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.

中文翻译：

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具有可调节机械性能的可逆水凝胶，用于光学控制细胞迁移

合成水凝胶广泛用作体外仿生对系统进行建模，以了解细胞如何响应复杂的微环境。水凝胶的机械性能对许多细胞行为（包括细胞迁移，扩散和分化）具有决定性作用。然而，对水凝胶进行工程设计以重新获得天然细胞外基质的动态机械性能仍然是一项重大挑战。在这里，我们提供了一种具有时空可调机械性能的新型水凝胶平台，可用于分析和定义光下的细胞行为。水凝胶的机械性能变化是由交联剂荧光蛋白Dronpa145N在四聚体和单体状态之间进行光诱导的转换而引起的，这对水凝胶的化学性能影响很小。如流变学测量和基于原子力显微镜的纳米压痕所证实的，可以使用可见光快速且可逆地调节多个循环的机械性能。我们进一步证明了通过光诱导的刚度转换在水凝胶上实时且可逆地调节细胞迁移行为，并且对侵入细胞的侵袭最小。具有可编程机械历史和空间定义的机械等级的水凝胶可以作为理想的模型系统，以更好地理解复杂的细胞功能。对培养细胞的侵袭极小。具有可编程机械历史和空间定义的机械等级的水凝胶可以作为理想的模型系统，以更好地理解复杂的细胞功能。对培养细胞的侵袭极小。具有可编程机械历史和空间定义的机械等级的水凝胶可以作为理想的模型系统，以更好地理解复杂的细胞功能。