Here we describe peptide amphiphiles (PAs) which can be self-assembled into nanofiber networks using divalent ions. These networks possess several key properties of extracellular matrix (ECM) including cell-adhesive ligands, enzyme-mediated degradation and self-assembly into hierarchical organization. The self-assembly of PAs and growth of nanofibers could be controlled by modifications of the chemical structure of the PA and/or addition of divalent ions. Altering the length of PAs alters the viscoelastic properties and degradation kinetics of nanofiber networks. Neural cells were successfully encapsulated within nanofiber networks by self-assembly of PAs. Cell adhesive ligands containing nanofiber networks supported neural cells growth, and their cellular behaviors depended on the concentration of cell adhesive ligands. Therefore, we have demonstrated that mechanical properties, degradability, and bioactivity of nanofiber networks could be tuned by altering the chemical composition and the length of PAs.