Cavendish Laboratory, University of Cambridge, Cambridge CB3 0HE, United Kingdom;
Cavendish Laboratory, University of Cambridge, Cambridge CB3 0HE, United Kingdom.
Proc Natl Acad Sci U S A. 2018 Aug 7;115(32):8137-8142. doi: 10.1073/pnas.1722206115. Epub 2018 Jul 25.
A key objective in DNA-based material science is understanding and precisely controlling the mechanical properties of DNA hydrogels. We perform microrheology measurements using diffusing wave spectroscopy (DWS) to investigate the viscoelastic behavior of a hydrogel made of Y-shaped DNA (Y-DNA) nanostars over a wide range of frequencies and temperatures. We observe a clear liquid-to-gel transition across the melting temperature region for which the Y-DNA bind to each other. Our measurements reveal a cross-over between the elastic [Formula: see text] and loss modulus [Formula: see text] around the melting temperature [Formula: see text] of the DNA building blocks, which coincides with the systems percolation transition. This transition can be easily shifted in temperature by changing the DNA bond length between the Y shapes. Using bulk rheology as well, we further show that, by reducing the flexibility between the Y-DNA bonds, we can go from a semiflexible transient network to a more energy-driven hydrogel with higher elasticity while keeping the microstructure the same. This level of control in mechanical properties will facilitate the design of more sensitive molecular sensing tools and controlled release systems.
DNA 基材料科学的一个主要目标是理解和精确控制 DNA 水凝胶的机械性能。我们使用扩散波谱（DWS）进行微流变测量，以研究 Y 型 DNA（Y-DNA）纳米星水凝胶在很宽的频率和温度范围内的粘弹性行为。我们观察到在 Y-DNA 相互结合的融解温度区域发生了明显的从液体到凝胶的转变。我们的测量结果揭示了在 DNA 构建块的融解温度 [Formula: see text] 周围，弹性 [Formula: see text] 和损耗模量 [Formula: see text] 之间的交叉，这与系统的逾渗转变相吻合。通过改变 Y 型之间的 DNA 键长，可以很容易地在温度上移动这个转变。我们还使用体流变学进一步表明，通过降低 Y-DNA 键之间的灵活性，我们可以在保持相同微观结构的情况下，从半刚性瞬变网络转变为更具弹性的、更多能量驱动的水凝胶。这种机械性能的控制水平将有助于设计更灵敏的分子传感工具和控制释放系统。
