Claims:Claims
We Claim:
1. A formulation of photo-stable silica embedded silver ion polymer complex, the formulation comprising:
a. a silver precursor in the range of 0.25% to 0.75% by weight;
b. a polyvinyl pyrrolidone polymer or vinylpyrrolidone-vinyl imidazole copolymer in the range of 3% to 8% by weight;
c. a silica precursor in the range of 0.5% to 2% by weight; and
d. a deionized water in the range of 40% to 85% by weight.

2. The formulation as claimed in claim 1, wherein silver precursor is selected from the group comprising silver citrate and silver sulfate.

3. The formulation as claimed in claim 1, wherein citric acid in the range of 10% to 50% by weight is used in combination with silver citrate as silver citrate is less soluble in water.

4. The formulation as claimed in claim 1, wherein silica precursor is selected from a group comprising tetraethyl orthosilicate, tetramethyl orthosilicate, tetrapropyl orthosilicate, tetrabutyl orthosilicate, tetrahexyl orthosilicate, diethoxydimethylsilane, ethoxy trimethylsilane, methoxy trimethylsilane, trimethoxy(octyl) silane, iethoxy(octyl)silane, methoxy(dimethyl) octylsilane, and 3-Aminopropyl-(diethoxy) methylsilane.

5. The formulation as claimed in claim 1, wherein the silver ion is complexed with polyvinyl pyrrolidone polymer or vinylpyrrolidone-vinyl imidazole copolymer in deionized water.

6. The formulation as claimed in claim 1, wherein silica embedded silver ion polymer exhibits low polydispersity index and particle size in the range from 750 nm to 1 micron and particle size in the range of 100 nm to 2 micron is achieved by varying the concentration of the precursors, catalysts or by varying the one or more process conditions.

7. The formulation as claimed in claim 1, wherein silica embedded silver ion polymer complex is photo-stable and exhibits antimicrobial activity against Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, Aspergillus niger and Candida albicans.

8. A process for preparing photo-stable silica embedded silver ion polymer complex, the process (100) comprising the steps of:
a. dissolving a silver precursor in the range of 0.25% to 0.75% by weight and a polymer in the range of 3% to 8% by weight in deionized water to form a silver ion polymer complex solution (101);
b. adding a solution of silica precursor in the range of 0.5% to 2% by weight and catalyst to the silver ion polymer complex solution to form a silica embedded silver ion complex solution (102);
c. maintaining the solution at temperature in the range of 350C to 400C to initiate the formation of silica particles and heating the silver ion complex solution at a temperature in the range of 500C to 750C (103); and
d. removing the solvent and the catalyst from silver ion complex solution to form an aqueous silver ion polymer complex embedded over silica (104).

9. The process as claimed in claim 8, wherein the process is a wet chemical process and the process takes place through complexation and sol gel route.

10. The process as claimed in claim 8, wherein silver precursor is selected from the group comprising silver citrate and silver sulfate.

11. The process as claimed in claim 8, wherein silica precursor is selected from a group comprising tetraethyl orthosilicate, tetramethyl orthosilicate, tetrapropyl orthosilicate, tetrabutyl orthosilicate, tetrahexyl orthosilicate, diethoxydimethylsilane, ethoxy trimethylsilane, methoxy trimethylsilane, trimethoxy(octyl)silane, triethoxy(octyl)silane, methoxy(dimethyl) octylsilane, and 3-Aminopropyl-(diethoxy) methylsilane.

12. The process as claimed in claim 8, wherein silica precursor is dissolved in a solvent selected from the group comprising methanol, ethanol, isopropyl alcohol and tetrahydrofuran.

13. The process as claimed in claim 8, wherein the catalyst is selected from the group consisting of ammonia, sodium hydroxide and potassium hydroxide.

, Description:[001] PREAMBLE TO THE DESCRIPTION
[002] The following specification particularly describes the invention and the manner in which it is to be performed:
[003] DESCRIPTION OF THE INVENTION
[004] Technical field of the invention
[005] The present invention relates to a composition of photo-stable silica embedded silver based complex as an antimicrobial preservative in cosmetics and personal care applications. The present invention also discloses a process of preparation of the silver based complex through a wet chemical synthesis.
[006] Background of the invention
[007] The presence of microbes in any formulation affects the efficacy and shelf-life of personal care products or formulations. The preservation and storage of formulations for long-time may result in microbial contamination. Microbial contamination refers to non-intended or accidental introduction of infectious organisms such as bacteria, yeast, mold, fungi, virus, prions, protozoa or their toxins and by-products into the formulation.
[008] Microbial contamination is a major concern in our daily life and has a great impact for personal care products and formulations. Generally, antimicrobial agents or preservatives are used in the formulations for preventing microbial spoilage, decay and conglomeration of biomass in cosmetic and personal care formulations. Antimicrobial ingredients play an important role in making sure that personal care products are free of microorganisms during storage and during the consumer use.
[009] The preservative system protects the product against microbial proliferation by exerting a wide spectrum of antimicrobial activity at low inclusion levels by maintaining the activity throughout product manufacture, shelf life and usage without compromising the quality or performance of product.
[0010] Personal care products or cosmetic products are used to improve and enhance the external appearance and majority of the formulations are useful as topical application. Any formulation or preparation intended for application in contact with the various external parts of the human body or with the teeth and the mucous membranes of the oral cavity. If the formulation is contaminated with microbes, the application of such formulations results in allergic and other adverse reactions. In light of this, a wide range of preservatives are developed to overcome the microbial contamination. Hence, a balance between protection against microbial contamination and limiting the health risks of preservative should be maintained by the manufacturers.
[0011] The control of microbial contamination of all products for human use which support microbial persistence or growth has been a considerable concern to manufacturers. There are different types of antimicrobial agents or preservatives available in the market. However, the current trends show that conventional synthetic preservatives such as parabens, formaldehyde releasers, isothiazolinones, organic acids and etc. are not well approved in view of regulatory affairs due to health and environmental hazards that include carcinogenicity, developmental and reproduction toxicity, endocrine disruption etc. Therefore, there is a real need of new harmless and compatible anti-microbial substances.
[0012] Silver is recognized and used from ancient times for its broad spectrum antimicrobial activity and non-toxicity. Different forms of silver such as metal particles, silver ion complex, silver salts etc. are used as preservatives. It is required to select the suitable form of silver in any formulation. Most of the conventional silver preservatives used currently are colored solution or in powdered form. Most of the silvers are very sensitive to light. The major disadvantage of colored silver is that, it alters the appearance and texture of cosmetic formulations. The powdered silver form, depending on its surface characteristics might have its own formulating challenges.
[0013] In order to achieve efficient antimicrobial property in cosmetics and personal care products, a very high level of silver concentration is being used and also majority of silver remains unused or deactivated by complexation with other compounds in the formulations. However, silver embedded in polymer complex helps to supply silver ions in controlled manner. Further, the embedded silver ion polymer complex is required in very low dosages compared to conventional antimicrobial compositions.
[0014] The PCT Application PCT/EP2004/009536 entitled “Body care product containing porous silver particles” discloses a body care product containing porous particles made of metal containing silver and having an average diameter size of between 1 and 100 µm. The invention discloses the manufacture of antimicrobial body care products with metallic silver products as antimicrobial agents for treatment of inflammation. The silver particles in personal care products are used in such concentration, which allows at a point of contact of the personal care by the skin and or mucosa an antimicrobially effective but less than cytotoxic concentration of silver ions. However, the cited invention requires silver in specific form of metallic products which increases the manufacturing cost.
[0015] The US Application US 10/383,345 entitled “Ionic silver complex” discloses a substantially non-colloidal solution prepared by combining ingredients comprising water, a source of free silver ions and a non-toxic, thiol-free, water-soluble complexing agent to overcome many of the limitations of ionic silver substances and has wide application in and on the body. The compositions are prepared by wet chemical route. The source of free silver ions is silver oxide, trisilver citrate or silver acetate. However, the process employed is complexation process and the silver particles may not be photostable.
[0016] The US Application US 11/729,175 entitled “Anhydrous silver dihydrogen citrate compositions” discloses an anhydrous silver dihydrogen citrate compositions comprising silver dihydrogen citrate and citric acid. The anhydrous compositions are prepared by freeze-drying and reconstituted with a suitable diluent to form silver dihydrogen citrate compositions. The anhydrous compositions are applied to a variety of substrates to impart an antimicrobial effect on the substrates. As the compositions are prepared by an electrolysis process in such a fashion that an electrical current is passed through a pair of silver electrodes that are immersed in a water solution of citric acid, the process may result in less yield than the conventional chemical synthesis.
[0017] The US Application US 12/191,477 entitled “Antimicrobial silver solutions” discloses a method for preparing a concentrated solution containing water, citrate ions and silver ions. The method includes providing an amount of trisilver citrate, providing an amount of citric acid, wherein the amount of the citric acid is at least 19 times the amount of the trisilver citrate by weight, and mixing the trisilver citrate and the citric acid in an amount of water to produce the concentrated solution. A concentrated solution containing water, citrate ions and silver ions has a silver ion concentration which is at least 10 grams per liter. A diluted solution prepared by adding water to a concentrated solution containing water, citrate ions and silver ions. However, the method results in synthesis if silver as solution, which may not be photostable for long-term preservation.
[0018] Hence, there is a need for silver antimicrobial composition that is colorless, less sensitive to light, low loading and compatible with wider applications.
[0019] Summary of the invention
[0020] The present invention relates to a composition of silver ion complex comprising photo-stable silica embedded silver based complex as an antimicrobial preservative in cosmetics and personal care applications. The present invention also discloses a process of preparation of the silver ion complex through a wet chemical synthesis. The composition of the silver ion complex comprises silver precursor in the range of 0.25% to 0.75% by weight, citric acid in the range of 10% to 50% by weight, polyvinyl pyrrolidone polymer or vinylpyrrolidone-vinyl imidazole copolymer in the range of 3% to 8% by weight, silica precursor in the range of 0.5% to 2% by weight and deionized water in the range of 40% to 85% by weight.
[0021] The present invention further discloses a wet chemical process for synthesis of preparation of the silver ion complex. The process starts by dissolving a silver precursor and a polymer in a solvent to form a silver ion polymer complex solution. The silver precursor used in the present invention is silver citrate or silver sulfate in the range of 0.25% to 0.75% by weight. Citric acid in the range of 10% to 50% by weight is used as a solvent for silver citrate as it is insoluble in water. The polymer used in the present invention is polyvinyl pyrrolidone polymer or vinyl pyrrolidone copolymer in the range of 3% to 8% by weight. The solvent used is deionized water in the range of 40% to 85% by weight. A solution of silica precursor and catalyst are added to the silver ion polymer complex solution to form a Silver ion complex solution. The silica precursor is used in the range of 0.5% to 2% by weight. Silica precursor is dissolved in a solvent selected from the group comprising methanol, ethanol, isopropyl alcohol or tetrahydrofuran. The solution is maintained at room temperature or just few degrees above room temperature in the range of 350C to 400C. There is formation of silica particles on the surface of the silver ion polymer complex by physical adsorption. The solution is then heated to a temperature in a range of 500C to 750C. The solvent and the catalyst are removed to form an aqueous silver ion polymer complex embedded over silica and the silica embedded silver ion polymer complexes formed by the wet chemical process are subjected to particle size distribution analysis and others. The whole process is carried out at a mixing speed in the range of 150-200 rpm.
[0022] The silica embedded silver ion polymer complexes exhibited low polydispersity index and particle size of the complex ranges from 750 nm to 1 micron. The silica embedded silver ion polymer complexes exhibited antimicrobial activity against Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, Aspergillus niger and Candida albicans.
[0023] The silica embedded silver ion polymer complexes obtained are useful as antimicrobial preservative in cosmetic and personal care products. The complex is photo-stable and does not impart any discoloration of the formulation. The silica embedded silver ion polymer complex is also effective in controlling of growth of bacteria on textile fabrics.
[0024] Brief description of drawings
[0025] FIG 1 tabulates a composition of a silver ion complex.
[0026] FIG 2 illustrates a flow chart for the process of preparation of the silver ion complex of the present invention.
[0027] FIG 3 illustrates the particle size distribution of silica embedded silver ion polymer complex.
[0028] FIG 4 illustrates the results of Scanning Electron Microscopy (SEM) analysis of silica embedded silver ion polymer complex.
[0029] FIG 5 illustrates the results of Energy Dispersive X-ray (EDAX) analysis of silica embedded silver ion polymer complex.
[0030] FIG 6 illustrates the bar chart quantifying the presence of different elements.
[0031] FIG 7 illustrates the Fourier Transform Infrared Spectroscopy (FTIR) analysis of silica embedded silver ion polymer complex.
[0032] FIG 8 illustrates the X-ray Photoelectron Spectroscopy (XPS) analysis of silica embedded silver ion polymer complex.
[0033] FIG 9 illustrates deconvoluted spectra of silver.
[0034] FIG 10 illustrates the area percentage of the chemical bonds present in silver.
[0035] FIG 11 tabulates the specific criteria for antimicrobial activity of the aqueous silica embedded silver ion polymer complex.
[0036] FIG 12 tabulates the results of antimicrobial activity of the aqueous silica embedded silver ion polymer complex against different categories of micro-organisms.
[0037] FIG 13 illustrates the time kill percentage of different microorganisms using ASTM E 2315-03 (2008) protocol.
[0038] FIG 14 illustrates the time kill percentage of Gram positive and Gram negative bacteria.
[0039] FIG 14a illustrates the time kill percentage of Gram positive and Gram negative bacteria using silica embedded silver ion polymer complex at a concentration of 0.4% w/v.
[0040] FIG 14b illustrates the time kill percentage of Gram positive and Gram negative bacteria using silica embedded silver ion polymer complex at a concentration of 0.5% w/v.
[0041] FIG 15 illustrates the effectiveness of silica embedded silver ion polymer complex using a standard EN 1276:1997 protocol.
[0042] FIG 15a illustrates the effectiveness of silica embedded silver ion polymer complex under clean condition.
[0043] FIG 15b illustrates the effectiveness of silica embedded silver ion polymer complex under dirty condition.
[0044] Detailed description of the invention
[0045] In order to make the matter of the invention clear and concise, the following definitions are provided for specific terms used in the following description.
[0046] The term “Anti-microbial agent” refers to an agent that kills micro-organisms or inhibits their growth.
[0047] The term “Photostability” refers to an ability of a product to retain its integrity upon exposure to light.
[0048] The present invention relates to a composition of silver ion complex comprising photo-stable silica embedded silver based complex as an antimicrobial preservative in cosmetics and personal care applications. The present invention also discloses a process of preparation of the silver ion complex through a wet chemical synthesis.
[0049] FIG 1 tabulates a composition of a silver ion complex. The composition of the silver ion complex comprises silver citrate and citric acid or silver sulfate, polyvinyl pyrrolidone polymer or vinylpyrrolidone-vinyl imidazole copolymer, silica precursor and deionized water. The composition comprises silver precursor in the range of 0.25% to 0.75% by weight, citric acid in the range of 10% to 50% by weight, polyvinyl pyrrolidone polymer or vinylpyrrolidone-vinyl imidazole copolymer in the range of 3% to 8% by weight, silica precursor in the range of 0.5% to 2% by weight and deionized water in the range of 40% to 85% by weight.
[0050] The present invention discloses the use of silver precursor as a main component of the composition. Generally, different silver precursors are used in the composition. The present invention discloses the use of silver citrate or silver sulfate in the reaction to form a complex with a polymer. Citric acid is used in combination with silver citrate as silver citrate is less soluble in water. Silver sulfate used in the present invention is a non-staining substitute for silver nitrate precursor and also avoids formation of nitrosamine as a byproduct in the reaction.
[0051] Generally, silver is sensitive to light and needs to be protected before using in any formulation of cosmetic and personal care products. Polyvinyl pyrrolidone polymer used in the present invention forms a metal bond with silver precursor thus controlling the particle size of silica formed in the reaction. Vinyl imidazole vinyl pyrrolidone copolymer used in the present invention acts as a capping agent and also as a photo stabilizer. Vinyl imidazole vinyl pyrrolidone co-polymer protects silver from light and helps in formation of uniformly sized silica particles on the surface of the silver ion-polymer complex. In formulations where only the polymer poly vinyl pyrrolidone is used, an additional light stabilizing agent suitable for cosmetic applications is recommended. Further, imidazole (INCI Name: Imidazole) is optionally used as a photo-stabilizer.
[0052] Silica precursors are selected from a group comprising tetraethyl orthosilicate, tetramethyl orthosilicate, tetrapropyl orthosilicate, tetrabutyl orthosilicate, tetrahexyl orthosilicate, diethoxydimethylsilane, ethoxy trimethylsilane, methoxy trimethylsilane, trimethoxy(octyl)silane, triethoxy(octyl)silane, methoxy(dimethyl)octylsilane, or 3-Aminopropyl-(diethoxy) methylsilane. The solvent used for silica precursor is selected from a group comprising methanol, ethanol, isopropyl alcohol or tetrahydrofuran.
[0053] The present invention discloses a wet chemical process for synthesis of preparation of the silver ion complex.
[0054] FIG 2 illustrates a flow chart for the process of preparation of the silver ion complex of the present invention. The process (100) of preparing the silver ion complex starts at step (101) of dissolving a silver precursor and a polymer in a solvent to form a silver ion polymer complex solution. The silver precursor used in the present invention is silver citrate or silver sulfate in the range of 0.25% to 0.75% by weight. Citric acid in the range of 10% to 50% by weight is used as a solvent for silver citrate as silver citrate is insoluble in water. The polymer used in the present invention is polyvinyl pyrrolidone polymer or vinyl pyrrolidone copolymer in the range of 3% to 8% by weight. The solvent used is deionized water in the range of 40% to 85% by weight. At step (102), a solution of silica precursor and catalyst are added to the silver ion polymer complex solution to form silica embedded silver ion complex solution. The silica precursor is used in the range of 0.5% to 2% by weight and selected from a group comprising tetraethyl orthosilicate, tetramethyl orthosilicate, tetrapropyl orthosilicate, tetrabutyl orthosilicate, tetrahexyl orthosilicate, diethoxydimethylsilane, ethoxy trimethylsilane, methoxy trimethylsilane, trimethoxy(octyl)silane, triethoxy(octyl)silane, methoxy(dimethyl)octylsilane, or 3-Aminopropyl-(diethoxy) methylsilane. Silica precursor is dissolved in a solvent selected from the group comprising methanol, ethanol, isopropyl alcohol or tetrahydrofuran. At step (103), the solution is maintained at room temperature or just few degrees above room temperature in the range of 350C to 400C to initiate the formation of silica particles on the surface of the silver ion polymer complex by physical adsorption and the silica embedded silver ion complex solution is heated with a temperature in a range of 500C to 750C. At step (104), the solvent and the catalyst are removed from ion complex solution to form an aqueous silver ion polymer complex embedded over silica.
[0055] The physically adsorbed silica onto the silver ion-polymer/copolymer complex is strongly bonded to the silver through polymer/copolymer by supplying thermal energy.
[0056] The particle size of the silica embedded silver ion polymer complex are be tuned by varying the concentration of silica precursors and the catalyst used for the reaction. The particle size is tuned to the range of 100 nm to 2 micron.
[0057] The silica embedded silver ion polymer complexes formed by the wet chemical process are subjected to particle size distribution analysis and other characterization analysis.
[0058] FIG 3 illustrates the particle size distribution of silica embedded silver ion polymer complex. The silica embedded silver ion polymer complex is subjected to particle size distribution using dynamic light scattering analysis to exhibit particle distribution by intensity, volume and number as illustrated in FIGs 3(a), 3(b) and 3(c) respectively. The low observed polydispersity index of 0.103 affirmed narrow particle size distribution.
[0059] FIG 4 illustrates the results of Scanning Electron Microscopy (SEM) analysis of silica embedded silver ion polymer complex. The silica embedded silver ion polymer complex is subjected to SEM analysis and the particle size of the silica embedded silver ion polymer complex varies from 750 nm to 1 micron.
[0060] FIG 5 illustrates the results of Energy Dispersive X-ray (EDAX) analysis of silica embedded silver ion polymer complex. The silica embedded silver ion polymer complex is subjected to EDAX analysis to detect the presence of elements in the aqueous sample and silica embedded silver ion polymer complex. EDAX analysis is carried out in different parts of the sample and it is found that the sample showed similar percentage of elements. The presence of silver is found within the particles as well as in multiple places of the particles which are analyzed by selecting different areas in the particle. This confirms that almost 90% of silver is complexed with the polymer and is present as silica embedded silver ion polymer complex. It is also observed that traces of silver i.e. less than or equal to 10% is present as free ions.
[0061] FIG 6 illustrates the bar chart quantifying the presence of different elements. The bar chart quantifies different elements in a particular area of the silica embedded silver ion polymer complex. The bar chart shows the presence of carbon at 75% by weight, silica at 18% by weight followed by silver at 5% by weight.
[0062] FIG 7 illustrates the Fourier Transform Infrared Spectroscopy (FTIR) analysis of silica embedded silver ion polymer complex. The FTIR analysis confirms the formation of silica particles. The FTIR analysis confirms the linkage between silver, copolymer and the silica particles. This confirms the formation of silver ion polymer complex.
[0063] FIG 8 illustrates the X-ray Photoelectron Spectroscopy (XPS) analysis of silica embedded silver ion polymer complex. The XPS spectrum of the silica embedded silver ion polymer complex shows the binding energy of silver, silica and the copolymer complex.
[0064] FIG 9 illustrates deconvoluted spectra of silver. The deconvolution of high resolution XPS spectrum of silver shows the intensity of the binding energy of silver.
[0065] FIG 10 illustrates the area percentage of the chemical bonds present in silver. The area percentage of the chemical bonds denotes that that the percentage of free ions is very less which is about 10% and maximum percentage of silver is present in the form of complex interacting with the oxygen from copolymer or silica. The silica embedded silver ion polymer complex prepared in the present invention is subjected to antimicrobial activity. The antimicrobial activity is tested against bacteria, yeast and molds.
[0066] FIG 11 tabulates the specific criteria for antimicrobial activity specified as per USP 51 protocol .The silica embedded silver ion polymer complex is subjected to antimicrobial activity analysis using standard USP 51 protocol. The antimicrobial activity is tested against bacteria, yeast and molds. For the purpose of testing the antimicrobial activity, the products are classified into four categories in USP 51 protocol :
[0067] Category 1: This category includes injections and other parenteral formulations including emulsions, sterile nasal products and ophthalmic products with aqueous bases or vehicles.
[0068] Category 2: This category includes topically used products with aqueous bases or vehicles, non-sterile nasal products, and emulsions, including those applied to mucous membranes.
[0069] Category 3: This category includes oral products other than antacids, made with aqueous bases or vehicles.
[0070] Category 4: This category includes antacids with aqueous bases or vehicles.
[0071] The criteria for microbial effectiveness are met if the specified criteria are met as specified in the Table (FIG 11). Silica embedded silver ion polymer complex falls under category 2. The results are interpreted as no increase, which is defined as not more than 0.5 log10 unit higher than the previous value measured.
[0072] FIG 12 tabulates the results of antimicrobial activity of the aqueous silica embedded silver ion polymer complex against different categories of micro-organisms. Based on the criteria specified in FIG 11, the antimicrobial activity of the aqueous silica embedded silver ion polymer complex is tested against Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, Aspergillus niger and Candida albicans. The results showed that the antimicrobial effectiveness testing for aqueous silica embedded silver ion polymer complex is effective as none of test organisms have survived over the period of 28 days of the test.
[0073] FIG 13 illustrates the time kill percentage of different microorganisms using ASTM E 2315-03 (2008) protocol. The antimicrobial activity of the aqueous silica embedded silver ion polymer complex is tested against different microorganisms using ASTM E 2315-03 (2008) protocol, which is a standard guide for the assessment of invite reduction of a microbial population of test organisms after exposure to silica embedded silver ion polymer complex. The results showed that the silica embedded silver ion polymer complex exhibited 99.9% efficacy and in most of the organisms it has shown > 99.9% efficacy within 30 mins of exposure against Gram Positive bacteria, Gram negative bacteria and fungi which are commonly found in cosmetics such as lotions, shampoos or conditioners etc.
[0074] FIG 14 illustrates the time kill percentage of Gram positive and Gram negative bacteria. The antimicrobial activity of the aqueous silica embedded silver ion polymer complex is tested against different Gram positive and Gram negative bacteria using ASTM E 2315-03 (2008) protocol within 1 min exposure time.
[0075] FIG 14a illustrates the time kill percentage of Gram positive and Gram negative bacteria using silica embedded silver ion polymer complex at a concentration of 0.4% w/v.
[0076] FIG 14b illustrates the time kill percentage of Gram positive and Gram negative bacteria using silica embedded silver ion polymer complex at a concentration of 0.5% w/v. Silica embedded silver ion polymer complex at two different concentrations exhibited quick antimicrobial activity against broad spectrum bacteria suggesting the use of this material for suitable cosmetic and personal care applications.
[0077] FIG 15 illustrates the effectiveness of silica embedded silver ion polymer complex using a standard EN 1276:1997 protocol. The effectiveness of silica embedded silver ion polymer complex at a concentration of 0.5% w/v is analyzed against Staphylococcus aureus under clean and dirty conditions.
[0078] FIG 15a illustrates the effectiveness of silica embedded silver ion polymer complex under clean condition.
[0079] FIG 15b illustrates the effectiveness of silica embedded silver ion polymer complex under dirty condition. The results showed that silica embedded silver ion polymer complex exhibited effective antimicrobial activity under clean and dirty conditions within 5 mins of the exposure.
[0080] In order that this invention to be more fully understood the following preparative and testing examples are set forth. These examples are for the purpose of illustration only and are not to be construed as limiting the scope of the invention in any way.
[0081] Example 1: Silica embedded silver ion polymer complex using silver sulfate precursor
[0082] Silver sulfate at a concentration of 0.45% by weight is mixed with 5-8% by weight of the vinyl pyrrolidone-vinyl imidazole copolymer in 95% by weight of water. The mixture is stirred at 300 rpm speed for 20 minutes and the pH of the solution is adjusted to 8. Silica synthesis reaction is then carried out to form silica embedded silver ion polymer complex. 45% iso propyl alcohol by weight is added to the silver ion polymer complex solution followed by addition of 3% ammonia and around 2% tetra ethyl ortho silicate by weight to the silver ion polymer complex solution to the silver ion polymer complex solution. The temperature of the solution is adjusted to 400C to initiate the silica formation reaction around the silver ion polymer complex. This reaction is carried out for 1 hour to ensure complete silica formation. After 1 hour, the reaction temperature is brought to around 750C to remove isopropyl alcohol and ammonia from the solution and also to ensure that silica is embedded to silver ion polymer complex. The removal of the solvent and the catalyst is to ensure the silica embedded silver ion polymer complex is completely present in aqueous medium. The product formed is colorless translucent solution by appearance.
[0083] Example 2: Silica embedded silver ion polymer complex using silver citrate/citric acid precursor
[0084] The process below describes the formation of silica embedded silver ion polymer complex using silver citrate as silver precursor. Silica is formed by the hydrolysis and condensation reaction of its precursor, tetra ethyl ortho silicate of around 2g in hydro alcoholic medium (water is around 33 g and iso propyl alcohol is around 30 g) with the vinyl pyrrolidone vinyl imidazole copolymer of around 3g as capping agent. This controls the rate of reaction in the presence of ammonia as catalyst which is around 2g. The solution obtained is distilled at 750C to remove isopropyl alcohol and ammonia from the hydro alcoholic medium to disperse the silica particles in the water medium. As silver citrate is minimally soluble in water, it is dissolved in citric acid solution to form the silver citrate citric acid complex where silver citrate is around 0.2 g and citric acid 7g by weight in 27g of water. Hydrogen peroxide of around 0.4 g is added to this solution. Both the solutions are blended together at around 500C for 2 hours to ensure silica embedded silver ion polymer complex. This solution formed can be used directly as a cosmetic ingredient.
[0085] Example 3: Silica embedded silver ion polymer complex using silver sulfate precursor and imidazole
[0086] Silver sulfate of 0.45 % by weight is mixed with 5-8% by weight of the vinyl pyrrolidone-vinyl imidazole copolymer in 90% by weight of water. The solution is then stirred at 300 rpm speed for 20 minutes. The pH of the solution is adjusted to 8. Silica synthesis reaction is then carried out to form silica embedded silver ion polymer complex. 45% iso propyl alcohol by weight is added to the silver ion polymer complex solution followed by addition of 3% ammonia and 2% tetra ethyl ortho silicate by weight to the silver ion polymer complex solution. The temperature of the solution is maintained at 400C to initiate the silica formation reaction around the silver ion polymer complex. This reaction is carried out for 1 hour to ensure complete silica formation. After 1hour, the reaction temperature is brought to around 750C to remove isopropyl alcohol and ammonia from the solution and also to ensure that silica is embedded to silver ion polymer complex. The removal of the solvent and the catalyst is to ensure that silica embedded silver ion polymer complex is present in aqueous medium. Finally, about 5% imidazole by weight of the solution is added and mixed for 10 mins at room temperature. The product formed is colorless translucent solution by appearance and is used as a cosmetic ingredient.
[0087] Example 4: Silica embedded silver ion polymer complex using silver citrate/citric acid precursor
[0088] The process below describes the formation of silica embedded silver ion polymer complex using silver citrate as silver precursor. Silica is formed by the hydrolysis and condensation reaction of its precursor, 2g of tetra ethyl ortho silicate in hydro alcoholic medium (water is around 33 g and Iso propyl alcohol is around 30 g) is added to 3g of polyvinyl pyrrolidone polymer as capping agent and to control the rate of reaction in the presence of 2g of ammonia as catalyst. The solution obtained is distilled at 750C to remove isopropyl alcohol and ammonia from the hydro alcoholic medium to disperse the silica particles in the water medium. As silver citrate is minimally soluble in water it is dissolved in citric acid solution to form the silver citrate citric acid complex where silver citrate is around 0.2 g and citric acid 7 g by weight in 27 g of water. Hydrogen peroxide of around 0.4 g is added to this solution. Both the solutions are blended together at around 500C for 2 hours to ensure silica embedded silver ion polymer complex. This solution is then stirred at 500C for further 8 hours which improves the photo stability of the product. This solution can be used directly as a cosmetic ingredient.
[0089] The silica embedded silver ion polymer complex obtained by the process of present invention is useful as antimicrobial preservative in cosmetic and personal care products. The complex is photo-stable and does not impart any discoloration of the formulation. The silica embedded silver ion polymer complex is effective in controlling of growth of bacteria on textile fabrics such as cotton, wool, silk, polyester, viscose, polypropylene, nylons, lycra, acrylics etc. The silica embedded silver ion polymer complex is useful in personal care products such as tooth brushes, soap, body lotion, hand wash, deodorants, shampoo, hand sanitizer, female hygiene products etc.