Modulating Protein Activity in Tissue Repair using Engineered Affinity-based Biomaterials

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PROJECT SUMMARY Coordinated protein signaling is required to orchestrate many functions in the body. During tissue repair, the spatiotemporal presentation of proteins in the injury site affects protein-receptor binding, downstream cellular responses, and overall healing outcomes. Many biomaterials have been designed to deliver proteins to treat injured tissues. However, few biomaterials can independently control the delivery of multiple proteins from a single material, limiting their utility for delivering numerous proteins involved in the natural wound healing cascade. One strategy to control protein delivery is the use of affinity-based biomaterials, which employ non- covalent affinity interactions between proteins and materials. My lab is developing affinity-based biomaterials to enhance tissue repair by determining how the timing and local presentation of complex combinations of proteins affect regenerative processes. Our objective is to develop new biomaterial tools to understand how protein- material affinity interactions impact protein release and activity, modulate complex healing responses, and interrogate the role of protein presentation in tissue repair. We will tackle two critical knowledge gaps that have hindered the development of effective biomaterials for protein delivery: 1) How do protein-material affinity interactions affect protein release and activity? 2) How does biomaterial-based control over protein presentation affect tissue repair? Our innovative approach involves engineering new protein-material affinity interactions using directed evolution and rational protein design. Yeast surface display will be used to evolve small protein domains (i.e., affibodies) that bind to proteins of interest with high specificity and a wide range of affinities. Computational modeling will be used to design affibodies that interact with different areas of the protein to inhibit or maintain protein-receptor binding. The resulting expansive array of affibodies will allow us to determine how protein- material affinity interactions affect protein release and activity over different timescales. Affibodies will be conjugated onto biomaterials to tune protein release and cellular responses. Using our library of affinity-based biomaterials, we will systematically investigate how the temporal presentation of multiple proteins affects the rate and quality of tissue repair. We will implant biomaterials to restore key aspects of the healing response by 1) using moderate affinity affibodies to provide sustained delivery of exogenous proteins to the injury site and 2) using high affinity affibodies to sequester endogenous proteins within the injury site and enhance, maintain, or inhibit protein activity. While our approach is flexible and tissue-agnostic, we will first test it in a bone injury model, which is a central area of expertise in my lab. By replicating the complex protein presentation of the wound healing cascade, we will gain new insights into the roles of many proteins that govern tissue repair and create a new class of highly modular biomaterials that can be tailored to orchestrate cellular responses to treat multiple types of injuries. Our approach will have an immediate benefit to society through the creation of a transformative new regenerative medicine strategy with the potential to significantly improve tissue repair.