WO2014195764A1

WO2014195764A1 - Anionic silicon dioxide derivatives adsorbed with pharmaceutically active cations for dental use

Info

Publication number: WO2014195764A1
Application number: PCT/IB2013/054650
Authority: WO
Inventors: Massimo Ferrari
Original assignee: Pavia Farmaceutici S.R.L.
Priority date: 2013-06-06
Filing date: 2013-06-06
Publication date: 2014-12-11
Also published as: EP3003252A1

Abstract

The present invention relates to a dioxide silicon or titanium derivative of formula (I): (MO₂) ^- (A^m+) _y, for dental use as antibacterial, antiviral or antimycotic agent. The present dioxide derivatives are particularly useful in the treatment of oral cavity diseases such as gingivitis or periodontitis, and can conveniently be formulated in admixture with known oral care active ingredient, such as chlorexidine and the like. Thus, the invention also relates to a dental care composition, e.g. in the form of toothpaste or cream, comprising at least the derivatives (I), in admixture with at least one physiologically acceptable carrier or excipient.

Description

ANIONIC SILICON DIOXIDE DERIVATIVES ADSORBED WITH PHARMACEUTICALLY ACTIVE CATIONS FOR DENTAL USE.

The present invention generally refers to a silicon or titanium dioxide derivative of formula (I): (M0₂) ^~ (A^m+) _y, wherein M is Si or Ti, as active ingredient for the preparation of a composition for dental use, e.g. as antibacterial agent in the treatment of oral pathologic conditions .

Background

Oral hygiene is the practice of keeping the mouth and teeth clean to prevent dental problems, most commonly, dental cavities, gingivitis, and bad breath. There are also oral pathologic conditions in which good oral hygiene is required for healing and regeneration of the oral tissues. These conditions included gingivitis, periodontitis, and dental trauma, such as subluxation, oral cysts, and following wisdom tooth extraction.

The clinical efficacy of the application of chlorhexidine as a component of oral rinses is well documented by many clinical studies, such as among others, Lang Niklausp et al. "Chlorhexidine digluconate, an agent for chemical plaque control and prevention of gingival inflammation", Journal of Periodontal Research (1986) 21:74-89.

It is also known the use of chlorexidine as active ingredient in some kind of mounthwash, particularly useful in reducing the dental plaque or even as antibacterial agent in general. However, prolonged use of products containing chlorhexidine can cause stains on teeth, tongue, and gingiva, also on silicate and resin restorations. Also, according to the literature (see e.g. In Block, Seymour S. Disinfection, Sterilization, and Preservation (5th ed. ) (2000) Lippincott Williams & Wilkins. pp. 321-36), chlorhexidine is deactivated by most of the anionic compounds commonly used in toothpastes and mouthwashes, such as surfactants and the like. For this reason, chlorhexidine mouth rinses are recommended to be used at least 30 minutes after other dental products.

The need thus arises to provide a new product alternative to chlorexidine, that is efficacious, e.g., in treating oral infections and inflammations, has a good oral stability and tolerability and is able to substantially avoid the above indicated problems.

Summary of the invention

In a first aspect, the invention refers to a derivative of formula (I) :

(M0₂)- (A^m+) Y (I) wherein :

is Si or Ti;

(M0₂)^~ represents an anionic negatively charged dioxide particle comprising tetrahedral Silicon or octahedral Titanium atoms, interconnected by bridging oxygen atoms,

A^m+ represents a positively charged active species, linked to the anionic silicon or titanium dioxide particle by electrostatic interaction, wherein m is the charge of the active species and it is comprised from 1 to 20, preferably from 1 to 10, Y represents the number of different active species

Aunco-adsorbed on the same anionic silicon or titanium particle and it is comprised from 1 to 4, for dental use as antibacterial, antiviral, sporicidal or antimycotic agent.

In a preferred embodiment, the present use concerns derivatives of formula (I), wherein M is Si, and the (M0₂)^~ represents anionic silica particles (Si0₂)^~.

In an equally preferred embodiment, the present use concerns derivatives of formula (I), wherein M is Ti, and the (M0₂)- represents anionic silica particles (Ti0₂)^~.

The above derivatives are characterised by the fact that the anionic particles (M0₂)^~ have an average particle size (ps), intended as average diameter, of at least 200nm, and that the positive A^m+ species is adsorbed on the surface of said anionic particles by electrostatic interactions.

In another aspect, the present invention also relates to a dental care composition comprising the above indicated derivatives of formula (I) in admixture with at least one physiologically acceptable excipient or carrier, and optionally, with another active ingredient, preferably in the form of toothpaste or mouthcream.

Detailed description of the invention

According to a first aspect of the invention, there is provided a dioxide silicon or titanium derivative having the general formula (I):

( 0₂)-(A^m+)_y (I) for dental use as antiviral, antimycotic, sporicidal or, preferably, antibacterial agent.

The term "dental use" means that the present derivatives can be used for the treatment of pathologies of the oral cavity in general, e.g. related to mouth or throat, or even for the treatment of dental diseases, such as gingivitis and the like.

In the above formula (I), M is silicon or titanium, whereas A^m+ represents a positively charged active species, linked to the selected anionic dioxide particle by electrostatic interaction. In particular, such positive A^m+ species is adsorbed on the surface of the anionic S1O₂ or T1O₂ particles by electrostatic interaction.

Y represents the number of the different kind of active species A^m+, co-adsorbed on the same anionic silicon or titanium particle, which can be of the same type or of different chemical nature. According to formula (I), the present derivative can present up to 4 different kind of A^m+, co-adsorbed on the same anionic particle. In a particular preferred embodiment, y is comprised from 2 to 4, even more preferably y=2. In a still preferred embodiment, M=Si and y=2.

According to an embodiment of the invention, the positively charged active species A^m+ is preferably selected from: an antibacterial, an antimycotic, an antiviral and/or sporicidal agent, whereas antibacterial agent is particularly preferred. In this respect, A^m+ is at least one compound selected from the group consisting of: chlorexidine cations, poliexamethylene biguanide hydrochorxde, quaternary ammonium cations, preferably didecyldimethylammonium cations.

In a more preferred embodiment, A^m+ is chlorexidine digluconate or acetate, or equally preferred, poliexamethylene biguanide hydrochloride cation or didecyldimethylarnmonium cations, still more preferably when M=Si.

The mentioned preferred Am+ species are illustrated in the Table 1 below:

Table 1: preferred Am+ spec es of the nvent on

In one embodiment, the invention refers to compounds of formula (I) wherein A^m+ can also be a cationic silver complex of general formula [Ag-L]⁺, wherein L is the chelating moiety (or ligand) . L is selected from optionally substituted 8-mercapto- quinoline hydrochloride, and 2-mercapto-4- (Ci-C₆-Alk) - pyrimidine, preferably 2-mercapto-4-methylpyrimidine, of formula :

The term "Ci-C₆-Alk" means an optionally substituted linear or branched hydrocarbon chain residue, having from 1 to 6 carbon atoms, e.g.: methyl, propyl, iso-propyl, butyl, isobutyl, ter-butyl and the like.

In a further embodiment, the present invention is referred to derivatives of formula (I) wherein A^m+ can be more than one of the above mentioned preferred compounds, e.g. 2 of them (corresponding to Y=2), self-assembled by electrostatic forces, to the same anionic particle.

In this respect, it has to be noted that when more than one A^m+ species is used (e.g. y≥2), these are co-adsorbed on the same anionic particle (M0₂)^~ by electrostatic interactions, thus providing poly-functionalized silica particles, having a broad spectrum of pharmacological activity, particularly suitable for the present dental use.

Preferably, the selected cationic silver complex Ag-L is co- adsorbed with chlorexidine cations, preferably gluconate or acetate, to form a multifunctionalised derivatives of formula (I), as described, e.g., in the herein enclosed experimental part. In this direction, and according to a still preferred embodiment, the derivatives for the dental use are derivatives of formula (I) co-adsorbed with chlorexidine and a complex Ag-L, wherein L is the 2-mercapto-4- methylpyrimidine hydrochloride.

By the combination of chlorexidine with a silver complex it is in fact possible to use a minor amount of chlorexidine, being the dental action synergically improved by the presence of the Ag⁺ ions from the silver complex. This results allows to overcome the majority of the problems of the prior art, related to the use of chlorexidine, such as stains on teeth, tongue, and gingival, also when a prolonged use is made.

Applicants have found that it is now possible to obtain the present derivatives (I), characterised by having a high and poly- functionalised anionic particles, suitable for the preparation of medicaments for dental use.

As above mentioned, the derivatives (I) of the invention have a chemical structure thereby a number of tetrahedral Si or octahedral Ti atoms are interconnected each other by bridging oxygen atoms. Of note, the present anionic silicon or titanium dioxide particles, are characterised by the fact that they have an average particle size of at least 200nm. Preferably, the dental use is referred to anionic particles having a diameter of the particles (i.e. the particle size) comprised from 200nm to 2μιη, being an average diameter comprised from 500nm and Ιμιη particularly preferred. It follows that the present invention is referred to derivatives not classifiable under the definition of "nano-material", since the diameter higher than 200 nm is indicative of a particle size which is not intended in the art as nano- particle. In fact, as for instance adopted by the European Commission, a nanomaterial is defined as a material having a size ranging from 1 nm to 100 nm (for a general reference about said definition, see e.g.

http : //ec . europa . eu/environment/chemicals/nanotech/#definitio n) . The particle size of the derivatives of the invention is particular relevant because, using particles with size higher than 200 ran allow to adsorb on the same particle an higher number of active A^m+ species, even of different chemical nature as above reported. Even further, another advantage in using a ps higher than 200nm, is that it is possible to obtain the present derivatives in form of a powder which can be easily separated by filtration during the industrial preparation .

Anionic silica particles (Si0₂)^~ may be produced, e.g., as reported in the following. In 1956, Kolbe (G. KOLBE, "Das komplexehemische Verhalten der Kiesels-ure" Dissertation, Jena (19564)) described the formation of silica particles by reacting tetraethyl silicate in alcoholic solution with water in the presence of bases. With very pure reactants he observed in several cases a slowly proceeding reaction leading to the formation of uniform spherical silica. Later, W. Stober et al . (Journal of Colloid and Interface Science 26, 62-69, 1968) developed a system of chemical reactions which allowed the controlled growth of spherical silica particles of uniform size by means of hydrolysis of alkyl silicates and susequent condensation of in alcoholic solutions. Ammonia was used as a morphological catalyst. Stober found that by reacting tetraethyl silicate with different amount of water ethanol and ammonium hydroxide it was possible to prepare monodispersed silica particles of different sizes.

Elemental analysis data of the silica powder obtained by hydrolysis of tetraethoxysilane in ethanol/water/ammonia reveals a content in Nitrogen higher than 0.3%, indicating the presence of ammonium cations which are needed to balance the negative charges at the surface of the solid particle. In addition the observation of a negative value of the zeta potential for silica powder suspensions in water demonstrates and gives a clear picture of the negative charge at the surface of the silica particles.

As far as the anionic titanium dioxide particles are concerned, it has to be noted that the T1O₂ exists in different allotropic forms: anastase, rutile and brookite, all of them commercially available. The oxide surface is nevertheless characterised by the presence of Ti-OH groups which may undergo deprotonation at a pH higher than 7, to form Ti-CT units, after treatment with a basic substance such as ammonium hydroxide or the like.

As a general example, treatment of Ti0₂ powders with an ethanol-acetone solution containing 10% ammonium hydroxide allow to obtain anionic powders which can be used as a starting substrate for the preparation of antimicrobial derivatives of formula (I), e.g. in the form of a powder.

Therefore, the derivative of formula (I) for the dental use of the invention can be prepared by a process comprising the electrostatic interaction of (Si0₂)^~ particles having a ps of at least 200nm, with at least one compound able to generate the selected positively charged species A^m+, thus linking the anionic silica particles by electrostatic interactions. The reaction can be carried out by mixing the reactive under stirring at room temperature (e.g. at a temperature comprised from 15 to 40° C) , for a period of time generally comprised from 1 to 3 hours.

All the reagents are commercially available on the market and known to the person skilled in the art.

As above introduced, the derivatives of the invention are useful in oral care or dental sector, in particular as antibacterial, antiviral and/or antimycotic agent for the treatment of oral cavity diseases, preferably gingivitis and periodontitis .

The present derivative (I) are also particularly useful to reduce dental plaque.

The derivatives (I) are preferably for the use in the treatment of: oral infections, inflammations, oral wounds and ulcers, dental traumas, oral cysts and even in the post- treatment therapy, following the wisdom tooth extraction. To this extent, the dioxide silica or titanium derivatives of formula (I), can also be employed to reduce dental plaque, or even in dental implantology, e.g. for preparing the implant- abutment junction of dental fixtureor in dental prosthesis or for preparing coronal part of the tooth before insertion of the prosthetic crown. In a further embodiment, the antibacterial composition are for the use as wound healing agent for oral cavity ulcer derived, e.g. from the use of orthodontic devices.

The derivatives (I) are particularly suitable for the preparation of composition for oral care, basically in virtue of their functionalization and versatility. In fact, the active species A^m+ is electrostatically linked to the anionic dioxide particle, so that the resulting derivative (I) can be admixed e.g. with additives and excipients commonly used in known oral care products. In particular, when A^m+ is chlorexidine, it is possible to obtain derivatives (I) that can be formulated preferably in form of mouth cream or toothpaste, by simple addition of said derivatives to already known oral care products. In this way it is possible to enhance the antibacterial, antiviral or antimycotic activity of common toothpaste or similar, without the use of any particular process preparation step or specific surfactants. Owing also to this peculiarity, it is possible to obtain oral care products having antibacterial properties, together with other curative properties, basically depending on the pharmaceutical profile of the active ingredient or composition they are added to. Therefore, the derivatives (I) are also useful as additives for compositions for dental use, thus allowing for instance the preparation of very efficacious oral cavity or throat treatment products, preferably in form of a cream.

According to a further aspect, the invention refers to a dental care composition comprising the derivative of formula (I) as above described, in admixture with at least one physiologically acceptable carrier or excipient, and preferably, also, in admixture with at least another active ingredient. The additional active ingredient can be properly selected among those active ingredient commonly used in the oral care field, where antibacterial, antiviral or antimycotic agent are particularly preferred.

The physiologically acceptable carriers and/or excipient of the present composition, can be selected among those commonly used in the art for the specific dental use, with preference for cationic surfactants. The composition of the invention may also further comprise additional ingredients, typically used in common toothpaste preparations, such as, inter alia, surface-active substances, aromatic oils, and sweeteners, humectants, viscosity regulators,■ and the like.

In a more preferred embodiment, the dental composition of the invention is in the form of: toothpaste, cream, gel, foam and mouthwash, whereas cream and gel are particularly preferred.

Finally, the present invention also refers to a method for the treatment of a dental pathology or disease in a mammal, including man, comprising the oral administration of an effective amount of a derivative of the above indicated formula (I), or a pharmaceutical composition thereof.

The present invention will now be described by way of examples, which are intended to better illustrate the invention, without limiting its scope.

EXPERIMENTAL PART

Example 1: Preparation of (Si0₂) ^" (A^m+) _y, where A^m+ is the NH⁺ cation .

The general procedure reported allows to obtain negatively charged silica particle of different size, depending by the proportion between reaction mixture components such as

Water, ethanol, ammonia and tetraethoxysiliane (TEOS) or tetrapropoxysilane or tetrabuthoxysilane or tetrapentoxysilane . Ammonia was used as the catalyst. In many cases, it can be applied by adding saturated alcoholic solutions of ammonia to the reaction vessel. In other cases, it can be added directly in aqueous solution.

Pure ethanol alcohol or alcohol mixtures and saturated alcoholic ammonia solution or aqueous ammonia and water are mixed in Erlenmeyer flasks with ground stoppers. Subsequently the alkyl silicate can be added and the flasks are mounted either on a shaker or in a water bath under ultrasonic vibration. The preparations can also be done maintaining the reaction mixture under magnetic stirring.

After addition for example of TEOS, the appearance of white silica is observed within a few more minutes. The reaction can be continued for 120-240 minutes after that the precipitate can be filtered off, washed several times with ethanol and acetone, until neutrality of the washings, and dried in an oven at 60-100 °C for 24 h. Preferably the following proportion between reactants is used: 95 % Ethanol, 350 ml; distilled water, 250 ml; concentrated ammonium hydroxide, 100 ml; TEOS 300 ml. In these conditions the amount of dry powder obtained is of the order of 82 - 83 gr. Elemental analysis of the powder gives 0.32%N, which considering the atomic weight of nitrogen, allow to infer the presence of ca 0.023 negative charges/100 gr of product which are carried by surface Si-0 groups. In repeated preparations, maintaining the above reported proportion between reactants the % of Nitrogen was observed in the range 0.30-0.40%. Size analysis of the particles composing the powder was done by using a Zetasizer Malvern Instrument 7.01. Measurements were performed on silica powder suspensions in neutral water after ultrasound irradiation for 30 min . The average size distribution obtained was in the range 680 ± 80 nm and the Zeta potential was -62 ± 5 V.

Example 2: Preparation of (Si0₂) ^" (A^m+) _Y, where A^m+ is the Chlorexidine cation .

20 gr of anionic silica prepared according to Example 1 were suspended in a 200 ml solution containing 160 ml of ethanol and 40 ml of a 20 % Chlorexidine Digluconate solution in water. After 30 min of stirring, 100 ml of acetone were added and the suspension kept under stirring for additional 30 min. The solid product was filtered off, dried first under vacuum and then in an oven at 50 °C for 12 h. 25.7 gr of final product were obtained.

Elemental analysis gave a C% of 10% which corresponds to about 20% of chlorexidine in the product.

Size analysis of the particles composing the silica- chlorexidine product gave an average size distribution of 840 + 90 ran, and a Zeta potential was + 25 ± β V, consistent with the binding of the chlorexidine dication to the negatively charged silica surface.

Example 3: Preparation of (Si0₂) ^" (A^m+)_y , where A^m+ is the cationic Silver complex Ag-L, with L = 2-mercapto-4- methylpyrimidine Hydrocloride .

20 gr of anionic silica prepared according to Example 1 were suspended in 200 ml of an ethanol solution containing dissolved 81.3 mg of the ligand (2-mercapto-4methylpyrimidine Hydrochloride) . The suspension was kept under stirring for ca 2 h after that a 84.9 mg amount of AgN0₃ , dissolved in 50 ml of methanol, was added. The color of the white suspension turns to yellow after addition of the silver ions indicating silver complex formation. Stirring was maintained for additional 30 min after that the solid was filtered off and dried in an oven at 50 °C for 4 h.

Silver analysis performed on the solid product by atomic absorption spectroscopy gave 0.27 % Ag and 0.077% S, confirming quantitative binding of the positively charged silver complex to the anionic silica.

Example 4: Preparation of (Si0₂) ^" (A^m+) _y , where A^m+ represents both the cationic Silver complex Ag-L, with L = 2-mercapto-4- methylpyrimidine Hydrocloride, as well as the Chlorexidine cation

The product was prepared with the procedure outlined in Example 2 by using as a starting material the Si0₂-Silver Complex adduct prepared according to Example 3.

Elemental analysis of the product gave 0.25% Ag, 0.073% S, 11% C, consistent with quantitative formation of the Si02- Chlorexidine-Silver complex. Example 5: Preparation of (Si0₂)^"(A )_y , where A^m is Polyhexametilene Biguande Hydrochloride (PHMB) .

10 gr of anionic silica prepared according to Example 1 were suspended in a 100 ml solution composed by 80 ml of 95% EtOH and 20 ml of 20% PHMB in water. After 30 min of stirring, 200 ml of acetone were added and the stiring kept for additioal 30 min. The solid was filtered off, air dried and then dried in an oven at 50 °C for 12 h giving 12.5 gr of product.

Size analysis of the Si0₂ particles with the electrostatically bound polymeric PHMB gave an average size distribution of 3000 + 360 nra and a Zeta potential was + 73 ± 7 V, consistent with surface binding of the positively charged polymeric cation.

Example 6 : Antibacterial activity as oral care agent

Preliminary tests were performed in order to evaluate the minimum bactericidal concentrations (MBC) of the (Si0₂) ^~ (A^m+) _y product of example 4, where A^m+ represents both the cationic Silver complex Ag-L, with L = 2-mercapto-4-methylpyrimidine Hydrocloride, as well as the Chlorexidine cation.

Test were performed according to internationally recognized standard procedures (National Committee for Clinical Laboratory Standards (2000) , Methods for Dilution. Antimicrobial Susceptibility Tests for Bacteria That Grow Aerobically. Approved Standard M7-A5. NCCLS) .

Activity test were performed by using Streptococcus pyogenes and Strepotococcus salivarius as gram-positive and Pseudomonas aeruginosa and Escherichia coli as gram negative bacteria. In all cases a remarkable bactericidal activity of 99.9% was observed at a very high sample dilution, of the order of 0.0003%.

Claims

1. A derivative of formula (I) :

(M0₂)- (A^m+) y (I)

wherein :

M is a Si or Ti atom;

( θ₂>^~ represents an anionic dioxide particle comprising tetrahedral Silicon or octahedral Titanium atoms interconnected through bridging oxygen atoms,

A^m+ represents at least one positively charged active species, linked to the anionic dioxide particle by elecrostatic interaction, wherein m represent the charge of said active species, and is comprised from 1 to 20, preferably from 1 to 10,

Y represents the number of different active species

A^m+ co-adsorbed to the same anionic silicon or titanium dioxide particle, and it is comprised from 1 to 4, preferably 2,

for dental use as antibacterial, antiviral, antimycotic or sporicidal agent.

2. The derivative of formula (I) for the use according to claim 1, wherein M=Si.

3. The derivative of formula (I) for the use according to claim 1, wherein M=Ti.

4. The derivative of formula (I) for the use according to claim 1 or 3, characterized by the fact that the anionic silicon or titanium dioxide particles have an average diameter of at least 200nm, preferably from 500nm to Ιμπι.

5. The derivative of formula (I) for the use according to any one of claims 1-4, wherein A^m+ is an antibacterial, antimycotic, antiviral and/or sporicidal agent.

6. The derivative of formula (I) for the use according to claim 5, wherein A^m+ is at least one compound selected from the group consisting of: chlorexidine cations, poliexamethylene biguanide hydrochloride cation, quaternary ammonium cations, a cationic silver complex of general formula Ag-L, and a mixture thereof.

7. The derivative of formula (I) for the use according to any one of the preceding claims, wherein A^m+ is chlorexidine digluconate or acetate.

8. The derivative of formula (I) for the use according to claims 1-6, wherein A^ra+ is didecyldimethylammonium cation.

9. The derivative of formula (I) for the use according to claims 1-6, wherein A^m+ is poliexamethylene biguanide hydrochloride cation.

10. The derivative of formula (I) for the use according to claims 1-6, wherein A^m+ is a cationic silver complex of formula Ag-L, wherein L is selected from: optionally substituted 8-mercapto-quinoline hydrochloride, and 2- mercapto-4- (Ci-CgAlk) pyrimidine hydrochloride, preferably 2- mercapto-4-methylpyrimidine .

11. The derivative of formula (I) for the use according to claims 1-10, wherein A^m+ is a chlorexidine cation and a silver complex of formula Ag-L, this latter preferably as defined in claim 9.

12. The derivative of formula (I) for the use according to claim 11, wherein Am+ is chlorexidine digluconate and 2- mercapto-4-methylpyrimidine .

13. The derivative of formula (I) for use according to any one of claims 1 to 12, as antibacterial, antiviral and antimycotic agent for the treatment of oral cavity diseases, preferably gingivitis and periodontitis.

14. The derivative of formula (I), for use according to any one of claims 1 to 12 in the treatment of: oral infections, inflammations, oral wounds and ulcers, dental traumas or oral cysts .

15. A dental care composition comprising at least the derivative of formula (I) as described in any one of the claims 1-12, in admixture with at least one physiologically acceptable carrier or excipient, and preferably, also, in admixture with at least another active ingredient.

16. The dental composition of claim 15, in the form of: toothpaste, cream, gel, mouthwash or foam.

17. A method for the treatment of a dental pathology or disease in a mammal, including man, comprising the oral administration of a derivative of formula (I) as described in any one of the claims 1-12 or a pharmaceutical composition thereof .