DNA‐Responsive Polyisocyanopeptide Hydrogels with Stress‐Stiffening Capacity

Biological materials have evolved to combine a number of functionally relevant properties. They are sensitive to chemical and mechanical signals and respond to these signals in a highly specific manner. Many biological hydrogels possess the ability to stress‐stiffen, a property that is difficult to mimic in synthetic systems. A novel synthetic hydrogel is described that possesses stress‐stiffening behavior in the biologically relevant stress regime and, at the same time, contains DNA cross‐links as stimuli‐responsive elements. The hydrogel scaffold is composed of oligo(ethylene glycol)‐functionalized polyisocyanopeptides (PIC), which show a sol‐to‐gel transition upon increasing the temperature. It is shown that the mechanical properties of the hybrid hydrogel depend on DNA cross‐linker concentration and temperature. At high temperature, a hydrophobically bundled stress‐stiffening PIC network forms. By contrast, gel formation is controlled by DNA cross‐linking at temperatures below the PIC sol‐to‐gel transition. The DNA cross‐linked hydrogel also exhibits stress‐stiffening behavior and its properties are controlled by the DNA cross‐linker concentration. The hydrogel properties can further be tuned when using DNA cross‐linkers with different melting temperature or when breaking cross‐links by strand displacement. This clearly shows the potential of DNA cross‐links as stimuli‐responsive elements, highlighting the possible applications of this hybrid hydrogel as a new sensor.