An embodiment of the present invention relates to a microneedle sheet used to assist administration of an active component through microneedles.
Microneedles through which an active component is administered via the skin and apparatuses including the microneedles have been known. For example, a rotatable microstructure apparatus disclosed in Patent Literature 1 described below includes a curved base material and a roller structure with a plurality of microelements affixed to a first surface of the base material. The plurality of microelements have a predetermined size and a predetermined shape so as to allow the microstructure apparatus to penetrate the stratum corneum in the skin when the microstructure apparatus is placed on the skin and rolls in a predetermined direction.
However, in the microstructure apparatus described in Patent Literature 1, the microelements are exposed on the roller, and thus, the needles may come into contact with or be caught on another object (for example, a user's skin or clothes) before the active component is applied to the skin via the microneedles. Thus, there has been a demand to ensure safety in handling of the microneedles.
A microneedle sheet according to an embodiment of the present invention comprises a plurality of microneedles formed on a sheet substantially along a principal surface of the sheet, wherein the sheet is bent to raise the microneedles from the principal surface, and the raised microneedles pierce a skin.
In such an embodiment, the microneedles are kept substantially along the principal surface of the sheet until the sheet is bent. This means that tips of the microneedles do not stick out from the principal surface before the microneedles are applied to the skin. Thus, the microneedles are prevented from coming into contact with or being caught on another object unless the microneedle sheet is applied to the skin. As a result, the safety in handling of the microneedles can be ensured.
In the microneedle sheet according to another embodiment, the sheet may be bent when a part of the sheet which does not contact the skin comes into contact with the skin, and the microneedles positioned in the part may rise from the principal surface. In this case, the microneedles rise from the principal surface immediately before the microneedles pierce the skin. Therefore, the safety in handling of the microneedles can be ensured.
Moreover, in the microneedle sheet according to yet another embodiment, the microneedles may be formed in lines extending along a direction orthogonal to a direction in which the sheet is guided to the skin, and the sheet may be guided to the skin to raise the microneedles line by line. Raising the microneedles line by line in this manner allows the microneedles on the sheet to be reliably raised before the microneedles pierce the skin.
In the microneedle sheet according to yet another embodiment, a maximum angle between the microneedle raised from the principal surface and a virtual line from a center of curvature of the sheet to a root of the microneedle may be larger than 90 degrees. In this case, the length of a part of the microneedle which pierces the skin increases, thus enhancing the cutaneous permeability of the active component.
In the microneedle sheet according to yet another embodiment, the maximum angle may be 95 to 130 degrees. In this case, the length of a part of the microneedle which pierces the skin increases, thus enhancing the cutaneous permeability of the active component.
In the microneedle sheet according to yet another embodiment, a ratio of a length of the microneedle to the radius of curvature of the sheet may be higher than 0.20. Setting the relation between the radius of curvature of the sheet and the length of the microneedle in this manner allows the microneedles to reliably pierce the skin.
In the microneedle sheet according to yet another embodiment, a puncture angle of the raised microneedle to the skin may be at least 34 degrees and smaller than 180 degrees.
In the microneedle sheet according to yet another embodiment, the sheet may be shaped like a band.
In the microneedle sheet according to yet another embodiment, the microneedle sheet can be used with another percutaneous absorption promotion technique, and the other percutaneous absorption promotion technique may include at least one of electricity, pressure, magnetic field, and ultrasonic wave.
According to an aspect of the present invention, the safety in handling of the microneedles can be ensured.
Embodiments of the present invention will be described below in detail with reference to the drawings. In the description of the drawings, identical or similar elements are denoted by identical reference, and duplicate descriptions are omitted.
The structures of a puncture apparatus 10 and a microneedle sheet 20 according to a first embodiment will be described using
First, the puncture apparatus 10 will be described. As depicted in
In the specification, a side of the puncture apparatus 10 which faces upward (the upper side in
A leading end of the acting portion 11 functions as a bending portion 14 used to bend the microneedle sheet 20. As depicted in
A plurality of guide portions 15 is provided on the outside of the acting portion 11, the gripping portion 12, and the intermediate portion 13 to guide the microneedle sheet 20 to the bending portion 14 while holding the microneedle sheet 20 along an outer surface of the puncture apparatus 10. The guide portions 15 are arranged at predetermined intervals along a longitudinal direction of the acting portion 11, the gripping portion 12, and the intermediate portion 13. In the first embodiment, each of the guide portions 15 is formed using a pair of inverted L-shaped members disposed opposite each other in a width direction of the puncture apparatus 10. Of course, the structure of the guide portions 15 is subject to no limitation, and the guide portions 15 may be configured using any mechanical means or control means.
Now, the microneedle sheet 20 will be described. As depicted in
Materials for the microneedle sheet 20 and the microneedles 22 are not limited. For example, the microneedle sheet 20 and the microneedles 22 may be produced using any of the materials such as stainless steel, polyethylene terephthalate (PET), another metal, another resin, a biodegradable material, a ceramic, and a bioabsorbable material. Alternatively, the microneedle sheet 20 and the microneedles 22 may be produced using a combination of these materials.
The microneedles 22 may be formed by etching. The microneedles 22 may be formed by punching a sheet with a chemical when the sheet is metal or by punching a sheet with a laser when the sheet is nonmetal. In these cases, a void is created around each of the microneedles 22. Of course, the microneedles 22 may be formed by means of a technique other than etching. As depicted in
The dimensions of the microneedle sheet 20 are also not limited. Specifically, a lower limit for thickness may be 5 μm or 20 μm, and an upper limit for thickness may be 1000 μm or 300 μm. A lower limit for length may be 0.1 cm or 1 cm, and an upper limit for length may be 50 cm or 20 cm. A lower limit for width may be 0.1 cm or 1 cm, and an upper limit for width may be 60 cm or 30 cm. The lower limits for the length and width of the microneedle sheet 20 are set taking into account the amount of active component administered. The upper limits for the length and width are set taking the size of the living body into account.
Parameters for the microneedles 22 are also not limited. Specifically, a lower limit for the height of the needle may be 10 μm or 100 μm, and an upper limit for the height of the needle may be 10000 μm or 1000 μm. A lower limit for the density of the needles may be 0.05/cm2 or 1/cm2, and an upper limit for the density of the needles may be 10000/cm2 or 5000/cm2. The lower limit for the density results from conversion of the number and area of needles through which 1 mg of active component can be administered. The upper limit for the density is a limit value set taking the shape of the needle into account.
The dimensions of the puncture apparatus 10 may be determined in accordance with the dimensions of the microneedle sheet 20. For example, the length of the puncture apparatus 10 (the sum of lengths of the acting portion 11, the intermediate portion 13, and the gripping portion 12) along an outer surface thereof may be equal to or smaller than the length of the microneedle sheet 20.
Possible methods for preparing an active component applied to the skin include a technique for pre-coating the active component on the microneedle sheet 20 itself, a technique for applying the active component onto the skin before the microneedles 22 pierce the skin, and a technique for applying the active component onto the skin after the microneedles 22 pierce the skin. When the active component is pre-coated on the microneedle sheet 20, a coating liquid with a predetermined viscosity is preferably applied all over the sheet to as uniform a thickness as possible. Since the microneedles 22 lie along the principal surface 21, such application can easily achieved. The coating may be performed using the principle of screen printing or any other method. When a biodegradable sheet is used, the active component may be contained in the sheet itself.
Now, using
Subsequently, as depicted
In this regard, the microneedles 22 that rise at a time are a line of microneedles 22 along a width direction (orthogonal to a direction in which the microneedle sheet 20 is guided). The angle between the each of the raised microneedles 22 and the principal surface 21 is obviously larger than 0 degrees and smaller than 180 degrees.
A puncture angle θ (the angle between each of the microneedles 22 and the skin S) at which the microneedles 22 with a height h raised from the principal surface 21 as depicted in
The value r in
Increasing the ratio (h/r) of a needle length h to the radius of curvature r above 0.20 enables the microneedles 22 to reliably pierce the skin S.
When the user moves the puncture apparatus 10 on the skin by a desired distance, the plurality of microneedles 22 within the range of the distance pierce the skin. Thus, the user can adjust the area of application of the microneedle sheet 20 to administer a desired amount of active component.
As described above, according to the first embodiment, the microneedles 22 remain extending substantially along the principal surface 21 of the sheet until the microneedle sheet 20 is bent by the bending portion 14 of the puncture apparatus 10. This means that the tips of the microneedles 22 do not stick out from the principal surface 21. Thus, unless the puncture apparatus 10 is used, the microneedles 22 are prevented from coming into contact with or being caught on another object (for example, the user's skin or clothes). As a result, the safety in handling of the microneedles 22 can be ensured. For example, the user can safely store and convey the microneedle sheet 20 and prepare the microneedle sheet 20 before use.
In this regard, the microneedle sheet 20 is thin and flexible and can thus be applied to the skin in accordance with the shape of the living body. As a result, the active component can be efficiently administered.
Furthermore, instead of exerting an impact on the microneedle sheet 20, the puncture apparatus 10 raises and pushes the microneedles 22 into the skin to allow the needles 22 to pierce the skin. Thus, the active component can be administered to the patient without offering a feeling of fear to the patient.
In the first embodiment, the guide portions 15 guide the microneedle sheet 20 to the bending portion 14 to gradually raise the microneedles 22, thus allowing adjustment of the range of application of the microneedles 22 to the skin. Furthermore, such guidance of the microneedle sheet 20 can be achieved by an easy operation of moving the bending portion 14 forward on the skin. Moreover, since the microneedles 22 rise one line at a time, each of the microneedles 22 on the microneedle sheet 20 can be reliably raised and pierce the skin.
In the first embodiment, the leading end of the bending portion 14 is round. Thus, when the microneedle sheet 20 is bent, pressure from the bending portion 14 is not concentrated at a particular position on the sheet 20. Therefore, when applied, the microneedle sheet can be more reliably prevented from being damaged. Furthermore, since the bending portion 14 is tapered as described above, the user can smoothly move the bending portion 14 forward on the skin. As a result, the microneedle sheet 20 can be easily applied.
Using
The base material 30 and the release film 40 are the same in shape and size. The length and width of these two members are larger than the length and width, respectively, of the microneedle sheet 20. Of course, the shapes of the base material 30 and the release film 40 may be optionally determined. Furthermore, the sizes of the base material 30 and the release film 40 may be optionally set. For example, the base material 30 and release film 40 may be used each of which has the same length and width as the length and width of the microneedle sheet 20.
Using
Then, microneedles 22 positioned in a bent portion of the microneedle sheet 20 rise line by line from a principal surface 21 of the sheet. The raised microneedles 22 pierce the skin S one after another. The angle between each of the raised microneedles 22 and the principal surface 21 and the puncture angle at which the microneedles 22 pierce the skin are similar to the corresponding angles in the first embodiment. In the second embodiment, the user can adjust the area of application of the microneedle sheet 20 to administer a desired amount of active component.
The second embodiment allows effects similar to the effects of the first embodiment to be exerted. Specifically, the microneedles 22 remain extending substantially along the principal surface 21 of the sheet until the microneedle sheet 20 is bent directly by the user. Thus, unless the microneedle sheet 20 is applied to the skin, the microneedles 22 are prevented from coming into contact with or being caught on another object. As a result, the safety in handling of the microneedles 22 can be ensured. Furthermore, the microneedle sheet 20 can be applied to the skin in accordance with the shape of the living body, and the microneedles 22 can be raised line by line to allow reliable puncture, as is the case with the first embodiment.
The present invention will be specifically described below based on examples. However, the present invention is not limited to the examples.
Experiments were conducted in which a gel sheet was used as an alternative to the skin and in which the microneedles of the microneedle sheet pierce the gel sheet. Specifically, a cylindrical thin rod (hereinafter referred to as a “cylindrical rod”) R was placed along the width direction of the microneedle sheet 20. The microneedle sheet 20 was folded back using the cylindrical rod R to raise triangular microneedles 22. Moreover, the cylindrical rod R was moved along an upper surface of the gel sheet G to allow the microneedles 22 to pierce the gel sheet G.
In Example 1, the relation between a rising angle and a puncture length was observed. The rising angle refers to the maximum angle between the microneedle raised from the principal surface of the microneedle sheet by folding back the microneedle sheet and a virtual line from the center of rotation of the cylindrical rod to a root of the microneedle. The rising angle is synonymous with an angle φ in
Three types of microneedle sheets were prepared which were 5 μm, 10 and 20 μm, respectively, in thickness. The lengths of the three microneedle sheets were all 500 μm. On the other hand, two types of cylindrical rods were prepared which were 1.2 mm and 2.0 mm, respectively, in diameter. Thus, the combination of the microneedle sheet and the cylindrical rod had six patterns.
In this example, the relation between the ratio of the length of the microneedle to the radius of curvature (hereinafter referred to as the “needle length/radius of curvature ratio”) and the puncture angle and puncture length was observed. As is the case with Example 1, in this example, experiments were performed using a gel sheet as an alternative to the skin. The manner of raising triangular microneedles and the puncture method were similar to the corresponding manner and method in Example 1 (see
For the microneedle sheet, six patterns were prepared which were combinations of two types of thickness (10 μm and 20 μm) and three type of needle length (200 μm, 250 μm, and 500 μm). Two types of cylindrical rods were prepared which were 1.2 mm and 2.0 mm, respectively, in diameter. The needle length/radius of curvature ratio involves the combinations of three types of needle length and two types of radius of curvature (0.6 mm and 1.0 mm) and thus has a total of six patterns as illustrated below.
0.5/0.6≈0.83
0.5/1.0=0.50
0.25/0.6≈0.42
0.2/0.6≈0.33
0.25/1.0=0.25
0.2/1.0=0.20
The results depicted in
The present invention has been described in detail based on the embodiments thereof. However, the present invention is not limited to the above-described embodiments. Many variations may be made to the present invention within a scope not departing from the spirit thereof.
In connection with the above-described first embodiment, when an element corresponding to the bending portion 14 is provided, the shape and structure of the puncture apparatus are subject to no limitation. For example, the puncture apparatus may be shaped like a single linear rod. Alternatively, the puncture apparatus may include any mechanical, electrical, or electronic structure or control means.
The shape of the microneedle sheet is not limited to a band-like shape. For example, the microneedle sheet may be a rectangle with a length and a width that are substantially the same, or a circle or an ellipse. In connection with the above-described first embodiment, means with functions similar to the functions of the guide portions 15, that is, a structure or control means that guides the microneedle sheet to the bending portion, may be omitted depending on the shape of the microneedle sheet.
In connection with the above-described second embodiment, the microneedle sheet 20 may be independently used, and thus, the base material 30 and the release film 40 are not indispensable.
The microneedle sheet according to the present invention can be used with another percutaneous absorption promotion technique such as electricity (iontophoresis), pressure, magnetic field, or ultrasound (sonophoresis). The use of the microneedle sheet with such another technique enables a further increase in the amount of drug absorbed.
10 . . . puncture apparatus, 11 . . . acting portion, 12 . . . gripping portion, 13 . . . intermediate portion, 14 . . . bending portion, 15 . . . guide portion, 20 . . . microneedle sheet, 21 . . . principal surface, 22 . . . microneedle, 30 . . . base material, 31 . . . affixing surface, 40 . . . release film.
Number | Date | Country | Kind |
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2012-133214 | Jun 2012 | JP | national |
Filing Document | Filing Date | Country | Kind |
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PCT/JP2013/066039 | 6/11/2013 | WO | 00 |