The need to control bleeding and bind damaged tissues represents a pressing and significant clinical need in the arenas of surgery, trauma, and emergency response medicine. Exsanguination remains the second most prevalent cause of death (27-39%) due to traumatic and polytrauma injury, with 34% of these deaths in the prehospital (e.g. ambulatory) setting. These numbers have persisted despite substantial efforts to develop and deploy synthetic systems that rapidly stem blood loss. The natural hemostatic system (fibrinogen/fibrin), while highly evolutionarily conserved and successful in modest injury situations, critically fails in situations of major hemorrhaging trauma and polytrauma, in part due massive dilution effects, inability to concentrate critical factors, and failure to generate tissue compressive forces during polymerization. In this proposal, our objective is to couple two enabling technologies, i) rationally designed, multivalent fibrin knob peptides, which bind the clotting factor fibrinogen and ii) stimuli-responsive microgels that display triggered assembly into swelling hydrogel assemblies, and to explore the dynamic range of these highly novel fibrinogen (i.e. wound) -triggered microgel assemblies. Our central hypothesis is that stimuli-responsive microgels displaying knob peptides will undergo fibrinogen-initiated assembly into networks that are controlled by the composition of the microgel (ie. peptide density, chain length, crosslinking) and peptide (ie. affinity and multivalency) constituents. To test this hypothesis we will first quantify the binding affinities of engineered synthetic fibrin knob peptides to fibrinogen (Specific Aim 1). Then, following the coupling of said fibrin knob peptides to stimuli-responsive microgels, perform micro-rheological studies to characterize the bio-synthetic hybrid matrix assembly (Specific Aim 2). Coupling our knob peptides, which are capable of sensing fibrinogen and fibrin, with stimuli-responsive microgels, which are capable of responding via rapid self-assembly into gel matrices, represents a highly innovative approach to hemorrhaging traumatic wounds. The benefit of the technology developed as a consequence of this study is the creation of a hemostatic system that is capable of both concentrating clotting factors and generating compressive forces through triggered swelling, thus serving patients in need of radical hemorrhage control following trauma and polytrauma.