Reversible hydrogels with tunable mechanical properties for optically controlling cell migration
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Synthetic hydrogels are widely used as biomimetic in vitro model systems to understand how cells respond to complex microenvironments. The mechanical properties of hydrogels are deterministic for many cellular behaviors, including cell migration, spreading, and differentiation. However, it remains a major challenge to engineer hydrogels that recapture the dynamic mechanical properties of native extracellular matrices. Here, we provide a new hydrogel platform with spatiotemporally tunable mechanical properties to assay and define cellular behaviors under light. The change in the mechanical properties of the hydrogel is effected by a photo-induced switch of the cross-linker fluorescent protein, Dronpa145N, between the tetrameric and monomeric states, which causes minimal changes to the chemical properties of the hydrogel. The mechanical properties can be rapidly and reversibly tuned for multiple cycles using visible light, as confirmed by rheological measurements and atomic force microscopybased nano-indentation. We further demonstrated real-time and reversible modulation of cell migration behaviors on the hydrogels through photo-induced stiffness switching, with minimal invasion to the cultured cells. Hydrogels with a programmable mechanical history and a spatially defined mechanical hierarchy might serve as an ideal model system to better understand complex cellular functions.
KeywordsDronpa photo-responsive hydrogel mechanical properties cell migration artificial extracellular matrix
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We thank Dr. W. Meng for his initial experiments on this project. This work is funded by the National Natural Science Foundation of China (Nos. 21522402, 21474003, 91427304, 11372279, 11572285, 11674153, 11374148, and 11334004), the Fundamental Research Funds for the Central Universities (Nos. 020414380070 and 020414380058), the National Basic Research Program of China (Nos. 2012CB921801 and 2013CB834100) and the National High-tech R&D Program of China (No. 2015AA020941).
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