device the membrane is sea- lingly mounted between the body members and its entire upper surface is in contact with the ointment to be studied. The amount of ointment to be examined is thus relatively large, and the device does not make it pos¬ sible to use several samples at the same time.

The object of the present invention is to avoid the mentioned disadvantages of the known device.

According to the invention this is achieved by provi¬ ding the ointment chamber with a hole disk to be brought into engagement with the upper surface of the membrane and provided with at least one hole for re¬ ceiving the ointment to be tested, as well as holding means for cooperation with the hole disk and the inner wall of the ointment chamber so that when the cell is assembled and closed, the holding means lock the hole disk into contact with the membrane.

The cell according to the invention may advantageously be used for so called "in vivo mimic"-studies, wherein percutanic absorption is studied by means of skin samp¬ les providing controlled conditions for the skin sample and advantageously also temperature control for the re¬ ceptor medium to correspond to body temperature. In this case, as the membrane, advantageously a hydrophilic polymer film, or such a film made hydrophilic, is used together with a skin sample, either a whole skin sample or its stratum corneum and epidermis layers, the hydro¬ philic membrane simulating the dermis. For this purpose the skin sample is placed in the cell on top of the membrane to align with the hole or the holes in the hole disk and the ointment to be studied is applied. Thereafter the hole disk is placed on top of the mem¬ brane and the skin samples, the holes providing a free air space above the skin samples. The ointment may also be applied through the hole(s). The holding means lock the hole disk with interleaved skin sample into contact with the membrane. As skin samples are used only at the place of the holes, and not to cover the whole surface of the membrane, the amount of skin samples needed is small compared to the amounts required previously.

By using, according to the invention, advantageously a hydrophilic membrane towards the receptor medium, and not a film membrane of lipophilic nature, the hyd- ration of the skin sample can be balanced better and its dehydration prevented, which is of importance with respect to obtaining reliable test results. The hydro¬ philic membrane does not affect the penetration per se of the active agent but stabilizes the prevailing con¬ ditions between the receptor phase and the ointment phase and together with the skin sample it can be con¬ sidered to provide a relatively good model for simulat¬ ing the dermis. The model may be further improved by keeping the ointment chamber at room temperature and the receptor medium at body temperature and thus a temperature gradient corresponding to in vivo-condi- tions is provided for in the system.

The polymers to be used as membrane are well known and as examples may be mentioned, for example, cellulose esters or mixed esters, such as cellulose acetate, nitrocellulose, polytetrafluorethylene, polyamides (nylon), polyvinylidene fluoridine, polycarbonate, regenerated cellulose, polyvinyl acetate, polyvinyl butyrate, cellophane, acrylonitrile/PVC/nylon, modified gelatine, etc. When the polymer is not per se hydro¬ philic, a film to which hydrophilic properties have been imparted may be used as the membrane.

When plain drug-release tests are to be carried out with the diffusion cell, the use of skin samples between the membrane and hole disk may be omitted, as also in the case of studying permeation phenomena in artificial membranes. In some instances the membranes may also be lipophilic in nature, e.g. membranes impregnated with silicone adhesive or other lipid solvents, for example when it is desired to study occlusion phenomena. The diffusion cell according to invention may also be used for studying inverse permeation, i.e. the inverse pro¬ cesses of permeation in a direction from the systemic circulation to the skin.

In order to provide for a laminar flow along the under¬ side of the membrane, a corrugated plate is advantage- ously used in the receptor chamber onto which plate the membrane rests. The receptor medium is fed as a conti¬ nuous flow through the inlet, it is made to flow along the underside of the membrane and is removed together with the active agent released therein from the ointment via the membrane, and out through the outlet for analysis.

In the hole disk there is used, depending on the test to be carried out, at least one through hole. It is, however, advantageous to use a system of several, for example 2 to 4 holes of the same size, for using seve¬ ral parallel samples. The same disk may also be provi¬ ded with several series, for example 2 to 4 series of holes, whereby in each series the size of the holes is the same. Consequently for the test, that particular series of holes in the hole disk may be used which corresponds best to the size of the available skin samples, as well as to the amount of ointment to be tested. By using in the same study simultaneously seve¬ ral holes of the same size and corresponding skin samp¬ les, possible variations in the type and quality of skin samples may be evened out.

The surface of the hole disk which is directed away from the membrane cooperates in turn with holding means which in turn cooperate with the inner wall of the ointment chamber, and its function is to lock the hole disk into contact with the membrane, optionally with interleaved skin samples. The holding means may vary in shape, and may form an integral part of the hole disk, e.g. a peg or similar extending from the hole disk for engagement with the inner wall of the ointment chamber. Advantageously it is, however, in the form of a disk and corresponds substantially to its shape and size to the hole disk. The holding disk is in such case advan- tageously provided with holes corresponding to the holes in the hole disk, whereby the holes in the hold¬ ing disk may be aligned with the holes in the hole disk and the skin samples may breathe freely. The holding disk is in such a case provided with a device, for example an extension in the center of the disk, which engages the inner wall of the ointment chamber opposite the membrane, for example in a recess or sleeve there¬ in, and due to which the hole disk, by means of the holding disk, may be brought into close contact against the membrane locking all the parts in their places. According to one embodiment, the holding disk with its holes is so designed that when it is turned around its axis it may in at least one of its positions be made to cover the holes in the hole disk. This mode is of ad¬ vantage, for example, when hydration of a skin sample is desired. The holding disk may be provided with lock¬ ing means, for example in the form of pegs, which, when in lowered position, cooperate with perforations in the hole disk and by means of which the holding disk may be locked to the hole disk in order to prevent a shift in their mutual position.

In the following reference is made to the accompanying drawing, wherein

Figure 1 illustrates an embodiment of a diffusion cell according to the invention, in cross-section through the cell and viewed from the side, the inner parts of the diffusion chamber being shown diagrammatically and in an exaggerated manner,

Figure 2 shows structural parts of the diffusion cham¬ ber of the cell according to the Figure 1,

Figure 3 shows alternative solutions to the structural embodiment according to the Figure 2, and Figures 4a to 4c show the cell according to the inven¬ tion viewed from above, in cross-section through the ointment chamber, whereby the Figures 4a and 4b refer to the Figure 2 and Figure 4c to the embodiment of Fi¬ gure 3.

In the Figure 1 the cell as a whole has been given the reference number 1, which cell to its outer shape cor¬ responds to that shown in the DE patent 30 09 843. The cell 1 is, in the embodiment shown, formed by two outer body members 2 and 3, which over a third body member 4 may be releasably connected to each other, the re¬ cesses of the body members 2 and 3 together with the aperture in the body member 4 forming a closed diffusion chamber. The body members 2, 3 and 4 may be sealingly mutually joined to form a cell using nuts 5 and bolts 6, which, when the cell is of rectangular shape, as in the embodiment shown, may be four in number, one in each corner of the cell, as is shown in the Figures 4a to 4c.

The diffusion chamber is divided into an ointment chamber 8 and a receptor chamber 9 by means of a membrane 7. The cross-section of the membrane 7 corresponds to the cross-section of the diffusion chamber, and it may be sealingly mounted, for example with a rubber gasket sur¬ rounding the membrane, in the diffusion chamber. Good results have been obtained with membranes of poly¬ carbonate polymer, for example Nuclepore^® (thickness 8 /um, porosity 5 to 10%) or a cellulose membrane (Sartorius SM 16754, C/D, thickness 150 /urn, porosity appr. 85%). The membrane 7 rests in the diffusion cham¬ ber 9 against a corrugated plate 10, which allows a la¬ minar flow of the receptor medium along the lower sur¬ face of the membrane. The surface of the membrane 7 which is directed towards the ointment chamber 8, i.e. its upper surface, in turn bears against a hole disk 11, whereby in the drawing the skins samples 12 to be inserted between the hole disk 11 and the membrane 7 are shown as well.

In the embodiment according to the Figure 2, the hole disk is provided with two series of holes, each of which has three holes 13 and 14 of the same size, which allows for the simultaneous use of three parallel samples. In the figure shown the series of bigger holes 13 have been used, but it is clear that in case the available skin samples are smaller, the series of the smaller holes 14 are used. - In the embodiment accord¬ ing to the Figure 3, there is only one central hole 15 in the hole disk. - The surface of the hole disk 11 directed away from the membrane bears against a holding disk 16, the function of which is to keep the hole disk 11 in close contact with the membrane and the skin samples. By turning the holding disk in the horisontal plane around its central axis according to the Figure 2 it may also be placed in such a position wherein it covers all the holes of the hole disk. In the embodi¬ ment of the Figure 2 the holding disk 16 is provided with three holes 17, the size and mutual arrangement of which corresponds to that of the holes 13 in the hole disk 11, whereby turning the holding disk 16 will align the holes 17 and 13 to form a through hole. Due to the symmetric arrangement of the holes 13 and 14 in the Figure 2, the holes 17 in the disk 16 may be aligned also with the holes 14.

The holding disk 16 is further provided with locking means in the form of pegs 18, which may be pushed down to cooperate with bores 19 in the hole disk 11, and by means of which the holding disk and the hole disk may be locked together, if necessary. The holding disk 16 is further provided with means 20 in the form of a peg, by means of which the holding disk may be fastened in a suitable manner to the upper part of the diffusion chamber and by means of which the hole disk with skin samples are maintained in close contact with the mem¬ brane 7.

In the embodiment of the Figure 3, the holding member 6 is a plug 21 which closes the single central opening. The plug 21 is supported against the upper wall of the diffusion chamber and by means of which the hole disk with its skin sample 12 and membrane 7 similarly may be kept in close contact with each other.

The body member 2 comprising the upper part of the ointment chamber is according to the Figure 1 provided with a recess 22 for regulating the temperature of the ointment, through which recess a heating medium of a suitable temperature may be circulated, such as water.

The Figures 4a to 4c show the cell when the upper body member 2 has been removed. Thus the Figure 4a shows the cell viewed from above when the holding disk is in its place and Figure 4b the corresponding Figure when even the holding disk 16 has been removed and the hole disk is shown as being uppermost. The Figure 4c in turn is a Figure similar to Figure 4b, wherein in place of the hole disk according to the Figure 2 there is used a hole disk according to the Figure 3, having one single central hole.

In use the cell is opened by turning the nuts 5 and lifting off the upper body member 2. The skin samples are placed on the membrane with the epidermis layer towards the membrane so as to align with the holes of the hole disk 11. The membrane with skin samples is co- vered with the hole disk 11 so that the skin samples show through the holes. The ointment to be tested with its active agents may be applied to the skin sample either when it is situated on the membrane, but uncove¬ red, or it may be applied through the holes 13 or 14. The holding disk 16 is mounted on top of the hole disk 11 and thereafter the body member 2 is mounted in place and tightened, whereby the hole disk is placed in close contact against the membrane by means of the holding disk 16. Through the receptor chamber the receptor me¬ dium is continuously circulated in a known manner which is introduced into the receptor chamber through its in¬ let, it flows along the corrugated plate sweeping one side of the membrane, whereby the active agent which has diffused from the ointment through the membrane in¬ to the receptor medium is removed together with the re¬ ceptor medium through the outlet, wherefrom it is transferred to a suitable analyzing apparatus for ana¬ lyzing.

Claims

1. Diffusion cell for testing ointments and the like, which cell comprises at least two body members (2 and 3) which define a closed diffusion chamber which is di¬ vided with a membrane (7) into two chambers, i.e. an ointment chamber (8) for the ointment to be tested, and a receptor chamber (9) for a receptor medium and provi¬ ded with an inlet and an outlet for the receptor me¬ dium, c h a r a c t e r i z e d in that the ointment chamber is provided with a hole disk (11) to be brought into engagement with the upper surface of the membrane (7) and provided with at least one hole (13, 14) for receiving the ointment to be tested, as well as holding means (16) for cooperation with the hole disk and the inner wall of the ointment chamber so that when the cell is assembled and closed, the holding means lock the hole disk into contact with the membrane.

2. Diffusion cell according to the Claim 1, c h a r a c t e r i z e d in that the membrane is a hyd¬ rophilic polymer film or such a film made hydrophilic.

3. Diffusion cell according to the Claim 2, c h a r a c t e r i z e d in that the polymer is a po¬ lycarbonate or cellulose membrane.

4. Diffusion cell according to the Claim 1, c h a r a c t e r i z e d in that the hole disk is provided with 2 to 4 holes of the same size for paral¬ lel samples.

5. Diffusion cell according to the Claim 4, c h a r a c t e r i z e d in that it is provided with two series each comprising three holes of the same size.

6. Diffusion cell according to the Claim 1, c h a r a c t e r i z e d in that the holding means is a holding disk (16) corresponding substantially in size and shape to the hole disk.

7. Diffusion cell according to the Claim 6, c h a r a c t e r i z e d in that the holding disk is provided with an upwardly extending central plug (20) which rests against the upper wall of the diffusion chamber, for example in a recess or sleeve provided thereon.

8. Diffusion cell according to the Claim 6, c h a r a c t e r i z e d in that the holding disk comprises holes (17) corresponding in shape and arran¬ gement to the holes of at least one series in the hole disk (11), preferably to the bigger holes.

9. Diffusion cell according to the Claim 6, c h a r a c t e r i z e d in that the holding disk (16) comprises means (18) for locking the holding disk to the hole disk (11).

10. Diffusion cell according to the Claim 9, c h a r a c t e r i z e d in that the locking means comprise at least one peg which cooperates with a bore (19) in the hole disk.

11. Diffusion cell according to the Claim 1, c h a r a c t e r i z e d in that the receptor chamber is provided with a corrugated plate (10) allowing a la¬ minar flow of the receptor medium.

12. Diffusion cell according to the Claim 1, c h a r a c t e r i z e d in that it is provided with means for regulating the temperature of the ointment chamber and/or the receptor chamber.

13. Diffusion cell according to the Claim 2, for use in percutanic absorption studies, c h a r a c t e r ¬ i z e d in that at least one hole (13, 14) in the hole disk is made to align with the skin sample to be used and supported by the membrane, the holding means locking the hole disk with interleaved skin sample into contact with the membrane.