Abstract: Complexes of polyanionic plant polysaccharides with biodegradable proteins, or proteolytic degradation products thereof, are useful in the formation of wound dressings and surgical implants, such as sutures, blood vessel grafts, and artificial organs. The biodegradable protein is preferably collagen, and the polysaccharide is preferably sodium alginate. The complexes are preferably formed by combining the protein and the polysaccharide at a pH which is no higher than the isoelectric point of the protein. The complexes may be crosslinked, such as by dehydrothermal crosslinking or by the use of chemical crosslinking agents such as aldehydes or carbodiimides. Multivalent cations may also be incorporated in the complex in order to give added strength.