Engineering Highly Cellularized Living Materials via Mechanical Agitation

Abstract Engineered living materials with high cell density are important in various applications such as hemostasis, tissue engineering, organoids, and biofabrication. However, it remains challenging to modulate the structure and mechanics of these highly cellularized living materials, while preserving cell viability and functionality. Here a mechanical strategy is reported to engineer living materials with cell densities as high as 1 billion cells per milliliter, without altering chemical and cellular compositions. Using blood clots as a clinically relevant model, mechanical agitation is shown to enables precise tuning a wide range of clot properties, including stiffness, toughness, contraction, and lysis. Notably, agitation can enhance the elastic modulus and fracture toughness of clots by up to fourfold compared to those degraded by agitation. Combined experimental and computational studies demonstrate that agitation‐induced 3D cell organization governs the macroscopic mechanical responses. In vitro cell culture and in vivo animal experiments further validate the safety and efficacy of this strategy. Furthermore, the strategy is applicable to various hydrogels and cellular inclusions such as red blood cells, fibroblasts, and microgels. This work offers new avenues for engineering living materials, with technological implications for biofabrication, tissue engineering, and treatments for blood clot‐related diseases.