RU2411077C1 - Method for producing chitosan and alginic acid coats for microcapsules containing phospholipid micelles - Google Patents

Abstract

FIELD: medicine, pharmaceutics.

SUBSTANCE: invention refers to preparing dosage forms of microcapsules containing phospholipid micelles (liposomes), particularly to technology of coats of various compositions for such microcapsules exhibiting the required properties. In a method for producing the chitosan and alginic acid coats of microcapsules containing phospholipid micelles, microcapsule nuclei are consistently kept in 0.5÷1.0 (wt/vol.) % medium or low viscosity chitosan solution, in 1.0 % acetic acid, in 2.5÷3.0 % earth metal chloride solution, in 0.5÷1.0 (wt/vol.) % sodium alginate solution and once again in 2.5÷3.0 % earth metal chloride solution, and aims at creation of a chitosan and alginic acid salt microcapsule coat through which phospholipid micelles penetrate at a preset speed due to using various viscosity chitosan and a different nature cation producing salt with alginic acid.

EFFECT: creation of a microcapsule coat through which phospholipid micelles penetrate at a preset speed.

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Description

This invention relates to the production of dosage forms in the form of microcapsules containing phospholipid micelles (liposomes), in particular, to the technology of creating shells based on chitosan and salts of alginic acid.

For oral dosage forms, the most important properties are the ability to protect the medicinal substance enclosed in them from the destructive effect of the stomach environment, deliver the drug to the lower sections of the gastrointestinal tract, where it is most effectively absorbed by the mucous cells, and to ensure a prolonged, stable release of the drug substance. The importance of these properties will also be true for phospholipid micelles (liposomes), "loaded" with drug substance.

One of the most promising bases for this kind of dosage forms are natural polysaccharides. In particular, salts of alginic acid and chitosan.

Known invention (RU No. 2287983, class A61K 9/58, A61K 47/36, B01J 2/00, 2006.11.27) "A method for producing a shell for enteric polymer capsules." The solution proposes a method for producing a modified Ca-alginate matrix and using it as a capsule shell capable of dissolving in the intestine and protecting the encapsulated substance in the stomach. The solution does not involve the use of modifying additives (polysaccharides) to the matrix, as well as liposomes as an encapsulator.

Known invention (RU No. 2231531, class C08G 77/24, A61K 9/58, A61K 9/52, 2004.06.27) "A new membrane or matrix for regulating the permeability of drugs". The technical result is the creation of an elastomer through which a drug substance penetrates at the desired speed. The basis of the mentioned elastomer is siloxane, and it does not include chitosan and alginates.

The invention is known (WO 03018186, class A23L 1/00, A23L 1/0532, A23L 1/30, A61K 9/20, A61K 9/50, A61K 47/04, 2003.03.06) "Stable coated microcapsules". The invention is a method for producing Ca-alginate-coated microcapsules containing lipophilic components. The method is a fairly close prototype, but has a number of significant differences. The metal cation is represented only by Ca ²⁺ , the shell contains only calcium alginate without any modifying additives, we are not talking about the controlled release of the encapsulated lipophilic substance in the gastrointestinal tract.

Known invention (US 4933185, class A61K 9/16, A61K 9/50, A61K 9/62, A61K 9/16, A61K 9/50, A61K 9/52, 1990.06.12) "System for controlled release of biologically compounds " The invention is a capsule with a core of calcium alginate, coated with a poly-L-lysine shell, which serves to control the diffusion of biologically active substances (from the capsule into the external environment) and the enzyme that destroys the core (from the external environment into the capsule). In this prototype, the differences are obvious and are in the shell material.

The invention is known (US 5738876, class C12N 11/04 (20060101), C12N 11/00 (20060101), A61K 9/16 (20060101), A61K 9/50 (20060101), C12N 5/06 (20060101), C12N 5 / 00 (20060101), A61K 35/12 (20060101), A61K 009/14, 1998.04.14) "Method of solution overcoating with gelling polymer". This patent in terms of a method for producing a shell (sequential aging of capsule nuclei in a solution of a crosslinking agent, a solution of a gelling polysaccharide), is the closest prototype. As a crosslinking metal cation, the authors use not only calcium, but also barium, strontium, and iron. However, chitosan is not part of the shells. The main difference is the purpose of the developed system. The authors propose using it to immobilize pancreatic cells. Therefore, such capsules are not originally intended for administration in the gastrointestinal tract, which is also indicated by the use of toxic strontium.

Thus, the analysis of patent documents revealed the presence of only indirect analogues of the proposed method for producing shells for microcapsules with micelles, "loaded" with drug substance. Speed control is necessary in the case of the use of prolonged-action liposomal drugs or with the possibility of targeted delivery of the active substance to various parts of the gastrointestinal tract.

The present invention is based on the task of creating a technological process, the implementation of which allows you to get a shell for microcapsules based on calcium alginate or barium alginate and chitosan with different viscosities that affect the relative percentage of phospholipid micelles from the nucleus of capsules in environments that mimic the conditions of the gastrointestinal tract person.

The technical result is the creation of a shell for microcapsules based on chitosan and salts of alginic acid, through which phospholipid micelles penetrate at a certain speed due to the use of chitosan of different viscosity and different nature of the cation forming a salt with alginic acid.

The problem and the technical result are achieved in that in the method for producing shells based on chitosan and salts of alginic acid for microcapsules containing phospholipid micelles, according to the invention, the cores of the microcapsules are sequentially maintained in a 0.5 ÷ 1.0% (weight / volume) chitosan solution medium or low viscosity in 1.0% acetic acid, in 2.5 ÷ 3.0% solution of alkaline earth metal chloride, in 0.5 ÷ 1.0% (weight / volume) sodium alginate solution and again in 2.5 ÷ 3.0% alkaline earth metal chloride solution.

The microcapsules are kept in a solution of chitosan for 25-30 minutes, in a solution of an alkaline earth metal chloride for at least 25-30 minutes, in a solution of sodium alginate for at least 5-10 minutes, and repeatedly in a solution of an alkaline earth metal chloride for at least 10-15 minutes. Chitosan is used of medium viscosity (viscosity of 1.0% (weight / volume) of a solution in 1.0% acetic acid at 20 ° C 200 ÷ 400 mPa · s) or low viscosity (viscosity of 1.0% (weight / volume) of a solution in 1.0% acetic acid at 20 ° C ≤200 MPa · s). As the alkaline earth metal chloride, calcium chloride or barium chloride is used.

As a result of the sequence of the method, a two-layer shell is formed on the surface of the nuclei of the microcapsules. The outer layer of calcium or barium alginate is resistant to dissolution in the stomach and reduces the loss of phospholipid micelles due to their release in the stomach. In a slightly alkaline environment of the intestine, the outer layer dissolves (calcium alginate) or becomes loose (barium alginate), exposing the second layer of the membrane from chitosan alginate. Chitosan is resistant to dissolution in media with pH> 7.0, therefore, the rapid dissolution of alginate nuclei of microcapsules does not occur, and phospholipid micelles leave the nuclei of microcapsules in the external environment with a certain speed, depending on the type of chitosan used.

The optimal value of the concentration of chitosan solution (low and medium viscosity) was recognized as a value in the range of 0.5 ÷ 1.0% (weight / volume). A decrease in the concentration of chitosan increases the required exposure time of the forming microcapsules in its solution, which leads to additional losses of phospholipid micelles due to their exit from the core of the microcapsules into the external liquid phase. An increase in the concentration of chitosan leads to an increase in the viscosity of the solution, which is why drops of the alginate containing phospholipid micelles supplied to the solution remain on the surface of the solution and do not take the necessary spherical shape.

The optimal exposure time of the microcapsules in the chitosan solution was 25–30 minutes; during this time, a uniform layer of chitosan alginate was formed on the surface of the microcapsules. Less time will not ensure uniformity of the chitosan alginate layer on the surface of the microcapsules. The increase in exposure time does not lead to the formation of a layer of chitosan alginate with better characteristics (in thickness and strength).

The optimal value of the concentration of a solution of alkaline earth metal chloride (calcium chloride or barium chloride) was recognized as 2.5 ÷ 3.0%. Lower concentrations make it necessary to increase the exposure time of microcapsules in a solution of a crosslinking agent, which leads to an increase in the loss of phospholipid micelles. High concentrations do not significantly affect the gelation rate inside the microcapsules. For the optimal exposure time of the microcapsules in a solution of alkaline earth metal chloride (25-30 minutes), the cores of the microcapsules are completely solidified as a result of the ionotropic gelation reaction and are saturated with an excess of Ca ²⁺ or Ba ²⁺ cations. When the microcapsules are kept in a solution of alkaline earth metal chloride for less than 25 minutes, the gelation process does not proceed to the end, and there is not enough saturation of the cores of the metal microcapsules. Increasing the exposure time does not give the best results.

The optimal value of the concentration of sodium alginate solution was recognized as 0.5 ÷ 1.0% (weight / volume). At concentrations of more than 1.0% (weight / volume), the viscosity of the solution increases, which complicates the process of introducing microcapsules into the volume of the solution. At concentrations less than 0.5% (weight / volume), it is necessary to increase the exposure time of the microcapsules in the solution. The optimal exposure time of microcapsules in 0.5 ÷ 1.0% sodium alginate solution was 5 ÷ 10 minutes. During this period of time, a uniform layer of calcium or barium alginate with a thickness of 0.3 to 1 mm is formed on the surface of the microcapsules. Reducing the exposure time is undesirable because of the possibility of forming a heterogeneous layer, the increase is impractical, since it does not lead to the formation of a layer with better characteristics.

The re-exposure time of the microcapsules in a 2.5 ÷ 3.0% solution of alkaline earth metal chloride (calcium or barium chloride), equal to 5 ÷ 10 minutes, was considered optimal. 5 minutes is the minimum obtained experimentally and necessary for the final fixation of the calcium or barium-alginate layer on the surface of microcapsules. Increasing the exposure time to values greater than 10 minutes is impractical, since it does not lead to an improvement in the result.

It was experimentally obtained that samples of medium and low viscosity chitosan possess the best characteristics. The use of high viscosity chitosan (viscosity of 1.0% (weight / volume) solution in 1.0% acetic acid at 20 ° C more than 400 MPa · s) complicates the process of introducing microcapsules into the volume of chitosan solution.

The invention is illustrated by a diagram of a process for producing a shell based on chitosan and salts of alginic acid for microcapsules containing phospholipid micelles, shown in the drawing.

To obtain shells based on chitosan and alginic acid salts for microcapsules containing phospholipid micelles, a 2.0% (weight / volume) sodium alginate solution containing phospholipid micelles is supplied dropwise (with a syringe) in 0.5 ÷ 1.0 % (weight / volume) solution of chitosan in 1.0% acetic acid. In this case, contact of drops with each other in an alginate solution should be avoided in order to avoid adhesion of the formed microcapsules. The residence time of the forming microcapsules in a solution of chitosan is 25-30 minutes. During this time, an ionic interaction occurs between the polysaccharides, resulting in the formation of spherical structures with a core from a viscous solution of sodium alginate and the outer layer of chitosan-alginate hydrogel. After 25–30 minutes, a sample of calcium chloride or barium chloride powder is added to the chitosan solution containing microcapsules in an amount necessary to obtain a 2.5–3.0% solution when the reagent is completely dissolved. After dissolution of CaCl ₂ or BaCl ₂ microcapsules incubated in the resulting solution for another 25 ÷ 30 minutes. In this case, the diffusion of calcium or barium cations and the ionotropic gelation reaction results in the formation of calcium or barium-alginate hydrogel in the microcapsule core, while the microcapsule material is saturated with an excessive amount of Ca ²⁺ or Ba ²⁺ cations.

Next, the microcapsules are removed from the solution and transferred to a 0.5 ÷ 1.0% (w / v) sodium alginate solution, in which they are kept for 5 ÷ 10 minutes. During this time, excess calcium or barium cations exit the microcapsules and react with alginate macromolecules, forming a layer of calcium or barium-alginate hydrogel on the surface of the microcapsules. To fix this layer after 5 ÷ 10 minutes, the microcapsules are again incubated in a 2.5 ÷ 3.0% solution of calcium or barium chloride for 10 ÷ 15 minutes.

Next, the microcapsules are removed from the solution, washed three times with distilled water and dried in an oven at a temperature of 30 ÷ 40 ° C until a constant mass is maintained. Dried capsules are stored in sealed glass or plastic bottles.

The table schematically presents the stages of the process of obtaining microcapsules with a shell of various compositions.

Example 1

5 ml of a 2.0% (w / v) sodium alginate solution containing dispersed phospholipid micelles in an amount of 500 mg was applied dropwise using a syringe with a needle into 100 ml of a 1.0% (w / v) low viscosity chitosan solution of 1 , 0% acetic acid. After 30 minutes from the moment the filing of the alginate solution was completed, 3 g of calcium chloride powder was added in small portions to the chitosan solution. After complete dissolution of the salt, the formed microcapsules were kept in the resulting solution for 30 minutes. Next, the microcapsules were separated from the solution and placed in 50 ml of a 1.0% (w / v) sodium alginate solution, which was kept for 5 minutes. Then the microcapsules were separated and placed in 100 ml of a 3.0% solution of calcium chloride and kept there for 15 minutes.

Next, the microcapsules were removed from the solution, washed three times with distilled water and dried in an oven at a temperature of 35 ° C until a constant weight was maintained.

The quality of the obtained membrane was evaluated by the percentage yield of phospholipid micelles from the microcapsules in media simulating the conditions of the human gastrointestinal tract for a certain time: “stomach” - 90 min in 0.1 N hydrochloric acid solution (pH 1.0) at 37 ° C, the duodenum - 30 minutes in phosphate buffer (pH 6.0) at 37 ° C, the small intestine - 90 minutes (or until the microcapsules are completely dissolved ) in phosphate buffer (pH 7.4) at 37 ° C.

The output of phospholipid micelles from microcapsules in the "stomach" was 14.6% of the initial amount in 90 minutes, in the "duodenum" - 29.5% of the initial amount in 30 minutes, in the "small intestine" - 89.5% of the initial quantities in 90 minutes

Example 2

The experiment was carried out analogously to example 1 except that barium chloride was used instead of calcium chloride.

The output of phospholipid micelles from microcapsules in the “stomach” was 18.0% of the initial amount in 90 minutes, in the “duodenum” - 64.8% of the initial amount in 30 minutes, in the “small intestine” - 93.2% of the initial quantities in 90 minutes

Example 3

The experiment was carried out analogously to example 1 except that medium chitosan was used instead of low viscosity chitosan.

The yield of phospholipid micelles from microcapsules in the “stomach” was 12.1% of the initial amount in 90 minutes, in the “duodenum” - 22.3% of the initial amount in 30 minutes, in the “small intestine” - 100% of the initial quantity in 40 min (microcapsules completely dissolved).

Example 4

The experiment was carried out analogously to example 1 except that medium chitosan was used instead of low viscosity chitosan, and barium chloride was used instead of calcium chloride.

The output of phospholipid micelles from microcapsules in the "stomach" was 13.5% of the initial amount in 90 minutes, in the "duodenum" - 28.3% of the initial amount in 30 minutes, in the "small intestine" - 52.0% of the initial quantities in 90 minutes

Example 5

To obtain nuclei of microcapsules based on calcium alginate without a shell, 5 ml of a 2.0% (w / v) sodium alginate solution containing 500 mg dispersed phospholipid micelles was added dropwise using a syringe with a needle into a 3.0% chloride solution calcium and kept the formed nuclei in this solution for 30 minutes

The obtained nuclei of microcapsules without a shell were placed in media simulating the conditions of the gastrointestinal tract of a person for a certain time: “stomach” - 90 min in 0.1 N hydrochloric acid solution (pH 1.0) at 37 ° C, the duodenum - 30 minutes in phosphate buffer (pH 6.0) at 37 ° C, the small intestine - 90 minutes (or until the microcapsules are completely dissolved ) in phosphate buffer (pH 7.4) at 37 ° C.

The output of phospholipid micelles from the nuclei of microcapsules in the "stomach" was 68.0% of the initial amount in 90 minutes, in the "duodenum" - 91.3% of the initial amount in 30 minutes, in the "small intestine" - 100.0% of initial amount in 25 minutes (the nuclei of the microcapsules completely dissolved).

Example 6

The experiment was carried out analogously to example 5 except that barium chloride was used instead of calcium chloride.

The output of phospholipid micelles from the nuclei of microcapsules in the "stomach" was 57.2% of the initial amount in 90 minutes, in the "duodenum" - 86.2% of the initial amount in 30 minutes, in the "small intestine" - 98.8% of initial amount in 90 minutes

This method of producing a shell of microcapsules is suitable for implementation in laboratory and semi-industrial conditions. Currently, the method is at the stage of laboratory experiments.

Claims (4)

1. A method of producing shells based on chitosan and salts of alginic acid for microcapsules containing phospholipid micelles, characterized by sequential exposure of the nuclei of microcapsules in 0.5 ÷ 1.0% (weight / volume) of chitosan medium or low viscosity in 1.0% - acetic acid, in a 2.5 ÷ 3.0% solution of alkaline earth metal chloride, in a 0.5 ÷ 1.0% (weight / volume) solution of sodium alginate and, again, in 2.5 ÷ 3.0% solution of alkaline earth metal chloride. 2. The method according to claim 1, characterized in that the microcapsules are kept in a solution of chitosan for 25-30 minutes, in a solution of alkaline earth metal chloride - at least 25-30 minutes, in a solution of sodium alginate - at least 5-10 minutes, repeatedly in solution alkaline earth metal chloride - at least 10 ÷ 15 minutes 3. The method according to claim 1, characterized in that calcium chloride is used as the alkaline earth metal chloride. 4. The method according to claim 1, characterized in that barium chloride is used as the alkaline earth metal chloride.

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