Method for producing niosomes

Abstract

To produce highly safe niosomes using a low-cost, low-energy-consumption method. [Solution] The method for producing niosomes includes a dispersing step in which an aqueous phase is dispersed in a solution in which a nonionic surfactant and liquefied dimethyl ether are dissolved to obtain a dispersion, and a removing step in which liquefied dimethyl ether is removed from the dispersion.

Description

[Technical Field]

[0001] The present invention relates to a method for producing niosomes. [Background technology]

[0002] Niosomes are closed endoplasmic reticulum composed of a bilayer membrane of a nonionic surfactant. Niosomes have been the subject of extensive research because they can be used as carriers in drug delivery systems (DDS).

[0003] For example, Patent Document 1 discloses nonionic vesicles (niosomes) formed from nonionic substances. According to Patent Document 1, niosomes can be used as drug carriers by incorporating a water-soluble medicinal ingredient into their closed aqueous internal aqueous phase or by incorporating a hydrophobic medicinal ingredient into their bilayer membrane.

[0004] The Bangham method is a well-known method for producing liposomes (Non-Patent Document 1). The Bangham method can also be applied to niosomes. In the Bangham method, a nonionic surfactant is dissolved in an organic solvent such as chloroform, the organic solvent is evaporated from the solution to form a thin film, and then this thin film is hydrated with water or a buffer solution to produce niosomes, which are microscopic endoplasmic reticulum.

[0005] Furthermore, Non-Patent Document 2 proposes a method for preparing niosomes using supercritical carbon dioxide (scCO2) (supercritical reverse phase evaporation method). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2004-075592 [Non-patent literature]

[0007] [Non-Patent Document 1] AD Bangham, MM Standish, JC Watkins, J. mol. Biol., 1965, 13, 238-252 [Non-patent document 2] Li Jinhua. "Development of nanomaterials using supercritical carbon dioxide: Construction of a new niosome preparation method." Journal of the Japanese Society of Cosmetic Chemists 41.1 (2007): 3-14. Summary of the Invention [Problem to be solved by the invention]

[0008] Incidentally, Patent Document 1 uses an organic solvent such as chloroform in the production of niosomes, with reference to the well-known Bangham method (Non-Patent Document 1). However, organic solvents such as chloroform are harmful to the human body. Therefore, in order to utilize niosomes obtained by the method described in Patent Document 1 etc. in the fields of cosmetics and pharmaceuticals, there remains a problem that organic solvents such as chloroform must be completely removed.

[0009] Furthermore, Non-Patent Document 2 uses supercritical carbon dioxide (scCO2) instead of organic solvents, which are harmful to the human body, to produce niosomes. It is believed that the method of Non-Patent Document 2 can produce niosomes with high retention efficiency with fewer steps without using organic solvents. However, in order to use supercritical carbon dioxide, it is essential to maintain the inside of the apparatus under high temperature and high pressure conditions. Therefore, the method of Non-Patent Document 2 has the problem of high installation costs for the apparatus and the need for high energy consumption when producing niosomes.

[0010] Therefore, the main object of the present invention is to produce highly safe niosomes using a low-cost, low-energy-consumption method. [Means for solving the problem]

[0011] As a result of intensive research into means for solving the problems of the prior art, the inventors of the present invention have found that by producing niosomes using liquefied dimethyl ether (liquefied DME) as a solvent, highly safe niosomes can be obtained using a method with low cost and low energy consumption. Based on this finding, the inventors have come to the conclusion that the problems of the prior art can be solved, and have completed the present invention. Specifically, the present invention comprises the following steps:

[0012] The present invention relates to a method for producing (preparing) niosomes. In the present invention, first, a dispersion is obtained by dispersing an aqueous phase in a solution in which a nonionic surfactant and liquefied dimethyl ether are dissolved (dispersion step). In the dispersion step, a solution in which a nonionic surfactant and liquefied dimethyl ether are dissolved may be obtained, and then a dispersion may be obtained by dispersing an aqueous phase in this solution. In the dispersion step, the nonionic surfactant, liquefied dimethyl ether, and the aqueous phase may be mixed simultaneously or in any order. Next, liquefied dimethyl ether is removed from the dispersion obtained in the above step (removal step). Dimethyl ether (DME) is a gas at room temperature and normal pressure, but is liquefied at a low temperature of about 1 to 40°C and a low pressure of about 0.2 to 5 MPa. Therefore, by using liquefied dimethyl ether as a solvent, it is not necessary to maintain high temperature and high pressure conditions, as is the case with supercritical carbon dioxide, and therefore the cost and energy consumption required for producing niosomes can be reduced. In addition, liquefied dimethyl ether easily vaporizes at room temperature and normal pressure, so liquefied dimethyl ether is less likely to remain in the final niosomes obtained. Furthermore, dimethyl ether is safer for the human body than solvents such as chloroform. Therefore, by using liquefied dimethyl ether as a solvent in the production of niosomes, highly safe niosomes can be obtained using a low-cost, low-energy method.

[0013] In the method for producing niosomes according to the present invention, the solution, aqueous phase, or dispersion preferably contains a water-soluble drug. That is, the water-soluble drug may be added to any of the solution, aqueous phase, and dispersion. It is particularly preferred that the water-soluble drug be contained in the aqueous phase. The water-soluble drug is retained in the internal aqueous phase of the niosome, which is enclosed by a bilayer membrane of nonionic surfactant molecules. Note that the water-soluble drug is not necessarily limited to a drug containing a physiologically active ingredient, and may also be a drug that does not exhibit physiological activity, such as a preservative, fragrance, stabilizer, etc.

[0014] In the method for producing niosomes according to the present invention, the solution, aqueous phase, or dispersion may contain a hydrophobic drug, which is retained within the bilayer membrane of nonionic surfactant molecules in the niosomes.

[0015] In the method for producing niosomes according to the present invention, the water-soluble drug preferably contains at least one physiologically active ingredient. A physiologically active ingredient is a substance that exhibits a specific physiological effect or pharmacological action in vivo.

[0016] In the method for producing niosomes according to the present invention, the molar concentration of the nonionic surfactant relative to the aqueous phase is preferably 1 to 1000 mM, and particularly preferably 5 to 300 mM.

[0017] In the method for producing niosomes according to the present invention, the volume ratio of liquefied dimethyl ether to the aqueous phase is preferably 1:1-10.

[0018] In the method for producing niosomes according to the present invention, it is preferable that the solution and the aqueous phase are mixed in a room temperature environment of 5 to 30°C in the dispersion step.

[0019] In the method for producing niosomes according to the present invention, the solution, aqueous phase, or dispersion may further contain a co-solvent, i.e., the co-solvent may be added to any of the solution, aqueous phase, and dispersion.

[0020] In the method for producing niosomes according to the present invention, the average particle size of the finally obtained niosomes is preferably 400 to 6500 nm.

[0021] In the method for producing niosomes according to the present invention, the dispersion step may involve introducing a nonionic surfactant and dimethyl ether gas into a preparation vessel, and then increasing the pressure inside the preparation vessel to liquefy the dimethyl ether gas, thereby dissolving the nonionic surfactant and the liquefied dimethyl ether. It is also possible to directly inject liquefied dimethyl ether into the preparation vessel. The dispersion step may involve injecting an aqueous phase into the preparation vessel and dispersing the aqueous phase in the solution inside the preparation vessel. The removal step may involve reducing the pressure inside the preparation vessel to vaporize the liquefied dimethyl ether, thereby removing the liquefied dimethyl ether from the dispersion. Thus, in the dispersion step, liquefied dimethyl ether gas is liquefied in the preparation vessel and mixed with the nonionic surfactant, thereby enabling the liquefied dimethyl ether and the nonionic surfactant to be dissolved efficiently in a short time. In the removal step, the pressure inside the preparation vessel is reduced to vaporize the liquefied dimethyl ether, thereby enabling the liquefied dimethyl ether to be removed efficiently in a short time, and also reducing the likelihood of liquefied dimethyl ether remaining.

[0022] In the method for producing niosomes according to the present invention, in the removing step, the liquefied dimethyl ether may be vaporized while stirring the dispersion.

[0023] In the method for producing niosomes according to the present invention, the nonionic surfactant preferably has an HLB value of 6 to 12. [Effects of the Invention]

[0024] According to the present invention, highly safe niosomes can be produced using a low-cost, low-energy-consumption method. [Brief explanation of the drawings]

[0025] [Figure 1]FIG. 1 is a comparative photograph showing the precipitation state of niosomes in Example 1 and Comparative Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0026] The following describes embodiments of the present invention. The present invention is not limited to the embodiments described below, and includes appropriate modifications of the embodiments described below within the scope obvious to those skilled in the art. In the present specification, "A to B" means "A or more and B or less."

[0027] The present invention relates to a method for producing niosomes. Niosomes are closed endoplasmic reticulum composed of a bilayer membrane of a nonionic surfactant. A niosome contains an aqueous internal aqueous phase at its center, surrounded by a bilayer membrane of nonionic surfactant molecules. Niosomes have a structure in which the internal aqueous phase is closed off from the outside world by this bilayer membrane. The internal aqueous phase of niosomes can encapsulate water-soluble drugs, and the bilayer membrane can solubilize (encapsulate) hydrophobic drugs. The endoplasmic reticulum structure of niosomes is formed by the self-assembly of nonionic surfactants during the formulation process. Adjusting the production conditions allows for a uniform and compact closed structure to be obtained.

[0028] The manufacturing method according to the present invention basically includes a dispersion step and a removal step.

[0029] First, the dispersion step will be described. The dispersion step is a step of obtaining a dispersion liquid by dispersing an aqueous phase in a solution in which a nonionic surfactant and liquefied dimethyl ether are dissolved. In particular, this dispersion step is preferably divided into a first step of obtaining a solution in which a nonionic surfactant and liquefied dimethyl ether are dissolved, and a second step of bringing the aqueous phase into contact with the solution obtained in the first step to disperse both.

[0030] Nonionic surfactants are the main structural component of niosomes. Self-association of nonionic surfactant molecules forms a closed bilayer membrane structure. Representative examples of nonionic surfactants include fatty acid ester, ether, alcohol, glyceride, and block copolymer surfactants. Examples of fatty acid ester nonionic surfactants include polyoxyethylene fatty acid ester sorbitan fatty acid esters, polysorbates (ethoxylated sorbitan esters), sucrose fatty acid esters, glycerin fatty acid esters, polyoxyethylene fatty acid esters, and polyglycerin fatty acid esters. Examples of ether nonionic surfactants include polyoxyethylene alkyl ethers, polyoxyethylene hydrogenated castor oil, alkyl polyglucosides, polyoxyethylene vegetable oil derivatives, and polyoxyethylene phytosterols. Examples of alcohol nonionic surfactants include fatty alcohol ethoxylates, alkylphenol ethoxylates, lanolin alcohol derivatives, ethoxylated sterols, and alkyl glucosides. Examples of amide-based nonionic surfactants include fatty acid alkanolamides, polyoxyethylene fatty acid amides, amine oxides (nonionic at low pH), ethoxylated fatty acid amides, and glucamides. Examples of glyceride-based nonionic surfactants include PEGylated glycerides, polyglycerin fatty acid esters, ethoxylated monoglycerides, PEGylated vegetable oils, and ethoxylated glycerol. Examples of block copolymer-based nonionic surfactants include polyoxyethylene-polyoxypropylene block copolymers (poloxamers), polyoxyethylene-polyoxypropylene-polyoxyethylene triblock copolymers, ethylene oxide-propylene oxide condensates, polyoxyethylene-polyoxybutylene block copolymers, and polyoxyethylene-polyoxypropylene star polymers. These nonionic surfactants may be used alone or in combination. Among these, it is preferable to employ polyoxyethylene phytosterol, polyoxyethylene hydrogenated castor oil, polyoxyethylene fatty acid ester, PEGylated glyceride, and / or polyglycerin fatty acid ester.In the examples described below, PEG-5 phytosterol, PEG-10 hydrogenated castor oil, PEG-4 laurate, PEG-20 glyceryl triisostearate, and polyglyceryl-10 diisostearate are used as nonionic surfactants.

[0031] The balance between hydrophilicity and hydrophobicity of nonionic surfactants can be adjusted by adjusting the type and ratio of the agent used. This balance is expressed by the HLB value. The HLB (Hydrophilic-Lipophilic Balance) value is an index that represents the balance between hydrophilicity and hydrophobicity of a nonionic surfactant. For the formation of niosomes, it is preferable to use a nonionic surfactant with an HLB value of 6 to 12. In particular, it is preferable for the HLB value of the nonionic surfactant to be 7.5 to 11.

[0032] The HLB value is an actual measured value. The HLB value was invented by W.C. Griffin and is a numerical value given to nonionic surfactants, which represents the balance between the strength of the lipophilic group (alkyl group) and the hydrophilic group (ethylene oxide chain) of the nonionic surfactant. The HLB value is measured in accordance with the emulsification method described in "Handbook - Cosmetics and Pharmaceutical Ingredients - Revised Edition," published by Nikko Chemicals Co., Ltd. on February 1, 1977, pages 854-855. Specifically, to determine the HLB value of a nonionic surfactant, the nonionic surfactant is combined with sorbitan monostearate (NIKKOL SS-10, HLB 4.7) as a standard emulsifier, and the total amount of these two emulsifiers is kept constant while only the ratio is varied to emulsify liquid paraffin (required HLB 10.1), which is the substance to be emulsified. After leaving the mixture overnight, the optimal ratio of emulsifiers that provides stability is determined from the amount of creaming, turbidity, and separation of water from the lower layer, and the HLB value x of the nonionic surfactant is calculated using the following formula (1). [Formula (1)] y=(x×Amount used (mass%)+z×Amount used (mass%)) / 100 In formula (1), "x" represents the HLB value of the nonionic surfactant, "y" represents the required HLB value of liquid paraffin, and "z" represents the HLB value of sorbitan monostearate (NIKKOL SS-10). The HLB value of liquid paraffin can be determined in a similar manner using a combination of sorbitan monostearate (NIKKOL SS-10, HLB 4.7) and POE sorbitan monostearate (NIKKOL TS-10, HLB 14.9).

[0033] Liquefied dimethyl ether functions as a solvent for uniformly dispersing nonionic surfactants in an aqueous phase. It also functions as a solvent for nonionic surfactants. Liquefied dimethyl ether has a boiling point of -24.8°C and is a gas at room temperature and normal pressure. However, it liquefies at a low temperature of about 1 to 40°C and a low pressure of about 0.2 to 5 MPa. Specifically, dimethyl ether liquefies at about -25°C under normal pressure (1 atmosphere, 1013.25 hPa) and at room temperature (20°C) at about 5.1 atmospheres (5167.57 hPa). Since liquefied dimethyl ether easily vaporizes at room temperature and normal pressure, it is unlikely to remain in niosomes. The temperature and pressure conditions under which dimethyl ether liquefies can be derived from known vapor pressure curves.

[0034] To obtain a solution in which a nonionic surfactant and liquefied dimethyl ether are dissolved, the two may be brought into contact in a sealed preparation vessel at a temperature and pressure that maintains the dimethyl ether in a liquefied state. More specifically, after injecting the nonionic surfactant into the preparation vessel, dimethyl ether gas may be injected into the same preparation vessel to replace the air in the preparation vessel with dimethyl ether gas, and then the pressure inside the preparation vessel may be increased to liquefy the dimethyl ether gas in the preparation vessel. Alternatively, after injecting the nonionic surfactant into the preparation vessel, dimethyl ether that is already in a liquefied state may be injected into the same preparation vessel. Furthermore, the method of injecting dimethyl ether gas into the preparation vessel and the method of injecting liquefied dimethyl ether into the preparation vessel may be used in combination.

[0035] The aqueous phase is a mixture of a nonionic surfactant and a solvent (liquefied dimethyl ether). It is believed that the self-assembly of the nonionic surfactant is promoted in this aqueous phase to form a bilayer membrane during the dimethyl ether removal process described below. The aqueous phase also functions as a medium for effectively encapsulating a drug within the niosomes. The aqueous phase contains water (purified water), a buffer solution, or a mixture thereof. Examples of buffer solutions include phosphate buffer, citrate buffer, Tris buffer, HEPES buffer, acetate buffer, carbonate buffer, and glycine buffer.

[0036] To disperse a solution of a nonionic surfactant and liquefied dimethyl ether in an aqueous phase, the aqueous phase is poured into a preparation vessel containing the solution. Preferably, the solution and the aqueous phase are stirred in the preparation vessel. This results in a dispersion in which the solution and the aqueous phase are dispersed. In other words, the dispersion is obtained by mixing the aqueous phase, the nonionic surfactant, and the solvent.

[0037] The mixing of the solution and the aqueous phase is preferably carried out in a room temperature environment of 5 to 30°C. As described above, liquefied dimethyl ether can be maintained in a liquefied state at low temperature and low pressure, so the mixing of the solution and the aqueous phase can be carried out in a room temperature environment. If the mixing can be carried out in a room temperature environment in this way, the introduction cost and running cost of the production equipment, including the preparation vessel, can be reduced. Furthermore, the pressure condition under which dimethyl ether liquefies at 5°C is approximately 3550 hPa, and the pressure condition under which dimethyl ether liquefies at 30°C is approximately 7090 hPa. Therefore, the temperature inside the preparation vessel may be set to 5 to 30°C, and the pressure inside the preparation vessel may be set to 3550 to 7090 hPa to maintain the liquefied state of dimethyl ether.

[0038] The volume ratio of liquefied dimethyl ether to the aqueous phase is preferably 1:1 to 10. More specifically, the aqueous phase may be contained in the dispersion in the same amount as or greater than the liquefied dimethyl ether, and the volume ratio to the liquefied dimethyl ether is preferably 1 to 10, and may be 1 to 5 or 1 to 2.

[0039] The molar concentration of the nonionic surfactant relative to the aqueous phase is preferably 1 to 1,000 mM (mmol / L). In other words, assuming that liquefied dimethyl ether is completely removed from the dispersion and 1 liter of a solution consisting only of the nonionic surfactant and the aqueous phase remains, the amount of the nonionic surfactant in this solution will be 1 to 1,000 mmol. The molar concentration of the nonionic surfactant relative to the aqueous phase is preferably 5 to 300 mM, particularly preferably 10 to 200 mM, and may be 10 to 100 mM or 10 to 50 mM.

[0040] In the dispersion process, both or either a water-soluble drug and a hydrophobic drug can be added to a solution (dissolved nonionic surfactant and liquefied dimethyl ether), an aqueous phase, or a dispersion (dispersed solution and aqueous phase). Examples of water-soluble drugs include glucose, hyaluronic acid, niacinamide, ascorbic acid, allantoin, panthenol, caffeine, and their derivatives. The water-soluble drug is preferably added to the aqueous phase. Examples of hydrophobic drugs include retinol, tocopherol, coenzyme Q10, ceramide, lipoic acid, squalane, resveratrol, and their derivatives. The water-soluble drug and hydrophobic drug are not limited to those containing physiologically active ingredients listed here; drugs that do not contain physiologically active ingredients, such as thickeners, antibacterial agents, stabilizers, penetration enhancers, anti-irritants, and emulsifiers, can also be used. The examples of water-soluble drugs and hydrophobic drugs listed here are merely examples, and other known drugs used in the cosmetics field, etc., can also be used as appropriate.

[0041] In the dispersion process, a cosolvent can be added to the solution, aqueous phase, or dispersion. Adding a cosolvent can change the solvent properties of liquefied dimethyl ether, such as its solubility and polarity. Examples of cosolvents include ethanol, propanol, glycerin, propylene glycol, and polyethylene glycol. Ethanol increases polarity and improves the solubility of hydrophilic substances. Propanol has moderate polarity, adjusting the balance between hydrophilicity and hydrophobicity. Glycerin increases viscosity and improves the stability of niosomes. Propylene glycol increases moisturizing properties and improves the texture of the formulation. Polyethylene glycol also functions as a surfactant, improving the dispersibility of niosomes. The cosolvent may be used alone or in combination with multiple solvents. The amount of cosolvent added is preferably at a concentration equal to or less than the solubility in liquefied dimethyl ether, more specifically, preferably 10% by mass or less or 7% by mass or less relative to the liquefied dimethyl ether.

[0042] Next, the removal step will be described. The removal step is a step of removing liquefied dimethyl ether from the dispersion obtained in the above-mentioned dispersion step. In the dispersion, the dimethyl ether is kept in a liquid state by maintaining the temperature and pressure in a sealed preparation vessel under conditions that liquefy the dimethyl ether. Therefore, in the removal step, the liquefied dimethyl ether is vaporized and removed from the dispersion by increasing the temperature or reducing the pressure inside the preparation vessel that holds the dispersion. For example, the pressure inside the preparation vessel is set to normal pressure (1013.25 hPa) and the temperature of the dispersion is set to -20 to 40°C, preferably 1 to 40°C, and more preferably 5 to 30°C, whereby the liquefied dimethyl ether is vaporized and removed from the dispersion.

[0043] In the removal step, it is preferable to gradually reduce the pressure inside the preparation vessel while stirring the dispersion in the preparation vessel. Stirring of the dispersion is preferably continued from the start of pressure reduction in the preparation vessel until the pressure inside the preparation vessel reaches normal pressure. This allows the liquefied dimethyl ether to be removed with almost no residue remaining in the dispersion.

[0044] The dimethyl ether gas removed from the dispersion can be recovered and reused for the production of niosomes. Specifically, the recovered dimethyl ether gas can be injected into a preparation vessel holding a nonionic surfactant and liquefied again in this preparation vessel, thereby being reused as a solvent for the nonionic surfactant. Alternatively, the recovered dimethyl ether gas can be liquefied by cooling and / or decompression, and the liquefied dimethyl ether can be injected into a preparation vessel holding a nonionic surfactant, thereby being reused as a solvent for the nonionic surfactant.

[0045] The dispersion from which the liquefied dimethyl ether has been removed is a translucent or opaque solution, and a large number of niosomes are dispersed in this dispersion. The average particle size of the niosomes in the dispersion is preferably 400 to 6500 nm. The average particle size of the niosomes may be adjusted to an appropriate size depending on the type of drug to be held in the niosomes and the use of the niosome formulation.

[0046] After the removal step, or between the dispersion step and the removal step, a step of adjusting the particle size of the niosomes (particle size adjustment step) may be carried out. For example, the particle size of the niosomes can be adjusted to the desired size by ultrasonic treatment using an ultrasonic probe or ultrasonic bath, extrusion in which the dispersion is extruded through a porous membrane such as a polycarbonate membrane, or high-pressure homogenization in which the dispersion is passed through a narrow gap under high pressure. Additionally, the particle size of the niosomes can be adjusted by adjusting the stirring conditions of the dispersion (stirring speed, temperature, time, etc.), adjusting the type and concentration of the nonionic surfactant, or adjusting the pH of the dispersion.

[0047] The particle size of the niosomes is measured by dynamic light scattering (ELSZneo, manufactured by Otsuka Electronics). The measured particle size is analyzed by the cumulant method. The average particle size of the niosomes means the average particle size based on the scattering intensity distribution.

[0048] Niosomes can be used as carriers for drug delivery systems (DDS). Niosomes obtained by the present invention are particularly suitable for incorporation into cosmetics. Niosomes are expected to improve the permeability of encapsulated ingredients, enabling active ingredients to be delivered deep into the skin. Furthermore, encapsulating ingredients that are susceptible to oxidation or decomposition within niosomes improves stability, allowing the effects of unstable ingredients such as vitamin C and retinol to be maintained for a long period of time. Furthermore, the gradual release of ingredients encapsulated in niosomes allows for prolonged medicinal efficacy. Furthermore, because niosomes can encapsulate a variety of ingredients, including hydrophilic and hydrophobic drugs, simultaneous encapsulation of multiple ingredients is expected to produce various synergistic effects. Considering these characteristics of niosomes, niosomes can be suitably incorporated into cosmetics such as serums, creams, whitening cosmetics, sunscreens, hair care products, and eye creams. [Example]

[0049] Examples of the present invention will be described. In Example 1 of the present invention, PEG-5 phytosterol (HLB value 9.5) was used as the nonionic surfactant. Specifically, the nonionic surfactant was weighed and placed in a preparation vessel at room temperature (20 to 25°C), and the preparation vessel was then sealed. The air in the preparation vessel was then replaced with dimethyl ether gas. The pressure in the preparation vessel was then increased to approximately 0.5 to 0.7 MPa, and liquefied dimethyl ether was further injected into the preparation vessel. After confirming that the nonionic surfactant had dissolved in the preparation vessel, purified water was injected as an aqueous phase while maintaining the pressure in the preparation vessel. The solution consisting of the nonionic surfactant, liquefied dimethyl ether, and aqueous phase was stirred and dispersed using a stirrer (rotation speed: 800 rpm). While continuing to stir the solution, the pressure in the preparation vessel was gradually returned to atmospheric pressure, and the dimethyl ether was degassed to obtain a bluish-white semitransparent to opaque niosome dispersion. The volumes (ml) of liquefied dimethyl ether and purified water, the HLB value of the nonionic surfactant, the stirring temperature, the stirring time, and the molar concentration of the nonionic surfactant relative to the aqueous phase are as shown in Table 1. That is, in Example 1, the volume of liquefied dimethyl ether was 10 ml, the volume of purified water was 10 ml, the stirring temperature was room temperature (RT), the stirring time was 10 minutes, and the molar concentration of the nonionic surfactant relative to the aqueous phase was 100 mM.

[0050] In Example 2, PEG-10 hydrogenated castor oil (HLB value 6.5) was used as the nonionic surfactant. Other than that, a niosome dispersion was obtained under the same conditions and steps as in Example 1. In Examples 2 to 5, the amount [mg] of the nonionic surfactant added was adjusted so that the molar concentration of the nonionic surfactant relative to the aqueous phase was the value shown in each table.

[0051] In Example 3, PEG-4 laurate (HLB value 10.0) was used as the nonionic surfactant. A niosome dispersion was obtained under the same conditions and steps as in Example 1.

[0052] In Example 4, PEG-20 glyceryl triisostearate (HLB value 8.0) was used as the nonionic surfactant. Otherwise, a niosome dispersion was obtained under the same conditions and steps as in Example 1.

[0053] In Example 5, polyglyceryl-10 diisostearate (HLB value 10.0) was used as the nonionic surfactant. A niosome dispersion was obtained under the same conditions and steps as in Example 1.

[0054] For each of the above Examples 1 to 5, the average particle size of the niosomes one day after preparation and one month after preparation were measured. To measure the average particle size, a sample of each Example was filled into a glass bottle, and stored at room temperature for one day and one month. The sample was then placed in a glass cell and measured by dynamic light scattering using an ELSZneo manufactured by Otsuka Electronics. The average particle size was analyzed using the cumulant method, and the average particle size (nm) based on the scattering intensity distribution was determined. The results of measuring the average particle size are shown in Table 1 below.

[0055] The stability of the niosomes was evaluated for each of the above Examples 1 to 5. Regarding stability, the rate of change between the average particle size of the niosomes one day after preparation and the average particle size of the niosomes one month after preparation (average particle size after one month / average particle size after one day (%)) was evaluated on a five-point scale according to the following criteria. In other words, a lower rate of change in average particle size from one day to one month was evaluated as higher. [Judgment criteria] 5:75~110% 4:110~150% 3:150~180% 2:180-200% 1:200%~

[0056] [Table 1]

[0057] In Examples 6 to 18, the same PEG-5 phytosterol (HLB value 9.5) as in Example 1 was used as the nonionic surfactant, but the other conditions were different from those in Example 1. The results of Examples 6 to 18 are shown in Tables 2 to 5 below.

[0058] In Example 6, the molar concentration of the nonionic surfactant relative to purified water was set to 10 mM. Otherwise, a niosome dispersion was obtained under the same conditions and steps as in Example 1.

[0059] In Example 7, the molar concentration of the nonionic surfactant relative to purified water was set to 20 mM. Otherwise, a niosome dispersion was obtained under the same conditions and steps as in Example 1.

[0060] In Example 8, the molar concentration of the nonionic surfactant relative to purified water was set to 50 mM. Otherwise, a niosome dispersion was obtained under the same conditions and steps as in Example 1.

[0061] In Example 9, the molar concentration of the nonionic surfactant relative to purified water was set to 200 mM. Otherwise, a niosome dispersion was obtained under the same conditions and steps as in Example 1.

[0062] In Example 10, the volume of liquefied dimethyl ether was set to 5 ml. Otherwise, a niosome dispersion was obtained under the same conditions and steps as in Example 1.

[0063] In Example 11, the volume of liquefied dimethyl ether was 1 ml. Otherwise, a niosome dispersion was obtained under the same conditions and steps as in Example 1.

[0064] In Example 12, the stirring time of the solution was set to 20 minutes. Otherwise, a niosome dispersion was obtained under the same conditions and steps as in Example 1.

[0065] In Example 13, the solution was stirred by inversion (a method of turning the preparation container upside down).Other than that, a niosome dispersion was obtained under the same conditions and steps as in Example 1.

[0066] In Example 14, 0.1 ml of ethanol as a co-solvent was poured into the preparation vessel together with liquefied dimethyl ether. Otherwise, a niosome dispersion was obtained under the same conditions and steps as in Example 1.

[0067] In Example 15, 0.2 ml of ethanol was added as a co-solvent together with liquefied dimethyl ether to the preparation vessel. Otherwise, a niosome dispersion was obtained under the same conditions and steps as in Example 1.

[0068] In Example 16, 0.5 ml of ethanol was added as a co-solvent together with liquefied dimethyl ether to the preparation vessel. Otherwise, a niosome dispersion was obtained under the same conditions and steps as in Example 1.

[0069] In Example 17, 0.75 ml of ethanol as a co-solvent was poured into the preparation vessel together with liquefied dimethyl ether. Otherwise, a niosome dispersion was obtained under the same conditions and steps as in Example 1.

[0070] In Example 18, 1 ml of ethanol as a co-solvent was poured into the preparation vessel together with liquefied dimethyl ether. Otherwise, a niosome dispersion was obtained under the same conditions and steps as in Example 1.

[0071] [Table 2]

[0072] [Table 3]

[0073] [Table 4]

[0074] [Table 5]

[0075] Next, comparative examples are described. In Comparative Example 1, PEG-5 phytosterol (HLB value 9.5) was used as the nonionic surfactant as in Example 1, and a niosome dispersion was produced by the conventional Bangham method without using liquefied dimethyl ether as the solvent. Specifically, the nonionic surfactant was weighed and placed in a preparation vessel at room temperature (20 to 25°C). Chloroform was then poured into the preparation vessel as an organic solvent to dissolve the nonionic surfactant and the organic solvent. The solution of nonionic surfactant and organic solvent was heated while stirring with a stirrer to evaporate the organic solvent and form a thin film. Purified water was then poured into the preparation vessel as an aqueous phase to hydrate the thin film, and the mixture was stirred again with a stirrer. The thin film was dispersed in the aqueous phase to obtain a bluish-white semitransparent to opaque niosome dispersion. The molar concentration of the nonionic surfactant relative to the aqueous phase was adjusted to 100 mM. Furthermore, for Comparative Example 1, the average particle size of the niosomes was measured in the same manner as in Example 1, and its stability was evaluated. The results are shown in Table 6 below.

[0076] [Table 6]

[0077] Furthermore, tests were conducted to confirm the drug retention efficiency for Examples 1, 5, 6, 9, 10, and Comparative Example 1. In the drug retention efficiency confirmation test, a 0.2 M glucose solution was poured into a preparation vessel as the aqueous phase to prepare each sample. Each sample was stored at room temperature for one day, and then the glucose in the external phase (i.e., glucose not retained within the niosomes) was removed by dialysis. An equal volume of ethanol was then added to each sample from which the glucose in the external phase had been removed to disrupt the niosome vesicle structure. Glucose was then quantified for each sample using the Mutarotase-GOD method (Labo Assay™ Glucose, Fujifilm Wako Pure Chemical Corporation), and the glucose retention efficiency of the niosomes was calculated. The formula for calculating retention efficiency is as follows: [Formula] Retention efficiency (%) = (quantified glucose amount / glucose amount injected into preparation vessel) × 100

[0078] Furthermore, for Example 19, a test was conducted to confirm the retention efficiency of tocopherol acetate as a hydrophobic drug. In Example 19, PEG-5 phytosterol (HLB value 9.5) was used as the nonionic surfactant, as in Example 1. However, in Example 19, the nonionic surfactant and tocopherol acetate were weighed and placed in a preparation vessel at room temperature (20 to 25°C), after which the preparation vessel was sealed and the air in the preparation vessel was replaced with dimethyl ether gas. Subsequently, a niosome dispersion was obtained for Example 19 under the same conditions and steps as in Example 1. The samples for Example 19 were stored at room temperature for one day, and the tocopherol acetate in the external phase was removed by dialysis. Then, an equal amount of ethanol was added to each sample from which the tocopherol acetate in the external phase had been removed to destroy the niosome vesicle structure. Thereafter, the amount of tocopherol acetate in each sample was quantified by HPLC (NexeraX2, Shimadzu Corporation), and the retention efficiency of tocopherol acetate by niosomes was calculated. The formula for calculating the retention efficiency is as follows: [Formula] Retention efficiency (%) = (quantified amount of tocopherol acetate / amount of tocopherol acetate injected into the preparation vessel) x 100

[0079] The calculation results of the retention efficiency in each Example and Comparative Example are shown in Table 7 below. As shown in Table 7, it can be seen that the retention efficiency of glucose by niosomes is improved according to the Examples of the present invention compared to Comparative Example 1. Since glucose is a drug that exhibits hydrophilicity, it is expected that similar results will be obtained for other hydrophilic drugs.

[0080] [Table 7]

[0081] Furthermore, Figure 1 shows a comparative photograph of the niosome dispersion obtained in Example 1 and the niosome dispersion obtained in Comparative Example 1. As shown in Figure 1, almost no precipitation was observed in the niosome dispersion of Example 1. On the other hand, in Comparative Example 1, precipitation was observed at about half the height of the solution. Therefore, according to the examples of the present invention, it can be seen that the dispersion state of the niosomes in the solution is good and a niosome dispersion with excellent stability can be obtained.

[0082] In the above, the present specification has described the embodiments and examples of the present invention in order to express the contents of the present invention. However, the present invention is not limited to the above embodiments and examples, and includes modifications and improvements that are obvious to those skilled in the art based on the matters described in the present specification. [Industrial Applicability]

[0083] The present invention relates to a method for producing niosomes. Therefore, the present invention can be suitably used in, for example, the cosmetics manufacturing industry.

Claims

1. a dispersing step of dispersing an aqueous phase in a solution of a nonionic surfactant and liquefied dimethyl ether to obtain a dispersion; a removal step of removing the liquefied dimethyl ether from the dispersion. Method for producing niosomes.

2. The solution, the aqueous phase, or the dispersion contains a water-soluble drug. The method for producing niosomes according to claim 1.

3. The solution, the aqueous phase, or the dispersion contains a hydrophobic drug. The method for producing niosomes according to claim 1.

4. The water-soluble drug contains at least one physiologically active ingredient. The method for producing niosomes according to claim 2 or claim 3.

5. The molar concentration of the nonionic surfactant relative to the aqueous phase is 1 to 1000 mM. The method for producing niosomes according to claim 1.

6. The volume ratio of the liquefied dimethyl ether to the aqueous phase is 1:1 to 10. The method for producing niosomes according to claim 1.

7. In the dispersion step, the solution and the aqueous phase are mixed in a room temperature environment of 5 to 30°C. The method for producing niosomes according to claim 1.

8. The solution, the aqueous phase, or the dispersion further comprises a co-solvent. The method for producing niosomes according to claim 1.

9. The average particle size of the niosomes is 400 to 6500 nm The method for producing niosomes according to claim 1.

10. The dispersion step comprises: After introducing the nonionic surfactant and dimethyl ether gas into a preparation vessel, the pressure in the preparation vessel is increased to liquefy the dimethyl ether gas and dissolve the nonionic surfactant and the liquefied dimethyl ether; and injecting the aqueous phase into the preparation vessel and dispersing the aqueous phase in the solution in the preparation vessel; The removing step includes: removing the liquefied dimethyl ether from the dispersion by reducing the pressure in the preparation vessel to vaporize the liquefied dimethyl ether. The method for producing niosomes according to claim 1.

11. The removing step includes vaporizing the liquefied dimethyl ether while stirring the dispersion. The method for producing niosomes according to claim 10.

12. The nonionic surfactant has an HLB value of 6 to 12. The method for producing niosomes according to claim 1.

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