Abstract: In a gel-like mass having natural or synthetic polymers, preferably polygalactomannans, at least one cross-linking agent and further ingredients, according to this invention that the at least one cross-linking agent is of amphiphilic core-shell nanoparticles. This invention further refers to a method for producing a gel-like mass, a composition for producing a gel-like mass comprising natural or synthetic polymers, preferably polygalactomannans and amphiphilic core-shell nanoparticles and the use of a gel-like mass as drug delivery system for topical medication.