WO2004020473A1

WO2004020473A1 - Microbeads of natural polysaccharide and hyaluronic acid and processes for preparing the same

Info

Publication number: WO2004020473A1
Application number: PCT/KR2003/001716
Authority: WO
Inventors: Kwang Yong Cho; Jin Hoon Kim; Jae Young Lee; Tae Seok Moon; Byung Hyuk Min
Original assignee: Lg Life Sciences Ltd.
Priority date: 2002-08-27
Filing date: 2003-08-25
Publication date: 2004-03-11
Also published as: KR20040018927A; AU2003251221A1; KR100523953B1

Abstract

The present invention relates to microbeads comprising natural polysaccharides selected from alginic acid and chitosan, and hyaluronic acid, and processes for preparing the same. The microbeads according to the present invention are biocompatible and have a high swelling property and thus can be used for various purposes such as post-operative adhesion-preventing gels or films, materials for wrinkle treatment, materials for plastic surgery, materials for arthritis treatment, and drug delivery vehicles. Especially, the chitosan-hyaluronic acid microbead and the chitosan-coated alginic acid-hyaluronic acid microbead, in which an amide bond is formed between the amine group of chitosan and the carboxyl group of hyaluronic acid and/or alginic acid, have an excellent swelling property, physical stability and viscoelasticity and thus can be used as biocompatible materials able to withstand various in vivo conditions.

Description

MICROBEADS OF NATURAL POLYSACCHARIDE AND HYALURONIC ACID AND PROCESSES FOR PREPARING THE SAME

FIELD OF THE INVENTION

The present invention relates to microbeads comprising natural polysaccharides selected from alginic acid and chitosan, and hyaluronic acid, and processes for preparing the same, and more particularly to alginic acid-hyaluronic acid microbeads, chitosan-hyaluronic acid microbeads and chitosan-coated alginic acid-hyaluronic acid microbeads, having biocompatibility and an excellent swelling property in aqueous solutions such as water and saline solution and very good physical stability and processes for preparing such microbeads. The microbeads according to the present invention can thus be used for various applications such as materials for prevention of post-operative adhesion, wrinkle treatment, plastic surgery, drug delivery, etc.

BACKGROUND OF THE INVENTION

Hyaluronic acid is a linear biocompatible polymer comprising linked repeating units of N-acetyl-D-glucosamine and D-glucuronic acid, which is present in high concentration in the vitreous body of the eye, the synovial fluid of joints, rooster comb, etc. Hyaluronic acid and its derivatives are described in Korean Patent No. 375,299, entitled "Cross-linking Type Amide Derivatives Of Hyaluronic Acid And Process For Preparation Of Them," which is incorporated herein as background material.

Hyaluronic acid derivatives have been widely developed to be used as post-operative adhesion-preventing films or gels, materials for wrinkle treatment, materials for plastic surgery, materials for arthritis treatment, vehicles for drug delivery systems, etc., and especially, much research into their commercial use as wrinkle treatment material and plastic surgery material has been performed (F. Manna, M. Dentini, P. Desider, O. De Pita, E. Mortilla, B. Maras, Journal of European Academy of Dematology and Venereology, 13 (1999) 183-192). Microparticles made using hyaluronic acid have a good physical stability and biodegradability, and, for example, U.S. Patent Nos. 6,066,340 and 6,039,970 disclose hyaluronic acid derivatives synthesized by coupling ethyl alcohol or benzyl alcohol into Ihe carboxyl group of hyaluronic acid. These derivatives are insoluble in water, but are soluble in organic solvents such as dimethyl sulfoxide. Accordingly, methods are known for preparing solid microparticles by emulsion solvent extraction based on such hydrophobic properties of the hyaluronic acid derivatives. However, the hyaluronic acid rnicroparticles of the prior art have some drawbacks such as the use of highly toxic organic solvent, particle sizes less than tens of micrometers and a low swelling property.

Meanwhile, alginic acid abundant in the surface of brown algae is a polysaccharide comprising 1 - 4 linkage of mannuronic acid and guluronic acid without any branch chains, where ratios and amounts of both acids are randomly provided. Biodegradable alginic acid bead can be prepared without using any organic solvents at room temperature and under mild conditions.

U.S. Patent No. 5,459,054 discloses that cells or genetically modified cells are encapsulated in alginic acid containing a high content of guluronic acid that impairs immune response upon transplantation or implantation. Further, U.S. Patent No. 5,472,648 discloses a process for production of alginate microbeads from drops of alginate solution delivered by a nozzle, with the drops being solidified by dropping them into an ionic solution and the alginate solution being converted into drops by high-frequency vibration. However, these alginic acid microbeads have inferior viscoelasticity and swelling property.

SUMMARY OF THE INVENTION

The object of the present invention is to provide novel biocompatible microbeads capable of overcoming the problems in the prior ar

More particularly, one object of the present invention is to provide microbeads having biocompatibility, excellent swelling property in aqueous solutions such as water and saline solutions, and very good physical properties, thereby being able to withstand various in vivo conditions.

Another object of the present invention is to provide processes for efficiently preparing such microbeads by simple methods.

In order to accomplish these objects, the inventors of the present invention have researched and performed many experiments, resulting in the finding that microbeads made by physically and/or chemically bonding natural polysaccharides selected from alginic acid and chitosan, and hyaluronic acid have biocompatibility, excellent swelling property and good physical stability. The present invention was accomplished based on this finding.

Accordingly, the present invention provides microbeads with a high swelling property, comprising natural polysaccharides selected from alginic acid, chitosan and hyaluronic acid.

The microbeads according to the present invention can be divided into three types depending upon the kinds of natural polysaccharides and the form of bonding thereof to produce microbeads: alginic acid-hyaluronic acid microbead (a); chitosan-hyaluronic acid microbead (b); and chitosan-coated alginic acid-hyaluronic acid microbead (c). In these three types of microbeads, the form of bonds between chitosan and hyaluronic acid (and/or alginic acid) can be again divided into physical bonds and chemical bonds.

Chitosan has an amine group capable of receiving hydrogen ions, which exhibits a cationic charge under acidic or neutral conditions, thus generating an electrostatic force to form an ionic bond with the carboxyl group of hyaluronic acid. This ionic bond is herein referred to as a "physical bond." This physical bond, however, cannot provide relatively good physical stability and viscoelasticity. Especially, microbeads formed by only physical bonding have low physical stability. Accordingly, these beads are limited in their in vivo use. Therefore, if a stronger bond such as an amide bond is formed between the amine group of chitosan and the carboxyl group of hyaluronic acid, microbeads having better physical stability and viscoelasticity can be made, in which the amide bond can be referred to as a "chemical bond" or "covalent bond." Alginic acid, having a carboxyl group like hyaluronic acid, also has an ability to form chemical bonds with chitosan. Accordingly, in these cases where chitosan is contained in microbeads according to the present invention, i.e., chitosan-hyaluronic acid microbead (b) and chitosan-coated alginic acid-hyaluronic acid microbead (c), a chemical bond is preferably formed between the hyaluronic acid and/or alginic acid, and the chitosan.

Moreover, among the above three types of microbeads, the chitosan-hyaluronic acid microbead (b) and the chitosan-coated alginic acid-hyaluronic acid microbead (c) are more preferable in terms of having relatively higher swelling property, physical stability and viscoelasticity.

Within the range of not reducing the effect of the present invention, any other components, as known in the art to which the present invention pertains, may be contained in the microbeads of the present invention.

In below, the present invention will be described in more detail. Many ranges as defined herein, e.g., the ranges of molecular weights, the ranges of concentrations, the ranges of reaction temperatures, the ranges of reaction times, etc, can be understood as ones defined for efficient performance of the present invention.

1. Components of Microbeads

Hyaluronic acid that can be used in the present invention includes hyaluronic acid itself and its salts. These salts of hyaluronic acid include, for example, such inorganic salts as sodium hyaluronate, potassium hyaluronate, calcium hyaluronate, magnesium hyaluronate, zinc hyaluronate and cobalt hyaluronate, and such organic salts as tetrabutylammonium hyaluronate, but are not limited thereto.

The molecular weight of hyaluronic acid and its salts are preferably in the range of 100,000 to 3,000,000 to form uniform and stable microbeads. Alginic acid that can be used in the present invention includes alginic acid itself and its salts. These salts of alginic acid include, for example, sodium alginate, potassium alginate, calcium alginate, magnesium alginate, etc. Generally, alginic acid is composed by linking mannuronic acid and guluronic acid, and may exist as a species containing less than 50% of guluronic acid or one containing more than 50% of guluronic acid, of which both can be used in the present invention. Since alginic acid-hyaluronic acid microbead among microbeads according to the present invention is formed with guluronic acid, various microbeads having somewhat different properties can be obtained depending upon formulations.

Chitosan used in the present invention includes chitosan oligomers as well as chitosan polymer itself, and is preferably a material soluble in an aqueous solution of pH 2 ~ 8. The molecular weight of chitosan is not particularly limited. That is, oligmers of molecular weight less than 1,600 and/or polymers of molecular weight 1,600 to 10,000,000 can be used for the present invention.

2. Processes for preparation of microbeads

Microbeads of the present invention can be prepared by various processes depending upon the type of components and the types of bonds thereof, as explained in below.

As mentioned previously, since hyaluronic acid in the present invention includes hyaluronic acid itself and its salts, the term "hyaluronic acid solution" as used herein includes a solution of hyaluronic acid, a solution of hyaluronate, and a mixed solution of hyaluronic acid and hyaluronate. Also, since alginic acid in the present invention includes alginic acid itself and its salts, the term "alginic acid solution" as used herein includes a solution of alginic acid, a solution of alginate, and a mixed solution of alginic acid and alginate. Furthermore, since chitosan in the present invention includes chitosan itself and its oligomers, the term "chitosan solution" as used herein includes a solution of chitosan, a solution of chitosan oligomers, and a mixed solution of chitosan and its oligomers.

( 1 ) Process for preparation of alginic acid-hvaluronic acid microbead (a) Alginic acid-hyaluronic acid microbead (a) can be made by spraying a mixture of an alginic acid aqueous solution and a hyaluronic acid aqueous solution into a mixed salt aqueous solution of 2- or 3-valent cationic salt and sodium chloride. When a mixed solution of alginic acid and hyaluronic acid is sprayed into the salt solution of 2- or 3-valent cationic salt and sodium chloride, microbeads of solid phase are precipitated by ion-exchange with the 2- or 3- valent cationic salt. In an embodiment, an alginic acid may be added to a hyaluronic acid aqueous solution or a hyaluronic acid may be added to an alginic acid aqueous solution to make a mixed solution of alginic acid and hyaluronic acid.

The ratios of alginic acid : hyaluronic acid in the mixture are preferably in the range of 1 : 10 ~ 10 : 1 for easy formation of solid microbeads. The concentrations of alginic acid and hyaluronic acid in the mixture are preferably in the range of 0.1 ~ 10% by weight for easy spraying.

2-valent cationic salts used in a mixed salt solution include, for example, calcium chloride, magnesium chloride, sfrontium chloride, barium chloride, etc, which may be used in the combination of two or more. A representative example of 3-valent cationic salts used in the mixed salt solution is aluminum chloride. The concentration of 2- or 3-valent cationic salt in the mixed salt solution is preferably in the range of 0.01 ~ 15 M so as to obtain solid microbeads.

2- or 3-valent cationic salts react very fast with alginic acid to form ionic bonds. If only 2- or 3-valent cationic salt is present, the crosslinking reaction will occur only at the surface of bead because the salt cannot penetrate to the inside of the bead owing to this rapid reaction. Accordingly, sodium chloride is necessary to control the rate of the ionic bond-forming reaction, in which the reaction of sodium chloride and alginic acid competes with the reaction of 2- or 3-valent cationic salt and alginic acid, resulting in forming homogeneous beads throughout uniform crosslinking reaction. For such control, the concentration of sodium chloride in the mixed salt solution is preferably in the range of 0.01 ~ 45 M.

Methods of spraying a mixture of alginic acid solution and hyaluronic acid solution into a mixed salt solution of 2- or 3-valent cationic salt and sodium chloride are not particularly limited; for example, using a spray device.

The temperature of the reaction solution in the preparation of microbeads is preferably in the range of 0 ~ 40°C, more preferably room temperature (20 ~ 25°C). The pH of the reaction solution is preferably in the range of 2 ~ 8. Moreover, the retention time for generation of microbeads in reaction solution is not particularly limited, and is preferably 1 ~ 4 hours.

Microbeads can be finally obtained by various methods. For example, in order to eliminate water contained in microbeads, they can be dried under nitrogen atmosphere for 2 ~ 24 hours. After elimination of water, microbeads are obtained in the form of solid phase.

Furthermore, where acetone, acetone aqueous solution (preferably, more than 90%) and/or C₂ ~ C₆ alcohol such as 2-propanol are added in a reaction solution and then a certain time elapses, microbeads are formed as a further solid phase, which can be centrifuged for separation. The time of reaction solution is preferably 2 ~ 24 hours after addition of acetone and the like.

The produced microbeads can be separated and/or refined by well-known methods in the art to which the present invention pertains. These separation and refinement methods include distillation under atmospheric pressure or reduced pressure, recrystallization, column chromatography, ion-exchange chromatography, gel chromatography, affinity chromatography, thin-layer chromatography, phase separation, solvent extraction, dialysis, washing, etc. Each refinement may be performed after any reaction or after a series of reactions.

The produced microbeads can be washed with water, alcohol such as ethanol, ether such as diethylether, and/or acetone. Washing may be performed two or more times so as to obtain microbeads of high purity.

(2) Process for preparation of chitosan-hyaluronic acid microbead (b)

In order for the chitosan-hyaluronic acid microbead (b) to have better physical stability and viscoelasticity and higher swelling property for its use as a biocompatible material, as mentioned above, chitosan and hyaluronic acid are preferably crosslinked to each other by amide bond (chemical bond) formed between the amide group of chitosan and the carboxyl group of hyaluronic acid. This microbead (b) can be prepared by the below methods.

An exemplary method (1) of preparing the chitosan-hyaluronic acid microbead (b) comprises:

(A) a step of preparing a hyaluronic acid aqueous solution containing a carboxyl group- activating agent, and a chitosan aqueous solution, respectively;

(B) a step of adding dropwise of these two solutions into a solution containing an emulsifier to form microbeads; and

(C) a step of separating and refining the microbeads.

In a preferred embodiment, between the step (B) and (C), a step can be further included of adding acetone, acetone aqueous solution (preferably, more than 90% acetone) and/or C₂ ~ C₆ alcohol to the solution containing microbeads to make the microbeads more hardening. This effect is expected to be due to the fact that acetone and the like eliminate water from the surface of the swelled chitosan-hyaluronic acid microbead. As a result, microbeads having become more hardening have merits of not clinging to each other and keeping their form in subsequent separation and refinement steps.

In a preferred embodiment, after the step (C), a step may be further included of dispersing the microbeads obtained from the step (C) in acetone or an acetone aqueous solution and then adding a carboxyl group-activating agent to induce an additional amide reaction. The additional amide reaction forms many more amide bonds between the remaining carboxyl groups of hyaluronic acid and the remaining amide groups of chitosan, thereby giving the microbeads improved physical stability and viscoelasticity.

Another exemplary method (2) of preparing chitosan-hyaluronic acid microbead (b) compnses:

(Al) a step of preparing a hyaluronic acid aqueous solution and a chitosan aqueous solution, respectively;

(Bl) a step of adding dropwise of these two aqueous solutions into a solution containing an emulsifier, to form microbeads;

(CI) a step of separating and refining the microbeads; and

(Dl) a step of dispersing the microbeads in acetone or an acetone aqueous solution and then adding a carboxyl group-activating agent thereto to induce an amidation reactioa

In the preparation method (2), an ionic bond (physical bond) between the carboxyl group of hyaluronic acid and the amine group of chitosan in the microbeads of the step (Bl) is converted to an amide bond (chemical bond) in the step (Dl).

In a preferred embodiment, between the steps (Bl) and (CI), a step may be further included of adding acetone, acetone aqueous solution, and/or C₂ ~ C₆ alcohol in the solution containing microbeads to make the beads more hardening.

Based upon these two preparation methods (1) and (2), other applied or modified methods are also possible, which should be understood to be included in the range of the present invention.

The more detailed reaction conditions for preparation of the chitosan-hyaluronic acid microbead (b) are described in below, without distinction between the above two exemplary methods (1) and (2).

The concentrations of chitosan aqueous solution and the concentration of hyaluronic acid aqueous solution are preferably in the range of 0.00001 ~ 10% by weight, respectively. The mixing ratios of the chitosan aqueous solution and the hyaluronic acid aqueous solution are in the range of 0.00001 : 1 ~ 100 : 1 (chitosan amine groups : hyaluronic acid carboxyl groups) for smooth performance of the amidation reaction.

The kinds of emulsifiers in the above preparation methods are not particularly limited and include, for example, lipid such as lecithin, phosphatidyl choline, phosphatidyl ethanol amine, phosphatidyl-serine and phosphatidyl inositol; their derivatives; and ester derivatives of fatty acids such as glyceryl stearate, sorbitan palmitate and sorbitan stearate. Among them, sorbitan-based emulsifiers are preferred and include, for example, polyoxyethylene sorbitan monolaurate (Tween 20), polyoxyethylene sorbitan monopalmitate (Tween 40), polyoxyethylene sorbitan monostearate (Tween 60), polyoxyethylene sorbitan monooleate (Tween 80), sorbitan monolaurate (Span 20), sorbitan monostearate (Span 60), sorbitan monooleate (Span 80), etc. Among them, lecithin, Tween 20, Tween 80 and Span 80 are particularly preferred.

The addition amount of emulsifier is preferably in the range of 0.05% ~ 10% by volume of the solution.

The solutions containing the emulsifiers include, for example, mineral oil (e.g., mineral light white oil), methanol, a mixture of mineral oil and methanol, a mixture of glycerol and 1- propanol, a mixture of glycerol and 2-propanol, a mixture of ethylene glycol and 1-propanol, a rnixture of ethylene glycol and ethanol, a mixture of ethylene glycol and methanol, a mixture of ethylene glycol and acetone, etc.

In the amidation reaction, the carboxyl group-activating agent acts as an activating the carboxyl group of hyaluronic acid to induce formation of the amide bond between the carboxyl group of hyaluronic acid and the amide group of chitosan. Preferably, in order to support the function of activating agent, e.g., to promote the main reaction and reduce side reactions, an auxiliary activating agent may be used together with the activating agent.

Examples of preferable activating agents include carbodiimide-based compounds, such as l-alkyl-3-(3-dimemylaminopropyl) carbocliimides (alkyl herein is an alkyl of 1-10 carbon atoms), l-e yl-3-(3-(trimethylammonio)propyl) carbodiimide ("ETC"), and l-cyclohexyl-3- (2-mo holinoethyl) carbodiimide ("CMC"). Among them, l-ethyl-3-(3-dimethylar__inopropyl) carbodiimide hydrochloride ("EDC") is particularly desirable.

Examples of preferable auxiliary activating agents include N-hydroxysu∞inimide ("ΝHS"), 1-hydroxybenzotriazole ("HOBt"), 3,4-dihydrO-3-hydroxy-4-oxo-l,2,3-benzotriazine ("HOOBt"), l-hydroxy-7-azabenzotriazole ("HO At"), and Ν-hydroxy-sulfosuccinimide ("Sulfo-ΝHS"). Among them, ΝHS is particularly desirable.

Addition amounts of the activating agent and auxiliary activating agent are decided by several factors such as the concentration of hyaluronic acid and the activity of agents. For example, the added amount of EDC is preferably in the range of 0.00001 to 100 mg/ml, and the added amount of ΝHS is preferably in the range of 0.00001 to 100 mg/ml.

The temperature and pH of the reaction solution, reaction time, methods for separating and refining the produced microbeads and the like are not largely different from those of the preparation method of the alginic acid-hyaluronic acid microbead (a).

(3) Process for preparation of chitosan-coated alginic acid-hyaluronic acid microbead (c)

Chitosan-coated alginic acid-hyaluronic acid microbead (c), more specifically, the microbead (c) in which alginic acid-hyaluronic acid bead is coated with chitosan, can be made by methods described below.

An exemplary method (1) for preparation of the chitosan-coated alginic acid-hyaluronic acid microbead (c) comprises:

(A) a step of preparing an alginic acid aqueous solution and a hyaluronic acid aqueous solution, respectively;

(B) a step of dispersing a mixture of the alginic acid aqueous solution and the hyaluronic acid aqueous solution in an aqueous solution containing 2- or 3-valent cationic salt and sodium chloride to form microbeads; (C) a step of adding the formed microbeads in a chitosan aqueous solution to coat the microbeads with chitosan; and

(D) a step of separating and refining the microbeads from a reaction solution.

In the above preparation method (1), the microbeads of the step (C) have an ionic bond (physical bond) between the carboxyl group of hyaluronic acid and/or alginic acid and the amine group of chitosan.

The mixing ratios of alginic acid and hyaluronic acid are the same as that in the preparation method of the alginic acid-hyaluronic acid (a).

The added amounts of chitosan for coating are preferably in the range of 1 : 100 ~ 100 : 1 in view of the ratio of the carboxyl group of alginic acid and/or hyaluronic acid to the amine group of chitosan, but it is not necessarily limited to the above range.

In an embodiment, an alginic acid may be added to a hyaluronic acid aqueous solution or a hyaluronic acid may be added to an alginic acid aqueous solution to make the mixture of alginic acid and hyaluronic acid of the step (B).

In a preferred embodiment, after the step (D), a step may be further included of performing an additional amidation reaction of the refined microbeads. As mentioned above, since alginic acid and hyaluronic acid have carboxyl group and chitosan has amine group, the carboxyl group of alginic acid, the carboxyl group of hyaluronic acid, or the carboxyl group of alginic acid and hyaluronic acid can be crosslinked to the amine group of chitosan by amide bond (chemical bond), whereby microbeads having improved swelling property, physical stability and viscoelasticity can be made. Such amidation reaction can be performed, for example, by dispersing the microbeads obtained from the step (D) in distilled water and then adding a carboxyl group-activating agent thereto, preferably together with an auxiliary activating agent. In an embodiment, the amidation reaction can be performed by adding microbeads obtained from the step (D) to distilled water in which a carboxyl group-activating agent, preferably together with an auxiliary activating agent, is dissolved. The kind and addition amount of the carboxyl group-activating agent and auxiliary activating agent for amidation reaction in the preparation method (1) are the same as those in the preparation method of the chitosan-hyaluronic acid microbead (b).

While acetone or an acetone aqueous solution is used as a solvent for additional amidation reaction of the chitosan-hyaluronic acid microbead (b), distilled water is used as a solvent for additional amidation reaction of the chitosan-coated alginic acid-hyaluronic acid microbead (c). In the case of the additional amidation reaction of the chitosan-hyaluronic acid microbead (b), the microbead (b) prior to completion of amidation reaction may be dissolved in an aqueous solvent such as distilled water and thus cannot keep its form, whereby it is necessary to use an organic solvent such as acetone (specifically, together with a trace of water contained in bead or in solvent for easy performance of the crosslinking reaction). Meanwhile, in the case of the additional amidation reaction of the chitosan-coated alginic acid-hyaluronic acid microbead (c), since the microbead (c) prior to completion of amidation reaction is not dissolved in distilled water, an aqueous solvent such as distilled water can be used as a solvent.

Another exemplary method for preparation of chitosan-coated alginic acid-hyaluronic acid microbead (c) comprises:

(Al) a step of preparing an alginic aqueous solution and a hyaluronic aqueous solution, respectively;

(B 1 ) a step of spraying a mixture of the alginic acid aqueous solution and the hyaluronic acid aqueous solution into a chitosan aqueous solution in which 2- or 3-valent cationic salt and sodium chloride are dissolved, to coat microbeads with chitosan while forming the microbeads; and

(CI) a step of separating and refining the microbeads from a reaction solution.

The preparation method (2) is the same as the preparation method (1) except that chitosan is coated on the surface of microbeads while the microbeads are formed.

In the preparation method (2), the mixing ratios of alginic acid and hyaluronic acid, the addition amounts of chitosan and so on are the same as those in the preparation method (1).

Likewise, after the step (CI), a step may be further included of performing an additional amidation reaction of the refined microbeads, in which carboxyl group-activating agent and auxiliary activating agent are the same as those in the preparation method (1).

3. Microbead

Microbeads according to the present invention can be made having various properties, depending upon the kinds of components comprising the beads, spray condition, whether chemical bonds (amide bond) are present or not, etc.

Microbeads according to the present invention have an approximately spherical shape, as seen in FIG. 2. Moreover, they have various particle sizes, for example, 30 ~ 1000 μm, depending upon reaction conditions, and thus are not particularly limited in their dimensions.

Microbeads according to the present invention are biocompatible and have an excellent swelling property in aqueous solutions such as water and saline solution. Accordingly, the microbeads can be used as post-operative adhesion-preventing films or gels, materials for wrinkle treatment, materials for plastic surgery, materials for arthritis treatment, vehicles for drug delivery system, etc.

Especially, where a very high swelling property, physical stability and viscoelasticity are required, the chitosan-hyaluronic acid microbead (b) and the chitosan-coated alginic acid- hyaluronic acid microbead (c) among microbeads according to the present invention are further preferable. Also, in both microbeads (b) and (c), microbeads having an amide bond between the carboxyl group of alginic acid and/or hyaluronic acid and the amide group of chitosan are especially desirable.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an IR analysis of microbeads produced using sodium hyaluronate of MW 500,000 in EXAMPLES 2, 4 and 8 according to the present invention;

FIG. 2 is a photograph taken by a scanning electron microscope of a microbead produced in EXAMPLE 8 according to the present invention;

FIG. 3 is a photograph taken by an optical microscope of microbeads produced in

EXAMPLE 8 according to the present invention, with the microbeads being dispersed in distilled water;

FIG. 4A and 4B are photographs taken by an optical microscope of microbeads produced in EXAMPLE 11 according to the present invention, FIG. 4A showing the microbeads under a dry condition and FIG. 4B showing the microbeads dispersed in saline solution, respectively;

FIG. 5A and 5B are photographs taken by an optical microscope of microbeads produced in EXAMPLE 12 according to the present invention, with the microbeads being dispersed in saline solution;

FIG. 6 is a photograph taken by an optical microscope of microbeads produced in

EXAMPLE 14 according to the present invention, with the microbeads being dispersed in saline solution;

FIG. 7 is a graph showing the viscoelasticity of microbeads produced in EXAMPLE 17 according to the present invention, compared to that of hyaluronic acid as a prior art;

FIG. 8 is a photograph taken by an optical microscope of microbeads produced in

EXAMPLE 18 aαOrding to the present invention, with the microbeads being dispersed in saline solution; and

FIG. 9 is a graph showing the viscoelasticity of microbeads produced in EXAMPLE 19 according to the present invention, compared to that of hyaluronic acid as a prior art. DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Hereinafter, the present invention will be described in more detail by EXAMPLES, but the scope of the present invention is not limited thereto. For convenience of explanation, the contents of alginic acid-hyaluronic acid microbead (a) and chitosan-coated alginic acid- hyaluronic acid microbead (c) are together described in EXAMPLES 1 ~ 10 and EXPERIMENTAL EXAMPLES 1 ~ 3, and the contents of chitosan-hyaluronic acid microbead (b) are separately described in EXAMPLES 11 ~ 20 and EXPERIMENTAL EXAMPLES 4 - 13.

EXAMPLE 1 : Preparation of alginic acid-hyaluronic acid microbead - 1

10 ml of an aqueous solution containing sodium hyaluronate (molecular, weight:

150,000, 250,000, 370,000 and 500,000; LG Life Science Ltd.) at a concentration of 10 mg/ml was prepared, and 10 mg of alginic acid was added thereto to make a mixed solution of alginic acid-hyaluronic acid, followed by stirring. 10 ml of the mixed solution was sprayed into an aqueous salt solution containing 200 mM calcium chloride and 150 mM sodium chloride by a spray device. The sprayed particles underwent ion-exchange in the aqueous salt solution to be converted into solid microbeads, which were precipitated (140 mg, yield: 70%). After 2 hours, the solid microbeads were centrifuged at 1,500 rpm and washed several times with distilled water and then dispersed in 20 ml of distilled water.

EXAMPLE 2: Preparation of alginic acid-hvaluronic acid microbead - 2

The process of EXAMPLE 1 was repeated except that 10 ml of an aqueous solution containing sodium hyaluronate (MW: 150,000, 250,000, 370,000 and 500,000) at a concentration of 20 mg/ml was used to produce microbeads (150 mg, yield: 50%).

Among the microbeads produced thus, microbead comprising sodium hyaluronate of MW 500,000 was analyzed by IR analysis. The IR analysis result is illustrated in FIG. 1. EXAMPLE 3: Preparation of chitosan-coated alginic acid-hyaluronic acid microbead - 1

10 ml of an aqueous solution containing sodium hyaluronate (molecular weight: 150,000, 250,000, 370,000 and 500,000) at a concentration of 10 mg/ml was prepared, and 100 mg of alginic acid was added thereto to make a mixed solution of alginic acid-hyaluronic acid, followed by stirring. To an aqueous salt solution containing 200 mM calcium chloride and 150 mM sodium chloride, chitosan (MW: less than 1,600; EugenBio) was added at a concentration of 5 mg/ml to prepare 10 ml of a reaction solution. 10 ml of the hyaluronic acid-alginic acid mixed solution was sprayed into the reaction solution by a spray device. The sprayed particles underwent ion-exchange in the aqueous salt solution to be converted into solid microbeads, which precipitated, and the microbeads were coated with chitosan (150 mg, yield: 75%). After 2 hours, the solid microbeads were centrifuged at 1,500 rpm and washed several times with distilled water and then dispersed in 20 ml of distilled water.

EXAMPLE 4: Preparation of chitosan-coated alginic acid-hyaluronic acid microbead - 2

The process of EXAMPLE 3 was repeated except that 10 ml of an aqueous solution containing sodium hyaluronate (MW: 150,000, 250,000, 370,000 and 500,000) at a concentration of 20 mg/ml was used to produce microbeads (180 mg, yield: 60%). Among the microbeads produced thus, microbead comprising sodium hyaluronate of MW 500,000 was analyzed by IR analysis. The IR analysis result is illustrated in FIG. 1.

EXAMPLE 5: Preparation of chitosan-coated alginic acid-hyaluronic acid microbead - 3

Microbeads (140 mg, yield: 70%) produced in EXAMPLE 1 were dispersed in 20 ml of an aqueous solution containing chitosan (MW: less than 1,600) at a concentration of 5 mg/ml and the solution was stirred for 2 hours to coat the surface of microbeads with chitosan. The coated solid microbeads were centrifuged at 1,500 rpm and washed several times, and then dispersed in 20 ml of distilled water. EXAMPLE 6: Preparation of chitosan-coated alginic acid-hyaluronic acid microbead - 4

Microbeads (150 mg, yield: 50%) produced in EXAMPLE 2 were dispersed in 20 ml of an aqueous solution containing chitosan (MW: less than 1,600) at a concentration of 5 mg/ml and the solution was stirred for 2 hours to coat the surface of microbeads with chitosan. The coated solid microbeads were centrifuged at the rate of 1,500 rpm and washed several times, and then dispersed in 20 ml of distilled water.

EXAMPLE 7: Preparation of alginic acid-hyaluronic acid microbead with chitosan connected bv amide bond - 1

Microbeads (150 mg, yield: 75%) produced in EXAMPLE 3 were washed with distilled water and then dispersed in 20 ml of distilled water. 50 mg of l-ethyl-3-(3- dimethylaminopropyl) carbodiimide (EDC) and 60 mg of N-hydroxysuccinimide (NHS) were added to this dispersion while stirring at room temperature, to perform an amidation reaction. After 4 hours, solid microbeads were centrifuged at 1500 rpm and washed with distilled water, and then dispersed in 20 ml of distilled water.

EXAMPLE 8: Preparation of alginic acid-hyaluronic acid microbead with chitosan connected bv amide bond - 2

Microbeads (180 mg, yield: 60%) produced in EXAMPLE 4 were washed several times with distilled water and then dispersed in 20 ml of distilled water. 50 mg of EDC and 60 mg of NHS were added to this dispersion while stirring to perform an amidation reaction. After 4 hours, solid microbeads were centrifuged at 1500 rpm and washed with distilled water, and then dispersed in 20 ml of distilled water. Among the microbeads produced thus, microbead comprising sodium hyaluronate of MW 500,000 was analyzed by IR analysis. The IR analysis result is illustrated in FIG. 1. EXAMPLE 9: Preparation of alginic acid-hyaluronic acid microbead with chitosan connected by amide bond - 3

Microbeads (140 mg, yield: 70%) produced in EXAMPLE 5 were washed several times with distilled water and then dispersed in 20 ml of distilled water. 50 mg of EDC and 60 mg of NHS were added to this dispersion while stirring to perform an amidation reaction. After

4 hours, solid microbeads were centrifuged at 1500 rpm and washed with distilled water, and then dispersed in 20 ml of distilled water.

EXAMPLE 10: Preparation of alginic acid-hvaluronic acid microbead with chitosan connected by amide bond - 4

Microbeads (150 mg, yield: 50%) produced in EXAMPLE 6 were washed several times with distilled water and then dispersed in 20 ml of distilled water. 50 mg of EDC and 60 mg of NHS were added to this dispersion while stirring to perform an amidation reaction. After 4 hours, solid microbeads were centrifuged at 1500 rpm and washed with distilled water, and then dispersed in 20 ml of distilled water.

EXPERIMENTAL EXAMPLE 1 : IR analysis of microbeads

Among alginic acid-hyaluiOnic acid microbeads (EXAMPLE 2), chitosan-coated alginic acid-hyaluronic acid microbeads (EXAMPLE 4) and alginic acid-hyaluronic acid microbeads with chitosan connected by amide bond (EXAMPLE 8), microbeads comprising sodium hyaluronate of MW 500,000 were analyzed by IR (infra-red) analysis. According to the IR analysis, 1529.55 cm^"1 peak was observed in the chitosan-coated alginic acid-hyaluronic acid microbeads (EXAMPLE 4), which was not observed in the alginic acid-hyaluronic acid microbeads (EXAMPLE 2). This peak indicates the existence of free amine groups of chitosan. Moreover, the broad tendency around 1639.49 cm^"1 peak was observed in the alginic acid- hyaluronic acid microbeads with chitosan connected by amide bond (EXAMPLE 8), which indicates the existence of amide bonds formed by the amidation reaction between the amine groups of chitosan and the carboxyl groups of hyaluronic acid and alginic acid.

EXPERIMENTAL EXAMPLE 2: Identification of shapes of microbeads

The shapes and sizes of microbeads, produced in EXAMPLES 1 to 10, were observed through a scanning electron microscope and optical microscope. The below TABLE 1 shows the sizes (diameter) of microbeads according to the content and the molecular weight of hyaluronic acid (HA).

[TABLE 1]

As can be seen in TABLE 1, as the molecular weight of hyaluronic acid increases, the size of microbead tends to increase.

FIG. 2 shows a photograph of the alginic acid-hyaluronic acid microbead with chitosan connected by amide bond (EXAMPLE 8) taken by a scanning electron microscope, and FIG. 3 shows a photograph of microbeads swollen in distilled water, taken by an optical microscope. As seen in these photographs, the microbeads generally have the shape of a sphere.

EXPERIMENTAL EXAMPLE 3: Measurement of swelling property of microbeads

Swelling property of some microbeads produced in EXAMPLES 1, 4 and 8 was measured. The swelling property was measured as a swelling ratio that was calculated based upon the following formula, in which W^ (dry weight) means a weight of microbeads, dried at room temperature for 24 hours in an oven, and W^ (swelling weight) means a weight of microbeads, swollen for 24 hours in distilled water, followed by removal of moisture of their surface.

Swelling Ratio = Wwe_t / W^

The below TABLE 2 shows the swelling ratios.

[TABLE 2]

As can be seen in TABLE 2, the chitosan-coated alginic acid-hyaluronic acid microbead (EXAMPLE 4) and alginic acid-hyaluronic acid microbead with chitosan connected by amide bond (EXAMPLE 8) have swelling ratios of more than 2 times that of the alginic acid-hyaluronic acid microbead (EXAMPLE 1). This is expected to be due to moisture caught by the remaining free amine groups of chitosan coated on or crosslinked to microbeads.

EXAMPLE 11: Preparation of chitosan-hyaluronic acid microbead - 1 (using mineral oil and Tween 80)

5 ml of an aqueous solution containing sodium hyaluronate (MW: 250,000) at a concentration of 10 mg/ml was prepared, and 5 ml of an aqueous solution containing chitosan oligomer (MW: less than 1,600) at a concentration of 5 mg/ml was prepared. To the hyaluronic acid aqueous solution, 25 mg of EDC and 30 mg of NHS based upon 100 mg of hyaluronate were added. These two solutions were simultaneously added dropwise to 100 ml of mineral oil containing 4 ml, 5 ml and 6 ml of Tween 80 as an emulsifier, respectively. After allowing an amidation reaction to proceed while stirring for 2 hours, the solution was dried under nitrogen atmosphere for 12 hours so as to remove water dispersed in the mineral oil. The reaction solution was centrifuged to obtain microbeads. The microbeads obtained thus were washed several times with ethanol, acetone and water and then dried under nitrogen atmosphere (weight of microbeads: 53.1 mg, 40 mg and 31 mg; yield: 70.8%, 53.3% and 41.3%).

EXPERIMENTAL EXAMPLE 4: Identification of shape of microbeads produced in EXAMPLE 11

The shape and size (diameter) of microbeads produced in EXAMPLE 11 were observed through an optical microscope, and the size of microbeads in accordance with the amount of emulsifier was measured under a dry condition and swelling condition, respectively, and are described in the below TABLE 3. As seen in TABLE 3, as the amount of emulsifier increases, the size of microbeads tends to decrease.

[TABLE 3]

FIGS. 4 A and 4B are photographs showing the dried shape of chitosan-hyaluronic acid microbeads, produced using 6 ml of emulsifier (Tween 80) in EXAMPLE 11, and showing the swollen shape of the microbeads, respectively. The microbeads generally exhibit the shape of spheres under both the dry condition (FIG.4A) and swollen condition (FIG.4B).

EXAMPLE 12: Preparation of chitosan-hyaluronic acid microbead - 2 (using mineral oil and Span 80) 5 ml of an aqueous solution containing sodium hyaluronate (MW: 500,000) at a concentration of 10 mg/ml was prepared, and 5 ml of an aqueous solution containing chitosan oligomer (MW: less than 1,600) at a concentration of 5 mg/ml was prepared. To the hyaluronic acid aqueous solution, 25 mg of EDC and 30 mg of NHS based upon 100 mg of hyaluronate were added. These two solutions were simultaneously added dropwise to 100 ml of mineral oil containing 0.75 ml, 0.85 ml, 0.1 ml and 0.15 ml of Span 80 as an emulsifier, respectively. After allowing an amidation reaction to proceed while stirring for 2 hours, the solution was dried under nitrogen atmosphere for 12 hours so as to remove water dispersed in the mineral oil. The reaction solution was centrifuged to obtain microbeads. The microbeads obtained thus were washed several times with ethanol, acetone and water and then dried under nitrogen atmosphere (weight of microbeads: 91.2 mg, 89.5 mg, 79.5 mg and 70.3 mg; yield: 91.2%, 89.5%, 79.5% and 70.3%).

EXPERIMENTAL EXAMPLE 5: Identification of shape of microbeads produced in EXAMPLE 12

The shape and size (diameter) of microbeads prepared in EXAMPLE 12 were observed through an optical microscope, and the size of microbeads in accordance with the amount of emulsifier was measured under a dry condition and swelling condition, respectively, and described in the below TABLE 4. As seen in TABLE 4, as the amount of emulsifier increases, the size of microbeads tends to decrease.

[TABLE 4]

FIGS. 5 A and 5B are photographs showing the shape of chitosan-hyaluronic acid microbeads taken by an optical microscope, which were produced using 0.1 ml and 0.15 ml of emulsifier (Span 80), respectively, and then dispersed in saline solution. The microbeads generally exhibit the shape of spheres using both 0.1 ml of Span 80 (FIG. 5 A) and using 0.15 ml ofSpan 80 (FIG. 5B).

EXAMPLE 13: Preparation of chitosan-hyaluronic acid microbead - 3 (using mineral oil and Span 80)

10 ml of an aqueous solution containing sodium hyaluronate (MW: 1,500,000) at a concentration of 5 mg/ml was prepared, and 5 ml of an aqueous solution containing chitosan oligomer (MW: 110,000; FMC BioPolymer Corporation) at a concentration of 0.5, 1 and 2 mg/ml, respectively, was prepared. To the hyaluronic acid aqueous solution, 25 mg of EDC and 30 mg of NHS based upon 100 mg of hyaluronate were added. These two solutions were simultaneously added dropwise to 100 ml of mineral oil containing 0.1 ml, 0.15 ml and 0.2 ml of Span 80 as an emulsifier, respectively. After allowing an amidation reaction to proceed while stirring for 2 hours, the solution was dried under nitrogen atmosphere for 12 hours so as to remove water dispersed in the mineral oil. The reaction solution was centrifuged to obtain microbeads. The microbeads obtained thus were washed several times with ethanol, acetone and water and then dried under nitrogen atmosphere. The detailed reaction conditions and their results are described in the below TABLE 5.

[TABLE 5]

EXPERIMENTAL EXAMPLE 6: Identification of shape of microbead produced in EXAMPLE 13

The shape and size (diameter) of microbeads produced in EXAMPLE 13 were observed through an optical microscope, and the size of microbeads according to the amount of emulsifier and the amount of chitosan were measured under a swelling condition, and the results are described in the below TABLE 6. As seen in TABLE 6, as the amount of emulsifier increases and the amount of chitosan decreases, the size of bead tends to decrease.

[TABLE 6]

EXAMPLE 14: Preparation of chitosan-hvaluronic acid microbead - 4 (using mineral oil and Span 80)

5 ml of an aqueous solution containing sodium hyaluronate (MW: 150,000, 500,000 and 1,148,000) at a concentration of 10 mg/ml was prepared, and 10 ml of an aqueous solution containing sodium hyaluronate (MW: 2,465,000) at a concentration of 5 mg/ml was prepared. Also, 5 ml of an aqueous solution containing chitosan (MW: 110,000) at a concentration of 0.2 and 1 mg/ml, respectively, was prepared. To the hyaluronic acid aqueous solutions, 10 mg of EDC and 12 mg of NHS based upon 100 mg of hyaluronate were added. These two solutions (hyaluronic acid aqueous solutions and chitosan aqueous solution) were simultaneously added dropwise to 100 ml of mineral oil containing 0.1 ml of Span 80 as an emulsifier, respectively. After allowing an amidation reaction to proceed while stirring for 2 hours, the solution was dried under nitrogen atmosphere for 12 hours so as to remove water dispersed in the mineral oil. The reaction solution was centrifuged to obtain microbeads. The microbeads obtained thus were washed several times with ethanol, acetone and water and then dried under nitrogen atmosphere. The detailed reaction conditions and their yields are described in the below TABLE 7.

[TABLE 7] Reaction Yields

EXPERIMENTAL EXAMPLE 7: Identification of shape of microbead produced in EXAMPLE 14

The shape and size (diameter) of microbeads produced in EXAMPLE 14 were observed through an optical microscope, and the size of microbeads according to the molecular weight and concentration of hyaluronic acid and the amount of chitosan were measured under a swelling condition, and the results are described in the below TABLE 8. As seen in TABLE 8, as the molecular weight and concentration of hyaluronic acid increase and the amount of chitosan increases, the size of bead tends to increase.

[TABLE 8]

FIG. 6 discloses a photograph showing the swollen shape of chitosan (0.1%, 5 mg)- hyaluronic acid (MW: 2,465,000) microbeads taken by an optical microscope, which were produced using 0.1 ml of emulsifier (Span 80) and then dispersed in saline solution. As seen in FIG.6, the microbeads generally exhibit the shape of sphere.

EXAMPLE 15: Preparation of chitosan-hyaluronic acid microbead - 5 (using a n ixture of mineral oil/ methanol and Tween 20)

10 ml of an aqueous solution containing sodium hyaluronate (MW: 2,465,000) at a concentration of 5 mg/ml was prepared, and 5 ml of an aqueous solution containing chitosan (MW: 110,000) at a concentration of 0.5 mg/ml was prepared. To the hyaluronic acid aqueous solution, 20 mg of EDC and 24 mg of NHS based upon 100 mg of hyaluronate were added. These two solutions were simultaneously added dropwise to 100 ml of a niixture of mineral oil and methanol (mineral oil : methanol = 7 : 3, 6 : 4, 5 : 5, 4 : 6). After allowing an amidation reaction to proceed while stirring for 1 hour, 250 ml of acetone was added thereto to make microbeads, dispersed in the mixed solution, more hardening. The microbeads were washed several times using diethylether and acetone. After washing, to chitosan-hyaluronic acid microbeads dispersed in 20 ml of acetone, 10 mg of EDC and 12 mg of NHS based upon 100 mg of HA derivative were added to perform the second amidation reaction for 2 hours. The microbeads obtained thus were washed 3 times with acetone and then dried under nitrogen atmosphere (weight of microbeads: 37.2 mg, 36.8 mg, 39.5 mg and 44.1 mg; yield: 70.87%, 70.1%, 15.24% and 84%). In the following experiment, the microbeads were added to saline solution at a concentration of 2% and then their rheological property was measured using a rheometer (PAAR PHYSICA Corporation), and they were diluted and their swollen shape was observed.

EXPERIMENTAL EXAMPLE 6: Identification of shape and measurement of viscoelasticity of microbead produced in EXAMPLE 15

The shape and size (diameter) of microbeads produced in EXAMPLE 15 were observed through an optical microscope, and the size of beads in accordance with the mixing ratio of mineral oil and methanol were measured under a swelling condition. The result of measurement is described in the below TABLE 9. As seen in TABLE 9, as the ratio of methanol increases, the size of beads tends to decrease.

[TABLE 9]

Microbeads produced in EXAMPLE 15 were adjusted to a concentration of 20 mg/ml to prepare a solution for measurement, and in order to identify their rheological property, 1 ml of the solution was randomly chosen for analysis. Complex viscosity was measured at 0.02 - 1 Hz using a rheometer. The complex viscosity measured at 0.02 Hz is described in the below TABLE 10. It can be seen in TABLE 10 that the complex viscosity of chitosan-hyaluronic acid microbead increased compared to the complex viscosity of hyaluronic acid (MW: 2,465,000), 1,258,100 cP (at 0.02 Hz).

[TABLE 10]

EXAMPLE 16: Preparation of chitosan-hvaluronic acid microbead - 6 (using a mixture of mineral oil/methanol and Tween 20)

10 ml of an aqueous solution containing sodium hyaluronate (MW: 2,465,000) at a concentration of 5 mg/ml was prepared, and 5 ml of an aqueous solution containing chitosan (MW: 110,000) at a concentration of 0.02 mg/ml was prepared. To the hyaluronic acid aqueous solution, 20 mg of EDC and 24 mg of NHS based upon 100 mg of sodium hyaluronate were added. These two solutions were simultaneously added dropwise to 100 ml of a mixture of mineral oil and methanol (mineral oil : methanol = 5 : 5). After allowing an amidation reaction to proceed while stirring for 1 hour, 250 ml of acetone was added thereto to make microbeads, dispersed in the mixed solution, more hardening. After 2 hours, the reaction solution was centrifuged to obtain the microbeads. The microbeads were washed several times using diethylether, acetone, etc. After washing, to chitosan-hyaluronic acid microbeads (HA derivative: 5 mg/ml) dispersed in 20 ml of acetone, 10 mg, 15 mg and 20 mg of EDC and 12 mg, 18 mg and 24 mg of NHS based upon 100 mg of HA derivative were added, respectively, to perform the second amidation reaction for 2 hours. The microbeads obtained thus were washed 3 times with acetone and then dried under nitrogen atmosphere (weight of microbeads: 39.92 mg, 29.9 mg and 37.5 mg; yield: 79.44%, 59.68% and 74.85%). In the foUowing experiment, the microbeads were added to saline solution at a concentration of 2% and then their rheological property was measured using a rheometer, and they were diluted and their swollen shape was observed.

EXPERIMENTAL EXAMPLE 9: Measurement of viscoelasticity of microbead produced in EXAMPLE 16

Microbeads produced in EXAMPLE 16 were adjusted to a concentration of 20 mg/ml to prepare a solution for measurement, and in order to identify their rheological property, 1 ml of the solution was randomly chosen for analysis. Complex viscosity was measured at 0.02 - 1 Hz using a rheometer. The complex viscosity measured at 0.02 Hz is described in the below TABLE 11. It can be seen in TABLE 10 that the complex viscosity of chitosan-hyaluronic acid microbeads increased compared to the complex viscosity of hyaluronic acid (MW: 2,465,000), 1,258,100 cP (at 0.02 Hz); however, where the second amidation reaction rate (crosslinking rate) was too high, the viscoelasticity tended to decrease.

[TABLE 11]

EXAMPLE 17: Preparation of chitosan-hvaluronic acid microbead - 7 (using a mixture of mineral oil/methanol and Tween 20)

50 ml of an aqueous solution containing sodium hyaluronate (MW: 2,465,000) at a concentration of 5 mg/ml was prepared, and 25 ml of an aqueous solution cOntaining chitosan (MW: 110,000) at a concentration of 0.02 mg/ml was prepared. These two solutions were simultaneously added dropwise to 500 ml of a mixture of mineral oil and methanol (mineral oil : methanol = 5 : 5) containing 25 ml of Tween 80 as an emulsifier. After allowing a reaction to proceed with stirring for 1 hour, 500 ml of acetone was added thereto to make microbeads, dispersed in the mixed solution, more hardening. After 2 hours, the reaction solution was centrifuged to obtain the microbeads. The microbeads were washed several times using diethylether and acetone. After washing, to 20 ml of 90% acetone solution in which the chitosan-hyaluronic acid microbeads were dispersed (HA derivative: 5 mg/ml), added were 1.49 mg, 3.39 mg, 5.24 mg, 6.23 mg, 12.32 mg, 22.17 mg, 69 mg and 70.35 mg of EDC, and 1.79 mg, 4.07 mg, 6.29 mg, 7.48 mg, 14.78 mg, 26.6 mg, 82.8 mg and 84.42 mg of NHS, based upon 100 mg of HA derivative, respectively, to perform an amidation reaction for 2 hours. The microbeads obtained thus were washed 3 times with acetone and then dried under nitrogen atmosphere (weight of microbeads: 202.2 mg, 176.8 mg, 173.95 mg, 192.86 mg, 182.97 mg, 228. 46 mg, 230.81 mg and 241.98 mg; yield: 80.72%, 70.59%, 69.44%, 76.99%, 73.04%, 91.2%, 92.14% and 96.6%). In the following experiment, the microbeads were added to saline solution at a concentration of 2% and then their rheological property was measured using a rheometer, and they were diluted and their swollen shape was observed.

EXPERIMENTAL EXAMPLE 10: Measurement of viscoelasticity of microbead produced in EXAMPLE 17

Microbeads produced in EXAMPLE 17 were adjusted to a concentration of 20 mg/ml to prepare a solution for measurement, and in order to identify their rheological property, 1 ml of the solution was randomly selected for testing. Complex viscosity was measured at 0.02 - 1 Hz using a rheometer. The complex viscosity measured at 0.02 Hz is described in the below TABLE 12. It can be seen in TABLE 12 that the complex viscosity of chitosan-hyaluronic acid microbeads increased compared to the complex viscosity of hyaluronic acid (MW: 2,465,000), 1,258,100 cP (at 0.02 Hz); however, where the crosslinking rate was too high, the viscoelasticity tended to decrease. Higher crosslinking rates caused microbeads to be dispersed in the saline solution without being swollen.

[TABLE 12]

The complex viscosities measured in the range of 0.02 - 1 Hz are depicted in FIG. 7.

EXAMPLE 18: Preparation of chitosan-hvaluronic acid microbead - 8 (using methanol and Tween 80)

25 ml of an aqueous solution ∞ntaining sodium hyaluronate (MW: 2,465,000) at a concentration of 10 mg/ml was prepared, and 12.5 ml of an aqueous solution containing chitosan (MW: 110,000) at a concentration of 0.04 mg/ml was prepared. These two solutions were simultaneously added dropwise to 250 ml of methanol containing 2.5 ml, 7.5 ml, 10 ml and 12.5 ml of Tween 80 as an emulsifier, respectively. After allowing a reaction to proceed with stirring for 1 hour, 250 ml of acetone was added thereto to make microbeads, dispersed in the mixed solution, more hardening. After 2 hours, the reaction solution was centrifuged to obtain the microbeads. The microbeads were washed several times using diethylether and acetone. After washing, to 20 ml of 90% acetone solution in which the chitosan-hyaluronic acid microbeads were dispersed (HA derivative: 5 mg/ml), added were 27.67 mg and 37.34 mg (Tween 80; 2.5 ml), 7.99 mg and 9.85 mg (Tween 80; 7.5 ml), 10.27 mg and 10.7 mg (Tween 80; 10 ml), and 6 mg and 7.34 mg (Tween 80; 12.5 ml) of EDC, and 33.2 mg and 44.81 mg (Tween 80; 2.5 ml), 9.59 mg and 11.82 mg (Tween 80; 7.5 ml), 12.32 mg and 12.84 mg (Tween 80; 10 ml), and 7.2 mg and 8.81 mg (Tween 80; 12.5 ml) of NHS, based upon 100 mg of HA derivative, respectively, were added to perform an amidation reaction for 2 hours. The microbeads obtained thus were washed 3 times with acetone and then dried under nitrogen atmosphere. Reaction conditions and results are described in the below TABLE 13. In the following experiment, the microbeads were added to saline solution at a concentration of 2% and then their rheological property was measured using a rheometer, and they were diluted and their swollen shape was observed.

[TABLE 13]

EXPERIMENTAL EXAMPLE 11: Identification of shape and measurement of viscoelasticity of microbead produced in EXAMPLE 18 The shape and size of microbeads produced in EXAMPLE 18 were observed through an optical microscope. The size (diameter) of beads in accordance with the amount of Tween

80 as an emulsifier was measured under the saline solution-swelling condition and the result is described in the below TABLE 14. As seen in TABLE 14, as the amount of emulsifier increases, the size of bead tends to decrease.

[TABLE 14]

Microbeads produced in EXAMPLE 18 were adjusted to a concentration of 20 mg/ml to prepare a solution for measurement, and in order to identify their rheological property, 1 ml of the solution was randomly selected for testing. Complex viscosity was measured at 0.02 - 1 Hz using a rheometer. The complex viscosity measured at 0.02 Hz is described in the below TABLE 15. It can be seen in TABLE 15 that the complex viscosity of chitosan-hyaluronic acid microbeads increased compared to the complex viscosity of hyaluronic acid (MW: 2,465,000), 1,258,100 cP (at 0.02 Hz); however, where the crosslinking rate was too high, the viscoelasticity tended to decrease. Higher crosslinking rates caused microbeads to be dispersed in saline solution without being swollen.

[TABLE 15]

EXAMPLE 19: Preparation of chitosan-hyaluronic acid microbead - 9 (using methanol and Tween 80)

40 ml of an aqueous solution containing sodium hyaluronate (MW: 2,465,000) at a concentration of 10 mg/ml was prepared, and 5 ml of an aqueous solution containing chitosan (MW: 110,000) at a concentration of 0.12 mg/ml was prepared. These two solutions were simultaneously added dropwise to 300 ml of methanol rontaining 12 ml of Tween 80 as an emulsifier. After allowing a reaction to proceed while stirring for 3 hours, 250 ml of acetone was added thereto to make microbeads, dispersed in the mixed solution, more hardening. After 2 hours, 4 hours, 15 hours and 24 hours, respectively, the reaction solution was centrifuged to obtain the microbeads. The microbeads were washed several times using diethylether and acetone. After washing, to 15 ml of 90% acetone solution in which the chitosan-hyaluronic acid microbeads were dispersed (HA derivative: 6.67 mg/ml), added were 5.34 mg (acetone treatment time: 2 hours), 6.78 mg, 7.32 mg, 8.3 mg, 8.8 mg and 9.58 mg (acetone treatment time: 4 hours), 4.967 mg (acetone treatment time: 15 hours), and 6.48 mg (acetone treatment time: 24 hours) of EDC, and 6.41 mg (acetone treatment time: 2 hours), 8.14 mg, 8.784 mg, 9.96 mg, 10.56 mg and 11.50 mg (acetone treatment time: 4 hours), 5.96 mg (acetone treatment time: 15 hours), and 7.78 mg (acetone treatment time: 24 hours) of NHS, based upon 100 mg of HA derivative, respectively, to perform an amidation reaction for 2 hours. The microbeads obtained thus were washed 3 times with acetone and then dried under nitrogen atmosphere. Reaction conditions and results are described in the below TABLE 16. In the following experiment, the microbeads were added to saline solution at a concentration of 2% and then their rheological property was measured using a rheometer, and they were diluted and their swollen shape was observed.

[TABLE 16]

FIG. 8 shows the shape of chitosan-hyaluronic acid microbeads (acetone treatment time: 2 hours) which are dispersed and swollen in saline solution. As seen in FIG. 8, it can be seen that the microbeads generally have the shape of spheres.

EXPERIMENTAL EXAMPLE 12: Measurement of viscoelasticity of microbead produced in EXAMPLE 19

Microbeads produced in EXAMPLE 19 were adjusted to a concentration of 20 mg/ml to prepare a solution for measurement, and in order to identify their rheological property, 1 ml of the solution was randomly selected for testing. Complex viscosity was measured at 0.02 - 1 Hz using a rheometer. The complex viscosity measured at 0.02 Hz is described in the below TABLE 15. It can be identified in TABLE 15 that the complex viscosity of chitosan-hyaluronic acid microbeads increased compared to the complex viscosity of hyaluronic acid (MW: 2,465,000), 1,258,100 cP (at 0.02 Hz); however, where the crosslinking rate was too high, the viscoelasticity tended to decrease.

[TABLE 17]

The complex viscosities measured in the range of 0.02 - 1 Hz are depicted in FIG. 9. EXAMPLE 20: Preparation of chitosan-hvaluronic acid microbead - 10 (using methanol and Tween 80)

40 ml of an aqueous solution containing sodium hyaluronate (MW: 2,465,000) at a concentration of 10 mg/ml was prepared, and 5 ml of an aqueous solution containing chitosan (MW: 110,000) at a concentration of 0.12 mg/ml was prepared. These two solutions were simultaneously added dropwise to 300 ml of methanol containing 12 ml of Tween 80 as an emulsifier. After allowing a reaction to proceed with stirring for 1 hour, 300 ml of 2-propanol was added thereto to make microbeads, dispersed in the mixed solution, more hardening. After 2 hours, the reaction solution was centrifuged to obtain the microbeads. The microbeads were washed several times using diethylether and acetone. After washing, to 15 ml of 90% acetone solution in which the chitosan-hyaluronic acid microbeads were dispersed (HA derivative: 6.67 mg/ml), added were 6.04 mg and 8.51 mg of EDC and 7.25 mg and 10.21 mg of NHS, based upon 100 mg of HA derivative, respectively, to perform an amidation reaction for 2 hours. The microbeads obtained thus were washed 3 times with acetone and then dried under nitrogen atmosphere (weight of microbeads: 342.51 mg and 342.91 mg; yield: 85.5% and 85.6%).

EXAMPLE 21: Preparation of chitosan-hvaluronic acid microbead - 9 (using methanol and Tween 80)

40 ml of an aqueous solution containing sodium hyaluronate (MW: 2,465,000) at a concentration of 10 mg/ml was prepared, and 5 ml of an aqueous solution containing chitosan (MW: 110,000) at a concentration of 0.12 mg/ml was prepared. These two solutions were simultaneously added dropwise to 300 ml of methanol containing 12 ml of Tween 80 as an emulsifier. After allowing reaction to proceed with stirring for one hour, 300 ml of acetone was added thereto to make microbeads, dispersed in the mixed solution, more hardening. After 4 hours, the reaction solution was centrifuged to obtain the microbeads. The microbeads were washed several times using diethylether and acetone. After washing, the microbeads were dispersed in 90% acetone solution to make them more solid. The microbeads were again washed with acetone and then dried under nitrogen atmosphere (weight of microbeads: 267.68 mg and 282.98 mg; yield: 66.82% and 70.64%). 50 mg of dried chitosan-hyaluronic acid microbeads, respectively, were dispersed in 7.5 ml of 90% acetone solution (HA derivatives: 6.67 mg/ml), and then 1.75 mg, 2.25 mg, 2.75 mg, 3.25 mg, 3.75 mg, 4.25 mg, 4.75 mg and 5.25 mg of EDC, and 2.1 mg, 2.7 mg, 3.3 mg, 3.9 mg, 4.5 mg, 5.1 mg, 5.7 mg and 6.3 mg of NHS were added thereto to perform an amidation reaction for 2 hours. The microbeads prepared thus were washed 3 times with acetone and then dried under nitrogen atmosphere (weight of microbeads: 44.75 mg, 43.67 mg, 47.09 mg, 47.5 mg, 45.93 mg, 46.16 mg, 40.08 mg and 48.99 mg; yield: 89.5%, 87.33%, 94.17%, 95%, 91.85%, 92.31%, 80.15% and 97.97%). In the following experiment, the microbeads were added to saline solution at a concentration of 2% and then their rheological property was measured using a rheometer, and they were diluted and their swollen shape was observed.

EXPERIMENTAL EXAMPLE 13: Measurement of viscoelasticity of microbead produced in EXAMPLE 21

Microbeads produced in EXAMPLE 21 were adjusted to a concentration of 20 mg/ml to prepare a solution for measurement, and in order to identify their rheological property, 1 ml of the solution was randomly selected for testing. Complex viscosity was measured at 0.02 - 1 Hz using a rheometer. The complex viscosity measured at 0.02 Hz is described in the below TABLE 18. It can be seen in TABLE 18 that the complex viscosity of chitosan-hyaluronic acid microbeads increased compared to the complex viscosity of hyaluronic acid (MW: 2,465,000), 1,258,100 cP (at 0.02 Hz); however, where the crosslinking rate was too high, the viscoelasticity tended to decrease. Higher crosslinking rates caused microbeads to be dispersed in saline solution without being swollen.

[TABLE 18]

EDC/NHS (mg)

Complex viscosity (cP) (based upon 100 mg of HA derivative)

INDUSTRIAL APPLICABILITY

As described above, the microbeads according to the present invention are biocompatible and have a high swelling property and thus can be used for various applications such as post-operative adhesion-preventing gels or films, materials for wrinkle treatment, materials for plastic surgery, materials for arthritis treatment, and drug delivery vehicles. Especially, the chitosan-hyaluronic acid microbead and the chitosan-coated alginic acid- hyaluronic acid microbead, in which an amide bond is formed between the amine group of chitosan and the carboxyl group of hyaluronic acid and/or alginic acid, have excellent swelling property, physical stability and viscoelasticity and thus can be used as biocompatible materials able to withstand various in vivo conditions.

As the present invention may be embodied in several forms without departing from the spirit or essential characteristics thereof, it should also be understood that the above-described examples are not limited by any of the details of the foregoing description, unless otherwise specified, but rather should be construed broadly within its spirit and scope as defined in the appended claims, and therefore all changes and modifications that fall within the meets and bounds of the claims, or equivalences of such meets and bounds are therefore intended to be embraced by the appended claims.

Claims

WHAT IS CLAIMED IS;

1. Biocompatible microbeads of a high swelling property comprising a natural polysaccharide selected from alginic acid, chitosan and hyaluronic acid.

2. The microbeads according to claim 1, wherein the microbead is an alginic acid- hyaluronic acid microbead (a), a chitosan-hyaluronic acid microbead (b), or a chitosan-coated alginic acid-hyaluronic acid microbead (c).

3. The microbeads according to claim 2, wherein the chitosan is connected to the hyaluronic acid and/or alginic acid by an amide bond.

4. The microbeads according to claim 1, wherein the microbead is a chitosan-hyaluronic acid microbead (b) in which the chitosan is crosslinked to the hyaluronic acid by an amide bond, or a chitosan-coated alginic acid-hyaluronic acid microbead (c) in which the chitosan is crosslinked to the hyaluronic acid and/or alginic acid by an amide bond.

5. The microbeads according to claim 1, wherein the hyaluronic acid is hyaluronic acid itself, its salts, or the combination of them, and the alginic acid is alginic acid itself, its salts, or the combination of them, and the chitosan is chitosan itself, its oligomers, or the combination of them.

6. The microbeads according to claim 5, wherein the salts of hyaluronic acid are such inorganic salts as sodium hyaluronate, potassium hyaluronate, calcium hyaluronate, magnesium hyaluronate, zinc hyaluronate and cobalt hyaluronate, or such organic salts as tetrabutylammonium hyaluronate, or the combination thereof.

7. The microbeads according to claim 5, wherein the molecular weights of hyaluronic acid and its salts are in the range of 100,000 to 3,000,000.

8. The microbeads according to claim 2, wherein the molecular weights of chitosan and its oligomers are in the range of 300 to 10,000,000.

9. The microbeads according to claim 1, wherein the average particle sizes of beads are in the range of 30 to 1000 μm.

10. A process for preparation of the alginic acid-hyaluronic acid microbead according to claim 1, comprising spraying a mixture of an alginic acid aqueous solution and a hyaluronic acid aqueous solution into a mixed salt aqueous solution of 2- or 3-valent cationic salt and sodium chloride.

11. The process according to claim 10, wherein the ratios of alginic acid : hyaluronic acid in the mixture are in the range of 1 : 10 - 10 : 1, and the concentrations of alginic acid and hyaluronic acid are in the range of 0.1 - 10% by weight

12. The process according to claim 10, wherein the cationic salt is one or more selected from the group consisting of calcium chloride, magnesium chloride, strontium chloride, barium chloride and aluminum chloride.

13. The process according to claim 10, wherein the concentrations of cationic salt are in the range of 0.01 - 15 M, and the concentrations of sodium chloride are in the range of 0.01 - 45 M.

14. A process for preparation of the chitosan-hyaluronic acid microbead according to claim 1 , comprising:

(A) a step of preparing a hyaluronic acid aqueous solution containing a carboxyl group- activating agent and a chitosan aqueous solution, respectively;

(B) a step of adding dropwise of these two solutions into a solution containing a emulsifier to form microbeads; and

(C) a step of separating and refining the microbeads.

15. The process according to claim 14, wherein a step is further included, between the step (B) and (C), of adding acetone, acetone aqueous solution (more than 90% acetone) and/or C₂ to C₆ alcohol into the solution containing microbeads to make the microbeads more hardening.

16. The process according to claim 14, wherein a step is further included, after the step (C), of dispersing the microbeads obtained from the step (C) in acetone or an acetone aqueous solution, and then adding a carboxyl group-activating agent thereto to induce an additional amidation reaction.

17. A process for preparation of the chitosan-hyaluronic acid microbead according to claim 1 , comprising:

(Bl) a step of adding dropwise of these two solutions into a solution containing an emulsifier to form microbeads;

(CI) a step of separating and refining the microbeads; and

(Dl) a step of dispersing the microbeads in acetone or an acetone aqueous solution and then adding a carboxyl group-activating agent thereto to induce an amidation reaction.

18. The process according to claim 17, wherein a step is further included, between the step (Bl) and (CI), of adding acetone, acetone aqueous solution (more than 90% acetone) and/or C₂ to C₆ alcohol to the solution containing microbeads to make the microbeads more hardening.

19. The process according to claim 14 or 17, wherein the concentrations of hyaluronic acid aqueous solution are in the range of 0.00001 - 10% by weight, and the concentrations of chitosan aqueous solution are in the range of 0.00001 - 10% by weights, and the mixing ratios of hyaluronic acid aqueous solution : chitosan aqueous solutions are in the range of 1 : 0.00001 - 1 : 100 (the carboxyl group of hyaluronic acid : the amine group of chitosan) for amidation reaction.

20. The process according to claim 14 or 17, wherein the emulsifier is a lipid such as lecithin, phosphatidyl choline, phosphatidyl ethanol amine, phosphatidyl-serine and phosphatidyl inositol; their derivatives; or ester derivatives of fatty acids such as glyceryl stearate, sorbitan palmitate and sorbitan stearate.

21. The process according to claim 20, wherein the emulsifier is one or more selected from the group consisting of polyoxyethylene sorbitan monolaurate (Tween 20), polyoxyethylene sorbitan monopalmitate (Tween 40), polyoxyethylene sorbitan monostearate (Tween 60), polyoxyethylene sorbitan monooleate (Tween 80), sorbitan monolaurate (Span 20), sorbitan monostearate (Span 60) and sorbitan monooleate (Span 80).

22. The process according to claim 21, wherein the emulsifier is lecithin, Tween 20, Tween 80 and Span 80.

23. The process according to claim 14 or 17, wherein the added amount of emulsifier is in the range of 0.05 - 10% by volume based upon the total volume of the solution.

24. The process according to claim 14 or 17, wherein the solutions containing the emulsifier include mineral oil, methanol, a mixture of mineral oil and methanol, a mixture of glycerol and

1-propanol, a mixture of glycerol and 2-propanol, a mixture of ethylene glycol and 1-propanol, a mixture of ethylene glycol and ethanol, a rnixture of ethylene glycol and methanol, a mixture of ethylene glycol and acetone.

25. The process according to claim 14, 16 or 17, wherein an auxiliary activating agent is used together with the carboxyl group-activating agent.

26. The process according to claim 25, wherein the carboxyl group-activating agent is one or more selected from the group consisting of _l_^l-3-(3-dimemylaminopropyl) carbodiimides (alkyl herein is alkyl of 1 - 10 carbon atoms), l-emyl-3-(3-(trimethylammonio)propyl) c^bodiimide ("ETC"), and l-cyclohexyl-3-(2-morpholinoethyl) carbodiimide ("CMC"), and the auxiliary activating agent is one or more selected from the group consisting of N- hydroxysucciriimide ("ΝHS"), 1-hydroxybenzotriazole ("HOBt"), 3,4-dihydro-3-hydroxy-4- oxo-l,2,3-benzotriazine ("HOOBt"), l-hydroxy-7-azabenzotriazole ("HO At"), and Ν-hydroxy- sulfosu∞ir_imide("Sulfo-ΝHS").

27. The process according to claim 26, wherein the carboxyl group-activating agent is 1- ethyl-3-(3-dimethylaminopropyl) carbodiimide ("EDC") and the auxiliary activating agent is NHS.

28. A process for preparation of the chitosan-coated alginic acid-hyaluronic acid microbead according to claim 1 , comprising:

(B) a step of dispersing a mixture of the alginic acid aqueous solution and the hyaluronic acid aqueous solution in a mixed salt aqueous solution containing 2- or 3-valent cationic salt and sodium chloride to produce microbeads;

(C) a step of adding the produced microbeads into a chitosan aqueous solution to coat the microbeads with chitosan; and

(D) a step of separating and refining the microbeads from a reaction solution.

29. The process according to claim 28, wherein a step is further included, after the step (D), of performing an additional amidation reaction of the refined microbeads.

30. A process for preparation of the chitosan-coated alginic acid-hyaluronic acid microbead according to claim 1 , comprising:

(Bl) a step of spraying a niixture of the alginic acid aqueous solution and the hyaluronic acid aqueous solution into a chitosan aqueous solution in which 2- or 3-valent cationic salt and sodium chloride are dissolved, to coat microbeads with chitosan while forming the microbeads; and

(CI) a step of separating and refining the microbeads from a reaction solution.

31. The process according to claim 30, wherein a step is further included, after the step (C 1 ), of performing an additional amidation reaction of the refined microbeads.

32. The process according to claim 28 or 30, wherein the ratios of the carboxyl group of alginic acid : the amine group of chitosan are in the range of 1 : 100 - 100 : 1.

33. The process according to claim 29 or 31, wherein the amidation reaction is performed by dispersing the microbeads obtained from the proceeding step in distilled water and then adding a carboxyl group-activating agent, or a carboxyl group-activating agent and an auxiliary activating agent thereto.

34. The process according to claim 33, wherein the carboxyl group-activating agent is one or more selected from the group consisting of a_kyl-3-(3-dimethylarninopropyi) carbodiimides (alkyl herein is alkyl of 1 - 10 carbon atoms), l-ethyl-3-(3-(trimethylammonio)propyl) carbodiimide ("ETC"), and l-cyclohexyl-3-(2-moφholinoethyl) carbodiimide ("CMC"), and the auxiliary activating agent is one or more selected from the group consisting of N- hy<_roxysuccinimide ("ΝHS"), 1-hydroxybenzotriazole ("HOBt"), 3,4-dihydro-3-hydroxy-4- oxo-l,2,3-benzotriazine ("HOOBt"), l-hydroxy-7-azabenzotriazole ("HO At"), and Ν-hydroxy- sulfosu∞inimide ("Sulfo-ΝHS").

35. The process according to claim 34, wherein the carboxyl group-activating agent is 1- ethyl-3-(3-dimethylaminopropyl) caxbodiimide ("EDC") and the auxiliary activating agent is ΝHS.

36. Use of the microbeads according to claim 1 as a compatible material.