Stimuli-responsive DNA hydrogels have shown great potential in sensing applications due to their attractive properties such as programmable target responsiveness, excellent biocompatibility, and biodegradability. In contrast to the extensively developed DNA hydrogel sensing systems based on the stimuli-responsive hydrogel-to-solution phase transition of the hydrogel matrix, the quantitative sensing application of DNA hydrogels exhibiting smart shape deformations has rarely been explored. Moreover, bulk DNA hydrogel-based sensing systems also suffer from high material cost and slow response. Herein, free-standing bilayer polyacrylamide/DNA hybrid hydrogel films with programmable responsive properties directed by the sequence of functional DNA units have been constructed. Compared with bulk DNA hydrogels, these DNA hydrogel films with a thickness at the micrometer scale not only greatly reduce the consumption of DNA materials but also facilitate the mass transfer of biomacromolecular substances within the hydrogel network, thus favoring their sensing applications. Therefore, a target-responsive smart DNA hydrogel film-based sensor system is further demonstrated based on the large amplitude macroscopic shape deformation of the film as a visual signal readout. As a proof of concept, Pb²⁺ or UO₂²⁺ ion-responsive DNA units were introduced into the active layer of the bilayer hydrogel films. In the presence of Pb²⁺ or UO₂²⁺ ions, the occurrence of a cleavage reaction within the DNA units leads to the release of DNA segments from the hydrogel film, inducing a dramatic shape deformation of the film, and thus sensing of Pb²⁺ or UO₂²⁺ ions with high specificity is achieved based on measuring the bending angle changes of these smart free-standing films. These smart DNA hydrogel film sensors with target-programmable responsiveness, simple operation, and ease of storage may hold promise for future rapid on-site testing applications.

中文翻译：

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基于智能独立式双层聚丙烯酰胺/DNA 混合水凝胶薄膜的传感系统，利用弯曲角度的变化作为视觉信号读数

刺激响应性 DNA 水凝胶由于其具有可编程目标响应性、优异的生物相容性和生物可降解性等引人注目的特性，在传感应用中显示出巨大的潜力。与广泛开发的基于水凝胶基质的刺激响应水凝胶到溶液相变的DNA水凝胶传感系统相比，具有智能形状变形的DNA水凝胶的定量传感应用很少被探索。此外，基于大容量 DNA 水凝胶的传感系统还存在材料成本高和响应慢的问题。在此，构建了独立式双层聚丙烯酰胺/DNA杂化水凝胶膜，其具有由功能性DNA单元序列指导的可编程响应特性。与块状DNA水凝胶相比，这些微米级厚度的DNA水凝胶薄膜不仅大大减少了DNA材料的消耗，而且有利于水凝胶网络内生物大分子物质的传质，从而有利于其传感应用。因此，基于薄膜的大幅度宏观形状变形作为视觉信号读出，进一步证明了基于目标响应的智能DNA水凝胶薄膜的传感器系统。作为概念证明，Pb ²⁺或 UO ₂ ²⁺离子响应 DNA 单元被引入双层水凝胶膜的活性层中。在Pb ²⁺或UO ₂ ²⁺离子存在的情况下，DNA单元内发生裂解反应导致DNA片段从水凝胶膜中释放，引起膜的剧烈形状变形，从而感应Pb通过测量这些智能自支撑薄膜的弯曲角度变化，实现了高特异性的²⁺或 UO ₂ ²⁺离子。这些智能 DNA 水凝胶薄膜传感器具有目标可编程响应能力、操作简单且易于存储，可能为未来的快速现场测试应用带来希望。