Method for preparation of a controlled release system

A controlled release system which is a three-dimensionally cross-linked intertwined polymer network comprising active ingredient molecules covalently coupled through a biodegradable linker to, and entrapped in, said three-dimensionally cross-linked polymer network, prepared by a method comprising:

• (i) mixing under conditions that do not result in cross-linking
• (a) active ingredient molecules coupled through said biodegradable linker to a polymerisable moiety with
• (b) an aqueous solution or dispersion comprising polymer chains, said polymer chains forming a non-cross-linked matrix and comprising polymerisable moieties that will polymerise under cross-linking conditions with the polymerisable moiety linked to the active ingredient molecules to entrap the active ingredient molecules within the polymer matrix,
• the polymer chains comprising polymerisable moieties that will result in cross-linking intra- or intermolecularly under cross-linking conditions
• thus non-covalently entrapping said active ingredient molecules in the non-cross-linked polymer matrix;
• and
• (ii) subjecting this mixture to cross-linking conditions, thereby forming a three-dimensionally cross-linked polymer network simultaneously with covalently coupling the molecules of the active ingredient both to the polymer network and to other active ingredient molecules included in said network;
• wherein said cross-linking conditions include a polymerisation initiator and wherein the controlled release system of polymer chains and active ingredient molecules is stabilized.