The invention provides a highly versatile system to promote vascularization in ischemic tissue. The system is composed of a fully defined, customizable hydrogel loaded with a potent cocktail of proangiogenic growth factors. The hydrogel's mechanical, degradation, and factor release behavior can be tailored to the specifications of any given target tissue or ischemic disease state. The growth factor cocktail can be optimized for maximal vessel density or size to meet the perfusion specifications required by the tissue. The embodiments of the disclosure concern methods and compositions of the system, with examples of preparation for both injectable and implantable delivery modes.