. "Representative biodegradable polymers include polylactide, polyglycolide, polycaprolactone, polycarbonate, poly(phosphoesters), polyanhydride, polyorthoesters, and natural polymers such as alginate and other polysaccharides including dextran, cellulose, collagen, and chemical derivatives thereof (substitutions, additions of chemical groups, for example, alkyl, alkylene, hydroxylations, oxidations," . . . .