The diffusion and transport of molecules are influenced by the mechanical and physical properties of the transport medium. In biomimetic hydrogels engineered to simulate lung tumors, diffusion can be hindered by the size and elasticity of the PEG mesh network that creates the hydrogel. For potential use as an in vitro model, the engineered hydrogels must allow the diffusion of molecules and will be studied in hydrogels of varying mechanical and physical properties.