To investigate the role of matrix stiffness in keloid invasion in vitro, substrates (from 10 kPa to 2 MPa) with covalently conjugated fibronectin were prepared (Figure S2a,b, Supporting Information), ensuring consistent adhesion moiety amounts and densities for cells, regardless of the stiffness (Figure S2c,d, Supporting Information). This evidence concerns the gene FN1 and keloid.