Patent ID: 12233156

DESCRIPTION OF EMBODIMENTS

A method of manufacturing a microneedle device according to an aspect of the present invention comprises a step (coating step) of coating microneedles with a coating liquid. After the coating step, a step (a drying step) of drying the coating liquid may be performed. Here, the microneedle device is a device comprising a substrate, microneedles disposed on the substrate, and a coating formed on the microneedles.

One embodiment of the microneedle device of the present invention is shown inFIG.1. The microneedle device10comprises a substrate2, a plurality of microneedles4disposed on a main surface of the substrate2, and a coating6formed on each of the microneedles4. In the present specification, a configuration in which the plurality of microneedles4are disposed on the substrate2is referred to as a microneedle array. Details of the coating6will be described later.

The substrate2is a base for supporting the microneedles4. A shape and a form of the substrate2are not particularly limited and may be, for example, rectangular or circular, and the main surface may be flat or curved. An area of the substrate2may be, for example, 0.5 cm2to 10 cm2, 0.5 cm2to 5 cm2, 1 cm2to 5 cm2, 0.5 cm2to 3 cm2, or 1 cm2to 3 cm2. A thickness of the substrate2may be 50 μm to 2000 μm, 300 μm to 1200 μm, or 500 μm to 1000 μm.

The microneedles4may be needle-shaped convex structures. A shape of each microneedle4may be, for example, a polygonal pyramid, such as a quadrangular pyramid, or a cone. Microneedles4are a microstructures, and a length (a height) HMof each microneedle4in a direction perpendicular to the main surface of the substrate2is preferably 50 μm to 600 μm, 100 μm to 500 μm, or 300 μm to 500 μm, for example.

The microneedles4are disposed on the main surface of the substrate in, for example, a square lattice pattern, a rectangular lattice pattern, an orthorhombic lattice pattern, a 45° staggered pattern, or a 60° staggered pattern.

A density (a needle density) at which the microneedles4are disposed on the substrate2is represented by the number of the microneedles4per unit area in a region substantially having the microneedles4. The region substantially having the microneedles4is a region obtained by connecting the outermost microneedles4among the plurality of microneedles4disposed in the microneedle device10. From the viewpoint of introducing a larger amount of biologically active substance into the skin, the needle density may be, for example, 10 needles/cm2or more, 50 needles/cm2or more, or 100 needles/cm2or more. From the viewpoint of reducing skin irritation, the needle density may be, for example, 850 needles/cm2or less, 500 needles/cm2or less, 200 needles/cm2or less, or 160 needles/cm2or less.

Examples of a material of the substrate2or the microneedles4include silicon, silicon dioxide, ceramics, metals, polysaccharides, and synthetic or natural resin materials. Examples of polysaccharides include pullulan, chitin, and chitosan. The resin material may be, for example, a biodegradable polymer such as polylactic acid, polyglycolide, polylactic acid-co-polyglycolide, polycaprolactone, polyurethane, a polyamino acid (for example, poly-γ-aminobutyric acid) or the like, or may be a non-degradable polymer such as polycarbonate, polymethacrylic acid, ethylene vinyl acetate, polytetrafluoroethylene, polyoxymethylene, or a cyclic olefin copolymer.

In the coating step in the method of manufacturing the microneedle device10according to one embodiment of the present invention, the coating liquid is coated on the microneedles4. The coating liquid comprises a biologically active substance and a sulfated polysaccharide.

The biologically active substance is a substance that exhibits a therapeutic or prophylactic effect in a subject to which it is administered. The biologically active substance may be, for example, peptides, proteins, nucleic acids such as DNA and RNA, sugars, glycoproteins, or other high-molecular or low-molecular compounds.

Specific examples of the biologically active substance include dexmedetomidine, interferon α, interferon β for multiple sclerosis, erythropoietin, follitropin β, follitropin α, G-CSF, GM-CSF, human chorionic gonadotropin, luteinizing hormone, follicle stimulating hormone (FSH), salmon calcitonin, glucagon, GNRH antagonist, insulin, luteinizing hormone releasing hormone (LHRH), human growth hormone, parathyroid hormone (PTH), filgrastin, somatropin, incretin, GLP-1 analogues (for example, exenatide, liraglutide, lixisenatide, albiglutide, and taspoglutide), snake venom peptide analogues, γ globulin, Japanese encephalitis vaccine, hepatitis B vaccine, rotavirus vaccine, Alzheimer's disease vaccine, arteriosclerosis vaccine, a cancer vaccine, nicotine vaccine, diphtheria vaccine, tetanus vaccine, pertussis vaccine, lyme disease vaccine, rabies vaccine, pneumococcal vaccine, yellow fever vaccine, cholera vaccine, vaccinia vaccine, tuberculosis vaccine, rubella vaccine, measles vaccine, influenza vaccine, mumps vaccine, botulinum vaccine, herpes virus vaccine, and pharmaceutically acceptable salts thereof. The biologically active substance may be, for example, dexmedetomidine or dexmedetomidine hydrochloride. The coating liquid may comprise one biologically active substance, or may comprise a plurality of biologically active substances.

In the present invention, the sulfated polysaccharide is a component (a carrier) which assists in carrying the coating liquid on the microneedles4. The sulfated polysaccharide has an affinity for skin tissues and is excellent in improving absorbability of biologically active substances into the skin. The sulfated polysaccharide is a polysaccharide with a sulfuric acid bound to a hydroxyl group or amino group.

The polysaccharide in the sulfated polysaccharide may be a natural polysaccharide or may be a semi-synthetic or synthetic polysaccharide. A main structure of the polysaccharide is preferably a mucopolysaccharide (also known as glycosaminoglycan). The mucopolysaccharide is a heteropolysaccharide having uronic acid and hexosamine as sugar units. A sulfate moiety in the sulfated polysaccharide may be in the form of a free acid or may form a salt. The sulfate moiety is preferably a monovalent metal salt, particularly a sodium salt. The coating liquid may comprise one sulfated polysaccharide or may comprise a plurality of sulfated polysaccharides.

Examples of a natural or biologically-derived sulfated polysaccharide include chondroitin sulfate, carrageenan, fucoidan, ascophyllan, heparin, heparan sulfate, heparin analogues (heparinoids), keratan sulfate, funoran, porphyran, agaropectin, furcellaran, rhamnan sulfate, glucuronoxylorhamnan sulfate, xyloarabinogalactan sulfate, glucuronoxylorhamnogalactan sulfate, and arabinan sulfate, and salts thereof. Examples of the semi-synthetic or synthetic sulfated polysaccharide include, for example, sulfated dextran, sulfated pentosan, sulfated curdlan, and sulfated cellulose, and salts thereof.

Examples of the sulfated polysaccharide having a mucopolysaccharide as a main structure include chondroitin sulfate, heparin, heparan sulfate, heparinoid, and keratan sulfate, and salts thereof. Among them, chondroitin sulfate and salts thereof are more preferable. A scope of the chondroitin sulfate includes chondroitin sulfate A, chondroitin sulfate B (dermatan sulfate), chondroitin sulfate C, chondroitin sulfate D, chondroitin sulfate E, chondroitin sulfate H, and chondroitin sulfate K.

Examples of the salt of chondroitin sulfate include salts with alkali metals such as sodium and potassium, salts with alkaline earth metals such as calcium and magnesium, salts with other metals such as aluminum, and salts with organic bases. The salt of chondroitin sulfate is preferably an alkali metal salt of chondroitin sulfate, more preferably sodium chondroitin sulfate.

The origin of the chondroitin sulfate and the salts thereof is not limited. The chondroitin sulfate and the salts thereof may be obtained from mammals such as pigs, fish such as salmon and sharks, or microorganisms.

Sulfated polysaccharides tend to have common physical, chemical, and physiological properties due to the presence of sulfate groups. As the proportion of sulfate groups in the sulfated polysaccharide increases, the affinity for water, water retentivity and the thickening effect increase, but the proportion of sulfate groups in the sulfated polysaccharide is not particularly limited. The number of sulfate groups in the sulfated polysaccharide may be 0.25N to 2N, preferably 0.5N to 1.5N per N sugar units mainly constituting the polysaccharide. When the polysaccharide has two main sugar units, the number of sulfate groups may be 0.5 to 4, preferably 1 to 3 per disaccharide unit mainly constituting the polysaccharide.

A viscosity average molecular weight of the sulfated polysaccharide may be, for example, 1000 Da to 500,000 Da, 1000 Da to 100,000 Da or 7000 Da to 40,000 Da, but is not limited thereto. The viscosity average molecular weight may be calculated from a limiting viscosity obtained in accordance with the viscosity measurement Method 1: Viscosity measurement by capillary tube viscometer in General Tests of the Japanese Pharmacopoeia, 15th edition, using the Mark-Houwink-Sakurada equation.

The coating liquid comprises at least one or more solvents that dissolves the biologically active substance and the sulfated polysaccharide. Examples of the solvent include water, polyhydric alcohols, lower alcohols, and triacetin. Water is preferable because it dissolves the sulfated polysaccharide well. Water is also preferable in that it also dissolves dexmedetomidine or pharmaceutically acceptable salts thereof well.

The coating liquid may further comprise other components (for example, a stabilizer, a pH adjuster, a component that promotes entry of the biologically active substance into blood, oils and fats, or inorganic substances) in addition to the biologically active substance, the sulfated polysaccharide, and the solvent. However, it is preferable that the coating liquid does not comprise a surfactant, a monosaccharide, and a disaccharide. Surfactants, monosaccharides, and disaccharides may reduce the surface tension and viscosity of the coating liquid and may reduce the amount of the biologically active substance carried per one microneedle4.

The stabilizer has, for example, an action in which oxygen oxidation and photooxidation of each component are suppressed and the biologically active substance is stabilized. Examples of the stabilizer are L-cysteine, sodium pyrosulfite, sodium bisulfite, ascorbic acid, ethylenediaminetetraacetic acid (EDTA) or salts thereof, or dibutylhydroxytoluene (BHT). These stabilizers may be used alone or in combination of two or more.

As the pH adjuster, those commonly used in the industry may be used. Examples of the pH adjuster include inorganic acids or organic acids, alkalis, salts, amino acids, or a combination thereof.

A concentration of the sulfated polysaccharide in the coating liquid may be, for example, 0.1 mass % or more, 0.5 mass % or more, 1 mass % or more, 1.3 mass % or more, 1.5 mass % or more, 2 mass % or more, 3 mass % or more, or 4 mass % or more, and may be 20 mass % or less, 16 mass % or less, 15 mass % or less, 14 mass % or less, 13 mass % or less, 12 mass % or less, 11 mass % or less, 10 mass % or less, 9 mass % or less, or 8 mass % or less. From the viewpoint of manufacturing the microneedle device10capable of carrying and administering more biologically active substance per one microneedle, the concentration of the sulfated polysaccharide in the coating liquid may be, for example, 1.3 mass % to 11 mass %, 1.5 mass % to 10 mass %, 2 mass % to 10 mass %, 0.5 mass % to 16 mass %, 0.5 mass % to 10 mass %, or 4.0 mass % to 10 mass %.

The concentration of the biologically active substance in the coating liquid may be adjusted according to the type of the biologically active substance, the purpose of treatment, the condition of disease, the condition of the patient, and the nature of the solvent. The concentration of the biologically active substance in the coating liquid may be, for example, 0.01 mass % to 90 mass %, 0.1 mass % to 80 mass %, and 1 mass % to 70 mass %.

A mass ratio of the sulfated polysaccharide to the biologically active substance in the coating liquid may be, for example, 0.01 or more, 0.02 or more, 0.025 or more, 0.03 or more, 0.035 or more, 0.04 or more, 0.05 or more, or 0.08 or more, and also may be 0.36 or less, 0.35 or less, 0.3 or less, 0.27 or less, 0.26 or less, 0.24 or less, 0.23 or less, 0.20 or less, 0.18 or less, or 0.17 or less. When the biologically active substance is dexmedetomidine or a pharmaceutically acceptable salt thereof, the mass ratio is preferably 0.011 to 0.222, 0.044 to 0.222, or 0.089 to 0.222.

The total amount of the other components other than the biologically active substance, the sulfated polysaccharide, and the solvent may be, for example, 80 mass % or less, 60 mass % or less, 30 mass % or less, or 20 mass % or less with respect to the total mass of the coating liquid. The coating liquid may comprise no other components other than the biologically active substance, the sulfated polysaccharide, and the solvent.

The concentration of each component contained in the coating liquid may be measured, for example, by liquid chromatography. Further, the concentration of each component other than the biologically active substance may also be calculated based on the concentration of the biologically active substance measured by a liquid chromatography method and the proportion of each component at the time of formulating the coating liquid.

From the viewpoint of coating the microneedles4with a larger amount of coating liquid and the viewpoint of forming the coating6on a tip portion of each microneedle4, a viscosity of the coating liquid at 25° C. is preferably 500 mPa·s to 30,000 mPa·s, more preferably 1000 mPa·s to 10,000 mPa·s. From the same viewpoints, a surface tension of the coating liquid is preferably 10 mN/m to 100 mN/m, more preferably 20 mN/m to 80 mN/m.

The method of coating the microneedles4with the coating liquid is not particularly limited, and the coating liquid may be coated by inkjet coating or dip coating, for example. Among these, dip coating is preferred. In the dip coating, the microneedles4are coated with the coating liquid by dipping the microneedles4in a reservoir in which the coating liquid is stored to a certain depth and then withdrawing the microneedles4from the reservoir.

Here, according to the coating liquid of the present invention comprising the sulfated polysaccharide, the microneedles4may be coated with a large amount of coating liquid, and thus, it is possible to manufacture the microneedle device10in which a larger amount of biologically active substance can be carried and administered per one microneedle.

The amount of the coating liquid coated on the microneedles4may be adjusted by the depth to which the microneedles4are dipped, for example, in the case of application by dip coating. Here, the depth to which the microneedles4are dipped indicates the distance from apexes of the dipped microneedles4to a surface of the coating liquid. The dipping depth depends on the length HMof the microneedle4, but may be HM/2 or less, for example. Among the biologically active substance contained in the coating6formed by drying the coating liquid, the biologically active substance contained in a portion formed in a base portion of the microneedle4is less likely to be introduced into the skin compared to the biologically active substance contained in a portion formed in a tip portion of the microneedle4. Therefore, a larger amount of the coating liquid is preferably coated, mainly, on the tip portion of the microneedle4. Here, the tip portion of the microneedle4is a portion in which a length measured from the apex of the microneedle4in a direction perpendicular to the main surface (that is, the base portion) of the substrate2is, for example, within 50% of the length HMof the microneedle4, as will be described later.

In a drying step after the coating step, the coating liquid may be dried to form the coating6on the microneedles4. Here, drying the coating liquid means volatilizing some or the whole of the solvent contained in the coating liquid. The drying of the coating liquid may be performed by, for example, a method such as air drying, vacuum drying, freeze drying, or a combination thereof. The preferred drying method is air drying.

Here, since the coating liquid according to the present invention comprising the sulfated polysaccharide has high viscosity and surface tension, downward flowing and spreading of the coating liquid before or during the drying of the coating liquid due to gravity can be further reduced. Therefore, even when then the coating liquid is dried with the microneedle array placed in such a way that the microneedles4face upward, the coating6can be formed mainly on the tip portions of the microneedles4.

The coating step and the drying step may be performed repeatedly. The amount of the coating6formed can be further increased by repeating these steps.

The microneedle device10according to one embodiment of the present invention manufactured by the above-described method comprises the coating6comprising the biologically active substance and the sulfated polysaccharide on the microneedles4.

The details of the microneedle array, the biologically active substance, and the sulfated polysaccharide which constitute the microneedle device10are as described above. The coating6is a coating obtained by removing some or the whole of the solvent from the above-described coating liquid. Therefore, the coating liquid and the coating6described above have the same components except for the solvent.

The amount of the sulfated polysaccharide may be, for example, 0.5 parts by mass or more, 1 part by mass or more, 1.9 parts by mass or more, 2 parts by mass or more, 2.5 parts by mass or more, 3 parts by mass or more, 3.5 parts by mass or more, 5.0 parts by mass or more, or 8.0 parts by mass or more, and may also be 27 parts by mass or less, 25 parts by mass or less, 22 parts by mass or less, 21 parts by mass or less, 20 parts by mass or less, 19 parts by mass or less, 18 parts by mass or less, 17 parts by mass or less, 14 parts by mass or less, or 13 parts by mass or less, with respect to 100 parts by mass of the coating6.

The amount of the biologically active substance may be, for example, 99 parts by mass or less, 95 parts by mass or less, 92 parts by mass or less, 90 parts by mass or less, 89 parts by mass or less, 88 parts by mass or less, or 87.5 parts by mass or less, or 87 parts by mass or less, and may also be 65 parts by mass or more, 70 parts by mass or more, 72 parts by mass or more, 73 parts by mass or more, 74 parts by mass or more, 75 parts by mass or more, 77 parts by mass or more, 78 parts by mass or more, 79 parts by mass or more, or 81 parts by mass or more. with respect to 100 parts by mass of the coating6.

A mass ratio of the sulfated polysaccharide to the biologically active substance in the coating6may be, for example, 0.01 or more, 0.02 or more, 0.025 or more, 0.03 or more, 0.035 or more, 0.04 or more, 0.05 or more, or 0.08 or more, and may also be 0.36 or less, 0.35 or less, 0.3 or less, 0.27 or less, 0.26 or less, 0.24 or less, 0.23 or less, 0.20, 0.18 or less, or 0.17 or less. When the biologically active substance is dexmedetomidine or a pharmaceutically acceptable salt thereof, the mass ratio is preferably, for example, 0.011 to 0.222, 0.044 to 0.222, or 0.089 to 0.222.

The total amount of the other components other than the biologically active substance, the sulfated polysaccharide, and the solvent may be, for example, 95 parts by mass or less, 75 parts by mass or less, 50 parts by mass or less, or 30 parts by mass or less, with respect to 100 parts by mass of the solid content in the coating6. In the present specification, the solid content refers to the component which remains when the solvent is removed from the coating liquid.

A preferable amount of the biologically active substance carried per one microneedle4depends on the type of the biologically active substance, the purpose of treatment, the condition of disease, and the condition of the patient. When the biologically active substance is dexmedetomidine or a pharmaceutically acceptable salt thereof, the amount of dexmedetomidine or the pharmaceutically acceptable salt thereof carried per one microneedle4is preferably 390 ng or more, 451 ng or more, or 670 ng or more, from the viewpoint of exhibiting a sufficient drug effect. The upper limit of the amount of the biologically active substance carried per one microneedle4is not particularly limited, but may be, for example, 2 μg or less, 1 μg or less, 755 ng or less, 545 ng or less, or 500 ng or less. The amount of the sulfated polysaccharide carried per one microneedle4may be, for example, 15 ng to 100 ng, 21 ng to 97 ng, 5 ng to 149 ng, or 67 ng to 149 ng. The amount of the coating6carried per one microneedle4may be, for example, 490 ng to 700 ng, 516 ng to 642 ng, 456 ng to 836 ng, or 819 ng to 836 ng.

The amount of each component contained in the coating6may be measured by, for example, a liquid chromatography method. Further, the amount of each component other than the biologically active substance may also be calculated based on the amount of the biologically active substance measured by the liquid chromatography method and the proportion of each component at the time of formulating the coating liquid. The amount of each component carried per one microneedle4may be obtained by dividing a value thus measured or calculated by the number of microneedles.

When there are a plurality of microneedles4, the coating6may be formed on all the microneedles4or may be formed on only some of the microneedles4. The coating6may be formed only on the tip portion of the microneedle4, or may be formed to cover the entire microneedle4. The coating6is preferably formed on the tip portion of the microneedle4. Here, the tip portion of the microneedle4is a portion in which a length measured from the apex of the microneedle4in a direction perpendicular to the main surface (that is, the base portion) of the substrate2is, for example, within 50%, within 40%, within 30%, or within 20% of the length HMof the microneedle4. An average thickness of the coating6may be less than 50 μm and may be 1 μm to 30 μm.

EXAMPLES

<Test Example 1> Comparison of Carriers

Coating liquids1to4were prepared by mixing components shown in Tables 1 and 2. In Table, γ-PGA is γ-polyglutamic acid. A pharmaceutical grade product of Maruha Nichiro Corporation was used as sodium chondroitin sulfate (hereinafter, may be referred to as CSNa). As the pullulan, a pharmaceutical product of Hayashibara Co., Ltd. was used. A product of Nippon Poly-Glu Co., Ltd. was used as γ-PGA. “Kuraray Poval PVA-205” (degree of saponification: about 87.0 mol % to 89.0 mol %, degree of polymerization: about 500) manufactured by Kuraray Co., Ltd. was used as polyvinyl alcohol.

TABLE 1ConcentrationComponent(mass %)Biologically activeDexmedetomidine45substancehydrochlorideCarrierRefer to Table 28StabilizerL-cysteine5Water for injection42Sum100

TABLE 2Coating liquidCarrier1 (Example)Sodium chondroitin sulfate2 (Comparative example)Pullulan3 (Comparative example)γ-PGA4 (Comparative example)Polyvinyl alcohol

For the coating liquids1and2, a contact angle with the microneedles of polylactic acid, a surface tension, and a viscosity were measured. The contact angle was measured by a droplet method (a θ/2 method) (temperature of 23° C. to 25° C.). The surface tension was calculated by a pendant drop method using an empirical equation of Andreas et al. (temperature of 24° C.). The viscosity was obtained from a pressure loss in a capillary channel (temperature of 23° C. to 25° C.). The results are shown in Table 3.

TABLE 3SurfaceCoatingContacttensionViscosityliquidCarrierangle(mN/m)(mPa · s)1Sodium103.9°42.53151chondroitinsulfate2Pullulan96.4°41.93243

As shown in Table 3, the surface tension and the viscosity were not significantly different between the coating liquid containing sodium chondroitin sulfate and the coating liquid containing pullulan.

Next, a microneedle array of polylactic acid in which microneedles were provided at a density of 156/cm2in a region of 1 cm2and the shape of each microneedle was a quadrangular pyramid having a height of 500 μm was prepared, and then the microneedles were dipped in the coating liquids1to4to a depth of about 140 μm. After the microneedles were pulled up from the coating liquids, the solvents of the coating liquids1to4on the microneedles were dried to obtain microneedle devices1to4.

After the solvents were dried, the amount of dexmedetomidine hydrochloride in the coating formed on the microneedles was quantified by a high performance liquid chromatography method, and the amount of the carrier and the amount of the coating per one microneedle were calculated therefrom. The results are shown in Table 4 andFIG.2.

TABLE 4DexmedetomidineMicroneedlehydrochlorideCarrierCoatingdeviceCarrier(ng/needle)(ng/needle)(ng/needle)1Sodium54597702(Example)chondroitinsulfate2Pullulan29052374(Comparativeexample)3γ-PGA32758421(Comparativeexample)4Polyvinyl37767486(Comparativealcoholexample)

By using sodium chondroitin sulfate as the carrier, it was possible to manufacture a microneedle device carrying a larger amount of biologically active substance per one microneedle compared to the case of using pullulan (nonionic polysaccharide), polyvinyl alcohol (nonionic polymer), and γ-PGA.

<Test Example 2> Comparison of Composition of Coating Liquids

Dexmedetomidine hydrochloride, sodium chondroitin sulfate, L-cysteine (stabilizer) and water for injection were mixed to prepare coating liquids5to13(Examples) shown in Table 5. The details of the sodium chondroitin sulfate used are the same as in Test Example 1. A microneedle array of polylactic acid in which microneedles were provided at a density of 156/cm2in a region of 1 cm2and the shape of each microneedle was a quadrangular pyramid having a height of 500 μm was prepared, and then the microneedles were dipped in the coating liquids5to13to a depth of about 140 μm. After the microneedles were pulled up from the coating liquids, the solvents of the coating liquids5to13on the microneedles were dried to obtain microneedle devices5to13(Examples).

TABLE 5Mass ratio ofDexme-sodiumdetomidineSodiumchondroitinhydro-chondroitinsulfate/dexme-CoatingchloridesulfateL-cysteineWaterdetomidineliquid(mass %)(mass %)(mass %)(mass %)hydrochloride5450.5549.50.01164515490.02274525480.04484545460.08994565440.133104585420.1781145105400.2221245125380.2671345145360.311

After the solvents were dried, the amount of dexmedetomidine hydrochloride in the coating formed on the microneedles was quantified by a high performance liquid chromatography method, and the amount of the carrier and the amount of the coating per one microneedle were calculated therefrom. The results are shown in Table 6.

TABLE 6Amount ofAmount ofdexme-sodiumdetomidinechondroitinAmount ofMicroneedlehydrochloridesulfatecoatingdevice(ng/needle)(ng/needle)(ng/needle)53354376635884067486225628449405399458615701040071516114379758312321864421326582377

FIG.3is a graph in which the amount of coating per one microneedle and the amounts of dexmedetomidine hydrochloride and carriers contained therein are plotted with respect to the concentration (mass %) of sodium chondroitin sulfate in the coating liquid. As shown inFIG.3, it was possible to manufacture a microneedle device carrying even larger amount of dexmedetomidine hydrochloride per one microneedle by adding sodium chondroitin sulfate in the coating liquid at a concentration in a specific range.

FIG.4is a graph in which the horizontal axis ofFIG.3is changed to the concentration (mass %) of dexmedetomidine hydrochloride in the coating liquid in terms of a solid content. The concentration of dexmedetomidine hydrochloride in terms of a solid content refers to the proportion of dexmedetomidine hydrochloride to the total amount of solid content (dexmedetomidine hydrochloride, sodium chondroitin sulfate, and L-cysteine) in the coating liquid.

FIG.5is a graph in which the amount of dexmedetomidine hydrochloride (amount of DEX) carried per one microneedle is plotted, with the mass ratio of sodium chondroitin sulfate to dexmedetomidine hydrochloride (CSNa/DEX ratio) being the horizontal axis. InFIG.5, a solid line shows a measurement value, and a broken line shows a theoretical value. The theoretical value indicates the amount of DEX estimated to be contained in the coating when the maximum amount of coating was carried per one microneedle. The theoretical value was calculated assuming that the amount of coating (562 ng) carried per one microneedle when the maximum value of the amount of dexmedetomidine hydrochloride in Table 6 (486 ng/needle) was obtained was the maximum amount of coating that can be carried per one microneedle. Equation used for calculating the theoretical value is as follows.
Theoretical value of the amount of DEX (ng/needle)=562 (ng/needle)×concentration (mass %) of dexmedetomidine hydrochloride in the coating liquid in terms of solid content/100

As shown inFIG.5, when the CSNa/DEX ratio was 0.044 to 0.222, the measurement value and the theoretical value were substantially the same, although there was some variation. On the other hand, when the CSNa/DEX ratio exceeded 0.222, the measurement value was below the theoretical value, and a difference between the values increased as the CSNa/DEX ratio increased. From these results, it is estimated that, when the CSNa/DEX ratio exceeds 0.222, some kind of change occurs in physical properties of the coating liquid, and this change acts in a way to inhibit the increase in the amount of DEX carried on the microneedles.

<Test Example 3> Comparison of Composition of Coating Liquids

Dexmedetomidine hydrochloride (the biologically active substance), sodium chondroitin sulfate (the carrier), and water for injection were mixed to prepare coating liquids14to23(Examples) shown in Table 7. The details of the sodium chondroitin sulfate used are the same as in Test example 1. A microneedle array of polylactic acid in which microneedles were provided at a density of 156/cm2in a region of 1 cm2and the shape of each microneedle was a quadrangular pyramid having a height of 500 μm was prepared, and then the microneedles were dipped in the coating liquids14to23to a depth of about 140 μm. After the microneedles were pulled up from the coating liquids, the solvents of the coating liquids14to23on the microneedles were dried to obtain microneedle devices14to23.

TABLE 7Mass ratio ofDexme-sodiumdetomidineSodiumchondroitinhydro-chondroitinsulfate/dexme-CoatingchloridesulfateWaterdetomidineTrans-liquid(mass %)(mass %)(mass %)hydrochlorideparency14450.554.50.011Transparent15451540.022Transparent16452530.044Transparent17454510.089Transparent18456490.133Transparent19458470.178Transparent204510450.222Transparent214512430.267Transparent224514410.311Transparent234516390.356Slightlycloudy

After the solvents were dried, the amount of dexmedetomidine hydrochloride in the coating formed on the microneedles was quantified by a high performance liquid chromatography method, and the amount of the carrier and the amount of the coating per one microneedle were calculated therefrom. The results are shown in Table 8.

TABLE 8Amount ofAmount ofsodiumdexmedetomidinechondroitinAmount ofMicroneedlehydrochloridesulfatecoatingdevice(ng/needle)(ng/needle)(ng/needle)14451545615525125371662128648177556782218738988371970612683120670149819216261677932256117573623510181691

FIG.6is a graph in which the amount of coating per one microneedle and the amounts of dexmedetomidine hydrochloride and carriers contained therein are plotted with respect to the concentration (mass %) of sodium chondroitin sulfate in the coating liquid. As shown inFIG.6, it was possible to manufacture a microneedle device carrying even larger amount of dexmedetomidine hydrochloride per one microneedle by adding sodium chondroitin sulfate in the coating liquid at a concentration in a specific range.

FIG.7is a graph in which a horizontal axis ofFIG.6is changed to the concentration (mass %) of dexmedetomidine hydrochloride in the coating solution in terms of a solid content. The concentration of dexmedetomidine hydrochloride in terms of a solid content refers to the proportion of dexmedetomidine hydrochloride to the total amount of solid content (dexmedetomidine hydrochloride and sodium chondroitin sulfate) in the coating liquid.

FIG.8is a graph in which the amount of dexmedetomidine hydrochloride (amount of DEX) carried per one microneedle is plotted, with the mass ratio of sodium chondroitin sulfate to dexmedetomidine hydrochloride (CSNa/DEX ratio) being the horizontal axis. InFIG.8, a solid line shows a measurement value, and a broken line shows a theoretical value. The theoretical value indicates the amount of DEX estimated to be contained in the coating when the maximum amount of coating was carried per one microneedle. The theoretical value was calculated assuming that the amount of coating (822 ng) carried per one microneedle when the maximum value of the amount of dexmedetomidine hydrochloride in Table 8 (755 ng/needle) was obtained was the maximum amount of coating that can be carried per one microneedle. Equation used for calculating the theoretical value is as follows.
Theoretical value of the amount of DEX (ng/needle)=822 (ng/needle)×concentration (mass %) of dexmedetomidine hydrochloride in the coating liquid in terms of solid content/100

As shown inFIG.8, when the CSNa/DEX ratio was 0.089 to 0.222, the measurement value and the theoretical value were substantially the same. On the other hand, when the CSNa/DEX ratio exceeded 0.222, the measurement value was below the theoretical value, and a difference between the values increased as the CSNa/DEX ratio increased. From these results, it is estimated that, when the CSNa/DEX ratio exceeds 0.222, some kind of change occurs in physical properties of the coating liquid, and this change acts in a way to inhibit the increase in the amount of DEX carried on the microneedles.

REFERENCE SIGNS LIST

2Substrate4Microneedle6Coating10Microneedle device