FR3069154A1 - NEW BACTERICIDES AND ANTIFUNGALS - Google Patents

Abstract

The present invention relates to the use as a bactericidal or antifungal of a transition metal.

Description

New bactericides and antifungals

The present invention relates to the production of new bactericides and fungicides.

There are an increasing number of bacteria that have become resistant to known antibiotics, and the search for new antibiotics is stalling.

There are also bacterial formations called biofilms, which are resistant to all known antibiotics.

Cosmetics and some medicines are made up of a pasty emulsion of water and oil. This emulsion risks being colonized by bacteria and mold. They are protected by adding parabens as a preservative, at a rate of 0.4% to 0.8%. Parabens have drawbacks that lead to seek to replace it.

In addition, in their use as anti-acne, the current drugs (Epiduo, Aczone, Finacea, Acanya, and Ziana) have serious drawbacks: they cause dryness of the skin, itching, flaking and slight edema, which often leads to discontinuation of treatment. In addition, they are teratogenic on the fetuses of pregnant women who use one of these current anti-acne.

One of the aims of the invention is therefore to provide new bactericides.

One of the aims of the invention is therefore to provide new antifungal agents

Another object of the invention is to replace the paraben present as a preservative in food, cosmetic and / or pharmaceutical compositions.

Another object of the invention is to use a transition metal to replace the paraben present as a preservative in food, cosmetic and / or pharmaceutical compositions.

Another object of the invention is to provide a composition devoid of parabens and comprising transition metal sulfides used as a preservative.

Another object of the invention is to use a transition metal in the treatment of acne.

The present invention relates to the use as a bactericide or as an anti fungal of a transition metal.

By "use as a bactericide" is meant, within the meaning of the present invention, a use for the purpose of killing at least one bacterium. The bacteria concerned are Gram positive or Gram negative bacteria, in particular, the bacteria concerned are chosen from Staphylococcus aureus, Staphylococcus aureus resistant to methicillin (MRSA), Staphylococcus aureus sensitive to methicillin (MS SA), Propionibacterium Acnes, Escherichia Coli Pseudomonas Aeruginas,

By "use as an antifungal" it is understood, within the meaning of the present invention, a use for the purpose of killing at least one yeast, for example Candida Albicans

Within the meaning of the present invention, a bactericide or antifungal means a substance whose minimum inhibitory concentration is less than or equal to 0.1 g / L.

In a first object, the present invention relates to the use of a transition metal as a paraben substitute.

It is understood, within the meaning of the invention, by "paraben", an alkyl parahydroxybenzoate, that is to say an ester, having broad-spectrum bactericidal and fungicidal properties. The antibacterial and antifungal properties of parabens means that they are generally used as a preservative in cosmetics, medicines and food.

By “use as a paraben substitute” is meant, within the meaning of the present invention, a use for replacing the parabens used as a preservative because of their antibacterial and / or antifungal properties.

For the purposes of the invention, “transition metal” is understood to mean a nucleus chosen from groups IVB, VB, VIB, VIIB, VIIIB, IB and IIB of the Mendeleev periodic table; preferably a nucleus chosen from column IB.

For the purposes of the present invention, the term “use of a transition metal” is understood to mean the use of at least one transition metal. The present invention therefore also relates to the use of a mixture of transition metals, in particular a mixture of two or three transition metals as a paraben substitute.

According to an advantageous embodiment, the invention relates to the use as a paraben substitute, of a transition metal in insoluble form, in particular in the form of a transition metal with oxidation state 0 or in the form of sulfide or of an oxide of the transition metal, or in soluble form, in particular of the salts of sulfates, nitrates or chlorides of the transition metal.

By “insoluble” is meant, within the meaning of the invention, a powder which does not dissolve in water, that is to say one whose maximum concentration in aqueous solution is less than 0.5 mg. ¹ at room temperature, that is to say at a temperature of about 25 ° C, and which is put into aqueous solution by the addition of an additive to form nanoparticles or complexes.

In the case of nanoparticles, the additive is a surfactant. The surfactant can be a trimethyl ammonium bromide R in which R represents an alkyl of 6 to 20 carbon atoms and in particular of 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, or 18 atoms of carbon .. Examples of surfactants include CTAB (cetyltrimethylammonium bromide; Br [N (CH ₃ ) ₃ (Ci6H33)]), OTAB (octyltrimethylammonium bromide; Br [N (CH3) 3 (C ₈ H ₁₇ )]), PEG-dithiol (Polyethylene glycol comprising terminal thiol functions) and PEG600 (Polyethylene glycol whose average molar mass is 600 g / mol). Preferably, the surfactant used to stabilize the nanoparticles is CTAB.

In the case of complexes, the additive is a solubilizing agent chosen from ammonia, citric acid, potassium dichromate or a mixture of these. When the solubilizer is a mixture of ammonia and citric acid, ammonium citrate is formed; the solubilizing agent thus formed is then either ammonium citrate with citric acid if the citric acid is present in molar excess relative to ammonia, or ammonium citrate with ammonia if the ammonia is introduced in molar excess relative to the citric acid.

In the insoluble form of the paraben substitute of the invention, therefore, the nanoparticles and the transition metal complexes as defined above are grouped together.

Conversely, a “soluble” salt, in the sense of the invention, is a powder which dissolves on contact with water, without the addition of an additive, that is to say of which the maximum concentration in aqueous solution is greater than 0.5 mg. L ' ¹ . In the soluble form of the paraben substitute of the invention, the salts and oxides of transition metals as defined above are included.

According to one embodiment, the diameter of the nanoparticles of the invention is from 1 to 10 nm, in particular from 1 to 5 nm, in particular from 2 nm.

According to another advantageous embodiment, the invention relates to the use as a paraben substitute, of a transition metal in insoluble form, said transition metal in insoluble form being placed in aqueous solution by the formation of nanoparticles or by the formation of a complex.

Within the meaning of the present invention the term "placed in aqueous solution" refers to the formation of a solution or an aqueous suspension including the transition metal concentration according to the invention is greater than 0.5 mgL ^"1 .

For the purposes of the present invention, the term “complex” is understood to mean a metal cation, formed from a transition metal as defined above, linked to several atoms, ions or molecules called ligands. Examples of ligands include water and the additives defined above.

According to another advantageous embodiment, the invention relates to the use as a paraben substitute of a transition metal chosen from column IB of Mendeleev, in particular chosen from copper, silver and gold.

Within the meaning of the present invention, the transition metal of column IB of Mendeleev is in the oxidation state 0, +1, +11 or +111. In particular, the invention relates to the use of a transition metal chosen from Cu (0), Cu (ll), Ag (0), Ag (l), Au (0) or Au (lll).

According to another advantageous embodiment, the invention relates to the use as a paraben substitute of a transition metal chosen from copper, silver and gold, and being in the form of sulfide.

According to another advantageous embodiment, the invention relates to the use as a paraben substitute of a transition metal chosen from copper, silver and gold, being in the form of sulphide and in the form of a complex .

Sulphides of gold, silver and copper, insoluble without additives, are soluble in the form of complexes.

For copper sulphide SCu, whose maximum concentration in aqueous solution is 0.33 mg / L, the addition of ammonia as an additive makes it possible to reach an aqueous Cu concentration at least equal to 0.2 g / L .

For silver sulfide SAg ₂ , the maximum concentration of which in aqueous solution is soluble at 6.2.10 ^-15 mg / L, the addition of citric acid or a mixture of citric acid and ammonia as additive makes it possible to reach an aqueous concentration of Ag at least equal to 0.2 g / L.

For gold sulfide S3AU2, the aqueous concentration without additive is undetectable. Adding either potassium dichromate alone, or an equimolar mixture of potassium dichromate and ammonia, achieves an aqueous concentration of Au at least equal to 0.2 g / L.

According to another advantageous embodiment, the invention relates to the use as a paraben substitute of a transition metal chosen from copper, silver and gold, being in the form of sulfide and in the form of nanoparticles.

Within the meaning of the present invention, when the transition metal is in the form of copper sulphide nanoparticles, silver sulphide nanoparticles or gold sulphide nanoparticles, the transition metal is, respectively, to the degree of oxidation + II, + l and + III, i.e. Cu (ll), Ag (l) and Au (lll).

For the purposes of the present invention, the term “use of a transition metal” is understood to mean the use of at least one transition metal. The present invention therefore also relates to the use of a mixture of transition metals, in particular a mixture of two or three transition metals as a paraben substitute.

According to another advantageous embodiment, the invention relates to the use, as a paraben substitute, of a transition metal chosen from copper, silver and gold, being at the oxidation state 0 and in the form of nanoparticles.

For the purposes of the present invention, the term “use of a transition metal” is understood to mean the use of at least one transition metal. The present invention therefore also relates to the use of a mixture of transition metals, in particular a mixture of two or three transition metals as a paraben substitute.

According to another advantageous embodiment, the invention relates to the use as a paraben substitute of a transition metal chosen from copper, silver and gold, being in the form of soluble salt.

For the purposes of the present invention, the term “use of a transition metal” is understood to mean the use of at least one transition metal. The present invention therefore also relates to the use of a mixture of transition metals, in particular a mixture of two or three transition metals as a paraben substitute.

According to another advantageous embodiment, the invention relates to the use of a transition metal in a composition containing water.

According to another advantageous embodiment, the invention relates to the use of a transition metal in a composition containing water and a reducing agent.

For the purposes of the present invention, the term “reducing agent” is understood to mean a compound capable of reducing the transition metal salt used during the formation of the transition metal nanoparticles according to the invention and of preventing the oxidation of the metal transition during its use according to the invention. An example of a reducing agent within the meaning of the invention is glycerol in basic medium (pH = 14), preferably glycerol in the presence of NaOH. The reduction is carried out at pH 14, and, once the metal nanoparticles are formed, the solution is neutralized and brought back to pH 7. According to another advantageous embodiment, the invention relates to the use of a transition metal in a composition containing water, said composition comprising of the order of 10 ⁶ grams of paraben substitute per gram of composition.

For the purposes of the present invention, it is understood by "of the order of 10 ' ⁶ grams'' an approximate range of values, which can also be otherwise formulated by a range ranging from 10 ' ⁵ to 10' ⁷ g.

This range of concentrations represents 100 to 10,000 times less product than when using parabens. (parabens are used at concentrations of 4 to 8 per 1000 outside Europe, and 3 times less in Europe)

According to another advantageous embodiment, the invention relates to the use of a transition metal in a composition containing water, in which the composition containing water is an emulsion.

According to another advantageous embodiment, the invention relates to the use of a transition metal in a composition containing water, in which the composition containing water is an oil-in-water emulsion or water-in-oil.

According to one embodiment, the percentage of water relative to the amount of oil present in these emulsions is from 65 to 99%, preferably from 70 to 95%, in particular from 70 to 80% of water.

According to another advantageous embodiment, the invention relates to the use as a paraben substitute of a transition metal in a food or cosmetic or pharmaceutical product.

The invention also relates to a composition in the form of an oil-in-water or water-in-oil emulsion, devoid of parabens, comprising copper sulfide, silver sulfide or gold sulfide; in particular, said composition comprising copper sulfide.

According to an advantageous embodiment, the invention relates to a composition in which the copper sulphide, silver sulphide or gold sulphide forms a complex or nanoparticles.

According to an advantageous embodiment, the composition of the invention comprises copper sulphide, silver sulphide or gold sulphide, in the form of complexes or nanoparticles as defined above, said composition also comprising and an additive.

According to an advantageous embodiment, the composition of the invention comprises copper sulphide, silver sulphide or gold sulphide, in the form of a complex as defined above, said composition also comprising water and an additive, said additive being chosen from ammonia, citric acid, potassium dichromate or a mixture of these.

According to an advantageous embodiment, the composition of the invention comprises copper sulfide, silver sulfide or gold sulfide, in the form of nanoparticles as defined above, said composition also comprising water and an additive, said additive being CTAB.

The invention also relates to a composition in the form of an oil-in-water or water-in-oil emulsion, devoid of parabens, comprising copper, silver or gold in the form of nanoparticles .

According to a particular embodiment, the composition of the invention in the form of an oil-in-water or water-in-oil emulsion, devoid of parabens, comprising copper, silver or gold in the form of nanoparticles, also comprises an additive such as CTAB and a reducing agent such as glycerol in basic medium, in particular glycerol in the presence of NaOH at pH 14. The reduction is carried out at pH 14, and, once the metal nanoparticles have been formed, the solution is neutralized and brought back to pH 7.

The present invention also relates to a transition metal for its use as a bactericide, or as an antifungal

In a second object, the present invention relates to a transition metal for its use in the treatment of acne.

For the purposes of the present invention, "acne treatment" is understood to mean a bactericidal action on a bacterium responsible for acne. In particular, the treatment of acne means a bactericidal action on Propionibacterium Acnes.

The present invention also relates to a process for the preparation of transition metal nanoparticles and transition metal sulfide nanoparticles. The process for preparing the soluble transition metal sulfide complexes of the invention is described in Examples 1 to 3.

Thus, in a third object, the present invention relates to a process (I) for the preparation of a bactericide comprising a transition metal in the form of nanoparticles of said transition metal, said process comprising a step of reducing the transition metal, by presence of an additive, in an aqueous solution at pH 14 comprising glycerol. The reduction is carried out at pH 14, and, once the metal nanoparticles are formed, the solution is neutralized and brought back to pH 7

In particular, in the process (I) of the invention, the transition metal is chosen from column IB of Mendeleev, in particular chosen from copper (0), silver (0) and gold (0).

In particular, in the process (I) of the invention, the transition metal is in the form of a metal salt before the reduction step. The metal salt is in particular chosen from copper (II), in particular copper nitrate Cu (NO ₃ ) ₂ , silver (I), in particular silver nitrate Ag (NO ₃ ), and gold (III), in particular AuCI ₃ gold chloride.

In particular, in the process (I) of the invention, the aqueous solution at pH 14 comprises water, glycerol and a base, in particular a hydroxide, in particular NaOH. The reduction is carried out at pH 14, and, once the metal nanoparticles are formed, the solution is neutralized and brought back to pH 7

In the context of this process (I), the additive is a surfactant. Examples of surfactants include CTAB (cetyltrimethylammonium bromide; Br [N (CH ₃ ) ₃ (Ci6H33)]), PEG-dithiol (Polyethylene glycol comprising terminal thiol functions) and PEG600 (Polyethylene glycol with an average molecular weight is 600 g / mol). Preferably, the surfactant used to stabilize the nanoparticles is CTAB.

The glycerol concentration is from 0.8 to 2.2 M, in particular from 1 to 2 M, in particular from 1 to 1.85 M in water after the step of reduction of the transition metal.

The process according to the invention is carried out either at 0 ° C, or at room temperature, or at a temperature of 60 to 100 ° C, especially from 80 to 100 ° C.

According to a particular embodiment, the method (I) of the invention comprises:

a step of forming a solution A comprising the transition metal in the form of a metal salt, an additive and water;

a step of forming an aqueous solution B at pH 14 comprising glycerol;

a step of reducing the transition metal by adding solution A to aqueous solution B to form a suspension of nanoparticles;

a step of neutralizing the suspension of nanoparticles obtained in the previous step by the addition of an acid.

In particular, in the neutralization step of the process (I) of the invention, the acid is an inorganic acid, in particular HCl. For the purposes of the invention, “neutralization” is understood to mean the passage from a basic solution, the pH of which is between 8 and 14, to a solution at pH 7.

The metal salt concentration during the formation of solution A is from 0.001 to 0.5 M, in particular from 0.01 to 0.04 M, in particular 0.013 M, 0.023 M or 0.04 M.

The concentration of additive during the formation of solution A is from 0.01 to 0.05 M, in particular from 0.02 to 0.04 M, in particular 0.02 M or 0.037 M.

According to a particular embodiment, the method (I) of the invention comprises:

a step of forming a solution A comprising the transition metal in the form of a copper (II) salt, CTAB and water;

a step of forming an aqueous solution B at pH 14 comprising glycerol;

a step of reducing the transition metal by adding solution A to aqueous solution B to form a suspension of copper nanoparticles (0);

a step of neutralizing the suspension of copper nanoparticles (0) obtained in the previous step by the addition of HCI.

According to a particular embodiment, the method (I) of the invention comprises:

a step of forming a solution A comprising the transition metal in the form of a silver salt (I), CTAB and water;

a step of forming an aqueous solution B at pH 14 comprising glycerol;

a step of reducing the transition metal by adding solution A to aqueous solution B to form a suspension of silver nanoparticles (0);

a step of neutralizing the suspension of silver nanoparticles (0) obtained in the previous step by the addition of HCI.

According to a particular embodiment, the method (I) of the invention comprises:

a step of forming a solution A comprising the transition metal in the form of a gold (III) salt, CTAB and water;

a step of forming an aqueous solution B at pH 14 comprising glycerol;

a step of reducing the transition metal by adding solution A to aqueous solution B to form a suspension of gold nanoparticles (0);

a step of neutralization of the suspension of gold nanoparticles (0) obtained in the previous step by the addition of HCI.

The optimal conditions for the preparation of transition metal nanoparticles according to the invention can be determined by a person skilled in the art, in particular in view of Examples 8 to 10 of the present invention.

According to an advantageous embodiment, the invention relates to nanoparticles obtained by the method (I).

According to a fourth object, the present invention relates to a process (II) for the preparation of a bactericide comprising a transition metal, said transition metal being in the form of a sulfide nanoparticle of said transition metal, said process comprising a step of precipitation of a soluble salt of the transition metal in the presence of sodium sulfide Na ₂ S.

In particular, in the process (II) of the invention, the soluble salt of the transition metal is chosen from copper (II), in particular copper sulphate Cu (SO ₄ ) or copper nitrate Cu (NO ₃ ) ₂ , silver (I), in particular silver nitrate Ag (NO ₃ ), and gold (III), in particular gold chloride AuCI ₃ .

In the context of this process (II), the additive is a surfactant. Examples of surfactants include CTAB (cetyltrimethylammonium bromide; Br [N (CH ₃ ) ₃ (Ci ₆ H ₃₃ )]), OTAB (octyltrimethylammonium bromide; Br [N (CH ₃ ) ₃ (C ₈ H ₁₇ )]), PEG-dithiol (Polyethylene glycol comprising terminal thiol functions) and PEG-600 (Polyethylene glycol whose average molar mass is 600 g / mol). Preferably, the surfactant used to stabilize the nanoparticles is CTAB.

According to a particular embodiment, the method (II) of the invention comprises:

a step of forming a solution A comprising the transition metal in the form of a soluble salt of the transition metal, an additive and water;

a step of forming a solution B comprising Na ₂ S and water;

a step of precipitating the soluble salt of the transition metal by adding solution A to solution B to form a suspension of metal sulfide nanoparticles;

In particular, in the neutralization step of the process (II) of the invention, the acid is an inorganic acid, in particular HCl. For the purposes of the invention, “neutralization” is understood to mean the passage from a basic solution, the pH of which is between 8 and 14, to a solution at pH 7.

The metal salt concentration during the formation of solution A is from 0.001 to 0.5 M, in particular from 0.01 to 0.03 M, in particular 0.013 M, 0.023 M or 0.025 M.

The additive concentration during the formation of solution A is from 0.01 to 0.05 M, in particular from 0.02 to 0.04 M, in particular 0.037 M. The molar concentration of the additive is 0, 2 times that of metallic salt

The Na ₂ S concentration is from 0.001 to 0.02 M, in particular from 0.003 to 0.02 M, in particular 0.003 M, 0.0065 M or 0.0185 M in water after during the step of formation of solution B. The Na ₂ S concentration is the stoichiometric concentration for the formation of the insoluble salt. If the salt is SO ₄ Cu, Na ₂ S and SO ₄ Cu are equimolar. According to a particular embodiment, the method (II) of the invention comprises:

a step of forming a solution A comprising the transition metal in the form of a soluble copper (II) salt, CTAB and water;

a step of forming a solution B comprising Na ₂ S and water;

a step of precipitation of the soluble copper (II) salt by the addition of solution A to solution B to form a suspension of copper (II) sulfide nanoparticles;

According to a particular embodiment, the method (II) of the invention comprises:

a step of forming a solution A comprising the transition metal in the form of a soluble silver salt (I), CTAB and water;

a step of forming a solution B comprising Na ₂ S and water;

a step of precipitating the soluble silver salt (I) by adding solution A to solution B to form a suspension of silver sulfide nanoparticles (I);

The Na ₂ S concentration is the stoichiometric concentration for the formation of the insoluble salt. If the salt is NO ₃ Ag, the molar concentration of Na ₂ S is half that of NO ₃ Ag

According to a particular embodiment, the method (II) of the invention comprises:

a step of forming a solution A comprising the transition metal in the form of a soluble gold (III) salt, CTAB and water;

a step of forming a solution B comprising Na ₂ S and water;

a step of precipitating the soluble gold (III) salt by adding solution A to solution B to form a suspension of gold (III) sulfide nanoparticles;

The Na ₂ S concentration is the stoichiometric concentration for the formation of the insoluble salt. If the salt is CI ₃ Au, the molar concentration of Na ₂ S is 1.5 times that of

CI ₃ Au

The optimal conditions for the preparation of metal sulfide nanoparticles according to the invention can be determined by a person skilled in the art, in particular in view of the examples of the present invention.

According to an advantageous embodiment, the invention relates to nanoparticles obtained by the process (II).

FIGURES:

FIG. 1 represents an HR-TEM image of the particles of SAg ₂ according to Example 4.

FIG. 2 represents the UV-visible absorption spectrum of an aqueous suspension of silver nanoparticles at a concentration of 0.2 wt% of silver according to Example 8B.

Figure 3 shows HR-TEM images of the silver particles of Example 8B. A, B, C and D correspond to different size scales.

Figure 4 shows the UV-visible absorption spectrum of the solution of silver nanoparticles at a concentration of 0.14 g. L ' ¹ (Example 8C) compared to the solution of Example 8B.

Figure 5 represents an image of HR-TEM microscopy carried out on the suspension at 0.14 g. L ' ¹ of Example 8C. A, B, C and D correspond to different size scales.

Figure 6 shows HR-TEM images of the 2 g solution. L ¹ prepared in Example 8C. A and B correspond to different size scales.

FIG. 7 represents an HR-TEM image of the colloidal solution of silver nanoparticles at 2 g.L ' ¹ obtained after vacuum distillation of part of the water from a suspension at 0.2 g.L' ¹ , according to the Example 8D.

Figure 8 shows a histogram of the size distribution of silver nanoparticles in a suspension concentrated to 2 g.L ' ¹ according to Example 8D. The counting of nanoparticles and the determination of the size of each of them are carried out on a microscopy image.

FIG. 9 shows an HR-TEM image of silver nanoparticles obtained according to method 8.B but in the presence of octyltrimethylammonium bromide (OTAB) according to Example 8E.

Figure 10 shows a histogram of the size distribution of the silver nanoparticles in a concentrated suspension at 0.2 g. L ' ¹ prepared in the presence of octyltrimethylammonium bromide (OTAB) according to Example 8E. The counting of nanoparticles and the determination of the size of each of them are carried out on a microscopy image.

FIG. 11 represents an HR-TEM image of the suspension of gold nanoparticles according to Example 9.

Figure 12 shows an HR-TEM image of the colloidal solution comprising the copper nanoparticles according to Example 10.

Figure 13 shows an HR-TEM image of the colloidal solution comprising the copper nanoparticles according to Example 10.

FIG. 14 represents an HR-TEM image of the colloidal solution comprising the sulfur nanoparticles according to Example 11.

EXAMPLES

I) Synthesis of complexes

Example 1. SCu solution

Dissolve 126 mg of SO ₄ Cu in 90 mL of water.

Dissolve 140 mg of Na ₂ S in 20 mL of water.

Mix the 90 mL of the SO ₄ Cu solution with 10 mL of the Na ₂ S solution. A precipitate of 75 mg of SCu is obtained. Separate it by filtration.

Place this precipitate in 100 mL of water, in a container with shaker.

While stirring constantly, drop a concentrated solution of NH ₃ into the water dropwise very slowly.

The maximum concentration of SCu in water is 0.33 mg.L ^-1 . SCu becomes more soluble in aqueous solution in the presence of ammonia. The addition of ammonia to copper sulphide makes it possible to reach an aqueous concentration at least equal to 0.2 gL ^-1 in Cu.

Example 2. SAg ₂ solution

Dissolve 79 mg of NOsAg in 97 mL of water.

Mix the 97 mL of the NOsAg solution with 3 mL of the Na ₂ S solution. A precipitate of 75 mg of SAg _{2 is} obtained. Separate it by filtration.

Place this precipitate in 100 mL of water, in a container with shaker.

While stirring constantly, drop a concentrated solution of ammonium citrate (NH ₄ ) 5 (C ₆ H ₄ O ₇ ) ₂ H ₃ very slowly into it.

The maximum concentration of SAg ₂ in water is 6.21.10 ^-15 gL ^-1 . SAg ₂ becomes more soluble in the presence of citric acid, or a mixture of ammonium citrate and citric acid, or a mixture of ammonium citrate and ammonia, the ammonium citrate being formed with a mixture of citric acid and ammonia. Adding citric acid, or a mixture of ammonium citrate and citric acid, or a mixture of ammonium citrate and ammonia, to silver sulfide allows a concentration to be reached. aqueous at least equal to 0.2 gL ^-1 in Ag.

Example 3. Solution S ₃ Au ₂

Dissolve 77 mg of CI ₃ Au in 95 mL of water.

Mix the 95 ml of the CI ₃ Au solution with 5 ml of the Na ₂ S solution. A precipitate of 62 mg of S ₃ Au ₂ is obtained. Separate it by filtration.

Place this precipitate in 100 mL of water, in a container with shaker.

With constant agitation, drop a concentrated solution of potassium dichromate dropwise very slowly. The maximum concentration of Au ₂ S ₃ in water cannot be detected. The aqueous solubility of Au ₂ S ₃ is increased in the presence of potassium dichromate, or of a mixture of potassium dichromate and ammonia. The addition of potassium dichromate, or of a mixture of potassium dichromate and ammonia, to the gold sulphide makes it possible to reach an aqueous concentration at least equal to 0.2 gL ^-1 in Au.

II) Synthesis of metallic sulfide nanoparticles

Example 4. SAg ₂ in Nanoparticles

Example 4A. SAg ₂ in nanoparticles

All reagents are used as received, without prior purification.

The water used to prepare the solution is degassed ultra-pure water and stored under Argon.

The reaction takes place under Argon, at room temperature (20 ° C).

The silver solution is handled in the dark (protection under aluminum).

• For the synthesis of 200 mL of 0.2 wt% colloidal solution (2 g.L ' ¹ ) of silver nanoparticles:

For the preparation of solution A, prepare 80 mL of ultra-pure water in a flask and first dissolve 1.35 g of cetyltrimethylammonium bromide (CTAB; 3,7.10 ^-3 mol) in water then 0, 4 g of Ag ⁺ in the form of AgNO ₃ (2.3.10 ^-3 mol) and adjust to 100 mL with ultra-pure water. Store cold, in the dark.

For the preparation of solution B, prepare 50 mL of ultra-pure water in a flask, dissolve 0.144 g of Na ₂ S (1.85.10 ^-3 mol) and adjust to 100 mL with ultra-pure water.

At room temperature, in the dark, under an argon atmosphere and with stirring (600 rpm), add solution A drop by drop to solution B. Leave to react for 4 h.

The particles of SAg ₂ are characterized by HR-TEM, FIG. 1. They have a wide size distribution with a majority presence of particles of size greater than 20 nm.

Example 4B. SAg ₂ in nanoparticles, effect of temperature

The silver sulfide nanoparticles are synthesized according to Example 4A, at 0 ° C.

There is an insignificant difference in bactericidal activity between the nanoparticles obtained at room temperature and those obtained at 0 ° C (see table 1 lines R and O)

Example 4C. SAg ₂ in nanoparticles, effect of the surfactant

The silver sulfide nanoparticles are synthesized according to Example 4A, using PEG-600 in place of CTAB.

Example 5. SCu in Nanoparticles

Example 5A. SCu in nanoparticles

All reagents are used as received, without prior purification.

The water used to prepare the solution is degassed ultra-pure water and stored under Argon.

The reaction takes place under Argon, at room temperature (20 ° C).

• For the synthesis of 200 mL of 0.2 wt% colloidal solution (2g.L ^-1 ) of copper nanoparticles:

For the preparation of solution A, prepare 80 mL of ultra-pure water in a flask and first dissolve 1.35 g of CTAB (3.7.10 ^-3 mol) in water then 0.4 g of Cu ²⁺ in the form of CuSO ₄ (2.5.10 ^-3 mol) and adjust to 100 mL with ultra-pure water. Store cold, in the dark.

For the preparation of solution B, prepare 50 mL of ultra-pure water in a flask, dissolve 0.5 g of Na ₂ S (0.64.10 ^-3 mol) and adjust to 100 mL with ultra-water pure.

At room temperature, in the dark, under an argon atmosphere and with stirring (600 rpm), add solution A drop by drop to solution B. Leave to react for 4 h.

Example 5B. SCu in nanoparticles, temperature effect

The copper sulfide nanoparticles are synthesized according to Example 5A, at 0 ° C.

There is no difference in bactericidal activity between the nanoparticles obtained at room temperature and those obtained at 0 ° C (see lines Q and T in Table 1)

Example 5C. SCu in nanoparticles, effect of surfactant

The copper sulfide nanoparticles are synthesized according to Example 5A, using PEG-600 in place of CTAB.

Example 6. S ₃ Au ₂ in nanoparticles

Example 6A. S ₃ Au ₂ in nanoparticles

All reagents are used as received, without prior purification.

The water used to prepare the solution is degassed ultra-pure water and stored under Argon.

The reaction takes place under Argon, at room temperature (20 ° C).

The gold solution is handled in the dark (protection under aluminum).

• For the synthesis of 200 mL of 0.2 wt% colloidal solution (2g.L ^-1 ) of gold nanoparticles:

For the preparation of solution A, prepare 80 mL of ultra-pure water in a flask and first dissolve 1.35 g of CTAB (3.7.10 ^-3 mol) in water then 0.4 g of d 'Au ³⁺ in the form of AuCI ₃ (1.3.10 ^-3 mol) and adjust to 100 mL with ultra-pure water. Store cold, in the dark.

For the preparation of solution B, prepare 50 mL of ultra-pure water in a flask, dissolve 0.234 g of Na ₂ S (0.3.10 ^-3 mol) and adjust to 100 mL with ultra-pure water.

At room temperature, in the dark, under an argon atmosphere and with stirring (600 rpm), add solution A drop by drop to solution B. Leave to react for 4 h.

Example 6B. S ₃ Au ₂ in nanoparticles, effect of temperature

The gold sulphide nanoparticles are synthesized according to Example 6A, at 0 ° C.

The nanoparticles obtained at room temperature are a little more effective than those obtained at 0 ° C (see table 1 lines P and S)

III) Synthesis of transition metal nanoparticles

Example 7. How to synthesize suspensions of metallic nanoparticles in water?

The metallic nanoparticles in water are generated by the reaction of a metal salt and a reagent:

- the reagent being an oxidant to obtain nanoparticles of metal oxides;

- the reagent being a reducing agent for obtaining metallic nanoparticles.

In addition, the metal salts must be stabilized in "cages" to prevent agglomeration of the nanoparticles into larger and more stable particles.

Cages are generally formed with surfactants having a hydrophilic part and a hydrophobic part. These cages, in an aqueous medium, are called micelles.

Example 8. Silver nanoparticles, Ag

Example 8.A Selection of reagents

The silver salt available (and the most common) is AgNO ₃ . (Aldrich, 99%, M = 169.9 g.mol · ¹ , assay 63.4% Ag).

The surfactant used is CTAB (cetyltrimethylammonium bromide).

The reducing agent chosen is glycerol.

The use of glycerol involves the use of a base to enhance its reducing properties. NaOH has been used for this purpose to produce a basic solution of glycerol in water. The purpose of these solutions is to reduce the metal salt of Ag ⁺ by the conversion of glycerol to dihydroxyacetone (DHA).

Example 8.B Synthesis of 200 mL of 0.2 wt% colloidal solution (2 g.L ' ¹ ) of silver nanoparticles

All reagents are used as received, without prior purification. The water used to prepare the solution is degassed ultra-pure water and stored under Argon. The reaction takes place under Argon, at room temperature (20 ° C). The silver solution is handled in the dark (protection under aluminum).

For the preparation of solution A, prepare 80 mL of ultra-pure water in a flask and first dissolve 1.35 g of CTAB (3.7.10 ^-3 mol) in water then 0.4 g of ion Ag ⁺ in the form of AgNO ₃ (2,3.10 ^-3 mol) and adjust to 100 mL with ultra-pure water. Store cold, in the dark.

For the preparation of solution B, prepare 50 mL of ultra-pure water in a flask, dissolve 34 g of glycerol (0.37 mol) then 8 g of NaOH (0.2 mol) and adjust to 100 mL with ultra-pure water.

At room temperature, in the dark, under an argon atmosphere and with stirring (600 rpm), add solution A drop by drop to solution B. Leave to react for 4 h.

At the end of the reaction, adjust the pH to 7 by adding concentrated commercial HCI (24 M). The corresponding volume to be added is from 0.8 to 0.9 mL.

The resulting solution is analyzed by UV-visible spectroscopy then the morphology and the size of the particles obtained are analyzed by high resolution transmission electron microscopy (HR-TEM).

The UV-visible absorption wavelength is specific to the size and quantity of the nanoparticles in suspension. The analysis by UV-visible spectroscopy of the colloidal suspension of silver nanoparticles at a concentration of 0.2 wt% is shown in Figure 2. The solution has no deposit, all the silver initially introduced is in colloidal form .

The distribution is mono-modal with a wavelength centered at 410 nm, indicating a size of nanoparticles less than 40 nm. The size of the nanoparticles is then confirmed by HR-TEM microscopy.

The images obtained by HR-TEM are presented in Figure 3, at different scales.

The nanoparticles are homogeneous in size, with an average diameter of 15 nm.

Example 8.C Effect of the concentration of reagents on the formation of nanoparticles

In order to increase the concentration of nanoparticles and reach a concentration of 2 gL ^-1 (i.e. 0.2 wt%) in silver, the quantity of reagents has been increased. However, the entire amount of CTAB is not soluble under these conditions and most of it precipitates. Stabilization of silver nanoparticles is no longer ensured.

The UV-visible absorption spectrum resulting from a suspension which has been diluted approximately 50 times in order to avoid saturation of the UV spectrum is presented in FIG. 4. It can be deduced from the comparison of this spectrum with the spectrum obtained. in Example 8.B that the solution has a silver concentration of 0.14 gL ' ¹ .

A HR-TEM microscopy analysis was performed on this suspension diluted to 0.14 g L ^'1 .The distribution is bimodal with nanoparticles having a diameter of about 30 nm and smaller nanoparticles with a diameter less than 5 nm. This behavior is directly linked to a stabilizer fault.

The solution obtained according to method 8.B but with a concentration of 2 g. ¹ in silver, is golden in color. The HR-TEM images of this 2 g.L ' ¹ solution (concentrated solution prepared in 8.C are reported in Figure 6. The particles obtained are not homogeneous. Figure 6A illustrates the presence of nanoparticles with an average diameter of 30 nm, these nanoparticles being of various shapes (rods, spheres) Small spherical nanoparticles, the average diameter of which is between 5 and 10 nm, are also present in the solution, as illustrated in FIG. 6B.

Example 8.D Effect of the silver concentration on the size of the silver nanoparticles.

The silver concentration is obtained by vacuum distillation of water (p = 15 mbar at 20 ° C) from the initial colloidal solution prepared according to Example 8.B.

A solution of silver nanoparticles of concentration 0.2 g.L ' ¹ and of size less than 15 nm (example 8.B) is concentrated by vacuum distillation of water to lead to a silver concentration of 2 g.L' ¹ The resulting solution is cloudy and golden.

The images obtained by HR-TEM of this new suspension are presented in Figure 7.

The generally spherical nanoparticles have a wide size distribution (5 to 20 nm), Figures 7 and 8.

It should however be noted that the CTAB precipitates during the elimination of the water.

Example 8.E Effect of the Nature of the Surfactant on the Formation of Nanoparticles

A nanoparticle solution is produced according to Example 8.B using octyltrimethylammonium bromide (OTAB) in place of cetyltrimethylammonium bromide (CTAB).

The solution obtained is green. A hypsochromic shift in the wavelength of the absorption maximum of this solution is in fact observed during the analysis by UV-visible absorption spectroscopy. The Plasmon generated at the surface is therefore more energetic than when the nanoparticles are formed in the presence of CTAB.

FIG. 9 represents an image obtained by HR-TEM microscopy of the green solution. The size of the nanoparticles is very small, with a diameter of less than 5 nm. An average diameter of 3.7 nm is determined by an analysis of the particle size distribution of the solution (Figure 10).

The counting of nanoparticles and the determination of the size of each are carried out on a microscopy image. 100 nanoparticles are necessary so that the determined size distribution is representative of the entire population of the starting colloidal solution. Then the distribution is adjusted by a log-normal law.

Example 8F. Effect of the nature of the surfactant on the formation of nanoparticles

A nanoparticle solution is produced according to Example 8.B using PEG-dithiol in place of cetyltrimethylammonium bromide (CTAB).

Example 9. Gold Nanoparticles, Au

All reagents are used as received, without prior purification. The water used to prepare the solution is degassed ultra-pure water and stored under Argon. The reaction takes place under Argon, at room temperature (20 ° C).

200 mL of 0.2 wt% colloidal solution (2 gL ^-1 ) in gold nanoparticles are synthesized by following the following steps:

For the preparation of solution A, prepare 80 mL of ultra-pure water in a flask and first dissolve 0.73 g of CTAB (2.0.10 ^-3 mol) in water then 0.4 g of Au ³⁺ in the form of AuCL (1.3.10 ^-3 mol) and adjust to 100 mL with ultra-pure water. Store cold.

For the preparation of solution B, prepare 50 mL of ultra-pure water in a flask, dissolve 0.2 mol of glycerol (18.4 g) then 0.2 mol of NaOH (8 g) and adjust to 100 mL with ultra-pure water.

At room temperature, under an argon atmosphere and with stirring (600 rpm), add solution A drop by drop to solution B. Leave to react for 4 h.

At the end of the reaction, adjust the pH to 7 by adding concentrated commercial HCI (24 M). The corresponding volume to be added is from 0.8 to 0.9 mL

FIG. 11 represents an HR-TEM image of the gold nanoparticles obtained. Their sizes vary between 10 and 30 nm.

Example 10. Copper, Cu Nanoparticles

Example 10A. Synthesis of copper nanoparticles, Cu

The copper nanoparticles are synthesized according to the protocol described in Example 8 B:

All reagents are used as received, without prior purification. The water used to prepare the solution is degassed ultra-pure water and stored under Argon. The reaction takes place under Argon, at room temperature (20 ° C).

For the preparation of solution A, prepare 80 mL of ultra-pure water in a flask and first dissolve 1.35 g of CTAB (3.7.10 ^-3 mol) in water then 0.4 g of Cu ²⁺ in the form of Cu (NO ₃ ) ₂ (Molar mass: 187.56 g / mol: 0.75 g Cu (NO ₃ ) ₂ = 4.10 ^-3 mol) and adjust to 100 mL with ultra-water pure. Store cold, in the dark.

For the preparation of solution B, prepare 50 mL of ultra-pure water in a flask, dissolve 0.37 mol of glycerol (34 g) then 8 g of NaOH (0.2 mol) and adjust to 100 mL with ultra-pure water.

At room temperature, in the dark, under an argon atmosphere and with stirring (600 rpm), add solution A drop by drop to solution B. Leave to react for 4 h.

At the end of the reaction, adjust the pH to 7 by adding concentrated commercial HCI (24 M). The corresponding volume to be added is from 0.8 to 0.9 mL.

FIG. 12 represents an HR-TEM image of the copper nanoparticles included in the colloidal suspension thus obtained.

Clusters of small particles are observed demonstrating that the surfactant does not allow complete stabilization of the copper nanoparticles. Some isolated nanoparticles are also present as illustrated in FIG. 13. These nanoparticles are homogeneous and small, with a diameter of about 2 nm.

Example 10B. Effect of the nature of the surfactant on the formation of copper nanoparticles

A nanoparticle solution is produced according to Example 10A using PEG-600 in place of cetyltrimethylammonium bromide (CTAB).

Example 11. Attempt to Prepare Sulfur Nanoparticles

According to procedure 8.B starting from Na ₂ S and PEG-600 as a surfactant: a colloidal solution at 0.2 g. The sulfur ¹ was obtained.

Homogeneous objects in size and diameter of about 5 nm but difficult to observe by HR-TEM microscopy due to low contrast (Figure 14), could be observed. These objects because of their size have been called sulfur nanoparticles.

IV) Organic results

EXAMPLE 12 MIC Test on MRSA and MSSA Bacteria: Materials and Methods

The bacteria MRSA (Meticillin Resistant Staphylococus Aureus; ATCC 43300) and MSSA (Meticillin Sensitive Staphylococus Aureus; ATCC 29213) were incubated on TSA 24 h at 37 ° C. The standardization of the bacteria was carried out by carrying out a 0.5mc farland with fresh colonies, representing 1.5.10 ⁷ CFU.mL ' ¹ then the bacterial suspension was diluted to 1/100 ^th in Mueller Hinton medium (MH) (sigma . 90922-500G) in order to obtain a final bacterial concentration (spf) corresponding to 1.5.10 ⁵ CFU.mL ' ¹ .

Each particle test was carried out on a line of a 96-well round bottom plate (ref. 353077) in duplicate. 50 μL of MH medium were deposited in the wells. 50 μL of the pure particle were deposited in the first column (column 1) of the plate then successive dilutions of reason 2 were carried out by taking 50 μl of each column redeposited in the next column until the last column (column 12). The 50 pl of the last column has been discarded. Then 50 μL of the bacterial suspension (spf) was deposited in each well representing a final bacterial concentration per well of 0.75 × 10 ⁵ CFU.mL ' ¹ . The final concentration of the particle in the first well (column 1) representing a final dilution to 1/4 with respect to its initial concentration.

Two negative controls were carried out with pure MH, and with 50 μL of MH and 50 μL of pure particle to verify that there was no contamination. A positive control was carried out with 50 μL of HD and 50 μL of the bacterial suspension (spf).

The plate was incubated for 24 h at 37 ° C in a humid chamber.

This method being the reference method for determining the MIC of a particle, a MIC control for oxacillin was carried out on these same MSSA and MRSA strains.

Example 13. MIC Test on MRSA and MSSA Bacteria: Results

The first cup without bacteria growth is determined as the Concentration

Minimum Inhibitory (MIC) of the particle.

Number Particle / quantity CMI MSSA (g / L) CMI MRSA (g / L) Control oxacillin 2.5.10 ^-4 0.256 AT Ag (according to Example 8B) 7.81.10 ^-4 7.81.10 ^-4 B Ag (according to Example 8F) 0.05 0.05 D S 0 (according to Example 11) 0.05 0.05 F Cu 0.2g / L (according to example 10A) 4.88.10 ^-5 9.71.10 ^-5 H Au (according to Example 9) 4.88.10 ^-5 3.9.10 ^-4 K Cu (according to Example 10B) 0,025 0.05 The Ag ₂ S PEG-600 (according to Example 4C) 0.0125 Not determined NOT CuS PEG-600 (according to Example 5C) 0.0125 Not determined 0 Ag ₂ S (according to Example 4A) 1.95.10 ^-4 3.9.10 ^-4 P Au ₂ S ₃ (according to Example 6A) 2.44.10 ^-5 4.88.10 ^-5 Q CuS (according to Example 5A) 9.71.10 ^-5 9.71.10 ^-5 R Ag ₂ S (according to Example 4B) 1.95.10 ^-4 1.95.10 ^-4 S Au ₂ S ₃ (according to Example 6B) 4.88.10 ^-5 9.71.10 ^-5 T CuS (according to Example 5B) 9.71.10 ^-5 9.71.10 ^-5

U CuS + NH ₃ (according to Example 1) 0.023 to 0.046 0,046 V CuSO ₄ 0.078 0.078 to 0.157 A + D 1/8 D + 7/8 A 7.81.10 ^-4 7.81.10 ^-4 H + D 1/8 D + 7/8 H 9.71.10 ^-5 9.71.10 ^-5 F + D 1/8 D + 7/8 F 4.88.10 ^-5 1.95.10 ^-4 D + A + H 1/8 D + 3.5 / 8 A + 3.5 / 8 H 9.71.10 ^-5 1.95.10 ^-4 D + E + F 1/8 D + 3.5 / 8 A + 3.5 / 8 F 9.71.10 ^-5 9.71.10 ^-5 D + M + F 1/8 D + 3.5 / 8 H + 3.5 / 8 F 4.88.10 ^-5 9.71.10 ^-5 D + A + M + F 1/8 D + 2/8 A + 2/8 H + 3/8 F 4.88.10 ^-5 9.71.10 ^-5 D + K 1/8 D + 7/8 K 0,025 0.05 O + P ^1/2 0 + ^1/2 P 9.71.10 ^-5 9.71.10 ^-5 P + Q ^1/2 P + ^1/2 Q 4.88.10 ^-5 9.71.10 ^-5 O + Q ^1/2 0 + ^1/2 Q 7.81.10 ^-4 1.95.10 ^-4

Table 1. Minimum Inhibitory Concentration Test (MIC) of the aqueous solutions obtained by the use of the present invention on the MRSA and MSSA bacteria. The nanoparticles of Ag (O) (according to Example 8), Cu (0) (according to Example 10) and Au (O) (according to Example 9) are denoted respectively Ag, Cu and Au , and the nanoparticles of silver sulphide (according to Example 4), copper sulphide (according to Example 5) and gold sulphide (according to Example 6) are respectively denoted Ag ₂ S, CuS and At ₂ S ₃ . CuSO ₄ relates to a solution of soluble copper salt within the meaning of the invention, that is to say to a solution of copper sulphate in water. S represents an aqueous solution of sulfur nanoparticles prepared according to Example 11. CuS + NH ₃ refers to the soluble copper sulfide complex of Example 1. This soluble complex has no activity because it is the suspension and not the nanoparticle solution which has bactericidal properties.

The control clearly represents the expected MIC for these strains. The MICs of the different particles show a bactericidal effect for the most part on the MSSA and MRSA strains at different concentrations.

It should be noted that the sulfur in the form of nanoparticles or the copper sulphate in solution, not belonging to the invention, exhibit only a weak inhibition of the bacteria MRSA and MSSA compared to the soluble complexes and nanoparticles of the invention .

In addition, the soluble complexes and nanoparticles of the invention are all better inhibitors of MRSA than oxacillin. Oxacillin, used here as a reference, is an example of an active substance used in the event of infection with Staphylococci.

Among the compounds of the invention, copper nanoparticles, gold sulfide nanoparticles and copper sulfide nanoparticles have the best inhibition rates, both of MSSA bacteria and of MRSA bacteria.

EXAMPLE 14 MIC Test on Gram Positive / Negative Bacteria and on Yeasts

The nanoparticle concerned is copper sulfide surfactant with CTAB, synthesized according to Example 5, the source of copper being copper nitrate, Cu (NO ₃ ) ₂ , and not copper sulfate. The tests are carried out according to the method described in Example 12

The activities are measured by the MICs (Minimum Inhibitory Concentration), the index generally used, expressed here in mg per liter. One mg per liter represents one ppm:

Gram positive bacteria Staphylococcus Aureus Propionibacterium Acnes 0.15 0.07 Gram negative bacteria Pseudomonas Aeruginosa 1.2 Yeast Candida Albicans 0.32

These nanoparticles are active in particular on the bacteria that produces acne: the minimum inhibitory concentration against propionibacterium acnes is 0.07 mg per liter.

Copper sulfide nanoparticles are not only active, but are also very well tolerated, especially since the concentration in an anti-acne cream is low: in the order of ppm.

Example 15

It should be noted that in all of the above examples involving CTAB, it can be reduced to a molar concentration equal to 0.2 times that of the metal.

Two suspensions of copper sulfide nanoparticles were also prepared with a CTAB / Cu ratio of 1 and 0.2 respectively by following the protocol of Example 5 and using the starting materials below.

CuSO ₄ .5H ₂ O Molar mass: 249.69 g

Na ₂ S.9H ₂ O Molar mass: 240.18 g

CTAB Molar mass: 364.45 g

2 g solution. The ¹ of Cu (molar mass: 63.55 g) or 0.2 g per 100 ml_ which corresponds to 3.15 mmol of CuSO ₄ .5H ₂ O

Two suspensions of CuS in 100 ml of water were prepared at room temperature.

Suspension 1 CTAB / Cu ratio = 1 in 100 ml_

3.15 mmol of CuSO ₄ .5H ₂ O Let m = 0.786 g

3.15 mmol of Na ₂ S.9H ₂ O Let m = 0.757 g

3.15 mmol of CTAB Let m = 1.148 g

These suspensions are stable after 48 h at room temperature

Suspension 2 CTAB / Cu ratio = 0.2

3.15 mmol of CuSO ₄ .5H ₂ O Let m = 0.786 g

3.15 mmol of Na ₂ S.9H ₂ O Let m = 0.757 g

0.64 mmol of CTAB Let m = 0.230 g

These suspensions are stable after 48 hours at room temperature

Example 16

The CTAB 0.2 tests on CuS (suspension 2 of Example 15) were carried out by Groupe Ideatest,. The bacteria tested is propionibacterium Acnes, responsible for acne.

The results are as follows:

The lethal concentration is 1 mg. L ' ¹ (one part per million)

There are two other measures, also determined by Groupe Ideatest.

The common measurement in Europe is the 4 log concentration (which divides the bacterial population by 10,000) in five minutes. This is achieved for propionibacterium acnes with 1 mg.L ' ¹ .

The AFNOR standard EN 1276, for medical, much more rigid use, is 5 log in five minutes (It divides the bacterial population by 100 000) .This is achieved for the Propionibacterium acnes with 2 mg L ^'1

A tolerance check was also carried out by the Ideatest Group. Europe now prohibiting tests on animals and on humans in this area, the laboratories have developed a new method. It consists of cultivating human skin cells, assembling them in layers to form “reconstructed skin” and testing on this reconstructed skin.

These tests were carried out with a concentration of 20 mg.L ' ¹ to have a very wide safety margin. Unlike all anti-acne currently on the market, the nanoparticle of the invention produces no irritation.

Other tests were carried out with CuS at 10 of CTAB, (example 5) in inhibitory concentration: they gave the following results, in mg.L ' ¹ . 1 mg. ¹ corresponds to one ppm, part per million:

Gram positive bacteria Staphylococus Aureus 0.15 Propionibacterium Acnes 0.07 Gram negative bacteria Escherichia Coli Pseudomonas Aeruginosa 1.2

yeasts

Candida Albicans

0.32

These results cover all the families of germs, gram positive, gram negative and fungi, especially yeasts. They are excellent. Example 17. Composition

Anti-acne cream, 80% water 20% oil, containing 2 ppm of SCu prepared with CTAB as surfactant, the molar concentration ratio of CTAB / Cu was 0.2, preparation made at room temperature.

Claims (21)

1. Use as a bactericide or anti-fungal of a transition metal. 2. Use as a bactericide or anti-fungal, according to claim 1, of a transition metal in insoluble form, in particular in the form of a transition metal with oxidation state 0 or in the form of sulfide or an oxide of the transition metal, or in soluble form, in particular of the salts of sulfates, nitrates or chlorides of the transition metal. 3. Use as a bactericide or anti-fungal, according to one of claims 1 or 2, a transition metal in insoluble form, said transition metal in insoluble form being placed in aqueous solution by the formation of nanoparticles or by the formation of a complex. 4. Use as a bactericide or anti-fungal, according to one of claims 1 to 3, of a transition metal selected from column IB of Mendeleev, in particular chosen from copper, silver and gold. 5. Use as a bactericide or anti-fungal, according to one of claims 1 to 4, a transition metal selected from copper, silver and gold, and being in the form of sulfide, especially in the form of 'a complex or in the form of nanoparticles. 6. Use as a bactericide or anti-fungal, according to one of claims 1 to 4, a transition metal selected from copper, silver and gold, being at the oxidation state 0 and in the form of nanoparticles. 7. Use as a bactericide or anti-fungal, according to one of claims 1 to 4, a transition metal selected from copper, silver and gold, being in the form of soluble salt. 8. Use as a bactericide or anti-fungal, according to one of claims 1 to 7, of a transition metal in a composition containing water, in particular comprising from 10 ' ⁵ to 10' ⁷ gram of said transition metal per gram of composition. 9. Use as a bactericide or anti-fungal, according to claim 8, wherein the composition containing water is an emulsion. 10. Use as a bactericide or anti-fungal, according to one of claims 8 or 9, wherein the composition containing water is an oil-in-water or oil-in-oil emulsion, in particular comprising copper , silver or gold in the form of nanoparticles. 11. Use as a bactericide or anti-fungal, according to one of claims 1 to 10, of a transition metal in a food or cosmetic or pharmaceutical product. 12. Transition metal for use in the treatment of acne. 13. A method of preparing a bactericide comprising a transition metal in the form of nanoparticles of said transition metal, said method comprising a step of reducing the transition metal, in the presence of an additive, in an aqueous solution at pH 14 comprising glycerol, then a neutralization step at pH 7. 14. The method of claim 13, wherein the transition metal is chosen from column IB of Mendeleev, in particular chosen from copper (0), silver (0) and gold (0). 15. Method according to one of claims 13 or 14, wherein the transition metal is before the reduction step in the form of a metal salt chosen from copper (II), in particular copper nitrate Cu (NO ₃ ) ₂ , silver (I), in particular silver nitrate Ag (NO ₃ ), and gold (III), in particular gold chloride AuCI ₃ . 16. Method according to one of claims 13 to 15, wherein the aqueous solution at pH 14 comprises water, glycerol and a base, in particular a hydroxide, in particular NaOH. 17. Method according to one of claims 13 to 16, wherein the additive is a surfactant. 18. A method of preparing a bactericide comprising a transition metal, said transition metal being in the form of a sulfide nanoparticle of said transition metal, said method comprising a step of precipitating a soluble salt of the transition metal in the presence of sodium sulfide Na ₂ S. 19. The method of claim 18, wherein the soluble salt of the transition metal is chosen from copper (II), in particular copper sulphate Cu (SO ₄ ) or copper nitrate Cu (NO ₃ ) ₂ , l silver (I), in particular silver nitrate Ag (NO ₃ ), and gold (III), in particular gold chloride AuCI ₃ . 20. Method according to one of claims 18 or 19, comprising: a step of forming a solution A comprising the transition metal in the form of a soluble salt of the transition metal, an additive and water; a step of forming a solution B comprising Na ₂ S and water; a step of precipitating the soluble salt of the transition metal by adding solution A to solution B to form a suspension of metal sulfide nanoparticles. 21. The method of claim 20, wherein the additive is a surfactant.