G-quadruplex DNA-based colorimetric biosensor for the ultrasensitive visual detection of strontium ions using MnO.sub.2 nanorods as oxidase mimetics

• Published in: Mikrochimica acta (1966) Vol. 191; no. 4
• Main Authors: Chen, Yiting, Gong, Chunhui, Chen, Kaiwei, Wang, Ziwei, He, Manli, Wang, Peng, Chen, Kai
• Format: Journal Article
• Language: English
• Published: Springer 01.04.2024
• Subjects: DNA; Genetic research; Oxidases; Sensors; Strontium
• ISSN: 0026-3672
• DOI: 10.1007/s00604-024-06293-5

Strontium-90 (.sup.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 Sr.sup.2+ ions is demonstrated. Simple colorimetric method for sensitive detection of Sr.sup.2+ with the help of single-stranded DNA was developed by preparing MnO.sub.2 nanorods as oxidase mimic catalysis 3,3',5,5'-tetramethylbenzidine (TMB). Under weakly acidic conditions, MnO.sub.2 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 MnO.sub.2-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 MnO.sub.2. Under the best experimental conditions, the absorbance exhibits a linear relationship with the Sr.sup.2+ concentration within the range 0.01-200 M, with a limit of detection of 0.0028 µM. When the concentration of Sr.sup.2+ from 10.sup.-8 to 10.sup.-6 mol L.sup.-1, a distinct color change gradient could be observed in paper-based sensor. We successfully applied this approach to determine Sr.sup.2+ 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. Graphical abstract