Synthetic biology has transformed how cells can be reprogrammed, providing a means to reliably and predictably control cell behavior with the assembly of genetic parts into more complex synthetic gene circuits. Using these approaches, we are programming stem cells with novel genetic tools to control genes and pathways that result in changes in their native function for desired outcomes. We have shown that megakaryocytes, the progenitor cells for platelets, can be loaded with non-native proteins to produce engineered platelets that can function as local and systemic delivery devices.