Applying Computational Protein Design to Engineer Affibodies for Affinity-controlled Delivery of Vascular Endothelial Growth Factor and Platelet-Derived Growth Factor

Vascular endothelial growth factor (VEGF) and platelet-derived growth factor (PDGF) play coordinated roles in angiogenesis. However, current biomaterial delivery vehicles for these proteins have a limited ability to precisely control the kinetics of protein release, preventing systematic exploration of their temporal effects. Here, we combined yeast surface display and computational protein design to engineer eight VEGF-specific and PDGF-specific protein binders called affibodies with a broad range of affinities for controlled protein release. Soluble affibodies modulated protein bioactivity as evidenced by changes in VEGF-induced endothelial cell proliferation and luminescent output of a PDGF-responsive cell line. Affibody-conjugated hydrogels enabled tunable protein release over 7 days. VEGF and PDGF released from affibody-conjugated hydrogels exhibited higher bioactivity than proteins released from hydrogels without affibodies, suggesting that these engineered affinity interactions could prolong protein bioactivity. This work underscores the power of computational protein design to enhance biomaterial functionality, creating a platform for tunable protein delivery.