Cell-matrix interactions form a crucial parameter for the design of synthetic ECM as these dictate cell fate and cell functions. Most commonly, synthetic biomaterials are conjugated with a linear or cyclic Arg-Gly-Asp (RGD) peptide. These peptides, however, lack selectivity towards integrin subtypes presented on the cell membrane and present low binding affinities. We conjugated bicyclic peptides with a strong affinity towards specific integrin subtypes to a synthetic fibrous hydrogel (polyisocyanide, PIC) and studied cell behavior in 3D cultures. In gels functionalized with an optimized bicyclic α5β1¬-integrin binder, human adipose-derived stem cells (hASCs) spread within 24 hours, which is much faster than in other PIC gels, including the default RGD-decorated gel, but also much faster than in the positive Matrigel control. YAP/TAZ staining showed that the rapid morphological change in the 3D microenvironments is YAP-independent. Our data highlights that the design of synthetic matrices with appropriate, optimized guiding signals is key to guide cells towards a predetermined outcome.