GLUCOSAMINE-POLYACRYLATE INTER-POLYMER COMPLEX AND APPLICATIONS THEREOF
FIELD OF THE INVENTION
The present invention relates to a solid, particulate composition formed by the inter-polymer complexation of a cationic polymeric glucosamine or its derivatives and an anionic, cross-linked, polyacrylic acid or its derivatives. This complex is particularly useful in oral solid pharmaceutical compositions, including tablets and capsules.
BACKGROUND OF THE INVENTION
Polyion, inter-polymer complexes are ionically cross-linked hydrogels formed by the interaction of oppositely charged macromolecules. The process of complexation is a useful technique to generate polymer systems, which are linked to interacting reactants without any strong bond formation. Instead, the link between the reactants is formed by means of weak secondary binding forces, such as electrostatic interaction, hydrogen bonding, Van der Waals forces, among others. The inter-polymer complex can synergize the individual properties of the interacting polymers by increasing the intensity of any one or more of the individual properties. Alternatively, the synergism may reflect in the separate manifestation in the complex of many of the properties of the interacting polymers.
US Patent No. 5,510,418 describes biocompatible, biologically inert conjugates comprising a chemically derivatized glycosaminoglycan chemically conjugated to a synthetic hydrophilic polymer, namely, polyethylene glycol. The
chemical conjugation may be by means of a variety of type of covalent linkages, including ether and ester linkages.
US Patent No. 3,962,158 describes hydrophilic polymer membranes useful as semi- permeable membranes or ultrafilter membranes, manufactured by forming a film from an aqueous solution containing polyvinyl alcohol and a chitosan salt and then subjecting the film to an alkali treatment.
US Patent No. 4,501,835 describes a composition of matter, which is a complex of polyacrylic acid and chitosan, wherein the molecular weight of the polyacrylic acid is less than about 10,000. The complex is prepared by combining, with mixing, an acidic solution of low molecular weight polyacrylic acid and an acidic solution of chitosan and can be employed to form membranes and films.
US Patent No. 4,956,170 discloses a high alcohol content skin moisturizing / conditioning antimicrobial gel. The gel comprises from about 60-75 weight percent of ethanol and from about 0.4- 2 weight percent of a thickening agent which is an addition polymer of acrylic acid cross-linked with an unsaturated polyfunctional agent.
U.S. Patent No. 5,167,950 describes a high alcohol content aerosol antimicrobial mousse composition comprising water-dispersible polymers gelling agents. The gelling agent preferably employed is an addition polymer of acrylic acid cross-linked with an unsaturated polyfunctional agent, such a polyalkyl ether of sucrose.
SUMMARY OF THE INVENTION
The present invention is directed to a solid, particulate complex formed by the inter-polymer complexation of a cationic polymeric glucosamine or its derivatives and an anionic, cross-linked, polyacrylic acid or its derivatives. The cross-linked polyacrylic acid or its derivatives has a molecular weight of greater than or equal to 700,000. The inter-polymer complex may optionally contain any pharmaceutical active and/or inactive ingredients.
The complexation process involves neutralization of an anionic, cross-linked polyacrylic acid or its derivatives using an aqueous solution of a cationic polymeric glucosamine or its derivatives. The polyacrylate is reacted as a colloidal dispersion and the neutralization results in the precipitation of a complex as an insoluble gel mass. The dispersion of the cross-linked acrylate polymer can either be in water or, more preferably, in a single or a mixture of organic solvent(s). The solvent of choice is absolute ethanol. Correspondingly, the interaction can be in completely aqueous media or in hydro-organic system, and preferably, in hydro-alcoholic system.
The polymer complex obtained from hydro-alcoholic solvent system is easy to process, has high yields, and forms very highly swelling gels especially when mixed in aqueous media of pH greater than 3. The gel obtained from aqueous media shows a lower water absorbing capacity and weaker texture properties.
DETAILED DESCRIPTION OF THE INVENTION
Glucosamine, which is formed in the body as glucosamine 6-phosphate, is 2-amino-2- deoxy-alpha-D-glucose. It is one of the two hexosamine sugars (6 carbon amino sugars) common in animal cells. Structurally, glucosamine is modified glucose with NH3-group replacing the OH-group found on carbon two (C-2). A glucosamine that is of particular relevance to this application is chitosan. Chitosan is poly-[l- 4]-beta-D- glucosamine and is a partially deacetylated chitin. As referred to herein, it is acid soluble and has at least 75% degree of acetylation, more preferably, the degree of acetylation is in excess of 85%. Other glucosamines, but not limiting to, include carboxymethyl chitosan, hydroxypropyl chitosan and glycol chitosan.
Cross-linked polyacrylic acid or its derivatives, as referred to in this application, include water- swellable, high molecular weight, cross-linked homopolymers and copolymers, which form hydrogels in aqueous media. The crosslinker types and levels can be modified, with regard to amounts and characteristics of the hydrophobic co-monomers. Commercial grades of cross-linked methacrylic acid are available from Noveon (formerly, BF Goodrich) as Carbopol®, Pemulen®, and Noveon resins. Specifically, the resins are -(i) homopolymers of acrylic acid cross-linked with allyl sucrose or ally! pentaerythritol (Carbopol homopolymers), (ii) homopolymers of acrylic acid cross-linked with divinyl glycol (Noveon polycarbophils), and (iii) copolymers of acrylic acid with minor levels of long chain alkyl acrylate co-monomers cross-linked with allylpentaerythritol (Carbopol copolymers and Pemulen polymeric emulsifiers). The molecular weight of these polymers is theoretically estimated to range from
700,000 to 3 or 4 billion. They swell in water up to 1000 times their original volume to form a gel when exposed to a pH environment above 4 -6. Since the pKa of these polymers is 6 ± 0.5, the carboxylate groups on the polymer backbone ionise, resulting in repulsion between the negative particles, which adds to the swelling of the polymer. Cross-linked polymers do not dissolve in water.
Non-aqueous gels are stable gels with a wide range of hardness and stability over a wide range of pH conditions. These gels utilize an anhydrous liquid component extending their usefulness into many areas not suited for the use of water-based gel systems. The gellants used in non-aqueous gels are in the form of alkyl amides of di- and/or tri-basic carboxylic acids or anhydrides. Reacting the di- or tri-basic organic acid or anhydride, or the methyl ester form thereof, with the desired alkyl amine produces the gellant materials. This gel-based technology makes use of an anhydrous or semi-hydrous liquid carrier.
Hydroalcoholic hand sanitizing gels have found increasing use due to their ability to instantly kill germs and bacteria, without the use of soap and water, together with pleasant after-feel on the hands owing to conditioning and moisturizing benefits. Carbopol® polymers are preferred in these hydroalcoholic gels. Hydroalcoholic gels with Carbopol® polymers also include neutralizing agents, which are effective at low levels of water in these systems.
Higher alcohol content in the solvent system is highly desirable during neutralization, as it is critical for the unique swelling and water absorption characteristics exhibited by the inter-polymer complexes of the present invention.
Commonly used neutralizing agents which can accommodate higher alcohol content in the solvent system such as triethanolamine (30%), tromethamine (60%), aminomethylpropanol, triisopropanolamine, diisopropanolamine and tetrahydroxypropylethylenediamine (all 80%), PEG-15 cocoamine (>90%) and the like are not recommended for oral use. In the present invention, we have found through extensive experimentation that glucosamines, particularly chitosan or its derivatives, are good neutralizing agents for cross-linked polyacrylic acids and wherein the resultant complexes are suitable for oral administration.
The interaction of cross-linked polyacrylic acid with chitosan or its derivatives in hydro- organic system produces stronger gels than the same interaction in a completely aqueous media. The organic solvent in hydro-organic system can be at least 20% by volume. The level of organic solvent can be raised to about 95% by volume. With high proportions of the organic solvent, the complex formation and separation from the media as a gel precipitate is more complete. This is of particular benefit for production at large scale. However, due to commercial considerations, the levels of organic solvent is from about 70 to 90% by volume.
The complexation process involves neutralization of anionic functional groups in cross-linked polyacrylic acid or its derivatives with cationic functional groups of polyglucosamine or its derivatives. The ratios of the interacting species can vary between 1:20 and 20:1. Preferably, the ratio is at least 1:10 and the most preferred ratio of the interacting species is 1:1. The neutralization is complete in 1:1 ratio of the two interacting polymers and the resulting complex has water absorbing capacity (at pH greater than 3) of very high magnitude and
results in a highly swollen gel. The rate of formation of the swollen gel is relatively fast.
The complex gel precipitate can be separated from the reacting carrier media by isolation techniques known in the art, which include but is not restricted to sedimentation, filtration, centrifugation, distillation, and evaporation. The gel can be optionally rinsed with more solvent. The gel is then dried by any suitable drying technique known in the art, which include but is not restricted to, oven drying, vacuum oven drying, fluid-bed drying, freeze drying, spray drying and microwave oven drying. The dried material is desirably milled to obtain the complex as a dry, particulate solid material.
One of the interacting polymers in this invention, namely, glucosamine or its derivatives, is preferably used as an aqueous solution. Depending upon solubility properties, the glucosamine under consideration may optionally be dissolved in an acidified solution. Any acid or acid derivative which impart an acidic pH to the aqueous solutions may be used for the purpose of solubilisation. It may be selected from a group consisting of sulphuric acid, hydrochloric acid, phosphoric acid, carboxylic acids, such as formic acid, acetic acid, malic acid, maleic acid, oxalic acid, succinic acid, tartaric acid, lactic acid, ascorbic acid, gluconic acid, amino acids and their derivatives/salts, glyceryl triacetate, polyvinyl acetate, and citric acid. The other interacting polymer, namely, cross- linked polyacrylic acid or its derivatives is preferably dispersed in an aqueous media as a colloidal hydro-gel or as a particulate dispersion in an organic solvent, preferably, an ester or a ketone. Preferred solvents include, methanol, ethanol, isopropyl alcohol and acetone. The solvent of choice is ethanol.
Interaction of the reacting polymers in two different phases and preferably in a hydro- organic solvent system produces the complex. If the solvent system is completely aqueous, the interaction results in a certain fraction that remains as a colloidal solution. Concentration of this phase by evaporation and subsequent drying in the oven gives relatively lower yield and also results in a film that is difficult to obtain as a solid particle. Experiments have shown this phase to contain around 50% of the yield. Use of hydro-alcoholic solvent system yields almost complete extraction of the complex from the solvent phase into the precipitated gel phase.
The complex forms a highly swelled gel in aqueous media of pH more than 3, entrapping 10 to 75 times its own mass of the solvent.
IR spectroscopy in KBr disc for both the interacting polymers and the resultant complex, show no formation of any covalent linkage representing ether or ester bonds.
The solid material so obtained as mentioned above has been evaluated for its degree of swelling in buffers of pH 7.5, which is an evaluation of its media absorption capacity. Simultaneously, the texture characteristics of the swollen gels in this medium have also been evaluated. The texture profiles of the reactants were found to be very different from the complex. The firmness of the gel complex from hydro-alcoholic phase was much stronger than that obtained from the aqueous system.
Texture Expert Exceed (Stable Micro Systems, UK) is versatile equipment for measuring the texture of materials. It has applications in pharmaceutical,
cosmetic, food and packaging industry . By suitable selection of tooling and probes, and by appropriate parameter settings, a wide range of materials can be evaluated for their texture properties. Measurement of texture properties in a gel includes its firmness, stiffness, resilience and stickiness. Using a cylindrical probe in a compression mode, the work of resistance during the penetration of the probe into the gel and the work of resilience as the probe withdraws, can be measured. The gels prepared, and not limiting to the examples cited herein, have been characterized and differentiated by means of the texture analyzer.
The texture analyzer, Model- XT2i, had an attached maximum load cell of 5 kg. With a 5 mm diameter stainless steel cylinder probe, the pre-test, test and post-test speeds were 2 mm per second, 1 mm per second and 1 mm per second, respectively. The travel distance in the gel was 10 mm. Other settings include, trigger type -auto; trigger force -0.5 g; 'Measure force in compression'; 'Return to start' and PPS -200.
The gel obtained in this invention can serve a number of useful functions in pharmaceutical dosage forms, including, as a high bulk substance for oral administration, as a matrix in oral controlled release, in taste-masking, as a tablet disintegrant, among others.
The following non-limiting examples illustrate the preparation of an interpolymer complex within the scope of the present invention.
Example-1
Chitosan (86.2 mg) was dissolved in glacial acetic acid (1 ml), followed by addition of pH 7.5 phosphate buffer (9 ml). The texture profile of the resulting gel has been shown in Fig. -1.
Example-2
Cross-linked polyacrylic acid (Carbopol 971P) (83.5 mg) was dispersed in pH 7.5 phosphate buffer (10 ml). The texture profile of the resulting gel has been shown in Fig. - 2.
Example -3
Chitosan (0.2 g) was dissolved in an acidified solution of citric acid (0.1 g) in water (20 ml). Carbopol 971P(0.02 g) was dispersed in absolute ethanol (60 ml). The solution of chitosan was added gradually into the ethanolic dispersion. The solvent was removed using vacuum distillation and the gel was freeze-dried.
Example -4
Chitosan (0.2 g) was dissolved in an acidified solution of acetic acid (2.0 ml) in water (10 ml). Carbopol 971P(0.2 g) was dispersed in absolute ethanol (60 ml). The solution of chitosan was added gradually into the ethanolic dispersion. The precipitated gel was isolated from the solvent phase and dried using hot-air oven. The dried material was milled and evaluated for degree of swelling and texture characteristics. Fig. -3 shows the texture profile of the swollen complex (83.4 mg), in pH 7.5 buffer (10 ml).
Table -1 shows consolidated data for degree of swelling and texture properties, determined in pH 7.5 phosphate buffer media.
Example-5
Chitosan (0.2 g) was dissolved in an acidified solution of acetic acid (2.0 ml) in water (10 ml). Carbopol 971P(0.2 g) was dispersed as a colloidal solution in water (60 ml). The aqueous solution of chitosan was added gradually into the aqueous polyacrylate dispersion. The precipitated gel was isolated from the solvent phase and dried using hot- air oven. The dried material was milled and evaluated for degree of swelling and texture characteristics. Fig. -4 shows the texture profile of the swollen complex (81.3 mg) in pH 7.5 buffer (10 ml).
Example -6
Glycol chitosan (0.1 g) was dissolved in water (6 ml). Carbopol 971P(0.1 g) was dispersed in absolute ethanol (100 ml). The solution of glycolchitosan was added gradually into the ethanolic dispersion. The precipitated gel was isolated from the solvent phase. The solvent phase was concentrated by evaporation and blend with the gel phase and dried using hot-air oven. The dried material was milled and evaluated for degree of swelling and texture characteristics.
Example-7
Chitosan (0.05 g) was dissolved in an aqueous solution of hydrochloric acid, containing 10 ml water and acidified to a pH of 2.0 prior to dissolution. Quinine sulphate (0.1 g) was dissolved in absolute ethanol (30 ml). Carbopol 974P(0.125 g) was dispersed in the ethanolic solution of quinine sulphate. The solution of chitosan was added gradually into the ethanolic phase. The precipitated gel was isolated from the solvent phase and dried using hot-air oven.
The dried material was milled and evaluated for taste masking of quinine sulphate. The taste masking was found to be effective
Example-8
Chitosan (0.2 g) was dissolved in an acidified solution of acetic acid (2.0 ml) in water (10 ml). Carbopol 971P (0.2 g) was dispersed in acetone (60 ml). The solution of chitosan was added gradually into the non-aqueous dispersion phase. The precipitated gel was isolated from the solvent phase and dried using hot-air oven. The dried material was milled and evaluated for degree of swelling and texture characteristics.
Example -9
Chitosan (0.2 g) was dissolved in an acidified solution of acetic acid (0.2 ml) in water (19.8 ml). Croscarmellose sodium NF (Ac-Di-Sol, FMC) (0.1 g) and Carbopol 971P(0.3 g) were dispersed in absolute ethanol (60 ml). The solution of chitosan was added gradually into the ethanolic dispersion. The precipitated gel was isolated from the solvent phase and dried using hot-air oven. The dried material was milled and evaluated for degree of swelling and texture characteristics.
Table-1 Degree of swelling and texture characteristics of glucosamine -polyacrylate complex, in pH 7.5 buffer
(Table Removed)
While the present invention has been described in terms of its specific embodiments, certain modifications and equivalents will be apparent to those skilled in the art and are intended to be included within the scope of the present invention.

We Claim:
1. An inter-polymer complex comprising a cationic polymeric glucosamine or its derivatives and an anionic, cross-linked, polyacrylic acid or its derivatives wherein the molecular weight of the cross-linked polyacrylic acid or its derivatives is greater than or equal to 700,000.
2. The inter-polymer complex of claim 1 wherein the polymeric glucosamine comprises a chitosan or its derivatives.
3. The inter-polymer complex of claim 2 wherein the chitosan is selected from the group consisting of chitosan, glycol chitosan, carboxymethyl chitosan and hydroxypropyl chitosan.
4. The inter-polymer complex of claim 1 wherein cross-linked polyacrylic acid or its derivatives is a homopolymer or a copolymer.
5. The inter-polymer complex of claim 4 wherein the cross-linked polyacrylic acid or its derivatives is a homopolymer.
6. The inter-polymer complex of claim 1 wherein the molecular weight of the cross-linked polyacrylic acid or its derivatives is greater than 2 billion Dalton.
7. The inter-polymer complex of claim 1 wherein the ratio of the polymeric glucosamine or its derivatives to the cross-linked polyacrylic acid or its derivative is at least 1:20.
8. The inter-polymer complex of claim 1 wherein the ratio of the polymeric glucosamine or its derivatives to the cross-linked polyacrylic acid or its derivatives is between 1:10 and 10:1.
9. The inter-polymer complex of claim 1 wherein the ratio of the polymeric glucosamine or its derivatives to the cross-linked polyacrylic acid or its derivatives is 1:1.
10. A composition comprising:
an inter-polymer complex comprising a polymeric glucosamine or its derivative and a cross-linked polyacrylic acid or its derivatives wherein the molecular weight of the cross-linked polyacrylic acid or its derivatives is greater than or equal to 700,000, and pharmaceutical active(s); and
inactive(s) ingredients.
11. The composition of claim 10 wherein the inter-polymer complex can be incorporated into oral solid pharmaceutical compositions, including tablets and capsules.
12. A process for preparing an inter-polymer complex composition comprising dissolving a polymeric glucosamine or its derivatives in an aqueous media and mixing with a cross-linked polyacrylic acid or its derivatives, which is dispersed in a suitable media, said blend containing pharmaceutical active(s) and inactive ingredient(s), and isolating the resulting precipitated gel complex by any suitable separation technique.
13. The process of claim 12 wherein the polymeric glucosamine or its derivatives is dissolved in acidified aqueous media.
14. The process of claim 13 wherein the aqueous media is acidified using any acid or acid derivative which imparts an acidic pH to the aqueous solution.
15. The process of claim 14 wherein the acid or acid derivative is selected from the group consisting of sulphuric acid, hydrochloric acid, phosphoric acid, carboxylic acids, such as formic acid, acetic acid, malic acid, maleic acid, oxalic acid, succinic acid, tartric acid, lactic acid, ascorbic acid, gluconic acid, amino acids and their derivatives/salts, glyceryl triacetate, polyvinyl acetate, and citric acid.
16. The process of claim 12 wherein the cross-linked polyacrylic acid or its derivatives is dispersed in an aqueous or a hydro-organic media.
17. The process of claim 12 wherein the cross-linked polyacrylic acid or its derivatives is dispersed in a hydro-organic system.
18. The process of claim 17 wherein the cross-linked polyacrylic acid or its derivatives is dispersed in a hydro-alcoholic system.
19. The process of claim 18 wherein the hydro-alcoholic system contains ethanol.
20. The process of claim 12 wherein the organic solvent in water is at least 20% by volume.
21. The process of claim 12 wherein the organic solvent in water is about 95% by volume.
22. The process of claim 21 wherein the organic solvent in water is from about 70 to 90% by volume.