Abstract：
Strontium-90 (90Sr) is a major radioactive component that has attracted great attention, but its detection remains challenging since there are no specific energy rays indicative of its presence. Herein, a biosensor that is capable of rapidly detecting Sr2+ ions is demonstrated. Simple colorimetric method for sensitive detection of Sr2+ with the help of single-stranded DNA was developed by preparing MnO2 nanorods as oxidase mimic catalysis 3,3\',5,5\'-tetramethylbenzidine (TMB). Under weakly acidic conditions, MnO2 exhibited a strong oxidase-mimicking activity to oxidize colorless TMB into blue oxidation products (oxTMB) with discernible absorbance signals. Nevertheless, the introduction of a guanine-rich DNA aptamer inhibited MnO2-mediated TMB oxidation and reduced oxTMB formation, resulting in blue fading and diminished absorbance. Upon the addition of strontium ions to the system, the aptamers formed a stable G-quadruplex structure with strontium ions, thereby restoring the oxidase-mimicking activity of MnO2. Under the best experimental conditions, the absorbance exhibits a linear relationship with the Sr2+ concentration within the range 0.01-200 μM, with a limit of detection of 0.0028 µM. When the concentration of Sr2+ from 10-8 to 10-6 mol L-1, a distinct color change gradient could be observed in paper-based sensor. We successfully applied this approach to determine Sr2+ in natural water samples, obtaining recoveries ranging from 97.6 to 103% with a relative standard deviation of less than 5%. By providing technical solutions for detection, our work contributed to the effective monitoring of transportation of radioactive Sr in the environment.
摘要：
锶-90(90Sr)是引起人们极大关注的主要放射性成分,但它的检测仍然具有挑战性，因为没有特定的能量射线表明它的存在。在这里，证明了能够快速检测Sr2离子的生物传感器。通过制备MnO2纳米棒作为氧化酶模拟催化3,3'，开发了借助单链DNA灵敏检测Sr2的简单比色法，5,5'-四甲基联苯胺(TMB)。在弱酸性条件下,MnO2表现出强的氧化酶模拟活性，可将无色TMB氧化为蓝色氧化产物（oxTMB），并具有可辨别的吸光度信号。然而，引入富含鸟嘌呤的DNA适体抑制了MnO2介导的TMB氧化并减少了oxTMB的形成，导致蓝色褪色和吸光度降低。在系统中加入锶离子后，适体与锶离子形成稳定的G-四链体结构，从而恢复MnO2的氧化酶模拟活性。在最佳实验条件下,吸光度在0.01-200μM范围内与Sr2浓度呈线性关系，检出限为0.0028µM。当Sr2+浓度从10-8到10-6molL-1时，在纸基传感器中可以观察到明显的颜色变化梯度。我们成功地将这种方法应用于天然水样中的Sr2+的测定,获得的回收率范围为97.6至103％，相对标准偏差小于5％。通过为检测提供技术解决方案，我们的工作有助于有效监测放射性Sr在环境中的运输。
