polymeric materials are used to make a pliable , non - toxic , injectable porous template for vascular ingrowth . the pore size , usually between approximately 100 and 300 microns , allows vascular and connective tissue ingrowth throughout approximately 10 to 90 % of the matrix following implantation , and the injection of cells uniformly throughout the implanted matrix without damage to the cells or patient . the introduced cells attach to the connective tissue within the matrix and are fed by the blood vessels . the preferred material for forming the matrix or support structure is a biocompatible synthetic polymer which degrades in a controlled manner by hydrolysis into harmless metabolites , for example , polyglycolic acid , polylactic acid , polyorthoester , polyanhydride , or copolymers thereof . the rate of tissue ingrowth increases as the porosity and / or the pore size of the implanted devices increases . the time required for the tissue to fill the device depends on the polymer crystallinity and is less for amorphous polymers versus semicrystalline polymers . the vascularity of the advancing tissue is consistent with time and independent of the biomaterial composition and morphology .