All the above biodegradable polymeric biomaterials could be generally divided into eight groups based on their chemical origin: (1) biodegradable linear aliphatic polyesters (e.g., polyglycolide, polylactide, polycaprolactone, polyhydroxybutyrate) and their copolymers within the aliphatic polyester family like poly(glycolide-

-lactide) copolymer and poly(glycolide-


-caprolactone) copolymer; (2) biodegradable copolymers between linear aliphatic polyesters in group 1 and monomers other than linear aliphatic polyesters like poly(glycolide-trimethylene carbonate) copolymer, poly(

-lactic acid-

-lysine) copolymer, Tyrosine-based polyarylates or polyiminocarbonates or polycarbonates, poly(


-lactide-urethane), and poly(ester-amide); (3) polyanhydrides; (4) poly(orthoesters); (5) Poly(ester-ethers) like poly-


-dioxanone; (6) biodegradable polysaccharides like hyaluronic acid, chitin and chitson; (7) polyamino acids like poly-

-glutamic acid and poly-

-lysine; (8) inorganic biodegradable polymers like polyphosphazene and poly[


(carboxylatophenoxy)phosphazene] which have a nitrogen-phosphorus backbone instead of ester linkage. Recently, there is a new approach of making new biodegradable polymers through melt-blending of highly accepted biodegradable polymers like those of glycolide and lactide base [Shalaby, 1994].