Hence, collagen I deposition by dermal fibroblasts was found to be more extensive on HD-30 PSPMA brushes coated with BMP2, compared to sparser brushes or uncoated brushes. This implies that brushes displaying higher densities of BMP2 promote collagen matrix deposition. Furthermore, the densely negatively charged surface of PSPMA brushes is intrinsically conducive to the adsorption of basic collagen I molecules (with an IP of 8-9 ) and this protein was previously found to adsorb strongly at the surface of PSPMA brushes . In addition to such direct mechanisms, BMP2 is known to bind ECM proteins such as fibronectin . Fibronectin fibre networks are in turn considered to be preliminary to the assembly of more complex ECM fibrous networks and were reported to precede the assembly of collagen I fibres . Examination of ECM fibres deposited at the surface of polymer brushes confirmed the abundance of rich and dense fibronectin fibre networks (Figure and Supplementary Figure ). Unlike collagen I, fibronectin was not previously found to adsorb to PSPMA brushes , owing to its relatively low IP (near 6 ). In agreement with this lack of direct interaction, relatively sparse fibronectin matrices were observed at the surface of all types of PSPMA brushes, with fibronectin density overall remaining low and relatively high gaps between fibronectin fibres (Supplementary Figure ). However, fibronectin adsorption was found be significantly enhanced by the presence of BMP2 at the surface of PSPMA brushes, resulting in denser fibre mats (Supplementary Figure ). In turn, the collagen fibres assembled at the surface of BMP2-coated PSPMA brushes, in particular with high density and thickness, were both more abundant and more tightly assembled.