Sensor built into plant tissue tracks arsenic levels in real time
Like many heavy metals, arsenic can contaminate soil and groundwater as a byproduct of mining operations, and this poses all kinds of threats to human health and the environment. A novel type of biosensor could help us negate the risks of this highly toxic chemical element, by working with plants to monitor levels of it in the underground environment in real time.
In 2018 we looked at an interesting research project investigating how aquatic moss could be used to clean arsenic from contaminated waterways. This new technology, developed by a team of scientists from the Singapore-MIT Alliance for Research and Technology, also looks to leverage the natural ability of some plant species to absorb arsenic, but pairs them with nanoscale optical sensors to offer real time readings of the concentrations of the element beneath the surface.
The work focuses on changes to the internal dynamics of a plant's tissue as arsenic is taken up from the soil, which sees the plant extract analytes and transport them via their root systems. Embedded in this plant tissue, the optical nanosensors show changes in the intensity of their fluorescence depending on the arsenic uptake of the plant. Paired with portable electronics, such as a Raspberry Pi platform and camera, the system can offer a real-time look at concentrations of the heavy metal in the soil.
“Our plant-based nanosensor is notable not only for being the first of its kind, but also for the significant advantages it confers over conventional methods of measuring arsenic levels in the below-ground environment, requiring less time, equipment, and manpower," says study author Salim Lew. "We envision that this innovation will eventually see wide use in the agriculture industry and beyond.”
To demonstrate how the technology could be used to prevent contamination of edible crops, the team was able to use this technique to detect arsenic in rice and spinach. They then turned their attention to a fern species called Pteris cretica, which has an ability to absorb and tolerate large amounts of arsenic.
This offered a platform for the team to develop an ultra-sensitive arsenic detector that could pick up very low concentrations of the metal, as low as 0.2 parts per billion. This is far below the maximum contaminant level of 10 parts per billion for municipal water supplies, as determined by the US FDA.
“This is a hugely exciting development, as, for the first time, we have developed a nanobionic sensor that can detect arsenic – a serious environmental contaminant and potential public health threat,” says co-lead principal investigator, and MIT Professor Michael Strano. “With its myriad advantages over older methods of arsenic detection, this novel sensor could be a game-changer, as it is not only more time-efficient, but also more accurate and easier to deploy than older methods.”
The research was published in the journal Advanced Materials.