Photodegradable hydrogels for external manipulation of cellular microenvironments with real-time monitoring

With the rapid progress of tissue engineering and regenerative medicine, the cell-friendly construction of a 3D extracellular matrix in a precisely controlled manner is needed. This biomimicry of the native extracellular matrix replicates major aspects of the native cellular microenvironment. Herein, we design a polyethylene glycol (PEG) based hydrogel combined with caging chemistry, which could achieve lighttriggered local control of the hydrogel. The crosslinking density of the hydrogel could be tuned with UV exposure by decomposing the structure of the hydrogel. Meanwhile, by introduction of the releasable Rhodamine 110 molecule, we could conveniently monitor the change of the crosslinking density of the hydrogels via fluorescence. By this approach, adjustable user-defined stiffness patterns with different fluorescence intensity in a range of soft tissue microenvironments have been obtained. This novel hydrogel design could be useful for the manipulation of cell fate in various other contexts.