DESCRIPTION

Microneedle

Technical Field

This invention relates to a microneedle and a microneedle array. More specifically, it relates to a microneedle capable of easily, safely and effectively injecting a chemical, etc., below a skin surface layer or skin cornified layer and a microneedle array.

Background Art

Conventionally, almost all methods of administering a chemical, etc., to a patient's living organism surface, i.e., the surface of a skin or a mucous membrane are methods of applying a liquid substance or powder substance. Since, however, the region to which a medical agent can be applied is limited to a skin surface, it is a daily experience to have an applied medical agent come unstuck due to sweating or a contact of a foreign matter, and it has been hence difficult to effectively administer a proper dose of a medical agent, etc.

As the alternative to the application of a medical agent to a living organism surface, there is proposed a method of administering a medical agent into a living organism with a microneedle. Further, there have been so far made proposals to improve the above microneedle in puncturing ability.

For example, Patent Documents 1 and 2 propose microneedles and microneedle arrays that are neither easily bendable nor easily curvable and methods of producing them. However, they have no sufficient puncturing ability.

Patent Document 3 proposes a method in which a surface of a circular cone or surfaces of a pyramid of a microneedle are curved inwardly to make it easily run into. However, the method disclosed in Patent Document 3 is a method that uses a volume contraction when a polymer solution is applied to a stamper and gelation-dried, and it is not suitable for thermoplastic resin.

Patent Document 4 describes a microneedle which is formed from a water-soluble or water-swellable resin and which has the form of a cone, a frustum of cone or "Konide" and has a surface coated with a lubricant component.

(Patent Document 1) JP-A 2007-130030
(Patent Document-2) JP-A 2007-190112
(Patent Document 3) JP-A 2008-142183
(Patent Document 4) JP-A 2010-029634

Disclosure of the Invention

It is an object of this invention to provide a microneedle that smoothly runs into a patient's skin surface layer, that has safety and simplicity and that is capable of administering a predetermined dose of a medical agent without causing a pain, and a microneedle array. It is another object of this invention to provide a microneedle that can hold not only a medical agent but also predetermined doses of a stabilizer and a thickener and that has excellent puncturing ability and a microneedle array. It is a further object of this invention to provide a microneedle device including a microneedle array.

According to this invention, the following inventions are provided.

1. A microneedle comprising a frustum and a forward end portion thereon, having a forward end apex angle (A) in the range of 15 to 60° and a forward end diameter (B) in the range of 1 to 20 μm and satisfying the following expression (1), H/D>5 (1)
(H: Height of the whole, D: Diameter of bottom surface of the frustum).

2. A microneedle as recited in the above paragraph 1, which has a surface roughness represented by the following expression (2),

5 nm5 (1)

(H: Height of the whole, D: Diameter of bottom surface of the frustum).

The upper limit of H/D is preferably 20 or less from the viewpoint of the object of this invention and moldability. When H/D is less than 5, the resistance in puncturing a skin is too greatly increased for a microneedle to run into the skin, and further, the forward end of the microneedle is easily deformed, which are disadvantage for an object and an effect. H/D is preferably from 5 to 10, more preferably from 5 to 6. (Forward end portion)

The diameter (d) of bottom surface of the forward end portion is preferably 1 to 170 μm, more preferably 10 to 80 μm. The diameter (d) of bottom surface of the forward end portion is represented by a diameter obtained when the bottom surface of the forward end portion approximates to a circle.

The forward end apex angle (A) is in the range of 15 to 60°, preferably 30 to 60°. When the forward end apex angle (A) is in the range of 30 to 45°, a further excellent effect is found. When the forward end apex angle (A) is outside the range of 15 to 60°, undesirably, the resistance in puncturing a skin is too greatly increased for a microneedle to run into the skin, and further, the forward end of the microneedle is easily deformed.

The forward end diameter (B) is 1 to 20 μm. From the viewpoint of an improvement in the effect of smoothly puncturing a skin surface layer of a patient, the forward end diameter (B) is preferably in the range of 1 to 10 μm. When the forward end diameter (B) exceeds 20 μm, undesirably, the resistance in puncturing a skin is too greatly increased for a microneedle to run into the skin, and the forward end of the microneedle is easily deformed.

The height (h) of the forward end portion is preferably 1 to 640 μm, more preferably 10 to 150 μm. (Height of the whole)

The height (H) of the whole is a total sum of a thickness (X) of a skin at which the effect of a medical agent is effectively exhibited and a length (a) of allowance that takes account of the flexibility of a skin when the microneedle is slowly pressed to run into the skin without causing a pain. Specifically, X is preferably 15 to 800 μm, more preferably 100 to 500 μm. Specifically, a is preferably 30 to 500 μm, more preferably 50 to 300 μm. (Surface roughness)

The surface roughness of the microneedle is preferably 5 nm

This invention relates to a microneedle device comprising a microneedle or a microneedle array which hold a medical agent, and an applicator for administering a medical agent to a living organism. The applicator can be selected from known applicators which work by pressing a microneedle array manually or mechanically.

The medical agent includes physiologically active substances such as hormone, vaccine, etc. The medical agent includes growth hormone-releasing hormone (GGRH), growth hormone-releasing factor (GHRF), insulin, insulotropin, calcitonin, octreotide, endorphin, TRN, NT-36 (chemical name: N-[[(s)-4-oxo-2-azetidinyl]carbonyl]-L-histidyl-L-prolineamide), lypressin, hypophyseal hormones (e.g., HGH, HMG, desmopressin acetate, etc.), follicle luteoid, aANF, growth factors such as growth factor releasing factor (GFRF), bMSH, GH, somatostatin, bradykinin, somatotropin, platelet-derived growth factor releasing factor, asparaginase, bleomycin sulfate, chymopapain, cholecystokinin, ciliate gonadotropin, erythropoietin, epoprostenol (antiplatelet drug), glucagon, HCG, bivalirudin, hyaluronidase, interferon a, interferon P, interferon y, interleukin, interleukin-10 (IL-10), erythropoietin (EPO), granulocyte-macrophage colony stimulating factor (GM-CSF), granulocyte colony stimulating factor (G-CFS), glucagon, luteinizing hormone releasing hormone (LHRH), LHRH analog (goserelin, leyprolide, buserelin, triputorelin, gonadorelin and nafarelin), menotropin (like urofllitropin (FSH and LH)), oxytocin, streptokinase, tissue plasminogen activator, urokinase, vasopressin, deamino [Val4, D-Arg8]arginine vasopressin, desmopressin, corticotrophin (ACTH), ACTH analog like ACTH (1-24), ANP, ANP disappearance repressor, angiotensin II antagonist, antidiuretic hormone agonist, bradykinin antagonist, Ceredase, CSI, calcitonin gene related peptide (CGRP), enkephalin, FAB fragment, IgE peptide inhibitor, IGF-1, neurotrophic factor, colony stimulating factor, parathyroid hormone and agonist, parathyroid hormone antagonist, parathyroid hormone (PTH), PTH analog like PTH (1-34), prostaglandin antagonist, pentigetide, protein C, protein S, renin inhibitor, thimosin α -1, thrombolytic agent, TNF, vasopressin antagonist analog, α -1 antitrypsin (recombinant) , and TGF- β.

Further, the medical agent includes protein, polysaccharide complex, oligosaccharide, and antigen in the form of lipoprotein. These subunit vaccine include bordetella pertussia (recombinant PT accine - acellular),

Clostridium tetani (purified, recombinant), corynebacterium diptheriae (purified, recombinant), cytomegalovirus (glycoprotein subunit), streptococcus group A (glycoprotein subunit, complex carbohydrate group A polysaccharide including tetanus toxoide, M protein/peptide combined with toxing subunit carrier, M protein, polyvalent specific epitope, cysteine protease and C5a peptidase), hepatitis B virus (recombinant pre-Sl, pre-S2, S and recombinant core protein), hepatitis C virus (recombinant-developed surface protein and epitope), human papilloma virus (capsid protein, TA-GN recombinant proteins L2 and E7 [from HPV-6], MEDI-50I recombinant VLPL1 from HPV-11, tetravalent recombinant BLP LI [from HPV-6], HPV-11, HPV-16 and HPV-18, and LAMP-E7 [from HPV-16]), Legionella pneumophila (purified bacterial surface protein), neisseria meningitides (conjugated polysaccharide including tetanus toxoid), pseudomonas aeruginosa (synthetic peptide), rubella virus (synthetic peptide), streptococcus pneumonia (conjugated polysaccharide combined with BOMP of meningococcus [1,4,5,6B,9N,14,18C,19V,23F], conjugated polysaccharide combined with CRM197 [4,6B,9V,14,18C,19F,23F], conjugated polysaccharide combined with CRM1970 [1,4,5,6B,9V,14,18C,19F,23F]), treponema pallidum (surface lipo-protein), varicella zoster virus (subunit, glycoprotein), and vibrio cholerae (compounded lipopolysaccharide)

Further, the medical agent includes adrenaline, nicotine, bisphosphonate, fentanyl, etc.

According to this invention, there is provided a method for administering a medical agent, comprising causing the above microneedle or microneedle array holding the medical agent to run into a skin surface. The medical agent includes those which are described above like physiologically active substances and vaccines. The administering method of this invention can be applied to living organisms, and can be also applied to mammals such as cows, swine, humans, etc. According to the administering method of this invention, the microneedle or microneedle array can be caused to run into with a smaller force without a pain.

Examples

Examples of working embodiments will be described below. Example 1 Microneedles were produced as follows. (Die) For a die, a metal was machined by cutting it to make a master for a die, and the master die was inverted by nickel electrocasting to make a die. In the form of a microneedle, the microneedle had a forward end diameter of 7 μm, the whole had a height (H) of 600 μm, the bottom surface of frustum of cone had a diameter (D) of 100 μm, a forward end apex angle of 45°, and 97 microneedles were made. (Die-forming)

For forming the microneedles, a melt fine transfer apparatus (registered trademark) supplied by Japan Steel Works, Ltd. was used.

For a resin, polyglycolic acid was used, and it was melted at 260°C and a molten resin was applied to a die at 200°C. Then, the resin was pressed at a pressure of 20 MPa for approximately 30 seconds, and then the die was cooled to 80°C to give a microneedle array from the die.

The thus-obtained microneedle array was observed through a scanning electron microscope to confirm that the form of the mold was accurately transferred without any breaking or deformation. Then, the microneedle array was evaluated for puncturing ability. Table 1 shows the results. After the above test, the microneedle array was evaluated for easiness in breaking of forward ends. Table 1 shows the results.

Example 2

A microneedle array was produced in the same manner as in Example 1 except that the form thereof was changed as shown in Table 1. Table 1 shows the evaluation results.

Example 3

A microneedle array was produced in the same manner as in Example 1 except that the form thereof was changed as shown in Table 1. Table 1 shows the evaluation results.

Comparative Example 1

A microneedle array was produced in the same manner as in Example 1 except that the form thereof was changed as shown in Table 1. Table 1 shows the evaluation results.

Comparative Example 2

A microneedle array was produced in the same manner as in Example 1 except that the form thereof was changed as shown in Table 1. Table 1 shows the evaluation results.

Comparative Example 3

A microneedle array was produced in the same manner as in Example 1 except that the form thereof was changed as shown in Table 1. Table 1 shows the evaluation results.

Table 1

Ex. = Example, CEx. = Comparative Example O: Good A: Slightly poor X: Poor

Evaluations

Microneedles obtained in Examples 1-3 and Comparative Examples 1-3 were evaluated by the following tests. (Evaluation 1) Evaluation of puncturing ability based on form
a) Materials: Evaluation sample

For evaluating the microneedles obtained in Examples 1-3 and Comparative Examples 1-3 for puncturing ability based on the form of the microneedles, single-needle microneedles made of stainless steel having the same forms as those of the microneedles obtained in Examples 1-3 and Comparative Examples 1-3 were produced. The microneedles made of stainless steel were produced by cutting predetermined forms on one end surface of each of SUS304 rods having a diameter of 3 mm with a fine forming machine (Rokuroku Sangyo "MEGA-S400"). Skin model:

An abdominal part skin of a Wistar rat (age 5 weeks, male) was set on an arc of a semispherical expanded polystyrene (930 mm). Machine for use:

Bench tension and compression tester (Ez-test, Shimadzu Corporation)
Plunger φ5 mm (Shimadzu Corporation)
Load cell ION (Measurement resolution 1/20000, Shimadzu Corporation)
Digital microscope (Keyence VHX-1000) b) Evaluation method:

As shown in Fig. 5, a needle was fixed to the top end of the plunger with a tape. A drop of a 2 % gentian violet Et-OH solution was caused to fall on the top end of the needle attached to the plunger to stain it. The plunger with the needle attached thereto was set in the bench tension and compression tester (Ez-test), and it was arranged that the top end of the needle was in contact with the rat skin. That position was used as a point zero.

The needle was moved in the skin model up to a set stress at a rate of 1 mm/minute. After the set stress was reached, the needle was caused to retreat from the skin model at a rate of 1 mm/minute.

Then, the needle was removed, and the materials were allowed to stand for approximately 1 minute. The punctured portion of the rat skin was washed with Et-OH, the dye (gentian violet) on the skin was cleaned, and then punctured portion was observed for a punctured mark with a digital microscope. The puncturing test was carried out three times per one needle for conducting the evaluation.

Symbols in Fig. 5 show the following.

1. Load cell
2. Plunger (φ5 ram)
3. Being fixed with a tape
4. Microneedle ((p5 mm)
5. Microneedle
6. Rat skin
7. Expanded polystyrene (φ30 mm) c) Evaluation results:

The needle was pressed to the rat skin until the set stress was reached, and it was evaluated whether or not the skin was punctured to be stained with the gentian violet. The skin was punctured three times, and when it was not punctured, such was expressed as 0/3, and when it was punctured three times, such as expressed as 3/3. The following Table 2 shows the results.

Table 2
Ex. = Example, CEx. = Comparative Example

When the forward end had a diameter of 7 μm, the microneedles of Examples 1 and 3 had the same puncturing ability although their apex angles were different like 45° and 60°. However, the microneedle of Comparative Example 2 showed extremely poor puncturing ability when its forward end had an apex angle of 90° although it had a forward end diameter of 7 μm. The microneedle of Example 2 had poor puncturing ability since it had a forward end diameter of 20 μm although its forward end angle was 45°. (Evaluation 2) Dose of medical agent held

Fig. 10 shows an image of the microneedle of Example 1 that holds a medical agent. If this form is maintained, the dose of the medical agent held thereon can be secured while maintaining sharpness.

The capability of holding the medical agent (needle form: Height H/D) was evaluated by three stages based on the value of H/D.

Index 3: 5 or more, index 2: 4 or more but less than 5, index 1: less than 4

Further, as an index for puncturing ability, puncture stresses at which puncturing was enabled 100 % were evaluated by the following four stages.

Index 3: Less than 0.05 N/needle, index 2: less than 0.1 N/needle, index 1: 1.0 N/needle or more, index 0: cannot be punctured.

A comprehensive evaluation was made on the basis of an index for capability of holding the medical agent x index for puncturing ability. Table 3 shows the results. As is clear from the comprehensive evaluation in Table 3, it is made clear that the forms of Examples 1-3 are suitable as the form of the microneedle.

Table 3

Ex. = Example, CEx. = Comparative Example
(Evaluation 3) Evaluation of puncture depth depending upon difference in form

There were produced single-needle microneedles made of stainless steel having the same forms as those of the microneedles obtained in Example 1 and Comparative Example 1. The microneedles made of stainless steel were produced by cutting predetermined forms on one end surface of each of SUS304 rods having a diameter of 3 mm with a fine forming machine (Rokuroku Sangyo "MEGA-S400"). a) Evaluation method

Single-needle microneedles having the same forms as those of the microneedles obtained in Example 1 and Comparative Example 1 were immersed in a dye liquid (PVPK-30 20 % and Brilliant Blue 3 %) to make dye liquid adhere thereto. The adhering liquids were air-dried, and the dye liquid was again made to adhere similarly. These procedures were repeated 3 to 5 times to coat the microneedles with the dye liquid.

The needle coated with the dye liquid was fixed to the top end of a plunger with a tape. The plunger with the needle attached thereto was set on a bench tensile-compression tester (Ez-test), and it was arranged that the top end of the needle was in contact with a rat skin. That position was used as a point zero. Then, the needle was moved in the skin model at a rate of 1 mm/minute up to a set stress of 0.03 N. After the set stress of 0.03 was reached, the needle was fixed in that state and allowed to stand for 1 hour. On an average, the needle stopped in a position where it moved approximately 200 μm from the position of zero point. Then, the needle was caused to retreat from the skin model at a rate of 1 mm/minute and removed from the skin.

The removed needle was observed through a digital microscope to evaluate how far from the top end the dye on the needle came off (decoloring depth). The puncturing test was carried out twice for each needle, and the length of the needle that was decolored was evaluated as a depth of puncturing of the needle in the skin, b) Evaluation results

The degree of puncture depths in the skin (puncturing depth) depending upon differences in the forms of the microneedles of Example 1 and Comparative Example 1 were evaluated, and summarized in the following Table 4.

Table 4

As shown in the above Table 4, the width of the needle is as small as an H/D of 6 in Example 1, while that of the needle in Comparative Example 1 is as large as an H/D of 2, so that the needle of Comparative Example 1 is too large to run into the skin. As compared with the needle having the form of Example 1, the entering depth of the needle having the form of Comparative Example 1 into the skin was 64.2 % of that of the needle of Example 1 (54.9 um/85.5 μ).

(Evaluation 4) Medical agent administering evaluation

Needle tips of microneedle arrays obtained in Example 7 were immersed in a 40 % ovalbumin (OVA) aqueous solution to apply it to them such that a dry OVA amount per each array was 50 μg, and they were used as samples for inoculation.

Abdominal parts of mice Nos. 1-5 were defurred, the sample surfaces with needles for inoculation were pressed thereto, kept pressing for 30 seconds and then fixed with a tape each, and they were held for 30 minutes. The samples for inoculation were removed, and the mice were raised for 2 weeks and then again inoculated similarly. For antibody titers (IgG) in blood before the test and 5 weeks after the test, UV absorbance values were measured by an Elisa test. (Control)

Mice Nos. 6-10 were inoculated with a 50 ng/0.2 ml OVA aqueous solution by subcutaneous injection, raised for 2 weeks and then additionally inoculated with the same dose of the OVA aqueous solution. For antibody titers (IgG) in blood before the test and 5 weeks after the test, UV absorbance values were measured by an Elisa test. The following Table 8 shows the results.

Table 8 : Administering by microneedle array
Table 8 : (Continued) Administering by subcutaneous injection

Examples 4 and 5

Microneedle arrays (97 needles each) shown in the following Table 5 were produced from a polyglycolic acid resin. It was evaluated by the following method how the puncture efficiency of the microneedle arrays (97 needles) would change depending upon the size of the needles (H/D).

In the above evaluation 3, the entering depths of the needles into the skin differ depending upon the sizes of the needles (H/D). It was hence evaluated how the puncturing efficiency of the microneedle array (97 needles) would change depending upon the size of the forward end portions of the needles (h/d). a) Materials:

Evaluation sample
Microneedle arrays (97 needles) shown in the following Table 5 were used for evaluation. Human skin model:

A 6-mm thick sheet was formed by melting 30 % of SIS and 70 % of liquid paraffin under heat and set, and further, a 9-mm thick sheet was formed by melting 15 % of SIS and 85 % of liquid paraffin under heat and stacked thereon to prepare a substrate of two layers. An abdominal part skin of Wister rat (male, 5 weeks) was set on the substrate to prepare a human skin model. Machine for use:

The same machine as that in Evaluation 1 was used, b) Evaluation method

A small bench tester (Ez-test) shown in Fig. 6 was used, a plunger (φ5 mm) was set on its load cell, and further, a polypropylene (PP) plate (pedestal 12 rnmφ, 0.8 mm thick) was attached to its forward end. Further, the microneedle array was set on the PP plate. The forward end portions of the needles were dyed with a 2 % gentian violet ET-OH solution.

The needle forward end portions of the above microneedles were brought into contact with the skin surface of the above human skin model, and the needles were moved a set distance of 10 mm at a rate of 60 mm/minute to be pressed into the skin model.

With regard to the rat skin of the human skin model surface, portions where holes were punctured in the skin with the microneedle array were colored with the gentian violet to turn purple. Therefore, colored portions were visually counted, and the puncturing efficiency (number of colored portions/number of needles) of each microneedle array was evaluated.

Symbols in Fig. 6 indicate the following.

8. SHIMAZU Eztest
9. Load cell
10. Plunger (φ5 mm)
11. Pedestal (12 mnup)
12. Microneedle array (12 mmφ, 97 needles)
13. Skin model (Upper layer: rat skin, intermediate layer: SIS 15 %, 6 mm, lower layer: SIS 30 %, 9 mm) c) Evaluation results
The puncturing efficiency of the microneedle arrays was determined, and Table 5 shows the results.

Table 5

As is clear in Table 5, it is shown that with an increase in H/D (as the needles get smaller in size), the puncturing efficiency is higher. When the pedestal (substrate) was 10 mmφ, the stress when the needles were pressed 10 mm deep in the above skin model was in the range of 4 to 6 N, and when the pedestal was 12 mmφ, that was 6 to 9 N.

Example 6

A microneedle array (97 needles) shown in the following Table 6 was produced from a polyglycolic acid in the same manner as in Example 1. The puncturing depth when the 97-needle microneedle array (φl3 mm) was pressed was evaluated by the following method, a) Materials:

Human skin model:

A 6-mm thick sheet formed by melting 30 % of SIS and 70 % of liquid paraffin under heat was set, and further, a 9-mm thick sheet formed by melting 15 % of SIS and 85 % of liquid paraffin under heat was stacked thereon to prepare a substrate of two layers. An abdominal part skin of Wister rat (male, 5 weeks) was folded in two such that the abdominal part skin faced outward and set on the substrate. Machine for use:
The same machine as that in Evaluation 1 was used.

b) Evaluation method:

Blue No. 1 (3 %) was dissolved in a 20 % PVP K30 aqueous solution to prepare a solution, and the forward ends of the above microneedle array were immersed therein three times to color the needle surfaces.

The microneedle array was set above on the human skin model such that the forward ends of needles faced downward. The microneedle array was fixed above the skin with a surgical tape (25 mm x 20 mm) thereon. The microneedle array was pressed with a plunger (5 mm5 (1) (H: Height of the whole, D: Diameter of bottom surface of the frustum).

2. The microneedle of claim 1, which has a surface roughness represented by the following expression (2), 5 nm