Angiogenesis underlies almost all biological processes of morphogenesis, including those in tissue repair and regeneration. Physiological angiogenesis is controlled by a complex interplay between cells and their environment: the extracellular matrix (ECM) provides signaling via numerous ECM adhesion molecules and growth factors bound to ECM polysaccharide components; and cells locally degrade and remodel the ECM to create pores into which angiogenic endothelial cells migrate during sprouting. Under physiological conditions, most of the signaling is provided by the solid phase, whether from the ECM as mentioned above or from contact with other endothelial cells (ECs). This observation, that physiological angiogenesis proceeds in response to ECM-bound cues, motivates our approach: to create materials that are bioresponsive (to cell-associated environmental signals such as extracellular proteases and endoglycosidases), that are bioactive (by virtue of bound peptide or recombinant protein adhesion ligands and growth factors), and that are injectable to be consistent with surgical practice in humans and capable of carrying cellular therapeutics.