The present invention relates to the production of endothelialized matrices and materials from immature endothelial cells using substrates to which particular peptides have been grafted. The resultant substrates can be used to capture and support immature endothelial cells. Further, the methods and compositions of the present invention provide viable cell delivery platforms that allow for production and provision of endothelialized medical devices and implants, including vascular grafts, stents, shunts, and valves, endothelialized surfaces and channels for in vitro testing devices, including microfluidic chips, and materials that support vascularization such as for use in engineered tissues. The present invention includes novel methods required for the successful production of cellularized substrates, systems and components used for the same, and methods of using the resultant cell and tissue compositions.