NID1 and neoplasm: Of note, even though the Matrigel used in this study is mostly a mixture of laminin, collagen IV, and enactin, and reflects a basement membrane [52], while in tumor tissues it is mostly collagen that lowers the diffusion coefficient [51], the transport properties of DARPins in cell-dense tumor tissues can be investigated properly when diffusion coefficients match what is found in vivo and specific binding to matrix components plays a negligible role, as is expected for hydrophilic DARPins with highly specific recognition surfaces.