Stabilisation of carbonate calcium nanoparticles

Method for forming core-shell nanoparticles, said method being characterized in that it comprises the following steps:

• a) providing calcium carbonate nanoparticles, to form a core selected from one or more of vaterite, proto-vaterite, and amorphous calcium carbonate as determined by X-Ray diffraction;
• b) dissolving at least one polyphenol in one or more polar solvents to form a solution of at least one polyphenol, wherein said at least one polyphenol is insoluble in water, shows a pH ranging from 5 to 9 when measured in a solution of said one or more polar solvents and water at a concentration of 10 wt. % based on the total weight of said solution and wherein said polyphenol has a solubility in said one or more polar solvents of at least 10% as determined by a solubility test A;
• c) mixing said calcium carbonate nanoparticles provided in step (a) with said solution of at least one polyphenol formed in step (b) to form a mixture;
• d) injecting said mixture in water to provide a solution of at least one core-shell nanoparticle;
• wherein the nanoparticle comprises a core being one or more selected from vaterite, proto-vaterite, and amorphous calcium carbonate as determined by X-Ray diffraction, wherein the nanoparticle further comprises a shell of polyphenol, wherein said polyphenol is selected to be insoluble in water and to show a pH ranging from 5 to 9 when measured in a solution of one or more polar solvents and water at a concentration of 10 wt. % based on the total weight of said solution and wherein said polyphenol has a solubility in said one or more polar solvents of at least 10% as determined by a solubility test.