Microneedle array, patch, and production method for microneedle array

Abstract

A microneedle array 1 has a plurality of microneedles 11 and is to be used as an acupuncture needle for acupuncture therapy. The length of the microneedles 11 of the microneedle array 1 is 250–1500 μm, and the tip strength of the microneedles 11 measured as the maximum value of the stress that occurs at the microneedles 11 when a compressive load is applied to tip parts of the microneedles 11 in the length direction is at least 50 mN. This microneedle array 1 makes it possible to achieve excellent acupuncture therapy effects.

Description

Micro needle array, patch, and method for manufacturing micro needle array

[0001] The present invention relates to a micro needle array used as an acupuncture needle in acupuncture treatment.

[0002] Acupuncture treatment is generally performed for the purpose of improving chronic pain in the body such as shoulder stiffness and low back pain, and promoting recovery from injuries. As a type of acupuncture treatment, there is a technique in which a micro needle is used to stimulate the affected area to bring about a therapeutic effect.

[0003] For example, Patent Document 1 discloses a contact needle in which a large number of convex portions are formed on one side of a substrate. In the contact needle, each of the convex portions has a predetermined elasticity and gives a stimulus to the skin without invading the skin. Further, Patent Document 2 discloses a needle including a plate-like pedestal having a through hole in the central portion, and a needle body inserted into the through hole of the pedestal and fixed in a state where the needle tip on the tip side protrudes from the surface of the pedestal and the base end side is cut on the back side of the pedestal. The needle gives a stimulus to the skin by shallowly inserting a single needle body into the skin.

[0004] JP-A-2008-259552 JP-A-2008-113714

[0005] However, the conventional techniques using the micro needles disclosed in Patent Documents 1 and 2 cannot be said to obtain a sufficient therapeutic effect, and an excellent technique with a higher therapeutic effect is required.

[0006] The present invention has been made in view of such a situation, and an object thereof is to provide a micro needle array that brings about an excellent effect of acupuncture treatment.

[0007] To achieve the above objective, firstly, the present invention provides a microneedle array having a plurality of microneedles and used as an acupuncture needle in acupuncture treatment, characterized in that the length of the microneedles is 250 μm or more and 1500 μm or less, and the tip strength of the microneedles, measured as the maximum value of stress generated in the microneedles when a compressive load is applied to the tip of the microneedles in the longitudinal direction, is 50 mN or more (Invention 1).

[0008] In the above invention (Invention 1), it is preferable that the number of microneedles having a length of 250 μm or more and 1500 μm or less is 500 or less (Invention 2).

[0009] In the above inventions (Inventions 1 and 2), it is preferable that the microneedles are made of a biosafe resin material (Invention 3).

[0010] In the above invention (Invention 3), it is preferable that the biosafe resin material is a water-insoluble biodegradable material (Invention 4).

[0011] In the above invention (Invention 4), the biodegradable material is preferably a copolymer containing polycaprolactone or caprolactone as a monomer (Invention 5).

[0012] In the above inventions (inventions 1 to 5), the shape of the microneedle is preferably a pyramidal or conical shape (invention 6).

[0013] In the above inventions (inventions 1 to 6), the shape of the group of microneedles when viewed from one side of the microneedle array is preferably hexagonal, octagonal, or decagonal (invention 7).

[0014] In the above inventions (Inventions 1 to 7), it is preferable that the microneedle does not have a flow channel inside (Invention 8).

[0015] Secondly, the present invention provides a patch comprising an adhesive sheet and the microneedle array (Inventions 1 to 8) laminated in the central part of one side of the adhesive sheet (Invention 9).

[0016] Thirdly, the present invention provides a method for manufacturing the microneedle array (Inventions 1 to 8), which includes preparing a mold having recesses corresponding to the microneedles, injecting molten material into the mold, and solidifying it by cooling to obtain a microneedle array equipped with the microneedles (Invention 10).

[0017] The microneedle array according to the present invention provides excellent results for acupuncture treatment.

[0018] This is a cross-sectional view of a patch for acupuncture treatment equipped with a microneedle array according to one embodiment of the present invention. This is an enlarged cross-sectional view of a part of the microneedle array according to one embodiment of the present invention. This is a plan view of a patch for acupuncture treatment equipped with a microneedle array according to one embodiment of the present invention.

[0019] Embodiments of the present invention will be described below. The microneedle array according to this embodiment has a plurality of microneedles and is used as an acupuncture needle in acupuncture treatment.

[0020] Furthermore, the length of the microneedle is between 250 μm and 1500 μm. In addition, the tip strength of the microneedle, measured as the maximum stress generated in the microneedle when a compressive load is applied to its tip in the longitudinal direction, is 50 mN or more.

[0021] The microneedles in this embodiment have a length of 250 μm or more and a tip strength of 50 mN or more, so that when the microneedle array according to this embodiment is attached, it penetrates the skin well. Furthermore, because the microneedle array according to this embodiment has multiple such microneedles, it can provide sufficient stimulation to the skin and generate a good axon reflex in the body. In other words, the microneedle array according to this embodiment can exhibit excellent therapeutic effects when used as an acupuncture needle in acupuncture treatment.

[0022] On the other hand, while some conventional acupuncture treatment products have multiple microneedles, each of them lacks sufficient tip strength to penetrate the skin, and as a result, they fail to provide sufficient stimulation to the skin. Furthermore, while some conventional products have only one microneedle with sufficient tip strength, the single microneedle also fails to provide sufficient stimulation. In contrast to these, the microneedle array according to this embodiment has multiple microneedles, each capable of penetration, thus providing sufficient stimulation to the skin and, as a result, exhibiting superior therapeutic effects.

[0023] As described above, the microneedle array according to this embodiment is used as an acupuncture needle in acupuncture treatment, and is suitably used, for example, as one of the components constituting a patch for acupuncture treatment. Figure 1 shows an example of such a patch as a cross-sectional view. As shown in the figure, the patch 100 comprises an adhesive sheet 2, a microneedle array 1, and a release sheet 3. The microneedle array 1 comprises a plurality of microneedles 11. The microneedle array 1 and the patch 100 will be described in detail below.

[0024] 1. Configuration of the microneedle array (1) Dimensions of the microneedles, etc. The dimensions and physical properties of the microneedles 11 in this embodiment are not particularly limited as long as they satisfy the length and tip strength conditions described above.

[0025] As mentioned above, the tip strength of the microneedle 11 in this embodiment is 50 mN or more, but from the viewpoint of making it easier to penetrate the skin, the tip strength is preferably 60 mN or more, and particularly preferably 70 mN or more. The upper limit of the tip strength may be, for example, 1000 mN or less, particularly 800 mN or less, and even 500 mN or less. Details of the method for measuring the tip strength are described in the test examples below.

[0026] The shape of the microneedle 11 in this embodiment is not particularly limited, but from the viewpoint of having a sharp tip and being easy to insert into the skin, it is preferably a pyramidal or conical shape, and from the viewpoint of being easy to form, it is particularly preferably a conical shape. In the case of a pyramidal shape, for example, it may be a triangular pyramidal, square pyramidal, pentagonal pyramidal, hexagonal pyramidal, etc. When the shape of the microneedle 11 has a sharp tip as described above, it is preferable that the microneedle 11 be made of a water-insoluble biodegradable material, as described later, so that the tip does not dissolve in biological fluids.

[0027] Figure 2 is an enlarged cross-sectional view of a part of the microneedle array 1 according to this embodiment. In Figure 2, the length of the microneedle 11 is indicated as "L", the width of the base of the microneedle 11 (or the diameter of the base if the shape of the microneedle 11 is cone-shaped) is indicated as "D", and the distance between the vertices of adjacent microneedles 11 (pitch) is indicated as "P".

[0028] As described above, the length L of the microneedle 11 in this embodiment is 250 μm or more and 1500 μm or less. However, from the viewpoint of facilitating insertion into the skin, the length L is preferably 300 μm or more, and particularly preferably 450 μm or more. Furthermore, from the viewpoint of reducing invasiveness to the skin, the length L of the microneedle 11 is preferably 1200 μm or less, and particularly preferably 900 μm or less. The length L of the microneedle 11 can be measured, for example, as shown in the test example described later.

[0029] In this embodiment, the width (diameter) D of the base of the microneedle 11 is preferably 150 μm or more, more preferably 200 μm or more, and even more preferably 450 μm or more, from the viewpoint of easily satisfying the tip strength conditions described above. Furthermore, the width (diameter) D is preferably 1500 μm or less, more preferably 1250 mm or less, and even more preferably 1000 mm or less, from the viewpoint of easily maintaining a sharp tip of the microneedle 11. The width (diameter) D of the base of the microneedle 11 can be measured, for example, as shown in the test example described later.

[0030] In this embodiment, the pitch P of the microneedle 11 is preferably 300 μm or more, more preferably 500 μm or more, and even more preferably 700 μm or more, from the viewpoint of facilitating penetration into the skin. Furthermore, the pitch P is preferably 3000 μm or less, more preferably 2500 μm or less, and even more preferably 2000 μm or less, from the viewpoint of maintaining the density of the microneedle 11 and facilitating sufficient stimulation of the skin. The pitch P of the microneedle 11 can be measured, for example, as shown in the test example described later.

[0031] In the microneedle array 1 according to this embodiment, the number of microneedles 11 that satisfy the condition of having a length of 250 μm or more and 1500 μm or less is preferably 2 or more, more preferably 5 or more, particularly preferably 10 or more, and even more preferably 25 or more, from the viewpoint of easily providing sufficient stimulation to the skin. Furthermore, the above number is preferably 500 or less, more preferably 300 or less, particularly preferably 200 or less, and even more preferably 100 or less, from the viewpoint of easily reducing invasiveness to the skin.

[0032] While there are no particular restrictions on the arrangement of the microneedles 11 in the microneedle array 1 according to this embodiment, it is preferable that the shape of the group of microneedles 11, when viewed from one side of the microneedle array 1, be polygonal or circular, from the viewpoint of easily providing sufficient stimulation to the skin. If it is polygonal, for example, it may be a square, hexagon, octagon, etc. If the shape of the group of microneedles 11 is a shape that differs greatly from a circle, such as a square, the force applied to the microneedles 11 near the vertices may be weak when attempting to insert the microneedles 11 into the skin by pressing with a finger. Therefore, from the viewpoint of more efficiently inducing axonal reflex, it is preferable that the shape of the group of microneedles 11 be hexagonal, octagonal, or decagonal, and from the above viewpoint and because the shape is not too complex, it is particularly preferable to be octagonal.

[0033] When arranging the microneedles 11 in an octagonal shape, for example, the arrangement shown in Figure 3 can be considered. Figure 3 is a plan view of a patch 100 equipped with the microneedle array 1 according to this embodiment, viewed from the microneedle array 1 and the release sheet 3 side. In the illustrated microneedle array 1, the microneedles 11 are divided into seven rows and arranged at equal intervals, with three in the first row, five in the second row, seven each in the third to fifth rows, five in the sixth row, and three in the seventh row, for a total of 37 microneedles 11.

[0034] (2) Materials of the microneedle array, etc. The microneedle array 1 according to this embodiment is not particularly limited in terms of materials, as long as it comprises a plurality of microneedles 11 having the length and tip strength described above. However, from the viewpoint of easily reducing adverse effects on living organisms, it is preferable that at least the microneedles 11 are made of a biosafe resin material, and it is even preferable that the entire microneedle array 1 is made of a biosafe resin material.

[0035] Examples of biosafe resin materials include polyvinyl alcohol, which is used as a thickener in eye drops, and materials used as cosmetic ingredients such as hyaluronic acid and its derivatives.

[0036] Another example of a biosafe resin material is a biodegradable material. Biodegradable materials are preferable because they decompose even if a part of the microneedle 11 remains in the body. Biodegradable materials include water-soluble and water-insoluble types, but from the viewpoint of easily avoiding the possibility of dissolution by bodily fluids at the tip of the microneedle 11 while it is inserted into the body, water-insoluble biodegradable materials are preferred. Examples of water-insoluble biodegradable materials include polylactic acid, polyglycolic acid, polycaprolactone, and resins obtained by copolymerizing monomers used in the synthesis of these polymers (such as polylactic acid / glycolic acid copolymers).

[0037] Furthermore, from the viewpoint of ease of molding at low temperatures, it is also preferable to use polycaprolactone or copolymers containing caprolactone as a monomer. Examples of copolymers containing caprolactone as a monomer include copolymers of monomers that serve as raw materials for biodegradable resins, such as copolymers of caprolactone and lactic acid.

[0038] (3) In addition, it is preferable that the microneedle 11 in this embodiment does not have a flow channel inside. The absence of a flow channel inside the microneedle 11 makes it easier to achieve the tip strength described above. More specifically, it is preferable that the microneedle 11 in this embodiment is not porous and does not have a hollow structure like an injection needle.

[0039] 2. Method for Manufacturing a Microneedle Array The method for manufacturing the microneedle array 1 according to this embodiment is not particularly limited as long as a plurality of microneedles 11 having the length and tip strength described above can be formed. For example, a mold can be prepared that has recesses corresponding to the microneedles 11, molten material can be placed and poured into the mold, pressure can be applied as needed, and then the material can be solidified by cooling to obtain a microneedle array 1 with the desired microneedles 11.

[0040] 3. Applications of the Microneedle Array As described above, the microneedle array 1 according to this embodiment is used as an acupuncture needle in acupuncture treatment, but the specific manner in which it is used for this purpose is not particularly limited.

[0041] A preferred embodiment is a patch 100 equipped with a microneedle array 1. Figure 1 shows a cross-sectional view of the patch 100. As shown in the figure, the patch 100 comprises an adhesive sheet 2, a microneedle array 1 laminated in the central part of one side of the adhesive sheet 2, and a release sheet 3 laminated in the peripheral part of one side of the adhesive sheet 2. In particular, in the patch 100, the microneedle array 1 is provided such that the side equipped with microneedles 11 faces the release sheet 3.

[0042] The adhesive sheet 2 further comprises an adhesive layer (not shown) provided on the side facing the microneedle array 1. This adhesive layer allows the adhesive sheet 2 to adhere to the microneedle array 1 and facilitates the fixation of the patch 100 to the skin during use. The adhesive used in the adhesive layer can be an acrylic adhesive, silicone adhesive, rubber adhesive, urethane adhesive, polyester adhesive, polyvinyl ether adhesive, or the like. Furthermore, it is preferable that the adhesive is biocompatible.

[0043] Figure 3 shows a plan view of the patch 100 as viewed from the side of the release sheet 3. As shown in the figure, the release sheet 3 has an annular shape, and the release sheet 3 is provided so as not to cover at least the portion where the micro needles 11 in the micro needle array 1 are present. Note that the release sheet 3 may be provided so as to overlap the peripheral edge portion (a part of the base portion) of the micro needle array 1 as shown in FIG. 1.

[0044] When the patch 100 in the present embodiment is used for acupuncture treatment, first, the release sheet 3 is peeled off and removed, and the patch 100 is attached so that the micro needle array 1 (particularly the portion of the micro needles 11) contacts the affected area. If necessary, the patch 100 may be pressed with a finger or the like to apply pressure, or further, the needle may be twirled (the patch 100 is moved along a circular orbit). The time for attaching the patch 100 can be set as appropriate. By attaching the patch 100, sufficient stimulation is brought to the affected area, the axon reflex occurs well, and as a result, an excellent therapeutic effect can be obtained.

[0045] The adhesive sheet 2 is not particularly limited as long as it can fix the micro needle array 1, and the same adhesive sheet as that used for conventional acupuncture treatment patches can be used. For example, the adhesive sheet 2 may be made of a non-woven fabric, a resin sheet, or the like as a base material, and among them, it is preferably made of a non-woven fabric as a base material.

[0046] The release sheet 3 is not particularly limited as long as it can protect the attachment site of the release sheet 3 on the adhesive sheet 2 until the patch 100 is used, and the same release sheet as that used for conventional acupuncture treatment patches can be used. For example, the release sheet 3 may be release paper, a resin release film, or the like, and among them, it is preferably release paper.

[0047] The embodiments described above are described to facilitate the understanding of the present invention, and are not described to limit the present invention. Therefore, each element disclosed in the above embodiments is intended to include all design changes and equivalents belonging to the technical scope of the present invention.

[0048] Hereinafter, the present invention will be described more specifically by way of examples and the like, but the scope of the present invention is not limited to these examples and the like.

[0049] [Example 1] (1) Preparation of Materials As a resin for forming a microneedle array, 1.5 g of pellet-shaped polycaprolactone (weight average molecular weight: 50,000, melting point: 60 ° C) was prepared.

[0050] The above weight average molecular weight (Mw) is the weight average molecular weight in terms of standard polystyrene measured under the following conditions (GPC measurement) using gel permeation chromatography (GPC). <Measurement Conditions> - Measuring device: HLC-8320 manufactured by Tosoh Corporation - GPC column (passed in the following order): TSK gel superH-H manufactured by Tosoh Corporation TSK gel superHM-H TSK gel superH2000 - Measuring solvent: Tetrahydrofuran - Measuring temperature: 40 ° C

[0051] (2) Formation of the Base Material On the lower stage of a hot press machine (manufactured by AS ONE Corporation, product name "AH-1T"), an 11 cm × 11 cm square stainless steel plate, a release film sized to fit the stainless steel plate, and a stainless steel plate of the same size with a hole in the center were placed in order. Here, the release film was placed on the stainless steel plate with the release surface facing up. The stainless steel plate with the hole had a square hole with sides of 8 cm and a thickness of 1.5 mm. Then, the above-mentioned pellet-shaped polycaprolactone was placed on the release treatment surface of the release film exposed from the hole. [[ID=...]] [[ID=...]]

[0052] Subsequently, as a preliminary step, the lower stage was heated at a set heating temperature of 120 ° C for 3 minutes to melt the polycaprolactone. The polycaprolactone became transparent from a turbid state when melted. Subsequently, while heating the upper stage at a set heating temperature of 110 ° C, a pressure of 2 MPa was applied and the melted polycaprolactone was pressed for 30 seconds.

[0053] Subsequently, in the main process, the polycaprolactone was compressed by applying a pressure of 10 MPa while the lower and upper stages were heated to the same temperature as in the preliminary process. In this process, after the pressure reached 10 MPa, the pressure was released without maintaining that state.

[0054] After pressing, the polycaprolactone, along with the stainless steel plate containing it, was removed from the heated press and solidified by refrigeration at 3°C ​​for 5 minutes. This yielded a polycaprolactone base material formed into a perfect circle with a diameter of 8 cm and a thickness of 1.5 mm.

[0055] (3) Preparation of the mold A mold made of polydimethylsiloxane and having multiple recesses for forming microneedles was prepared as a mold for heating and pressing.

[0056] The details of the individual recesses provided in the above mold are as follows: • Recess shape: Conical (the cross-section when cut perpendicular to the depth direction is a perfect circle) • Recess depth: 600 μm • Maximum cross-sectional diameter of the recess (diameter of the cross-section at depth 0 μm): 300 μm

[0057] Furthermore, the arrangement of the recesses corresponds to the arrangement of the microneedles 11 shown in Figure 3. That is, when the mold is viewed from above, the 37 recesses are arranged in an octagonal shape. In particular, these recesses are divided into seven rows and arranged at equal intervals, with 3 recesses in the first row, 5 in the second row, 7 each in the third to fifth rows, 5 in the sixth row, and 3 in the seventh row. The pitch between adjacent recesses is 1000 μm, resulting in a distance of 6.3 mm from the first to the seventh row. The mold consists of a total of nine sets of these 37 recesses, arranged in a 3x3 grid.

[0058] (4) Formation of the microneedle array The polycaprolactone base material obtained in step (2) was placed on the surface of the mold prepared in step (3) in which the recesses were formed, and a 100 mm square sheet (lid) made of polydimethylsiloxane was placed on top of it.

[0059] Then, with the mold, base material, and sheet secured using masking tape to prevent shifting, they were placed on the heating press used in step (2) above. As a preliminary step, the lower stage was heated to 115°C and the upper stage to 105°C, while applying a pressure of 2 MPa for 1 minute and 30 seconds. Subsequently, as the main step, a pressure of 4 MPa was applied for 30 seconds. After that, the base material, along with the mold, was removed from the heating press and solidified by refrigeration at 3°C ​​for 5 minutes.

[0060] As a result, multiple microneedles were formed on the surface of the base material. More specifically, a base material was obtained in which a cluster of 37 microneedles, positioned at locations corresponding to the aforementioned recesses, was provided at nine locations.

[0061] Then, a microneedle array was obtained by cutting out a region containing one of the microneedle clusters (a circular region with a diameter of 10 mm, where the microneedle cluster is located in the center) from the base material.

[0062] (5) A nonwoven fabric (circular shape, diameter: 18 mm) with a biosafe adhesive applied to one side was used as the adhesive sheet for forming the patch. The side of the microneedle array obtained in step (4) that was opposite to the side on which the microneedles were formed was attached to the center of the adhesive-coated surface. Furthermore, a release sheet (release paper) cut to the same shape (annular) as the adhesive-coated surface was attached to the area of ​​the adhesive-coated surface where the microneedle array was not attached. This resulted in obtaining a patch for acupuncture treatment.

[0063] [Examples 2-4] Patches for acupuncture treatment were obtained in the same manner as in Example 1, except that the maximum diameter and pitch of the cross-section in the recess of the mold were changed as shown in Table 1.

[0064] [Comparative Example 1] A microneedle patch made of elastomer resin (product name "Somarezon L"), commercially available from Toyo Resin Co., Ltd., was used as Comparative Example 1. This product is equipped with multiple fine protrusions made of elastomer resin.

[0065] [Comparative Example 2] A microneedle patch made of plastic resin (product name "Somacept L"), commercially available from Toyo Resin Co., Ltd., was used as Comparative Example 1. This product is equipped with multiple fine protrusions made of a relatively hard resin.

[0066] [Test Example 1] (Measurement of Microneedle Dimensions, etc.) For the microneedle arrays manufactured in Examples 1 to 4 and the products used in Comparative Examples 1 to 2, the length of the microneedle ("L" in Figure 2), the diameter of the base ("D" in Figure 2), and the pitch ("P" in Figure 2) were measured. Specifically, after photographing the microneedles of each example with a digital optical microscope, the above dimensions were measured based on the obtained images. The results are shown in Table 1.

[0067] Although the microneedles used for measurement were selected arbitrarily, visual inspection using a digital optical microscope revealed no dimensional differences between the selected and unselected microneedles in any of the cases.

[0068] [Test Example 2] (Measurement of Tip Strength) The tip strength of the microneedles in the microneedle arrays manufactured in Examples 1 to 4 and the products used in Comparative Examples 1 to 2 was measured.

[0069] Specifically, the microneedle array prepared in the example and the product used in the comparative example were placed on the microscope stage with the microneedles facing upwards, and one microneedle with a sharp tip shape was selected by observation. Then, the attachment (made of iron, 2 mm in diameter) of the measuring instrument (manufactured by Imada Corporation, product name "Digital Force Gauge") was brought close to the selected microneedle. At this time, care was taken to ensure that the attachment did not come into contact with the microneedles surrounding the selected microneedle. Furthermore, the vertical position of the attachment was moved to a position where it contacted the tip of the selected microneedle, but no force was applied to the tip.

[0070] Next, the attachment was raised 0.1 mm vertically, and then lowered at a descent rate of 5 mm / min while measuring the stress on the attachment (measurement range: 1 to 5000 mN). At this time, the measurement temperature was 23°C and the relative humidity was 50%.

[0071] Normally, as the attachment is lowered, the stress increases from the moment the attachment contacts the selected area, but a decrease in stress is observed at the moment of fracture at the tip. The stress value (maximum value) at the boundary between this increase and decrease was read from the graph output as a measurement result. If no decrease in stress was observed before the attachment's descent distance reached 100 μm, the stress value at the point when the attachment's descent distance reached 100 μm was read.

[0072] For any 10 microneedles, the stress was measured as described above, and the average value was defined as the tip strength of the microneedle. The results are shown in Table 1.

[0073] [Test Example 3] (Measurement of Blood Flow) The blood flow was measured before and after use of the patches manufactured in Examples 1 to 4 and the products used in Comparative Examples 1 to 2, as follows.

[0074] A 15 mm diameter blood flow meter probe (ADVANCE, product name "Laser Doppler, L-type laser blood flow meter probe", contact type, capable of measuring tissue blood flow dynamics within approximately 1 mm hemisphere) was attached to the center of the anterior forearm of the subject (midpoint of the line connecting the center of the anterior wrist crease and the center of the cubital crease) and the blood flow rate before use was measured for 1 minute.

[0075] Subsequently, the probe was removed, and the patches manufactured in Examples 1-4 or the products used in Comparative Examples 1-2 were applied for 30 seconds. Specifically, the patch or product was placed on the measurement site so that the microneedles were in contact perpendicularly with the skin, and then, while pressing the patch or product with the pad of the thumb, the patch or product was twisted twice to the right (moving the patch or product in a circular trajectory), and then the pressure from the thumb was released. The twisting was completed within 30 seconds of applying the patch or product. The patch or product was then removed, the blood flow meter probe was reattached, and the blood flow rate after use was measured for 5 minutes.

[0076] The measurement results were digitally processed using an AD converter (AD Instruments, product name "PowerLab") for real-time display, recording, analysis, and data storage. In particular, blood flow measurements were acquired every 0.001 seconds. Based on these results, the blood flow before patch or product use (average blood flow from 10 seconds to 40 seconds after probe attachment) (ml / sec) and the blood flow after patch or product use (blood flow 240 seconds after removal of the patch or product and after probe attachment) (ml / sec) were calculated and identified. These results are shown in Table 2.

[0077] Furthermore, the percentage change in blood flow associated with the use of the patch or product was calculated based on the following formula. The results are also shown in Table 2. Percentage change = (Blood flow after use - Blood flow before use) / Blood flow before use

[0078]

[0079]

[0080] As can be seen from Table 2, the patch manufactured in the example resulted in a significant increase in blood flow compared to the product used in the comparative example. In particular, it was found that the blood flow after using the patch in the example increased by approximately 10 to 20 times compared to the blood flow before use. Therefore, it can be said that the patch manufactured in the example effectively induces axon reflex, thereby resulting in superior acupuncture treatment effects.

[0081] The microneedle array of the present invention can be suitably used as an acupuncture needle in acupuncture treatment.

[0082] 1...Microneedle array 11...Microneedle 2...Adhesive sheet 3...Release sheet 100...Patch

Claims

1. A microneedle array having a plurality of microneedles and used as an acupuncture needle in acupuncture treatment, wherein the length of the microneedles is 250 μm or more and 1500 μm or less, and the tip strength of the microneedles, measured as the maximum value of stress generated in the microneedles when a compressive load is applied to the tip of the microneedles in the longitudinal direction, is 50 mN or more.

2. The microneedle array according to claim 1, characterized in that the number of microneedles having a length of 250 μm or more and 1500 μm or less is 500 or less.

3. The microneedle array according to claim 1, characterized in that the microneedles are made of a biosafe resin material.

4. The microneedle array according to claim 3, characterized in that the biosafe resin material is a water-insoluble biodegradable material.

5. The microneedle array according to claim 4, characterized in that the biodegradable material is polycaprolactone or a copolymer containing caprolactone as a monomer.

6. The microneedle array according to claim 1, characterized in that the shape of the microneedles is a pyramidal or conical shape.

7. The microneedle array according to claim 1, characterized in that the shape of the group of microneedles when viewed from one side of the microneedle array is hexagonal, octagonal, or decagonal.

8. The microneedle array according to claim 1, characterized in that the microneedles do not have internal channels.

9. A patch comprising an adhesive sheet and a microneedle array according to any one of claims 1 to 8, laminated in the central part of one side of the adhesive sheet.

10. A method for manufacturing a microneedle array according to any one of claims 1 to 8, comprising: preparing a mold having recesses corresponding to the microneedles; injecting molten material into the mold; and solidifying it by cooling to obtain a microneedle array comprising the microneedles.

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