EP2473444A1

EP2473444A1 - Novel inorgano-bioorganic nanocomposite materials, their preparation and use

Info

Publication number: EP2473444A1
Application number: EP10720643A
Authority: EP
Inventors: Andriy Grafov; Markku Leskelä
Original assignee: Licentia Oy
Current assignee: Licentia Oy
Priority date: 2009-05-04
Filing date: 2010-04-30
Publication date: 2012-07-11
Also published as: WO2010128204A1; FI20095502A0

Abstract

A uniform nanocomposite material and a method of producing the same. The novel material comprisesan inorganic component of layered double hydroxide nanolamellae bound to at least one glycan molecule to form particles having an average size of less than 1 μm. The materialcan be produced bycontacting and reacting in aqueous phasea dehydrated and decarbonated layered double hydroxide witha dissolved glycan to afford the formation of particles of a uniform nanocomposite material comprising a layered doublehydroxide nanolamellae bound to the glycan.The materials can be used,for example,within the pharmaceutical industry.

Description

NOVEL INORGANO-BIOORGANIC NANOCOMPOSITE MATERIALS, THEIR PREPARATION AND USE

Background of the Invention

Field of the Invention

The present invention relates to hybrid materials. In particular, the present invention concerns novel inorgano-bioorganic hybrid nanocomposite materials that consist of an inorganic component bound to at least one glycan. The invention also concerns methods of producing such nanocomposite materials and various uses of the new materials.

Description of Related Art

Nanocomposite materials encompass a large variety of systems made of distinctly dissimilar components and combined at the nanometer scale.

Properties of nanocomposite materials depend not only on the properties of their individual precursors but also on their structure (morphology and interfacial characteristics).

This rapidly expanding field of inorgano -organic nanocomposites is generating many exciting new materials with novel properties, which can be derived by combining properties from the constituents into a single material. There is also the possibility of achieving new properties which are unknown in the precursor materials.

Experimental work has generally shown that virtually all types and classes of nanocomposite materials lead to new and improved properties when compared to their macrocomposite counterparts.

Inorganic layered materials exist in great variety. They possess a well defined, ordered intralamellar space potentially accessible by foreign species. This ability enables them to act as matrices or hosts for organic molecules and polymers, yielding interesting hybrid materials obtained by intercalation. Lamellar composites can be divided into two distinct classes, intercalated hybrids and exfoliated nanocomposites. In the former, the polymer chains alternate with the inorganic layers in a fixed compositional ratio and have a well defined number of polymer layers in the interlamellar space. The intercalated hybrid materials are more compound-like because of the fixed polymer/layer ratio. In exfoliated nano-composites, the number of polymer chains between the layers is almost continuously variable, making them more interesting owing to superior functional properties.

A number of methods of producing nanocomposites with lamellar anionic components are known in the art.

US Patent Application Publication No. 2005/0244439 concerns intercalation of a wide range of functional organic compounds into anionic clay layered host materials. Based on the application, functional organic compounds are derivatized with carboxylic, sulphonic or sulphate groups in order to facilitate intercalation. The derivatized compounds are then introduced inside the layers of the host material. Polymers are used for forming compositions by mechanical mixing but the polymers have no interaction with the intercalated host materials.

International Published Patent Application No. WO2007/074184 concerns a method for producing nanocomposite materials for multi-sectorial applications use. The nanocomposite preparation comprises mixing of the natural clay suspensions with biopolymer solutions. The disclosed procedure involves a multi-step process, containing milling, washing and exfoliation. Since the suggested procedure is applied to natural clays (i.e. cationic phyllosilicates), it also includes separation. The known procedure involves laborious reagent and energy- consuming steps. Based on the examples and the supporting drawings of the publication, the materials obtained are micro-scale rather then nano-scaled.

In some earlier studies (cf. Chem. Mater. 2005, 17, 1969-1977, and J. Solid State Chem. 2004, 177, 245-250) intercalation of different anionic polysaccharides into the LDH using formation by a co-precipitation method are reported. The obtained compositions may be highly contaminated with alkali owing to the procedure employed; moreover highly alkaline precipitation medium will seriously damage the polysaccharides. It is a well known fact that polysaccharides hydrolyse, changing their chemical structure at extreme pH conditions. The cited articles contain no proofs for the potential integrity of the macro molecules used by the authors. Furthermore, it should be pointed out that the known procedure is performed under highly alkaline (i.e. highly toxic) conditions and none of materials obtained this way can be suitable as such for biomedical applications. Rather, a multi-step resource- and energy-consuming purification should be applied to the known products before any use.

To complete the survey it can be noted that there are some publications which deal with intercalation of monomeric sugars or cage-like cyclodextrin molecules (Sasaki, S. et al. Intercalation of natural cyclodextrins into layered double hydroxide by calcinations-rehydration reaction. Chem. Lett. 2005, Vol. 34, No. 8, pp. 1192-1193, and Aisawa, S. et al. Sugar-anionic clay composite materials: intercalation of pentoses in layered double hydroxide. J Solid State Chem. 2003, Vol. 174, pp. 342-348).

As is evident from the above review, there are considerable problems in the prior art. Thus, inorgano-bioorganic composites and nanocomposites, especially those of synthetic anionic clays (LDHs) and polysaccharides (glycans), are typically obtained through mechanical mixing of the components, since they are often incompatible in solutions, owing to intrinsic properties of natural polysaccharides. This is, in fact, an origin for numerous difficulties relating to the production of inorgano -organic materials and to the purification of them. Data obtained for small monomeric molecules can never be used to discuss or analyse polymer based products.

Another problem resides in the fact that a majority of glycans, especially those of high molecular weight, are non-soluble or scarcely soluble in water, and even when they are slightly soluble, dissolution can only take place in a very strict specific pH range. This is the reason why the compositions, known in the art, and methods of their preparation typically involve a step of chemical or biochemical (e.g. enzymatic) glycan derivatization to improve their solubility, or use of special binder agents to ensure suitable contacts between different phases of the material.

A further problem is that chemical or biochemical derivatization produces several by-products that must be removed from the modified glycan prior to its further utilisation. Moreover, biochemical enzymatic derivatization or polymer chain scission occur at very strict conditions, including specific buffer solutions, additional reagents being needed to ensure a proper enzyme function. Thus, the final product often contains unavoidable and undesirable contaminants (e.g. ions or groups bonded to the polymer chain), which must be removed by a thorough, multi-step, and resource-consuming purification (e.g. electro- dialysis, membrane ultra-filtration, preparative chromatography, etc.). The above renders the final product highly expensive.

There are also other problems in the art in the respect that all above mentioned processes involve, beyond natural glycans, biologically and environmentally incompatible or toxic reagents, binders, and additives.

Summary of the Invention

It is an aim of the present invention to eliminate at least a part of the problems of the art and to provide novel hybrid nanocomposite materials.

It is another aim of the present invention to provide a novel method of producing nanocomposite materials.

It is a third aim to provide new uses of nanocomposite materials comprised of a combination of layered double hydroxides (LDHs, synthetic anionic clays) and natural biopolymers (e.g. glycans).

The present invention is based on the finding that it is possible to combine an inorganic component having an anionic nature not only with anionic glycans but with neutral and cationic ones as well by introducing the inorganic component in dehydrated form into a solution of the bioorganic component and intimately contacting the components.

The composites are provided in the form of a homogeneous material in the shape of particles having an average particle size (diameter or smallest dimension) generally smaller than 1 micrometre.

The invention also comprises a method of preparing a uniform nanocomposite material of this kind. In the method, a dehydrated and preferably decarbonated layered double hydroxide is first dispersed in an aqueous solution of the corresponding glycan to form a suspension. The layered double hydroxide is then reacted with the glycan and the reaction is allowed to proceed under mixing at non-boiling conditions of the medium for a suitable time period to yield particles of a uniform nanocomposite material comprising a layered double hydroxide nano lamellae bound to glycan.

A number of uses are devised for the new products.

More specifically, the product according to the present invention is mainly characterized by what is stated in the characterising part of claim 1.

The method according to the present invention is characterized by what is stated in the characterising part of claim 11.

Considerable advantages are obtained by the present invention. Thus, the present invention provides a universal method for obtaining inorgano-bioorganic (layered double hydroxide (LDH) - glycan) nanocomposites. The invention allows for a combination of the LDHs with any kind of natural glycans and their derivatives (neutral, cationic or anionic) under controlled conditions and composition. The invention is based on in-situ formation of the composite during the synthesis, and not on mechanical mixing of the components or classical co-precipitation and ion exchange techniques.

Incompatibility of positively charged LDH layers with positively charged cationic biopolymers (glycans) has been resolved by the invention. Reliable and steady fixation of indifferent neutral polysaccharides has been achieved. Novel energy- and resource-saving procedure for fixation of natural glycans of anionic nature has been developed. All three methodologies (for neutral, cationic, and anionic natural glycans) are based on the same inexpensive fundamental technique - "memory effect" of the inorganic layered material, i.e. its structural reconstitution from thermally dehydrated and decarbonated precursor.

The invention provides simple and atom-efficient methodology of natural glycan solubilisation in a way suitable for subsequent formation of nanocomposites with the LDHs. The process does not require derivatization although it can be applied to functionalized glycans as well as to unmodified glycans. According to one aspect, the present method provides highly functional, stable, nature identical (when applicable) nanodispesions, sols, or gels of the LDH. I.e. direct obtaining of nanoscaled non-modified LDH materials. These objectives have never been achieved in the prior art. Always, the LDH particles were irreversibly modified by chemical treatments, which were performed in order to obtain nanoscale particles. The latter are practically useless, since they are both not stable without a particular reagent applied for the treatment and may not be recovered in their original nature identical form without decomposition (either chemical or physical - reaggregation into bulk).

As may appear from the above discussion on the known art, in a majority of cases, the LDHs and the glycans are used as excipients in drug and cosmetic formulations or as components of a composition. In those applications, the components are indifferent to each other. By contrast, the present invention gives rise to composites, wherein the components interact to a certain extent with each other; they are uniformly distributed in the material, providing a synergy of their unique functional properties.

The indicated procedures are by-product free, inexpensive and do not involve any biologically incompatible and non-biodegradable reagents. Moreover, the liquid medium used to perform chemical transformations is water.

The invention is of primary interest for pharmaceutical companies and dietary additive producers. In the pharmaceutical area, individual ingredients (hydrotalcite, some polysaccharides) are known, e.g. as active compounds and excipients for antacide formulations. A combination of those components into the nanocomposite in question would give rise to more mild and prolonged antacide effect owing to synergy of valuable properties of each individual component: enveloping and mitigating effect of polysaccharides, high buffer capacity of both ionic glycans and the LDHs, ion exchange and transport (drug delivery) properties of the LDHs. The nanocomposites under the present invention have controlled composition and structure; they are not a mechanical mixture.

In the domain of dietary additives, the individual components of the nanocomposites in question are known as supplements. The glycans applied are both soluble and non-soluble (in a nutritional meaning of the term, i.e. they may be or may not be fermented and absorbed in the gastrointestinal tract). Hence, the nanocomposites in question may be used as dietary supplements, reducing diets, diabetic food components, etc.

The invention enables to render the material biodegradable or non-degradable and biocompatible in a controlled way.

Next the invention will be examined more closely with the aid of a detailed description with reference to some working examples.

Brief Description of the Drawings

Figure 1 shows the particle size distribution in the LDH-alginic acid nanocomposite prepared according to Example 1 ; and

Figure 2 shows an SEM micrograph of the LDH-chitosan (low M_w) nanocomposite prepared according to Example 3.

Detailed Description of Preferred Embodiments

Definitions

For the purpose of the present invention, an "acid" (often represented by the generic formula HA or [H⁺ A ]) is considered any chemical compound that is capable of donating a hydrogen ion or proton (H⁺) to another compound (called a base, a proton acceptor).

"Nanoparticle" is a three-dimensional particle whose smallest dimension lies in the nanometre range, i.e. each one of its three dimensions is less than about lμm (10^"6m or 1000 nm) and at least one of those is less than 200 nm.

By "uniform nanocomposite material" is meant a material characterised by structural and compositional uniformity both in bulk, and at the level of individual nanoparticles.

"Glycan" stands for a natural or modified natural polymer or oligomer that consists of several or many (more than 7, preferably more than 10, in particular more than 12) monose (monosaccharide) units bound together solely by O-glycosidic linkages. Glycans may have solely initial monose -OH functional groups, in the present application those are referred to as "neutral" glycans. Based on the above, the term "glycan" is therefore used to cover "glycan and functionalised glycan molecules". Although the term "glycan" is herein frequently used in the singular voice, mixtures of two or more glycans can, naturally, also be employed.

As known in the art, according to the IUPAC definition, glycan or polysaccharide, or polyose is a polymer that consists of different (typically unknown) large number of monosaccharide monomer units.

Both natural and modified glycans may also bear different functional groups, typically -COOR; -SO₃R; -0(PO₂OR)_xR; or -NR₂ (where R may be a proton, a metal ion, a hydrocarbon moiety, a deprotonised alcohol, phenol, carboxylic acid, heterocycle, etc. moieties). In the present application those "functionalised glycans" are referred to as "cationic" or "anionic" with respect to their capability to produce exchangeable positively or negatively charged species in aqueous media.

"Lamella" is a particle of fine layered structure that is the most typical form of existence of layered double hydroxides. It consists of the hydroxides' layer building blocks of M²⁺ and M ⁺ octahedra, interstratified by interlayer spaces, which can be occupied by water, charge compensating anions, and adsorbed neutral molecules. Individual layer sheets are stacked into the lamellar particle, hence, its x and y dimensions are more developed than the z-dimension. ' TSf ano lamella" is a nanosized lamella.

"Pharmaceutically active acid", or "P.a.c", is any chemical compound that can be classified as a Brønsted-Lowry acid and is "intended to affect the structure or any function of the body of man or other animals" as well as "for use in the diagnosis, cure, mitigation, treatment, or prevention of disease in man or other animals" . Pharmaceutical activity of the P.a.c.'s is confirmed by including those in the Pharmacopoeia (here the Pharmacopoeia means the USP, European Pharmacopoeia, and National Pharmacopoeias or other similar Acts of National drug regulatory authorities in the countries of the patent's validity).

"Nutraceutical" is any substance that is a food, a part of a food, or dietary supplement and provides medical or health benefits. The present invention provides novel nanocomposite materials. These new uniform materials comprise an inorganic component of a layered double hydroxide nano lamellae bound to at least one glycan. The nanocomposite materials are present essentially in the form of particles having an average size (size of smallest dimension or diameter) of less than 1 μm.

According to one embodiment, the inorganic component of the particles is formed by a layered double hydroxide having the general formula I

[M²⁺ _!__XM³⁺ _X(OH)₂] [Aⁿ _x/n-zH₂O]

wherein M²⁺ is selected from Mg²⁺, Ca²⁺, Mn²⁺, Fe²⁺, Co²⁺, Ni²⁺, Cu²⁺, and Zn²⁺ M³⁺ is selected from Al³⁺, V³⁺, Cr³⁺, Fe³⁺, Co³⁺, Sc³⁺, Ga³⁺, Y³⁺, Rh³⁺, Zr⁴⁺ A^n~ stands for an anion, x stands for a value in the range from 0.2 to 0.33, n is an integer from 1 to 4 and z is an integer from 1 to 10.

In the novel nanocomposite materials, the glycan molecule is bound to the layered double hydroxide nano lamellae at a ratio of approximately 1 monomer-mole of glycan to 0.5 to 1.5 moles of layered double hydroxide. The glycan is immobilised on and/or absorbed to the layered double hydroxide. In particular, the glycans (i.e. the "glycan") are chemically bonded to the layered double hydroxide nanolamellae.

Typically, M²⁺ is selected from the group consisting of the bivalent ions of earth alkaline metals, such as Mg²⁺ and Ca²⁺ as well as transition metals, such as Zn²⁺. A suitable trivalent metal ion, M³⁺, is represented by Al³⁺. These ions will assist in rendering the material biocompatible and biodegradable.

The layered double hydroxide hosts interlayer anions to balance a charge of the hydroxide layers. The former can be selected for example from the group of OH , CO3² , CH3COO , CF and fully or partially deprotonated moieties of Brønsted-Lowry acids, particularly, nutraceuticals, or pharmaceutically active acids.

Examples of nutraceuticals and pharmaceutically active acids are, e.g., phosphoric acids, lactic acid, citric acid, derivatives of salicylic and propionic acids, etc. Naturally, also pharmaceutically acceptable acids can be used for the purpose of forming acid addition salts. Such acid include in addition to the foregoing acids also other organic acids, such as acetic acid, propionic acid, gly colic acid, oxalic acid, malonic acid, succinic acid, fumaric acid, benzoic acid, cinnamic acid, methane sulphonic acid, p-toluene sulphonic acid and salicylic acid, and inorganic acids, such as hydrochloric acid, hydrobromic acid and sulphuric acid.

The glycan can be selected from, for example, the group consisting of aminoglycans, completely or partially deacetylated aminoglycans, such as chitosan; glycuronans and glycans functionalised with other anionogenic groups, such as alginic acid, carrageenan, chondroitin, gellan or hyaluronan; or a neutral glycan, such as inulin, amylose, or galactomannans .

As pointed out above, mixtures of two or more glycans can be employed. Thus, for example mixtures of 2 to 10 anionic glycans or 2 to 10 neutral glycans or 2 to 10 cationic glycans can be used. Preferably the glycans of the mixtures have properties which with regard to dissolution in water are similar as to provide suitable solutions for the contacting step.

The particles have an average particle size (size of smallest dimension or diameter) in the range of 50 to 950 nm, in particular about 100 to 900 nm, preferably about 150 to 850, typically about 200 to 800 nm.

In the method of preparing a uniform nanocomposite material comprising a nanocomposite of the above kind, a particular combination of steps is taken:

First a dehydrated and decarbonated layered double hydroxide is dispersed in an aqueous solution or, potentially, dispersion of the corresponding glycan, e.g. native glycan or functionalised glycan, to form a suspension. The aqueous solution can be purified water, deionised water, tap water or a mixture of water and another solution or solvent, typically miscible with water. In particular, the glycan is preferably dispersed or dissolved in water that has been chemically purified, e.g. by deionisation.

Next, the layered double hydroxide is reacted with the glycan in the aqueous environment and the reaction is allowed to proceed for a prolonged time preferably under mixing. The conditions are preferably "non-boiling", i.e. the temperature is maintained between the melting and boiling points of the aqueous medium. Typically, in case of a medium predominantly composed of water, a temperature in the range of about 20 to 80 ⁰C is suitable. At these conditions, the formation of particles of a uniform nanocomposite material comprising a layered double hydroxide nanolamellae bound to the glycan takes place.

The nanocomposite material can be used in dispersion, but it can also be recovered from the suspension, for example by centrifugation and separation of the aqueous phase. For example, the uniform nanocomposite material produced can be further purified from non-specifically bonded glycans by repeated washing with deionised or otherwise purified water and subsequent centrifugation.

Before the reaction, in order to pre-treat the layered double hydroxide (e.g. to remove water and carbonate residues), it is suitably thermally dehydrated and decarbonised before it is contacted with the glycan. Suitably, the layered double hydroxide is heat treated at a temperature of about 250 to 450 ⁰C, preferably at 400 to 430 ⁰C, for 1 to 24 hours to dehydrate and decarbonise the layered double hydroxide.

As mentioned above, the layered double hydroxide is reacted with the glycan in an aqueous medium, in which the glycan preferably has been dissolved. For enhancing dissolution of the glycan, the pH can be adjusted or additional components added. The pH is typically neutral, although slightly alkaline or acidic conditions (pH about 5 to 9) are equally possible, depending on the specific type of glycan.

Typically, during reaction with the layered double hydroxide, the glycan containing aqueous medium has a pH which is roughly neutral, in particular about 6 to 8.

According to one particular embodiment, the glycan is selected from hydro lysed aminoglycan and completely or partially deacetylated aminoglycan, and said aminoglycan or deacetylated glycan is dissolved in an aqueous medium by

- forming a dilute dispersion of said aminoglycan or deacetylated glycan in water,

- adjusting the pH of the aqueous phase to 3.5 or less, and

- hydro lysing said aminoglycan or deacetylated aminoglycan in the water for 1 to 20 hours for hydro lysing said aminoglycan or deacetylated aminoglycan so as to provide an aqueous solution of said aminoglycan or deacetylated aminoglycan which is stable at a pH in the range of 6 to 8.

Particularly in the indicated embodiment, but generally in the present method, the dilute aqueous suspension of said aminoglycan or deacetylated aminoglycan has a concentration of about 0.1 to 5 % by weight, in particular about 0.5 to 3 % by weight, in particular about 1 to 1.5 % by weight of the glycan in water.

The hydrolysis is performed for 1 to 20 hours, in particular 4 to 16 hours. The temperature is for example about 80 to 100 ⁰C at atmospheric pressure, or about 100 to 125 ⁰C at excess pressure (pressure higher than 1 at abs).

According to another preferred embodiment, wherein the dissolved glycan comprises a glycuronan or glycans functionalised with other anionogenic groups, such as alginic acid, carrageenan, hyaluronan, chondroitin, and gellan; the glycan is dissolved in an aqueous medium by adjusting the pH of the aqueous phase to about 6.0 to 7.5.

For adjusting the pH of the aqueous medium an inorganic or organic base can be employed.

In a further preferred embodiment, the dissolved glycan comprises a neutral glycan, such as inulin, or a galactomannan, which is dissolved in an aqueous medium by adjusting the pH of the aqueous phase to 7.5 to 8.0. For that purpose, pH of the aqueous medium can be adjusted with an aid of a carbonate-free solution of alkali metal or earth alkaline metal hydroxide.

As discussed above, acid derivatives are interesting embodiments of the present nanocomposite products. Thus, the dehydrated and decarbonated layered double hydroxide can be contacted with chloride-anions and fully or partially substituted moieties of Brønsted-Lowry acids, particularly, nutraceuticals or pharmaceutically active acids and/or their salts, such as phosphoric acids, lactic and citric acids, during the dispersing of the layered double hydroxide or immediately after, before the layered double hydroxide is being contacted with the glycan or functionalised glycan.

In the indicated embodiment, the pH of the aqueous phase of the dispersion is adjusted to 6 to 8 after the addition of the anions. Specific embodiments:

Based on the above, in one working embodiment, the process for preparing the above compositions comprises the steps of

- dispersing of thermally dehydrated and decarbonated LDH material in deionised or otherwise purified water and subsequently

- adding the suspension to the solution of the glycan in water in the range of pH 6 - 8; the reaction proceeds for at least 70 h under vigorous stirring (> 1200 rev/min) in the temperature range from about 40 to 70 ⁰C to afford the formation of nanoparticles.

The nanocomposite in the form of paste or gel can be separated by centrifugation for 0.5-3 hours.

According to one embodiment, cationic glycans (e.g. chitosan) can be solubilised by hydrolysis of their 1÷1.5 % solutions in deionised or otherwise purified water, acidified by few drops of 0.1 M ÷ O.01 M HCl until the pH = 3. The hydrolysis is performed in an autoclave at 120 ⁰C for 4 to 16 hours depending on the molecular weight of the starting polymer. Such a treatment provides a diminution of the chitosan's molecular weight, necessary for existence of its solutions within the above mentioned range of pH. According to another embodiment, anionic glycans (e.g. alginic acid, carrageenan, hyaluronan, etc.) are dissolved in deionised or otherwise purified water. Several drops of 0.1 M ÷ 0.01 M carbonate free NaOH or other alkali solution may be added to enable the solubilisation and regulate the pH level between 6.0 and 7.0 values.

According to a third embodiment, neutral polysaccharides (e.g. inulin, guar) are dissolved in deionised or otherwise purified water and the solution pH is regulated to 7.5÷8.0 by addition of 0.1 M ÷ 0.01 M carbonate free NaOH solution.

There are numerous potential applications of the above-described new biocompatible inorgano-bioorganic composites.

In recent years, inorgano -organic composites have attracted increasing attention due to their fascinating properties as biodegradable materials, drug release systems, electrochemical sensors, packaging materials, and so on. The new nanocomposite materials developed under present invention reveal a synergic combination of valuable properties of the constituents: synthetic layered double hydroxides (LDH) and natural glycans. Since the latter are relatively complex carbohydrates that are made up of many monosaccharide units joined together by glycosidic bonds, such natural polymers exhibit a wide variety of structures and extraordinary diversity of functional properties. Additionally, glycans are biologically produced (bio-based) materials that have a unique combination of valuable properties and environmentally friendly features. They are renewable materials, produced from other biological compounds, and generally are non-toxic, and biodegradable.

The LDHs are easily obtained, and such synthetic anionic clays have a uniform structure and composition, possess valuable sorption, ion-exchange, and carrier properties. The above properties enable a direct use of Mg-Al and Zn-Al LDHs in humans and animals, harmlessness of these materials has been proven by the FDA several decades ago.

Synergic combination of mechanical and functional properties of individual components ensure a myriad of potential applications for novel LDH-glycan nanocomposite materials, making them a natural fit for sustainable development.

Particularly, one can propose the following principal application areas that are closely interconnected between each other:

- Active pharmaceutical ingredients and dietary supplements;

- Care and decorative cosmetics;

- Drug delivery devices; - Specific sorbents and support materials;

- Materials for implants and tissue engineering;

- Biosensor and electrode materials;

- Heterogeneous catalysts;

- Packaging materials.

The potential applications may be more wide and non-limited by the proposed ones.

Next, the above applications will be described in more detail. Active pharmaceutical ingredients

Individual components used to produce nanocomposites have been known for a while as antacid drugs (e.g. Mg-Al LDH, hydrotalcite, as Talcid® by Bayer AG and Topalcan® by Pierre Fabre Medicaments), as well as excipients in different pharmaceutical formulations, oral and personal hygiene preparations (glycans).

For example, in gastroenterology the requirements for antacid drugs are: lowering and maintaining of gastric pH levels (pH~3; 18/24h); protection of (gastric) mucosae; improvement of gastrointestinal tract (GIT) peristalsis.

New nanocomposite materials will have the following advantages over known formulations: synergy of the components' buffering properties; non-resorbability of the LDH, as a consequence of the composite formation (optional and adjustable); prolonged action and higher efficiency (owing to nano-scale and bottom-up assembling; adsorption of ulcerogenic agents, e.g. H. pylori cytotoxin); gel form that enables catheter administration in newborns, infants, and serious patients. The nanocomposites in question are mucosae-friendly and may contain and deliver another pharmaceutically active compounds.

Dietary supplements

The dietary supplements, also known as food supplements or nutritional supplements, are preparations intended to supply nutrients, such as vitamins, minerals, fatty or amino acids, dietary substances that are missing or are not consumed in sufficient quantity in a person's diet. They could be further divided as nutraceuticals, designed to promote a healthy lifestyle, and parapharmaceuticals that are non-prescription health care products. The former are intended to supplement a deficiency in essential nutrients, to guide the metabolism correction, to perform an immunomodulatory action, and for nutritional care.

Parapharmaceuticals are mainly used for prophylaxis, supplementary care and maintaining of physiological standards, for protection of gastric mucosa, and for improvement of the GIT peristalsis. New nanocomposite materials have the following advantages over known formulations: capability to bind and excrete fats, to improve the cholesterol metabolism, to improve intestinal peristalsis, to provide a sense of fullness, to lower dietary calories, to correct a carbohydrate deficiency. They may also be diabetic dietary products.

Care and decorative cosmetics

The nanocomposites in question contain glycans known for their pronounced water-retention effect (e.g. hyaluronan, carrageenan, etc.) that would enable to prevent skin and hair dehumidifϊcation. From the other hand, they also contain the LDHs, known for their pore-constringing effect, drying and healing properties. A synergic combination of the above properties may render the nanocomoposites highly attractive for creams and gels for and after shave, baby care, sun-block, for moisturizing of sensitive and hypersensitive skin, as well as for anti-acne applications.

Since a major part of cosmetics is based on emulsions (w/o or o/w) or suspensions, their stability is of particular importance. Additionally, the formulation must possess antimicrobial/antibacterial resistance and to be adapted to the skin pH.

Advantages are as follows: owing to nano-scaled particle size of new materials, they easily form stable gels and films characterised by transparency and tailorable elasticity. Synergic sorption properties of the nanocomposites in question enable their modification with cosmetically active ingredients (DNA, RNA, vitamines, etc.) or colouring agents. pH of the resulting nanocomposite gel or film may be controlled in a wide range (pH = 5÷8). Upon necessity, the materials could be provided with high sorption, buffer, and ion-exchange capacities.

Particular application areas may include creams and gels for purification of skin, cleansing and anti-comedogenic formulations; hydrating and nutrition masks for different types of skin, e.g. both for mixed-oily and tired, fragile, and hypersensitive skin; for exfoliation formulations, UV-protection formulas, baby-care products, etc. Drug delivery (DD) devices

Both bioorganic and inorganic individual components are known as excellent drug carriers that could be tuned for a targeted release.

The nanocomposites in question may have the following advantages: the materials are made from fully biocompatible components; they are suitable for internal use, topical applications, and for implanted DD devices; the composites possess a synergism of antiseptic, buffer, and sorption properties; the materials are characterised by improved compatibility with mucosa and soft tissues. The devices may be used to maintain normal physiological pH in the case of severe infections (gynaecology, gastroenterology), DD vectors for ulcer therapy (dermatology, gastroenterology), adjuvant therapy means (oncology, embryo implantation).

Specific sorbents and support materials

The materials in question must possess high sorption and/or ion exchange capacity, must be stable in media of application, to be easily recyclable and environmentally compatible.

The LDHs are known for a while as versatile sorbents for any kind of anions. They have found applications ranging from metallurgy and nuclear power industry to biomedical ones. The glycans are also known both as filters/adsorbents for metal extraction, waste water management, as well as for a variety of medical uses including high-affinity sorbents for therapy and diagnostics.

The principal advantage of the proposed materials over existing in the prior art consists in a synergic combination of sorption properties of the individual components (LDH and the glycan) at the nano-level. The materials exhibit improved mechanical properties, more wide pH range of application, improved stability towards aggressive organic and biological media.

Materials for implants and tissue engineering

New materials consist of bio-resorbable glycans and inorganic nano-particles suitable for bone formation. They may be applied as resorbable or non-resorbable gels, pastes, and powders; the resorbability being tailored through ingredient choice (structure) and composition. The materials may be applied for guided bone generation. New nanocomposite materials are supposed to have the following advantages: tailorable bio-resorbablility and mineral content owing to molecular assembly of the material from properly chosen natural structural polysaccharides, lamellar structure of the mineral component is expected to improve a contact of the tissue engineering scaffolds with periosseum and osseointegration. Gels may be used as filers, implants and adhesives with improved compatibility with soft tissue and mucosa.

Biosensor and electrode materials

For that kind of materials high sorption and ion exchange capacities, high ionic conductivity, mechanical and environmental stability, and tailorable permeability are of particular importance.

New materials may be advantageous due to: a synergic sorption properties of the components that enable specific immobilisation of electrochemically active probe biomolecules (e.g. enzymes, nucleic acids, probe peptides or proteins, etc.); suitability of the nanocomposites for application in red/ox conditions; high water (and other polar solvent, e.g. methanol) retention properties (particularly important for PEMFC - proton exchange membrane fuel cells); tailorable behaviour of the materials towards non-specific interactions with analyte biomolecules.

Heterogeneous catalysts

The materials in question have to possess high sorption and (optionally) ion exchange capacity, high permeability and/or surface resistance, mechanical and environmental stability, and environmental compatibility.

Advantages of the proposed materials arise from: synergic sorption properties that enable immobilisation of different catalytic species (inorganic, coordination, and enzymatic); suitability for application in different solvents; bio compatibility, and suitable for tandem catalysis (including the asymmetric one, owing to asymmetric character of natural glycans). Packaging materials

Glycan-based materials are well known packaging materials (chemically modified celluloses, starches, chitosan, alginates). They are non-toxic, easily mouldable and extrudable from solutions. The packaging materials produced are characterised with a good mechanical and weathering stability, they are environmentally compatible. Among the advantages of the proposed materials may be: a possibility of application in direct contact with foodstuffs, tailorable oxygen permeability and germistatic/germicidal properties.

The following examples are given to illustrate the invention, and are not to be considered as limiting its scope.

Materials

Mg-Al layered double hydroxide (Mg-Al LDH) of the formula Mg₀,67Alo,33(OH)₂(Cθ3)o,i65 x 0.4H₂O was obtained according to classic procedures, known from the prior art (e.g. U. Costantino, F. Marmottini, M. Nocchetti, R. Vivani, Eur. J. Inorg. Chem. 1998, 1439) and calcined at 430⁰C for 12 h to obtain a mixture of metal oxides (further referred to as cLDH), which was cooled in vacuo and stored in an argon filled dry-box.

Ultra high purity freshly deionised water has been used throughout the experiments. All manipulations were carried out under CO₂-free atmosphere.

Residual glycan concentrations in supernatant solutions were determined by polarimetry and spectrophotometry.

Particle size measurements were performed by dynamic light scattering on a Zetasizer Nano (Malvern Instruments) using 1% solutions of re-suspended gels in water in a 1 cm polystyrene cuvettes.

Example 1

A specified amount of anionic glycan (see Table 1) was dissolved in 90 ml of water, the pH was adjusted to the values of 7.0 ÷7.5 by addition of carbonate free 0.1M NaOH solution, and the resulting solution was brought to the volume of 100 ml. 0.5 g of cLDH was pre-mixed with a small amount of water (typically 0.5 - 1.5 ml) to form a homogeneous paste that was added to a glycan solution at a specified temperature and vigorous stirring, typically >1000 rpm. The reaction continued for 72 h (120 h for carrageenan). Gel-like nanocomposite was separated from the supernatant liquid by centrifugation and analysed. The reaction conditions and results are shown in the Table 1 and Figure 1.

Example 2

A specified amount of neutral glycan (see Table 1) was dissolved in 90 ml of water, the pH was adjusted to a value of 7.5 ÷ 8.0 by addition of carbonate free 0.01M NaOH solution, and the resulting solution was brought to the volume of 100 ml. 0.5 g of cLDH was pre-mixed with a small amount of water (typically 0.5 - 1.5 ml) to form a homogeneous paste that was added to a glycan solution at a specified temperature and vigorous stirring, typically >1000 rpm. The reaction continued for 72 h (120 h for guar). Gel-like nanocomposite was separated from the supernatant liquid by centrifugation and analysed. The reaction conditions and results are shown in the Table 1.

Table 1. LDH treatment with anionic and neutral glycans

Example Glycan Glycan Stoichiom. Temp., ⁰C Glycan Particle weight, g ratio uptake, % size, nm

1 Alginic acid * 0.610 1 : 1 60 99 300

1 Carrageenan 0.676 1 : 1 70 76 1001

1 Chondroitin 0.900 1 : 0.8 45 91 387 sulphate *

1 Hyaluronic acid 0.663 1 : 1 45 87 483

2 Inulin * 0.756 1 : 1.2 50 94 343

2 Guar 0.630 1 : 1 70 72 * for 50 ml of solution

The nanocomposites in question containing 50-80 % w/w LDH were successfully used in cell culture test using 3T3 fibroblasts that showed good growing rates Example 3

A specified amount of chitosan (glucosaminoglucan), see Table 2, was dissolved in 30 ml of water, acidified to pH ~ 3 by addition of 0.1 M HCl. Resulting viscous solution were transferred into a closed Teflon container placed in a stainless steel autoclave and hydrolysed at 120 ⁰C for a specified period of time. After cooling of the autoclave, its content was poured into 60 ml of water, the pH was adjusted to the values of 6.5 ÷ 7.0 by addition of carbonate free 0.05M NaOH solution, and the resulting solution was brought to the volume of 100 ml. 0.5 g of cLDH was pre-mixed with a small amount of water (typically 0.5 - 1.5 ml) to form a homogeneous paste that was added to the glycan solution at 50⁰C and vigorous stirring, typically >1000 rpm. The reaction continued for 120 h. Gel- like nanocomposite was separated from the supernatant liquid by centrifugation and analysed. The reaction conditions and results are shown in the Table 2 and Figure 2.

Table 2. LDH treatment with chitosans

Glycan Hydrolys Glycan Stoichiom. Temp., ⁰C Glycan Particle is time, h weight, g ratio uptake, % size, nm

Low Mw chitosan 12 0.450 1 : 1 50 98 241 High Mw chitosan 16 0.450 1 : 1 50 83 469

Claims

1. A uniform nanocomposite material comprising an inorganic component of layered double hydroxide nano lamellae bound to at least one glycan molecule to form particles having an average size of less than 1 μm.

2. The material according to claim 1, wherein the inorganic component of the particles is formed by a layered double hydroxide having the general formula I

[M²⁺ _!__XM³⁺ _X(OH)₂] [Aⁿ _x/n-zH₂O]

wherein M²⁺ is selected from Mg²⁺, Ca²⁺, Mn²⁺, Fe²⁺, Co²⁺, Ni²⁺, Cu²⁺, and Zn²⁺

M³⁺ is selected from Al³⁺, V³⁺, Cr³⁺, Fe³⁺, Co³⁺, Sc³⁺, Ga³⁺, Y³⁺, Rh³⁺, Zr⁴⁺ A^n~ stands for an anion, x stands for a value in the range from 0.2 to 0.33, n is an integer from 1 to 4 and z is an integer from 1 to 10.

3. The material according to claim 2, wherein the glycan is bound to the layered double hydroxide nano lamellae at a ratio of approximately 1 monomer-mole of glycan to 0.5 to 1.5 moles of layered double hydroxide.

4. The material according to claim 2 or 3, wherein the M²⁺ is selected from Mg²⁺, Ca²⁺, Zn²⁺, and M³⁺ = Al³⁺ in order to render biocompatibility and biodegradability to the material.

5. The material according to any of claims 1 to 4, wherein the glycans are immobilised on and/or absorbed to the layered double hydroxide.

6. The material according to any of claims 1 to 5, wherein the layered double hydroxide exhibits anions selected from the group of OH , CO3² , CH3COO , Cl^" and fully or partially deprotonated moieties of Brønsted-Lowry acids, particularly, nutraceuticals, or pharmaceutically active acids.

7. The material according to claim 6, wherein the nutraceuticals or pharmaceutically active acids are selected from the group of phosphoric acids, lactic acid, and citric acid.

8. The material according to any of claims 1 to 7, wherein the glycan is selected from aminoglycans, completely or partially deacetylated aminoglycans, such as chitosan; glycuronans and glycans functionalised with other anionogenic groups, such as alginic acid, carrageenan, chondroitin, gellan or hyaluronan; or neutral glycans, such as inulin, amylose or galactomannans.

9. The material according to any of the preceding claims, wherein the particles have an average particle size in the range of 50 to 950 nm, in particular about 100 to 900 nm, preferably about 150 to 850, typically about 200 to 800 nm.

10. The material according to any of claims 1 to 9, wherein the glycans are chemically bound to the layered double hydroxide nanolamellae.

11. A method of preparing a uniform nanocomposite material comprising an inorganic portion of layered double hydroxide nanolamellae bound to at least one glycan, said method comprising the steps of

- dispersing a dehydrated and decarbonated layered double hydroxide in an aqueous solution of the corresponding glycan to form a suspension,

- reacting the layered double hydroxide with the glycan, and

- allowing the reaction to proceed for a prolonged time under mixing at non-boiling conditions of the medium to afford the formation of particles of a uniform nanocomposite material comprising a layered double hydroxide nanolamellae bound to glycan.

12. The method according to claim 11, wherein the nanocomposite material is recovered from the suspension.

13. The method according to claim 11 or 12, wherein the layered double hydroxide is thermally dehydrated and decarbonised before it is being reacted with the glycan.

14. The method according to claim 13, wherein the layered double hydroxide is heat treated at a temperature of about 250 to 450 ⁰C, preferably at 400 to 430 ⁰C, for 1 to 24 hours to dehydrate and decarbonise the layered double hydroxide.

15. The method according to any of claims 11 to 14, wherein the layered double hydroxide is reacted with the glycan in an aqueous medium, in which the glycan has been dissolved.

16. The method according to any of claims 11 to 15, wherein the layered double hydroxide is reacted with the glycan at a pH of about 6 to 8.

17. The method according to any of claims 11 to 16, wherein the glycan is selected from the group of hydro lysed aminoglycan and completely or partially deacetylated aminoglycan, said aminoglycan or deacetylated glycan being dissolved in an aqueous medium by

- adjusting the pH of the aqueous phase to 3.5 or less, and

18. The method according to claim 17, wherein the dilute aqueous suspension of said aminoglycan or deacetylated aminoglycan has a concentration of about 0.1 to 5 % by weight, in particular about 0.5 to 3 % by weight, for example about 1 to 1.5 % by weight of the glycan in water.

19. The method according to claims 17 or 18, wherein the hydrolysis is performed for 1 to 20 hours, in particular 4 to 16 hours in particular at a temperature of about 80 to 100 ⁰C at atmospheric pressure, or about 100 to 125 ⁰C at excess pressure.

20. The method according to any of claims 11 to 16, wherein the dissolved glycan comprises a glycuronan or glycan functionalised with other anionogenic groups, such as alginic acid, carrageenan, hyaluronan, chondroitin or gellan etc., dissolved in an aqueous medium by adjusting the pH of the aqueous phase to a value in the range from 6.0 to 7.0.

21. The method according to claim 20, wherein the pH of the aqueous medium is adjusted with the aid of an inorganic or organic base.

22. The method according to any of claims 11 to 16, wherein the dissolved glycan comprises a neutral glycan, such as inulin, amylose, or galactomannans etc., dissolved in an aqueous medium by adjusting the pH of the aqueous phase to 7.5 to 8.0.

23. The method according to claim 22, wherein the pH of the aqueous medium is adjusted with the aid of a carbonate-free solution of an alkali metal or earth alkaline metal hydroxide.

24. The method according to any of claims 11 to 23, wherein the glycan is dispersed or dissolved in water that has been chemically purified, e.g. by deionization.

25. The method according to any of claims 11 to 24, wherein the dehydrated and decarbonated layered double hydroxide is contacted with chloride-anions and fully or partially substituted moieties of Brønsted-Lowry acids, particularly nutraceuticals or pharmaceutically active acids and/or their salts, such as phosphoric acids, lactic and citric acids, during the dispersing of the layered double hydroxide or immediately after the layered double hydroxide has been contacted with the glycan.

26. The method according to claim 25, wherein the pH of the aqueous phase of the dispersion is adjusted to a value in the range from 6 to 8 after the addition of the anions.

27. The method according to any of claims 11 to 26, wherein the uniform nanocomposite material is further purified from non-specifically bonded glycans by repeated washing with deionised or otherwise purified water and subsequent centrifugation.

28. The method according to any of claims 11 to 27 comprising recovering a material comprising at least one glycan species bound to particles of a layered double hydroxide, said particles having an average particle size in the range of 50 to 950 nm, in particular about 100 to 900 nm, preferably about 150 to 850, typically about 200 to 800 nm.

29. The method according to any of claims 10 to 27, wherein the glycan is allowed to react with the layered double hydroxide for at least 10 hours, in particular at least 15 hours, preferably about 20 to 200 hours, typically about 24 to 150 hours.

30. The material according to any of claims 1 to 10 obtainable by a method according to any of claims 11 to 29.

31. Use of a uniform nanocomposite material according to any of claims 1 to 10 or 30 as an active pharmaceutical ingredient.

32. Use of a uniform nanocomposite material according to any of claims 1 to 10 or 30 as a vehicle for drug delivery.

33. Use of a uniform nanocomposite material according to any of claims 1 to 10 or 30 as a dietary supplement.

34. Use of a uniform nanocomposite material according to any of claims 1 to 10 or 30 as a resorbable or non-resorbable implant or tissue engineering material.

35. Use of a uniform nanocomposite material according to any of claims 1 to 10 or 30 as a heterogeneous catalyst.

36. Use of a uniform nanocomposite material according to any of claims 1 to 10 or 30 as a biosensor, electrode, or a membrane material.

37. Use of a uniform nanocomposite material according to any of claims 1 to 10 or 30 as a sorbent or support.

38. Use of a uniform nanocomposite material according to any of claims 1 to 10 or 30 as a cosmetic ingredient.

39. Use of a uniform nanocomposite material according to any of claims 1 to 10 or 30 as a packaging material.