Changing mechanical properties of photopolymerized, dityrosine-crosslinked protein-based hydrogels

Hydrogels based on renewable resources are a promising class of materials for
future applications in pharmaceutics, drug delivery and personalized medicine.
Thus, optional adjustments of mechanical properties such as swelling behavior,
elasticity and network strength are desired. In this context, hydrogels based on
the biological raw materials bovine serum albumin and casein were prepared by
dityrosine-crosslinking of their tyrosine residues through visible light-induced
photopolymerization. Changing the tyrosine accessibility by urea addition
before photopolymerization increased the storage modulus of the hydrogels
by 650% while simultaneously being more elastic. Furthermore, contributions
of the buffer system composition, variation of protein concentration and
storage medium towards mechanical properties of the hydrogel such as
storage moduli, elasticity, fracture strain, compressive strength and relative
weight swelling ratio are discussed. It could be shown, that changes in
precursor solution and storage medium characteristics are crucial
parameters towards tuning the mechanical properties of protein-based
hydrogels.