Angiogenesis is the formation of new blood vessels from a pre-existing vascular network. Angiogenesis is stimulated by proteins called growth factors. Growth factors have been used to treat ischemic tissue for some time. When they were first used to induce angiogenesis, application of a single growth factor was used; this had limited success. Hence, there has been a move towards releasing two or more pro-angiogenic growth factors to induce blood vessel formation. Three growth factors were investigated: vascular endothelial growth factor (VEGF); platelet derived growth factor (PDGF); and endothelial growth factor (EGF). These growth factors were chosen due to potential for binding and, to a lesser extent, for size variation. Two novel systems have been developed that can successfully bind and release various heparin binding proteins by electrostatic binding of the growth factors on to or within the outer layer of polymer particles. It has been concluded that the protein size and the shell architecture have the main effect upon the release profile of the proteins.