Stimuli-responsive polymers are capable of reacting to an external trigger. We report self-regulated, enzymatically active, and pH-responsive hydrogels that show dynamic behavior without an external trigger. This is enabled by a feedback loop between the enzymatic conversion of glucose into gluconic acid and the pH-induced volume phase transition that leads to a modulation in glucose permeability. The synthesized hydrogel spheres combine all required properties for sustained oscillation including enzymatic activity, switchable reactivity, hysteresis in volume phase transition and feedback between the reaction and permeation. A simple model of the system identified possible operating points where sustained oscillations are possible. Experiments at these operating points revealed that the system is able to perform a self-regulated oscillation cycle under a constant nutrient supply. A sensitivity analysis showed that the system is especially sensitive around the point of oscillation, so that precise control of the process parameters is essential to achieve sustained oscillations.

中文翻译：

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促进酶活性水凝胶球体中的协同振荡

刺激反应性聚合物能够对外部触发物起反应。我们报告自我调节，酶活性和pH响应水凝胶显示动态行为而无需外部触发。这是通过葡萄糖酶促转化为葡萄糖酸与pH诱导的体积相变之间的反馈回路实现的，该相变导致葡萄糖渗透性的调节。合成的水凝胶球具有持续振荡所需的所有特性，包括酶活性，可转换的反应性，体积相变中的滞后以及反应和渗透之间的反馈。系统的简单模型确定了可能发生持续振荡的可能工作点。在这些工作点进行的实验表明，该系统能够在恒定的养分供应下执行自调节的振荡周期。灵敏度分析表明，该系统在振荡点附近特别敏感，因此精确控制过程参数对于实现持续振荡至关重要。