Particles prepared by transacylation reaction between an esterified polysaccharide and a polyamine, methods of preparation therefor and compositions containing same

DETAILED DESCRIPTION OF THE INVENTION According to the present invention, it has been discovered, entirely unexpectedly, that the creation of a stable membrane involving covalent bonds, at least at the surface of spheres formed of a gelling polysaccharide or of a gelling polyamine in gelled form by a gelling agent, could be achieved in an extremely simple manner, for example by dissolving an esterified polysaccharide and a polyamine in the initial solution of a gelling polysaccharide such as sodium alginate.
The solution obtained is added in drop form to a gelling bath such as, for example, a solution of a calcium salt, so as to individualize the particles by gelation.
The particles are washed with water and then redispersed in water.
It then suffices to basify the aqueous suspension in order to trigger immediately the transacylation reaction between the esterified polysaccharide and the polyamine which are incorporated with the spheres.
It is also possible to disperse the spheres directly in an alkaline aqueous solution, or alternatively to basify directly the gelling bath after formation of the gelled particles.
It is then observed that a membrane forms at least at the periphery of the spheres.
After reaction, the suspension is neutralized using an acid and the particles are washed with water.
Spheres formed of the gelling polysaccharide in gelled form, which spheres are surrounded at least at the surface by a membrane consisting of a polyamine directly associated via amide bonds with the polysaccharide bearing initially-esterified carboxyls, are thus obtained.
It has also been discovered that a stable membrane could be created at least at the surface of spheres formed of the gelling polysaccharide in gelled form, for example formed of alginate gelled with a polyvalent cation such as, for example, a calcium salt, by incorporating only the esterified polysaccharide into the initial solution of the gelling polysaccharide.
The spheres are individualized by gelation, for example on contact with a calcium salt, and are washed and then dispersed in an aqueous solution containing the polyamine