Co-cross linked cohesive gel comprises a first gel of polysaccharide strongly cross linked in the form of particles evenly distributed in a second weakly cross linked polysaccharide gel, where the first gel is bound covalently with second gel and the rate of cross linking of the strongly cross linked polysaccharide is higher than the cross-linking rate of weakly cross linked polysaccharide. Independent claims are included for: (1) a composition comprising the gel； (2) a preparation of the gel comprising providing the first strongly cross linked polysaccharide particles, mixing the obtained particles in the providing step in an aqueous medium to obtain a suspension, adding a second polysaccharide to the suspension, where the second polysaccharide is identical or different from the first polysaccharide, cross linking the second polysaccharide until a rate of cross linking X2 to obtain a second weakly co-cross linked polysaccharide of the second polysaccharide weakly cross linked with the particles in the presence of a cross-linking agent to obtain a co-cross linked gel, and recovering co-cross linked gel comprising particles of first strongly cross linked polysaccharide covalently bound to a matrix of second weakly cross linked polysaccharide； and (3) a kit for injecting a gel comprising the co-cross linked gel, preferably in the form of ready to use hydrogel, conditioned in sterile syringe and needed for injection comprising an injection needle.
