Uronate-containing polysaccharide hydrogels that can be photo-patterned are described. The method involves forming a hydrogel and imetal-coordinating it with a reducible metallic cation and exposing the hydrogel to light in a desired pattern. The exposure to light reduces the metallic cation and results in an irreversible change in the elastic moduli and pore size of the irradiated portions of the patterned hydrogel. The method aha the benefit of allowing the user to produce such a hydrogel in any pattern desired. Patterned hydrogels and cell substrates formed by this method are also described.
