Prolonged-release ionic coniugate

The present invention relates to biodegradable polymer, microparticles containing biodegradable polymer and microparticles of sustained release ion conjugate containing biodegradable polymer.

Drug delivery preparations from biodegradable polymers have been developed and found for controlled release of drugs in vivo. See, e.g., U.S. Patent Nos. 3773919 and 4767628. Such preparations from biodegradable polymers are intended to allow slow diffusion of the drug contained therein through a matrix or polymer coating when depolymerization of the biodegradable polymer occurs.

International publication no. WO 94/15587 describes ionic molecular conjugates of polyesters and sustained release drugs. Because the degradation of polyester is an important step in the release process, it is by changing the size of the surface

188 517 conjugate particles can regulate the release profile of the drug from the conjugate. Therefore, conjugate particles should have similar size and shape to provide both minimal and reproducible surface, e.g., microspheres.

The biodegradable polymer according to the invention is characterized in that it contains lactic acid, s-capronic acid, glycolic acid, trimethylene carbonate, p-dioxanone, or tartaric acid copolymer thereof.

Preferably, the biodegradable polymer comprises lactic acid, glycolic acid and tartaric acid.

More preferably, in the biodegradable polymer, the ratio of lactic acid to glycolic acid to tartaric acid is about 66 to about 33 to about 1, or about 66 to about 32 to about 2, respectively.

The microparticles according to the invention are characterized in that they contain a biodegradable polymer comprising lactic acid, s-capronic acid, glycolic acid, trimethylene carbonate, p-dioxanone, or tartaric acid copolymer thereof.

The microparticles of the invention contain a biodegradable polymer comprising lactic acid, glycolic acid and tartaric acid.

The microparticles of the invention contain a biodegradable polymer wherein the ratio of lactic acid to glycolic acid to tartaric acid is about 66 to about 33 to about 1, or about 66 to about 32 to about 2, respectively.

The microparticles of the sustained release ionic conjugate according to the invention are characterized in that they contain a biodegradable polymer containing lactic acid, ε-capronic acid, glycolic acid, trimethylene carbonate, p-dioxanone, or a tartaric acid copolymer thereof and a drug containing one or more number of free amino groups, the polymer and drug being ion-bound.

The extended-release conjugate microparticles of the invention contain a biodegradable polymer comprising lactic acid, glycolic acid and tartaric acid, and a drug containing one or more free amino groups, wherein the polymer and drug are ionically bound.

The extended release conjugate microparticles of the invention contain a biodegradable polymer wherein the ratio of lactic acid to glycolic acid to tartaric acid is about 66 to about 33 to about 1, or about 66 to about 32 to about 2, respectively, and a drug containing one or more free amino groups, the polymer and drug being ion-bound.

Preferably, the microparticles of the invention contain a drug selected from the group consisting of growth hormone releasing peptide, luteinizing hormone releasing hormone, adrenomedulin, growth hormone, somatostatin, bombesin, gastrin releasing peptide, calcitonin, bradykinin, galanin, melanotropic hormone, growth hormone releasing factor, amine , secretin, parathyroid hormone, enkephalin, endothelin, calcitonin-releasing gene, neuromedin, parathyroid hormone related protein, glucagon, neurotensin, adrenocorticotropic hormone, YY peptide, glucagon releasing peptide, intestinal vascular polypeptide, peptide activating adenylated pituitary cyclase, motilin, substance P, neuropeptide Y, TSH and their analogues and their fragments. More preferably, the drug is somatostatin or LHRH, or an analogue or fragment thereof, most preferably the somatostatin analog, Dp-Nal-c [Cys-Tyr-D-Trp-Val-Cys] -Thr-NH2.

The biodegradable polymer may contain at least 1 free carboxyl group, e.g. 2-10 carboxyl groups in the polymer chain. Examples of biodegradable polymers containing carboxylic acid moieties include polyesters containing mers derived from lactic acid, s-caproic acid, s-caprylic acid, p-dioxanane, optionally substituted trimethylene carbonate, 1,5-dioxepan-2-one, 1, 4-dioxane-2-one, glycolic acid, alkylene oxalate, cycloalkylene, cycloalkylene oxalate, alkylene succinate or 3-hydroxybutyrate, in optically active forms or as racemates; or copolymers of any of these compounds Additional free carboxyl groups can be introduced into the biodegradable polyester by reaction, e.g. ring-opening polymerization or polycondensation, with acids

188 517 polycarboxylic acids, such as malic acid, tartaric acid, pamoic acid, citric acid, succinic anhydride, and glutaric anhydride. Thus, the biodegradable polymer may be a water-insoluble polyester containing lactic acid units, with or without glycolic acid units. Other biodegradable polymers such as polyorthoesters, polyorthocarbonates and polyanhydrides may also be used. The average degree of polymerization, i.e. the average number of monomers in the polymer chain in a biodegradable polymer, can be 10-300.

This medicine contains one or more (e.g. 1-10) free amino groups. In one embodiment, the drug is an acid resistant peptide. Exemplary acid-resistant peptides are the above-mentioned peptides. The drug may dissolve in the first liquid, e.g. in an amount of more than 0.1 mg / ml, preferably more than 1.0 mg / ml.

The microparticle ionic extended release drug conjugate can be prepared according to a method comprising the steps of (1) producing a first solution in which the conjugate is dissolved; (2) mixing the first solution added in the form of small droplets, e.g. through a spray nozzle, such as a sound nozzle, pneumatic nozzle, rotary atomizer or pneumatic nozzle) with the first liquid to form the first dispersion, the first liquid being mixed with the first solution, the conjugate being insoluble in the first liquid and precipitating from the first dispersion ; and (3) isolating the conjugate from the first dispersion.

The drug is soluble in the first liquid, which may be alcohol (e.g., ethanol or isopropyl alcohol), hexane or water, or a mixture thereof. When ethanol is used as the first liquid, it can be kept at 0 to -30 ° C when used. When isopropyl alcohol is used, it can be kept at a temperature of from 0 to -70 ° C, e.g. by cooling by adding dry ice.

The first solution, which may contain acetone, dichloromethane, acetonitrile, ethyl acetate, tetrahydrofuran or glim or mixtures thereof, can be obtained by (1) dissolving the biodegradable polymer in a second liquid (e.g. in acetone, tetrahydrofuran, ethyl acetate, methyl acetate, acetonitrile, ethyl formate or glyme or mixtures thereof) to form a second solution; (2) dissolving the drug in a third liquid (e.g. in water or acetone or a mixture thereof) to form a third solution, the third liquid being mixed with the first liquid and the second liquid; and (3) mixing the second solution with the third solution to form a first solution, the mixing resulting in ionic binding of the drug to the biodegradable polymer to form the conjugate in the first solution. The first solution may contain up to 40% by weight of the conjugate (e.g., 25-35% by weight of the conjugate). In one example, a base, e.g. NaOH or KOH, can be added to the second solution before mixing the second solution with the third solution. Base neutralization of carboxyl groups in the biodegradable polymer facilitates the formation of ionic conjugate.

Alternatively, the first solution can be obtained by dissolving the biodegradable polymer and drug in a second liquid (e.g., in acetone or a mixture of acetone and water) to form the first solution, and thereby to form the conjugate in the first solution. According to this method, the biodegradable polymer can first be dissolved in the second liquid, add bases to the second solution, and then dissolve the drug in the second liquid. In addition, if desired, the first solution may be fully or partially or completely evaporated from the first dispersion prior to isolation of the conjugate. The treated conjugate can conveniently be isolated by centrifugation or filtration of the first dispersion, and the isolated conjugate can be mixed with an aqueous mannitol solution before vacuum drying (e.g., lyophilization). The isolated conjugate can also be shaped into a foil or rod. In addition, microspheres with an average diameter of 5-200 pm can be formed from the conjugate, e.g. The term "ball formation" means the treatment of microparticles resulting in their shape deflected into a ball.

According to the method described above, microparticles of ionic extended release drug conjugate containing a biodegradable polymer with free carboxyl groups (polyester made from monomers such as,

188 517 e.g. lactic acid, s-caproic acid, ε-caprylic acid, glycolic acid, trimethylene carbonate or p-dioxanone; or a copolymer thereof; whereby the monomers may optionally be isomers or racemates) and a drug containing free amino groups (such as somatostatin or LHRH) joined together ionically.

The extended release ionic conjugate described above can be formulated as microspheres. This method includes the steps of (1) mixing the conjugate with the first liquid, e.g. with an oil such as silicone oil, mineral oil, sesame oil or vegetable oil) to form a first dispersion in which the conjugate is in the form of microparticles and is not soluble in the first liquid; (2) heating the first dispersion to a temperature higher than Tz (glass transition temperature) or Tt (melting point) of the conjugate; (3) cooling the first dispersion to a temperature lower than Tz or Tt of the conjugate; (4) mixing the first dispersion with a second liquid (e.g. with hexane, heptane, isopropyl myristate, or an alcohol such as ethanol or isopropyl alcohol) to form a second dispersion, the second liquid being mixed with the first liquid and the conjugate not dissolving in the second liquid; and (5) isolating the conjugate from the second dispersion. The conjugate can be in the shape of microcapsules with an average diameter of 5-200 pm before mixing with the first liquid, and the first dispersion thus obtained is intensively mixed, heating it to facilitate particle separation. After isolation, the conjugate can be washed with a second liquid and then dried under vacuum. Optionally, it can be mixed with an aqueous mannitol solution before vacuum drying.

The ionic sustained release conjugate described above (e.g., in the form of microcapsules with an average diameter of 5-200 pm) can be made into beads. The process of forming the conjugate beads comprises the steps of (1) mixing the conjugate with a first liquid (e.g., water) to form a first dispersion, in which the conjugate is in the form of microparticles, the conjugate being insoluble in the first liquid; (2) mixing the first dispersion;

(3) combining the first dispersion being mixed with the second liquid (e.g., dichloromethane or chloroform) in such an amount that it will be absorbed by the conjugate but will not dissolve the conjugate, the second liquid being mixed with the first liquid;

(4) evaporating the second liquid from the first dispersion; and (5) isolating the precipitated conjugate from the first dispersion. If desired, the method may further include the step of adding a surfactant (e.g. lecithin, Tween 20, polysorbate or lauryl sulfate) to the first dispersion to facilitate stabilization of the first dispersion, and the isolated conjugate may be washed with the first liquid and dried under vacuum. Also in this case, the conjugate can be mixed with an aqueous mannitol solution before vacuum drying.

Another method of forming beads from the above described extended release ionic conjugate includes the steps of (1) dissolving the conjugate in a first liquid (e.g., acetonitrile) to form a first solution; (2) mixing the first solution with a second liquid (e.g. with oil) to form a first dispersion, wherein the second liquid is not mixed with the first liquid; (3) evaporating the first liquid from the first dispersion to precipitate the conjugate from the first dispersion; and (4) isolating the precipitated conjugate from the first dispersion. In the mixing step, the first solution can be added to the second liquid in the form of small droplets.

The above method may include the step of washing the isolated conjugate with a third liquid (e.g., hexane, heptane or octane) which is mixed with the second liquid and is not a solvent for the isolated conjugate. If desired, the isolated conjugate can be mixed with an aqueous mannitol solution before vacuum drying.

Example 1

18.0 g copoly of imer 6 (^ / ^ 2/2 poly2 L-lactic-co-glycol-co-DL-malic acid with a molecular weight of 2000 gimol (22% L-lactic acid, 32% glycolic acid and 2% malic acid; acid number 0.373 millirovas; g) dissolved in 180 g of acetone (10% by weight copolymer solution), 14.4 ml of 0.5 N aqueous NaOH was added to obtain the polymer as sodium carboxylate. 4.28 g Lanrcotide ™ peptide acetate (Krnerton, Dublin, Ireland; D-Nal-c ['Cas-Taτ-D-Trp-Val-ιCasj-Thl'-NH ^; acetate content = 9.20% by weight) separately dissolved in a mixture of 10 g acetone and 10 g deionized water.

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The amount of dissolved peptide corresponded to the stoichiometric ratio of acid groups in the copolymer (one) to free amino groups in the peptide (two). The peptide solution was then added dropwise to the copolymer solution, and the resulting solution was stirred for 2 hours to allow salt exchange and resulting in the formation of an ionic polymer / peptide conjugate (PPIC).

Example 2

In a jacketed and temperature-controlled reactor (Schott Glass AGB, Dublin, Ireland), 2 liters of deionized water were cooled to 0 ° C with vigorous stirring. Then the PPIC solution of example 1 was slowly added to the reactor by means of a Masterflex pump (Bioblock Scientific, Illkvch, France), providing a flow rate of 10-15 ml / minute, through a silicone tube equipped with a needle No. 19 at the end. The PPIC solution was introduced through the needle located over water bath surface at 0 ° C. PPIC precipitated in the bath as small, solid particles. The solid particles were then separated from the supernatant by centrifugation (30 minutes at 5000 rpm at 0-5 ° C), washed with fresh deionized water, redispersed in water, centrifuged again and lyophilized. The isolated conjugate was sieved through a 100 sieve (to remove any large particles that could not be injected through the needle No. 21. The size analysis of the resulting particles is given in Table I.

Example 3

The PPIC solution of Example 1 was used to precipitate the conjugate as described in Example 2, except that an -20 ° C ethanol bath was used instead of a 0 ° C water bath. The analysis of the particle size obtained is given in Table I.

Example 4

The PPIC solution of Example 1 was dispersed by means of a spray tip with a hollow tip (Bioblock; 50 W, 20 kHz) at a controlled flow rate of 4 ml / minute, over an ethanol bath at -10 ° C, in a jacketed reactor with temperature control. With this spraying method, the copolymer solution comes out of the nozzle in the form of a subtle mist of small droplets. Small droplets fall into the ethanol bath, which causes the deionized water and acetone to be extracted from the droplets. As a result, the copolymer droplets solidify as small, solid particles. The particles were then separated by centrifugation and lyophilized. The analysis of the particle size obtained is given in Table I. Diameter -10 (i.e. D 0.1), diameter -50 (i.e. D 0.5) or diameter -90 (i.e. DO.9) means the smallest diameter larger than the diameter of 10, 50 and 90% respectively particles. The specific surface is the specific surface of the particles obtained.

Table I

<td>Example</td><td>Diameter -10 (nm)</td><td>Diameter -50 (ąm)</td><td>Diameter -90 (gm)</td><td>Specific surface area (m²/ G)</td>

<td> 2</td><td> 10</td><td> 30</td><td> 62</td><td> 18,64</td>

<td> 3</td><td> 9</td><td> 37</td><td> 89</td><td> 6,42</td>

<td> 4</td><td> 13</td><td> 46</td><td> 95</td><td> 22,61</td>

Example 5

5.0 g PPIC OP^{with &lt;}Example 2 a was dissolved in 2 () g of PPIC acetgnum 20% by weight). This solution was sprayed at a flow rate of 4.0 ml / min over a 500 ml ethanol bath at -10 ° C as in Example 4. After obtaining PPIC particles in the bath, 500 ml of ionized water was added to it and the bath was brought to 0 ° C . The bath was then stirred for 30 minutes, brought to 20 ° C and stirred for an additional 30 minutes. The PPIC particles were filtered off and dried in vacuo at room temperature. The analysis of the particle size obtained is given in Table II.

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Table II

<td>Example</td><td>D 0 1 (pm)</td><td>D 0.5 (pm)</td><td>D 0 9 (pm)</td><td>Specific surface area (m²/ G)</td>

<td> 4</td><td> 13</td><td> 46</td><td> 95</td><td> 22,61</td>

<td> 5</td><td> 50</td><td> 99</td><td> 180</td><td> 0,11</td>

As can be seen from Table II, particles with different morphology were obtained. The particles of example 4 were larger and their specific surface area was smaller. As demonstrated by studies using a scanning electron microscope, the particles obtained in Example 4 were also more porous, probably due to the presence of frozen water that remained in the particles after their precipitation. When the dispersion was again warmed to room temperature, the ice melted and the water flowed out into the ethanol bath, leaving open channels in the micro-tunnels. As a result, these particles were more fragile and crumbled into small fragments.

Example 6

The PPIC solution described in Example 5 above was sprayed at a rate of 2.5 ml / minute over 1.5 liters of deionized water at 0 ° C. The analysis of the particle size obtained is given in Table III.

Example 7

The PPIC solution described in Example 5 above was sprayed at a rate of 2.5 mL / min over 1.5 liters of ethanol at -10 ° C. The analysis of the obtained particle size is given in Table III. The abbreviation no means that the given determination has not been made.

Table III

<td>Example</td><td>D 0 1 (pm)</td><td>D 0 5 (pm)</td><td>D 0 9 (pm)</td><td>Specific surface area (m²/ G)</td>

<td> 6</td><td> 53,4</td><td> 154,3</td><td> 329,1</td><td>Well</td>

<td> 7</td><td> 42,4</td><td> 87,2</td><td> 170,1</td><td> 0,20</td>

Example 8

Two PPIC solutions in acetone were prepared as described above in Example 5. In the first solution the PPIC concentration was 15% and in the second solution the PPIC concentration was 20%. The solutions were sprayed over the ethanol bath at -10 ° C at a flow rate of 2.5, 3.5 and 5.0 ml / min as described in example 5. An analysis of the particle size obtained is given in Table IV.

Table IV

<td>Concentration (%)</td><td>Feed rate (ml / minute)</td><td>D 0 1 (pm)</td><td>D 0 5 (pm)</td><td>D 0 9 (pm)</td><td>Specific surface area (m²/ G)</td>

<td> 15</td><td> 2,5</td><td> 35,9</td><td> 81,6</td><td> 191,1</td><td> 4,455</td>

<td> 15</td><td> 3,5</td><td> 34,4</td><td> 80,2</td><td> 188,3</td><td> 8,336</td>

<td> 15</td><td> 5,0</td><td> 49,4</td><td> 163,6</td><td> 397,8</td><td>Well</td>

<td> 20</td><td> 2,5</td><td> 33,3</td><td> 73,8</td><td> 145,6</td><td> 0,199</td>

<td> 20</td><td> 3,5</td><td> 50,8</td><td> 112,7</td><td> 241,9</td><td> 0,579</td>

<td> 20</td><td> 5,0</td><td> 108,3</td><td> 219,1</td><td> 395,9</td><td>Well</td>

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Particle analysis using a scanning electron microscope confirmed that the particle size and specific surface area increase as the rate of administration increases.

Example 9

5.0 ąPIC microspheres from the example kl diluted with 5 g acetone (concentration 10% by weight). The solution is then poured into 500 ml of n-hexane with vigorous stirring at room temperature. The n-hexane solution began to become cloudy as PPIC particles precipitated. The PPIC was filtered off and dried in vacuo at room temperature.

Example 10

In the jacketed reactor, the 3.0 PPIC microparticles described in Example 2 were dispersed under vigorous stirring in 250 ml of silicone oil for medical applications, with a viscosity of 12500 mm²/ s (12500 cSt) (Dow Corning, Midlan, MI) (PPIC amount 1% by weight). After mixing, the mixture was heated to 120 ° C, higher than the glass transition temperature (Tz) PPIC, which is 55 ° C, and held at that temperature for 30 minutes. During heating, the individual particles melted to form spherical droplets. The dispersion was then cooled to 20 ° C and diluted with 1250 ml hexane. The solidified hard miCroCulCi was then filtered off, washed with fresh hexane and finally dried in vacuo. The characteristics of the obtained microspheres are given in Table V. The obtained miCroCules had a smaller diameter compared to the particles of Example 2 due to the compaction of the particles during melting.

Table V

<td>Example</td><td>D 0.1 (pm)</td><td>D 0 5 (| am)</td><td>D 0.9 (pm)</td><td>Specific surface area (m²/ G)</td>

<td> 2</td><td> 10</td><td> 30</td><td> 62</td><td> 18,64</td>

<td> 7</td><td> 2</td><td> 10</td><td> 47</td><td> &lt;01,33</td>

Example 11

0.2 g of the PPIC microparticles described in Example 2 cdyspergzwanz in 5 ml of deionized water and subjected to intensive mixing on a Vortex shaker. 100 (and dichloromethane (DCM) was then added to the dispersed mix. The addition of a small amount of DCM caused the surface of the PPIC particles to swell. Stirring at room temperature was continued for 4 hours to cause DCM to evaporate and thus harden the swollen surface of the particles. Scanning electron microscopy showed that the obtained particles had a spherical shape and a smoother surface compared to the starting material. There has been both a narrowing of the particle size distribution and a reduction in the maximum particle size due to an increase in their density.

Example 12 liter of gVitemins ocular oil, hic., CnicaCO, IL) was placed in a nave flask submerged in a water bath. The oil was mixed at 6 () () rpm using a Teflon stirring blade connected to the stirrer motor above the reactor. 500 mg of surfactant, soy lecithin (Sigma Chemicals, St. Louis, MO) was added to the sesame oil and mixed for 10 minutes. 10 g of the PPIC preparation was dissolved in 100 ml of Alitonitrile to form a clear solution. The PPIC preparation was obtained from Lanreotide ™ peptide conjugated with one of the following 3 polymers, copolymer 64/34/2 solic acid DL-lactic acid-co-glycolic-co-D, L-Apples (average molecular weight 6000) (formulation 1); 74/24/2 copolymer DL-lactic-co-glycol-co-D ^ -alcoholic acid (average molecular weight 6000) (formulation 2); and a 98/2 copolymer of DL-lactic-co-D, L-apple copolymer (formulation 3).

A clear PPIC solution was instilled from the dropping funnel. After completion of the pouring, the bath temperature was raised to 40 ° C and the oil was stirred for 20 hours. 1 liter of hexane was added for the sesame oil, and the oil was filtered through a medium-density sintered glass funnel. The microliters collected on the filter funnel were washed several times with hexane, total

188 517 with a volume of 500 ml. The particles were dried at 36 ° C for 2 days under vacuum. The characteristics of the obtained microspheres are given in Table VI.

Table VI

<td>Preparation</td><td>D 0 1 (pm)</td><td>D 0 5 (pm)</td><td>D 0.9 (pm)</td><td>Specific surface area (m²/ G)</td>

<td> 1</td><td> 13</td><td> 28</td><td> 57</td><td> 0,1426</td>

<td> 2</td><td> 13</td><td> 25</td><td> 59</td><td> 0,1395</td>

<td> 3</td><td> 14</td><td> 25</td><td> 51</td><td> 0,1480</td>

Example 13

Monomers, glycolide (Purac Biochem, The Netherlands, 84.83 g), lactide (Purac Biochem, The Netherlands, 210.67 g) and L - (+) - tartaric acid (Riedel-de Haen, Seelze, Germany, product) were introduced into the reactor. No. 33801, 4.50 g) and stannous 2-ethylhexanoate (Sigma, St. Louis, Missouri, USA, product No. S-3252) in toluene (Riedel-de Haen, Seelze, Germany) (0.1025 M, 4, 34 ml). L - (+) - tartaric acid was pre-dried over phosphorus pentoxide (Riedel-de Haen, Seelze, Germany) in an Abderhalden drying apparatus for 10 hours. The contents of the reactor (connected to the pump via a liquid nitrogen freezer) were placed under a vacuum of 4 Pa ​​(0.04 mbar) and stirred for 50 minutes to remove toluene. Then the reactor, operating in an oxygen-free nitrogen atmosphere (BOC Gases, Dublin, Ireland, moisture content 8 vpm (parts by volume)) was immersed in an oil bath (temperature = 200 ° C) for 30 minutes. The reactor, operating in an oxygen-free nitrogen atmosphere (BOĆ Gases, moisture content 8 vpm, volume per million), was then immersed in an oil bath and the stirring speed increased to 125 rpm. Before immersion, a heating band (Thermolyne type 45500, setting = 4) was placed on the lid of the reactor. The time to complete melting of the reactor contents was recorded, with a load of 300 g it was usually 10 minutes at 200 ° C. Samples were taken during the reaction and analyzed by GPC to determine the residual monomer content and the number average (Mn) and weight (Mw) molecular weight. Usually the reaction time was about 6 hours.

The obtained amorphous copolymer (66/33/1 PLGTA) contained 66.21% lactide units, 33.11% glycolide units and 0.68% tartaric acid units. The acid number determined by titration was 0.303 millirazines / g (meq / g = NaOH normality multiplied by the volume of NaOH solution needed to neutralize 1 g of polyester). The number average molecular weight of the copolymer was 10250 and the weight average molecular weight of 11910, which corresponds to a ratio of Mw / Mn of 1.16.

41.32 g of the above copolymer 66/33/1 poly L-lactic-co-glycolic acid-co- (L) - (+) - tartaric acid with a molecular weight of 10,000 g / mol (acid number = 0.303 meq / g) dissolved in 165 , 52 g acetone (Riedel-de Haen, Seelze, Germany) by ultrasonic treatment in a Branson ultrasonic bath (Branson, Danbury, Connecticut, USA) to give a solution with a PLGTA concentration of 19.98% by weight.

To this solution, 37.6 mL of 0.2 N sodium carbonate (Aldrich, Gillingham, Dorset, UK) was added, which provided a 1.2-fold excess of sodium relative to the carboxyl groups in the copolymer. The solution was stirred for 30 minutes to ensure salt formation. It was then introduced into the spray nozzle at a rate of 8 ml / min using a Masterflex pump (Cole Palmer, Barrington, Illinois, USA). The solution was sprayed into a 6-liter jacketed reactor containing 2 liters of deionized water cooled to 2.5 ° C using a circulation bath (Huber, Offenburg, Germany). This water was mixed with a four-blade stirrer connected to the engine

After spraying, the dispersion was transferred to 6 centrifuge bottles and centrifuged at 5000 rpm for 30 minutes in a Sorvall centrifuge (DuPont Sorvall Products, Wilmington, Delaware, USA). The centrifuge cake obtained was again dispersed in deionized water and the dispersion was again centrifuged. Supernatant

188 517 were discarded and the cakes were frozen in the freezer (overnight) before drying the next day in a small scale freeze dryer (Edwards, Crawley, West Sussex, UK). 33.16 g of washed copolymer were obtained, which corresponds to a yield of 80.24%.

4.92 g of the above copolymer 66/33/1 poly L-lactic-co-glycolic acid-co- (L) - (+) - tartaric acid with a molecular weight of 10,000 g / mol (66% L-lactic acid, 33% glycolic acid and 1% tartaric acid) was dissolved in 11.58 g acetonitrile (Riedel-de Haen, Seelze, Germany, HPLC purity) by ultrasonic treatment in an Branson ultrasonic bath (Branson, Danbury, Connecticut, USA) and mixed on a mixing plate in resulting in a 29.82 wt.% PLGTA solution.

The resulting copolymer solution in acetonitrile was directed from the glass container through a spray nozzle using an FMI rotary piston pump (FMI, Oyster Bay, NY, USA) set to deliver 2 mL / min. The atomizer output power was set at 50 W, with an amplitude of 80%. The solution was sprayed in a 6-liter jacketed reactor containing 1.5 liters of isopropyl alcohol (Labscan, Dublin, Ireland) in the quality of a universal reagent, cooled to -70 ° C with solid CO2 pellets (AIG, Dublin, Ireland) and subjected to mixing at a rate of 300 rpm with a four-blade stirrer connected to the engine. The temperature of the isopropyl alcohol was maintained at -70 ° C throughout the spraying period, which lasted about 8 minutes.

After spraying, the dispersion was allowed to warm to 10 ° C spontaneously for 5.5 hours. It was filtered through a Whatman No. 1 filter paper disc (9 cm diameter) using a vacuum. The filter cake paper was placed with drying silica gel flakes in a desiccator and a vacuum connected through an automatic freezer at -110 ° C. After 24 hours, 4.24 g of material was recovered. The analysis of the particle size obtained is given in Table VII.

Table VII

<td>Example</td><td>D 0.1 (pm)</td><td>D 0 5 (pm)</td><td>D 0.9 (pm)</td><td>Specific surface area (m²/ G)</td>

<td> 13</td><td> 31</td><td> 68</td><td> 139</td><td> 0,16</td>

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