A tissue adhesive sealant includes a cross-linkable protein in a solution that when combined with a cross-linking agent solution including an aldehyde and amino acid containing species reactive with the aldehyde cross-links to form a seal. The sealant is well suited for bonding tissue alone or in combination with a patch. The ratio between the aldehyde and the amino acid containing species is between 20:1 and 1:1 on an aldehyde moiety:amino acid or peptide subunit molar basis. Particularly strong seals are formed when the protein and cross-linking agent are present in a molar ratio of between 15:1 and 1:1.