The present study investigates the use of SiO 2 networks combined with polyurethane prepolymer (PUP) as filler and crosslinker for biological scaffolds. We also studied its effect on the in vitro biostability, the macrophage adhesion/proliferation and the tensile viscoelastic response. The biocomposite was prepared by the simultaneous crosslinking/filling of pericardial extracellular matrix (ECM) with PUP and hydrolysis-condensation of tetraethylorthosilicate (TEOS). This modification was used to regulate some biological and structural features of the tissue engineering scaffold. The PUP—SiO 2 —ECM material shows equivalent viscoelastic response to that densely-crosslinked matrix (either glutaraldehyde or PUP), and equal macrophage adhesion and in vitro biostability that non-crosslinked ECM scaffold.