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Sensitive Electrochemical Detection of Microcystin-LR in Water Samples Via Target-Induced Displacement of Aptamer Associated [Ru(NH3)6]3+
Citation:
Vogiazi, V., A. DelaCruz, E. Varughese, W. Heineman, R. White, AND D. Dionysiou. Sensitive Electrochemical Detection of Microcystin-LR in Water Samples Via Target-Induced Displacement of Aptamer Associated [Ru(NH3)6]3+. ACS ES&T Engineering. American Chemical Society, Washington, DC, 1(11):1597–1605, (2021). https://doi.org/10.1021/acsestengg.1c00256
Impact/Purpose:
The presence of high concentrations of cyanotoxins during harmful blooms of cyanobacteria in sources of drinking water supplies seriously threatens human and environmental health. One of the major challenges to assessing the associated health risks is the development of simple, highly selective, and fast-responding sensors to detect these toxins. Thus far, tremendous efforts and resources have been focused on the removal of anthropogenic pollutants from groundwater and drinking water, but relatively little attention has been given to rapid point-of-care monitoring and quantification of cyanotoxins in surface waters experiencing harmful blooms. This proposal aims to address this urgent need by developing highly-selective and fast-responding sensors for cyanotoxins in sources of drinking water where harmful blooms of cyanobacteria frequently occur. Electrochemical biosensors show similar capabilities as immunoassays such as ELISA, a popular screening test for cyanotoxins. Biosensors may be used as a routine quantitative screening and point-of-use water monitoring, mainly because of their high portability. Electrochemical biosensors are developing rapidly and new sensor applications/technologies on multi-cyanotoxin analysis are expected to emerge to properly assist the assessment of toxicity in real time. Real-time/on-line biosensors will certainly allow fast cyanotoxins detection and efficient drinking water quality control, providing people with clean and safe drinking water and prevent recreational exposure.
Description:
In this study, we demonstrate the successful development of an electrochemical aptamer-based sensor for point-of-use detection and quantification of the highly potent microcystin-LR (MC-LR) in water. The sensor uses hexaammineruthenium(III) chloride ([Ru(NH3)6]3+) as redox mediator, because of the ability of the positively charged (3+) molecule to associate with the phosphate backbone of the nucleic acids. We quantitatively measure the target-induced displacement of aptamer associated, or surface confined, [Ru(NH3)6]3+ in the presence of MC-LR. Upon the addition of MC-LR in the water, surface-confined [Ru(NH3)6]3+ dissociates, resulting in less faradaic current from the reduction of [Ru(NH3)6]3+ to [Ru(NH3)6]2+. Sensing surfaces of highly packed immobilized aptamers were capable of recording decreasing square wave voltammetry (SWV) signals after the addition of MC-LR in buffer. As a result, SWV recorded substantial signal suppression within 15 min of target incubation. The sensor showed a calculated limit of detection (LOD) of 9.2 pM in buffer. The effects of interferents were minimal, except when high concentrations of natural organic matter (NOM) were present. Also, the sensor performed well in drinking water samples. These results indicate a sensor with potential for fast and specific quantitative determination of MC-LR in drinking water samples. A common challenge when developing electrochemical, aptamer-based sensors is the need to optimize the nucleic acid aptamer in order to achieve sensitive signaling. This is particularly important when an aptamer experiences only a small or localized conformational change that provides only a limited electrochemical signal change. This study suggests a strategy to overcome that challenge through the use of a nucleic acid-associated redox label.
URLs/Downloads:
DOI: Sensitive Electrochemical Detection of Microcystin-LR in Water Samples Via Target-Induced Displacement of Aptamer Associated [Ru(NH3)6]3+