A method of forming a cross-linked protein structures includes preparing a solution of protein dissolved in a benign solvent and forming an intermediate protein structure from the solution. The intermediate protein structure can be cross-linked by providing for a specific ratio of chemical cross-linking agents to form the cross-linked protein structure. The solution can be prepared by adding a cross-linker of N-hydroxysuccinimide (NHS) and 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC) at a ratio of two-to-one of NHS to EDC to alcohol. PBS buffer (20×) can be added to the solution until the volume ratio of PBS buffer (20×) to alcohol is about one-to-one. About 16 percent by weight of protein can be dissolved in the solution. The solution can be electrospun to form an intermediate protein structure. After a period of time, the protein structure can be cross-linked to form the cross-linked protein structure.