While most chemical bonds weaken under the action of mechanical force (called slip bond behavior), nature has developed bonds that do the opposite: their lifetime increases as force is applied. Most attention has been given to biological catch bonds in adhesive contacts, where they play a crucial role, for example, in the rolling of leukocytes at conditions of high stresses. However, more recently, catch bonds have been found also in the cytoskeleton of cells, which raises the question what their role is in the mechanoresponse of filamentous networks. In this presentation I will first show computer simulations that show how polymer networks crosslinked with either slip or catch bonds respond to mechanical stress. Our results reveal that catch bonding may be required to protect dynamic networks against fracture, in particular for mobile linkers that can diffuse freely after unbinding. While mobile slip bonds lead to networks that are very weak at high stresses, mobile catch bonds accumulate in high stress regions and thereby stabilize cracks, leading to a more ductile fracture behavior. This allows cells to combine structural adaptivity at low stresses with mechanical stability at high stresses. In the second part of the talk, I will highlight our recent, combined numerical and experimental, efforts to create synthetic catch bonds based on DNA nanotechnology. REFERENCES [1] J. Ruiz-Franco, J. Tauber, J. van der Gucht, Cross-linker Mobility Governs Fracture Behavior of Catch-Bonded Networks, Physical Review Letters 130, 118203 (2023). [2] M. van Galen, A. Bok, T. Peshkovsky, J. van der Gucht, B. Albada, J. Sprakel, De novo DNA-based catch bonds. Submitted.