Controlled delivery of proteins and other biologics is a growing medium of therapy for diseases previously untreatable. Here we report a self-assembling, tunable vesicle for the controlled delivery of growth factors and cytokines. Coacervate made of heparin and a biocompatible polycation, PEAD, forms the core of the vesicle; lipids form the membrane of the vesicle. We call this vesicle lipocoacervate (LipCo), which has a high affinity for growth factors and cytokines due to heparin. LipCo is a tunable protein delivery vehicle. The vesicle size is controlled through polymer and salt concentrations. Membrane functionalization enables potential for targeting capabilities with long-term storage through lyophilization. Importantly, the controlled delivery of therapeutics also avoids high toxicity to treated cells in vitro. Here we report on these key principles of LipCo assembly and design.