Presentation of active morphogens (e.g. soluble growth factors) in three-dimensional matrices is crucial towards the development of effective regenerative therapies addressing the fact that soluble growth factors quickly diffuse away from the site of interest and may exhibit different functional profiles when immobilized. Therefore we investigate how the efficiency of growth factor signaling could be modulated by immobilization to heparin-starPEG networks. For this, selected factors (e.g. bFGF and VEGF) are coupled to these matrices in different concentrations and via distinct mechanisms such as electrostatic interactions or physical entrapment in the gel. Characterization of loading and subsequent release is performed with the help of common analytical methods (e.g. fluorescence or radio labelling, amino acid analysis by hydrolysis followed by HPLC-analysis, and enzyme-linked immunosorbent assay [ELISA]).