Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N19/00—Investigating materials by mechanical methods
  • G01N19/04—Measuring adhesive force between materials, e.g. of sealing tape, of coating
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
  • G01N2203/0001—Type of application of the stress
  • G01N2203/0005—Repeated or cyclic
  • G01N2203/0007—Low frequencies up to 100 Hz
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
  • G01N2203/0014—Type of force applied
  • G01N2203/0016—Tensile or compressive
  • G01N2203/0019—Compressive

Definitions

• the invention relates to a method and a device for determining the adhesive behavior of pressure-sensitive adhesive fabrics such as medical adhesive tape and in particular pressure-sensitive adhesive application systems such as transdermal therapeutic systems (TTS) on the skin of humans or mammals.
• pressure-sensitive adhesive fabrics such as medical adhesive tape
• pressure-sensitive adhesive application systems such as transdermal therapeutic systems (TTS) on the skin of humans or mammals.
• the temporary connection by means of PSA covers a period of a few hours to 14 days.
• skin also includes the mucous membrane of the upper airways, the eye and the genital organs.
• pressure-sensitive adhesive application systems which are to be understood as medicinal forms which release one or more active substances or test substances primarily from an adhesive layer to the skin or through this to the body.
• such systems can also be used to absorb chemical substances from the body through the skin.
• Such an application is useful for diagnostic purposes or for detoxification.
• the method and the device according to the invention relates to transdermal therapeutic systems (TTS) for the controlled, long-term delivery of one or more active ingredients to the skin. The distribution of these active ingredients can remain local or extend to the entire organism of the carrier.
• TTS transdermal therapeutic systems
• TTS are well known in the pharmaceutical industry and in large numbers on the market.
• the invention is particularly suitable as a means of researching the pressure-sensitive adhesive of such products on the skin, especially when worn for a long time.
• contour-fit means that edge detachment of the TTS from the skin is avoided.
• this layer can contain active ingredients and also contain pharmaceutical adjuvants that promote skin permeation of the active ingredient.
• the adhesive behavior of the layer is influenced to a greater or lesser extent by the type and amount of the active ingredients or auxiliaries contained. Any additional layers of the system can also change the condition of the adhesive layer on the skin by absorbing or releasing substances.
• TTS skin exudates
• skin exudates include the secretion of gaseous water (perspiration), liquid water (sweat), salts (sweat) and fatty substances (sebum).
• sweat gaseous water
• sweat liquid water
• salts sweat
• fatty substances sebum
• TTS internal structure of a TTS can change significantly and unexpectedly due to the release of individual components to the application site with regard to cohesion, shear strength and adhesive strength.
• the setting of optimal adhesive properties is a task which mainly affects the formulation of the adhesive layer and is also highly dependent on the internal and external structure of the TTS.
• the associated variability makes the generalization of successful formulations largely impossible.
• a more or less complex optimization of the adhesive properties is required for each new TTS.
• TTS in development are advantageously tested under real conditions on humans or animals.
• such examinations require a very high financial outlay because of the often medicinal product status of a clinical study as well as the number of individuals statistically required for clear statements.
• Experience has shown that the optimization of adhesive properties is also a process that has to be repeated several times in the course of product maturation.
• TTS adhesive strength
• the tests can be carried out in a wide range by varying parameters such as the nature of test surfaces and the temperature and humidity.
• the individual tests only physically reflect a fraction of the dynamic stress process on the skin.
• an exchange of substances between the system and the carrier is difficult or impossible to simulate.
• the mechanical loads are one-sided and practically always aim at an extreme load on the adhesive that is not common on the skin.
• these methods are primarily suitable as a means of quality control in ensuring the uniformity of a product and less for optimizing its properties in the development phase.
• the physico-chemical affinity of an adhesive to the application surface can be determined, but the mechanical properties, such as the ability to adapt quickly to a rough surface, are completely ignored.
• the methods of rheology and dynamic mechanical analysis are aimed in particular at the mechanical, internal properties of the adhesive.
• DMA dynamic mechanical analysis
• investigations on thin adhesive layers under the influence of torsional forces can be carried out.
• the type of torsion load as well as the temperature and humidity during the test can be varied within wide limits.
• torsional forces bending, stretching and compressive forces are also allowed to act on a test material.
• the invention is based on the object of specifying a method and a test apparatus which make it possible to test the pressure-sensitive adhesive behavior of fabrics on human or animal skin under realistic conditions and to determine the pressure-sensitive adhesive formulations which are optimal for this purpose for each active substance composition.
• a part is understood to be a flat section separated from the TTS, the layer structure of which is identical to the TTS.
• a part can also be a flat structure that only partially matches the TTS in terms of its layer structure, the outer shape of which is congruent with or different from the TTS.
• the TTS and any part thereof to be tested have an identically formulated pressure-sensitive adhesive layer and at least one further layer which may differ from one another.
• the term TTS also includes parts of a TTS as defined above.
• the TTS to be tested is first glued onto a piece of a film-shaped, elastic carrier.
• the TTS has a smaller area than the carrier and is glued on in such a way that there is a distance to its edge on all sides.
• the carrier is placed together with the TTS in the manner of a separating membrane between two half-shell elements.
• the two half-shell elements are congruent along their edge and join together to define a defined interior, in principle similar to the shells of a walnut.
• the halves of each enclosed volumes can be the same size or differ from one another.
• the two shells are held firmly and contiguously against one another by suitable devices.
• the carrier with the TTS is fixed wrinkle-free, planar and at most slightly pre-stretched between the halves. This device is referred to below as a "test cell”.
• the TTS lies completely inside the test cell and keeps a safe distance from its wall on all sides.
• This load covers the entire surface of the carrier over time and is preferably carried out from the surface of the carrier facing away from the TTS. This corresponds to the conditions when worn on the skin in that the mechanical load is transferred from the bonded surface to the TTS.
• the mechanical load on the carrier can be brought about by a piston moving back and forth like a piston, which is introduced into the test cell through a corresponding opening.
• the loading is realized by a solid body moving in a circle at a low speed over the surface which is modified from the TTS. This body lies completely inside the test cell, presses itself into the elastic support and thus causes it to stretch. This stretch does not go beyond the elastic deformability of the wearer, so that practically no plastic deformation occurs.
• the deformations of the beam are mainly transferred to the TTS as shear, stretch, compression, bending and bending forces.
• the rotation of the above-mentioned body about an axis lying inside or outside of it, as well as its pressing force against the TTS carrier, can be effected in various ways become.
• the body can roll freely and lies on the surface of the TTS carrier only by gravity. The rolling of the body is then achieved by tilting the test cell against gravity and the pressure force results from the weight and the contact surface of the body.
• pressure forces and movement of the rollable body are determined by an external, variable magnetic field.
• the body can be moved from outside the test cell using suitable mechanical connecting elements (e.g. rod-shaped axis or push rod).
• suitable mechanical connecting elements e.g. rod-shaped axis or push rod.
• the special performance of the model consists in the connection of the mechanical load with a mass transfer between the TTS and its environment.
• test cell which in the simplest case contain air, can also be completely or partially filled with liquid, semi-solid or solid substances.
• the transpiration of the skin can be simulated, for example, by completely or partially filling the half of the cell opposite the TTS with water or an aqueous solution.
• the water can penetrate the TTS in the form of water vapor if a water-impermeable but water-vapor-permeable carrier is selected.
• the type and scope of this "perspiration" can be controlled within wide limits via the choice of the carrier film, the temperature and osmotically active additives to the water phase. If a microporous carrier film is used, this includes conditions, it is even possible for the TTS to come into contact with liquid water and any substances dissolved in it. This corresponds to sweating through the pores in the skin.
• a continuous release of substances from the TTS can be achieved parallel to the mechanical load. This is made possible if the half of the test cell opposite the TTS is completely or partially filled with the medium, which is able to absorb the low molecular weight constituents of the TTS by diffusion.
• the type and extent of the diffusion can also be influenced by the choice of the intermediate carrier film.
• a permeation-enhancing auxiliary or a plasticizer can be simulated from a TTS.
• the adhesive behavior of TTS on the skin can change significantly and unpredictably as a result of such processes.
• such processes can be linked in a simple manner with mechanical influences.
• the half of the test cell facing the TTS can also be filled with liquid. This then comes into direct contact with the TTS.
• water or dilute aqueous solutions the effects of washing, showering, bathing or swimming on the adhesive behavior of a TTS on the skin can be simulated.
• the tests can be evaluated qualitatively and quantitatively using the model shown above.
• the period is recorded after the TTS has completely detached itself from the carrier.
• this evaluation can be carried out by visual observation at intervals, whereby the exact point in time may not be recorded.
• An optical control device is attached or introduced to the model in order to precisely determine the point in time of complete detachment. It is preferably a signal-modulated light barrier in the visible or infrared range.
• test cell is aligned with the light barrier so that a completely detached TTS falls through the light beam in the direction of gravity and interrupts it.
• the test cell is equipped in such a way that the TTS falling in the direction of gravity interrupts or closes an electrical circuit.
• the TTS In order to close a circuit, it may be necessary to equip the TTS with at least one current-conducting layer, which can be formed from metals or conductive polymers.
• a TTS can be completely detached from the carrier by measuring the conductivity between the two.
• the electrical resistance increases continuously during the detachment of the TTS and increases suddenly when the detachment is complete.
• the quantitative recording of the detached area of the TTS is preferred. This takes place at one or more points in time before it has been completely replaced.
• the conductivity measurement mentioned above can also be used for this purpose, since the conductivity between the carrier and the TTS is proportional to their contact area. In this way, the degree of detachment can be recorded continuously.
• the test is stopped after a defined period of time and the TTS and carrier are removed from the test cell. Those parts of the TTS that have detached from the carrier material can be stained with a dye solution or suspension. However, where there is still a bond between the TTS and the support, the dye solution cannot reach the surface of the TTS or the support and cannot stain it. In this way, only those detached parts can be stained that are in direct contact with the edge of the TTS. Detachments enclosed on all sides by remaining contact surfaces are not detected.
• test apparatus An example of a preferred construction of the test apparatus is described below with reference to the figures:
• both half-shells (1, 2) of the test cell (21) consist of glass.
• the circular test cell (21) is shown in Figure 1 in a lateral cross-section, while Figure 2 shows the top view.
• the test cell (21) consists of an upper (1) and a lower half-shell (2).
• the upper half-shell (1) preferably encloses a larger volume than the lower one.
• Both half-shells (1, 2) are designed with reinforcement (3) at their edges.
• the edges of both half-shells (1, 2) are congruent and ground in a kind that enables the half-shells (1, 2) to be placed on one another with a contour.
• the laterally protruding reinforcing edges (3) allow the half-shells (1, 2) to be pressed together mechanically by a holding clip or clamp (not shown).
• a carrier film (4) is located between the two half-shells (1, 2) and covers their cross-section, including the protruding reinforcements (3).
• the sheet (5) for example a TTS, is glued to this carrier film (4), specifically on that side of the carrier film (4) which faces the lower part of the test cell (21).
• the TTS (5) has the shape of a circular ring, which is approximately the same distance from the walls of the test cell (21) and is consequently arranged centrally in the test cell (21).
• the TTS (5) consists of a pressure-sensitive adhesive layer (6) which sticks to the carrier film (4) and a back layer (7) covering the adhesive layer (6).
• the lower half-shell (2) of the test cell (21) there is a cylindrical support body (8) in a central arrangement.
• the free surface of this body (8) is preferably face-ground and lies in one plane with the face-ground edges (3) of the lower half-shell (2).
• the support body (8) forms a support surface for the carrier film (4).
• the distance between the edge of the support body (8) and the edge of the circular recess in the TTS preferably corresponds to the distance between its outer edge and the inner wall of the test cell (21).
• the stirring element (9) can preferably be a product as is used as standard for laboratory requirements. It has a smooth and soft surface, e.g. made of Teflon.
• the distance between the two contact surfaces of the stirring element (9) on the carrier film (4) preferably corresponds to the mean value of the outer and inner diameter of the flat structure in the form of the TTS (5). If the test cell (21) is placed on a magnetic stirrer with a support plate, then the stirring element (9) in the test cell (21) can be rotated in a circle around its center.
• the two contact surfaces of the stirring element (9) describe a circular path on the carrier film (4) during the course of the experiment.
• the center of this circular path preferably corresponds to that of the TTS (5).
• magnetic power transmission is dispensed with in favor of a mechanical one (FIG. 3).
• the body that loads the TTS is once again rotated by a shaft (10) fed in from the outside in the form of a dumbbell shape.
• the two end pieces (11) of the stirring element (9) are preferably freely rotatably mounted on its transverse axis (12) so that they can roll over the carrier film (4) when the stirring element (9) rotates.
• the penetration depth of the stirring element (9) into the carrier film (4) can be adjusted via the shaft (10).
• the choice of a circular TTS (5) in connection with the central support body (8) in the lower half of the test cell results in a particularly favorable loading geometry.
• the TTS (5) can be loaded until it completely detaches from the carrier film (4). This detachment process is shown successively by FIGS. 6a to 6c.
• the circular ring shape of the TTS further increases the ratio of the edge zone to the inner surface compared to a full-surface design.
• the ratio between the detaching and the still adhering surface also increases, so that the differentiation capacity of the model increases.
• the circular ring shape reduces the likelihood of central detachments that lie entirely within the area of the TTS and that are not accessible to a preferred quantification technique.
• the material quality of the carrier film is of particular importance for the test result.
• Preferred materials are polymers which have a pronounced elasticity and good water vapor permeability and at the same time are practically insoluble in water. These properties are particularly evident in polyurethanes and ethyl vinyl acetate copolymers, as well as silicone rubbers.
• Polyethylene and polypropylene as well as the block polymers styrene-isobutylene-styrene (SIS) and styrene-butadiene-styrene (SBS) are available with sufficient elasticities.
• SIS styrene-isobutylene-styrene
• SBS styrene-butadiene-styrene
• their water vapor permeability is low and not very suitable for simulating the transpiration of the skin.
• Human or animal skin can also be used as a carrier material for the TTS. This can be used as full skin or in the form of isolated skin
• the transpiration of the skin can be included in the test procedure ⁇ by completely or partially filling the upper part of the test cell (21) with water or an aqueous solution. This is done by first filling the lower half-shell (2) with liquid and assembling the test cell (21) upside down. Then it is turned over so that the liquid comes into contact with the carrier film (4) and covers it in whole or in part.
• the liquid (13), hereinafter referred to as medium A completely covers the carrier film (4) here.
• Preferred liquids are water or isotonic saline.
• the arrangement of FIG. 4 can also be used to simulate the release of low molecular weight substances (molecular weight up to 1000 Da) from the TTS into or through the skin during wearing, provided a carrier film (4) with sufficient diffusibility is used for these substances.
• Substances are to be understood here in particular as active ingredients and permeation enhancers and plasticizers. The latter two groups are available in large numbers for the formulation of TTS and are known to the person skilled in the art. If these substances are poorly soluble in the purely aqueous medium A, other liquids can also be considered. In particular, these are mixtures of water with mono- or polyhydric alcohols, polyethylene glycols or Polyvinyl pyrrolidones. Anionic, cationic, amphoteric or nonionic surfactants can be present as solubilizers. Proteins, preferably human or animal serum albumin, can also be used for this purpose.
• a water-insoluble film which is water-permeable due to micropores (pore diameter below 100 ⁇ m) is used as the carrier.
• Microporous polyethylene or polypropylene film may be mentioned as an example.
• the pores of this film are preferably treated with a hydrophilizing agent in order to facilitate the passage of liquid water.
• the medium A comes into direct contact with the TTS via the pores. This corresponds to sweating on human skin, in which liquid water together with salts from the glands of the skin is released via pores to the surface of the skin.
• this form of water contact leads to a deterioration in the adhesive properties or detachment from the skin in many pressure-sensitive adhesives, with the formation of a moisture film which occurs between the adhesive layer and the skin.
• the TTS can finally be brought into direct contact with liquid (medium B) from the outside during the test.
• Medium B (14) is preferably water or a solution of surfactants in water to simulate the effect of washing, showering, bathing or swimming on the TTS.
• the test is evaluated by quantifying the detached area of the TTS in relation to the total area of the TTS.
• the procedure described below is shown in FIGS. 8a to 8c.
• the carrier film (15) and the still adhering TTS (16) are removed from the test cell at the end of the test.
• the edges of the TTS are drizzled with a dye solution (17) which is able to penetrate into the cavities between the TTS and the carrier film (18) which are caused by detachment.
• the dye must be able to stain either the carrier film or the adhesive layer of the TTS.
• the back layer of the TTS (the layer of the TTS furthest away from the carrier film) must practically not be dyeable with the dye in a short time (5 to 10 minutes). After a short exposure time (5 to 10 minutes), the excess dye solution is wiped off with a cloth.
• the back layer of the TTS is optionally cleaned briefly with the solvent of the dye solution.
• the colored surface of the carrier film which goes beyond the surface of the TTS is removed. This is done by punching away excess carrier film.
• the identical tool with which the TTS was originally shaped serves as the punching tool.
• annular TTS (19) is obtained, some of which adheres to a carrier film of the same geometry. Only the detached surface parts (20) are stained by the dye and are therefore accessible for further evaluation.
• this evaluation is carried out by photocopying the stained TTS on a scale of 1: 1 or another defined scale on paper with a uniform basis weight.
• the colored areas are cut out of the photocopy and their proportion in the total area of the TTS is determined by weighing.
• the image of the stained TTS is done using a commercially available scanner or a Digital camera (CCD camera) generated and brought into computer readable form.
• CCD camera Digital camera
• the ratio of the colored area to the total area and thus the detached portion of the TTS can then be calculated in a computer-aided manner in this image.
• a large number of computer programs are available to the specialist for this purpose (e.g. LECO 2003 from LECO Corporation, Image Analysis Group).
• TTS were investigated which consisted only of a monolithic adhesive layer and a backing layer.
• the backing layer preferably consisted of a transparent film (Hostaphan® RN from Hoechst).
• the test duration was 24 hours.
• the saturated solution of Sudan Red 7B in ethanol was used as the coloring solution.
• the evaluation was carried out using a Sony CCD color camera on a tripod with a connected image processing system LECO 2003 on a conventional PC.
• the uncrosslinked Durotak 1051 acrylic adhesive shows a significantly larger release area than the crosslinked adhesive of the same type (Durotak 1052).
• the moisture sensitivity of these systems was already known from wearing tests. Three of these formulations were still tested on an EVA film and again under the influence of water (now only water vapor). The degree of detachment matched the experience from attempts to wear.
• One of the systems turned out to be particularly bad and had a special effect in the test: the initially cloudy matrix was crystal clear at the end, which demonstrated the water absorption during the test procedure.

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• Physics & Mathematics (AREA)
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• Life Sciences & Earth Sciences (AREA)
• Chemical & Material Sciences (AREA)
• Analytical Chemistry (AREA)
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• General Health & Medical Sciences (AREA)
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• Investigating Or Analysing Biological Materials (AREA)
• Medicinal Preparation (AREA)

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• 1997
  • 1997-04-16 DE DE19715747A patent/DE19715747C2/de not_active Expired - Fee Related
• 1998
  • 1998-03-31 KR KR1019997009589A patent/KR20010006499A/ko not_active Application Discontinuation
  • 1998-03-31 EP EP98919197A patent/EP0975950A1/de not_active Withdrawn
  • 1998-03-31 WO PCT/EP1998/001869 patent/WO1998046980A1/de not_active Application Discontinuation
  • 1998-03-31 AU AU72133/98A patent/AU730861B2/en not_active Ceased
  • 1998-03-31 US US09/403,280 patent/US6308560B1/en not_active Expired - Fee Related
  • 1998-03-31 CA CA002286069A patent/CA2286069A1/en not_active Abandoned
  • 1998-03-31 JP JP54341798A patent/JP2001519034A/ja active Pending
• 1999
  • 1999-10-08 NO NO994935A patent/NO994935D0/no not_active Application Discontinuation

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