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Plant-Based Sensor Detects Arsenic Levels in Real Time

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Dec 14 2020

Scientists have designed a novel living plant-based sensor that can detect and track arsenic levels in the soil in real time.

*Food crops can be contaminated with arsenic through water, given that the chemical is naturally present at high levels in groundwater in certain areas. Image Credit: Mufid Majnun from Pixabay.*

Arsenic is known to be a highly noxious heavy metal. In fact, arsenic pollution is a significant threat to human beings and ecosystems in several Asia-Pacific nations.

According to the World Health Organization (WHO), food preparation, drinking water and irrigation of food crops contaminated with arsenic present the greatest threat to public health, because high concentrations of this toxic chemical naturally exist in the groundwater of many countries.

Detecting arsenic level in the soil is important to ensure minimal contamination of our food chain. If we can have a convenient way to measure arsenic concentration in the soil in real time, we would be able to take preventive measures to keep arsenic level at the minimum, strengthening our food safety.

Tedrick Thomas Salim Lew, Study Co-Author and Graduate Student, Massachusetts Institute of Technology

The study was recently published in the Advanced Materials journal on November 26^th, 2020.

Investigators from Disruptive and Sustainable Technologies for Agricultural Precision (DiSTAP), an Interdisciplinary Research Group at the Singapore-MIT Alliance for Research and Technology (SMART)—Massachusetts Institute of Technology (MIT)’s research enterprise based in Singapore—designed nanoparticles to identify arsenic and then integrated these nanoparticles inside the leaf tissue of a plant.

We show that the combination of the living plant and embedded sensor can function as the most sensitive detector for this toxic molecule available today. We used a molecular recognition technology that allows the surface of the nanoparticle to bind to the specific chemistry of the arsenic like a lock and key. The binding changes the near-infrared fluorescence of the sensor which can be picked up even on a cell phone camera.

Michael Strano, Study Co-Author and Lead Principal Investigator, SMART DiSTAP

The innovative nano-bionic optical sensor offers considerable benefits over traditional techniques used to quantify the presence of arsenic in the environment.

According to the investigators, one point of novelty is that since the sensor is very small, it can be integrated into certain parts of the plant cell to accurately quantify the uptake and metabolism of arsenic and this sensor can also detect arsenic concentrations down to 0.2 parts per billion (ppb).

Our approach made use of plants’ natural ability to take up arsenic to convert them into a living sensor that can sample their environment autonomously. This approach enables arsenic monitoring in real time and in a non-destructive manner (i.e. no plant needs to be sacrificed to extract arsenic from its tissue).

Tedrick Thomas Salim Lew, Study Co-Author and Graduate Student, Massachusetts Institute of Technology

“Conventional approaches rely on regular sampling of the soil and extensive purification, followed by analysis by bulky and expensive lab instruments such as mass spectrometer, which requires long time delay, high cost and non-portable instrumentation,” Lew further added.

Several common agricultural products, like rice, tea leaves and vegetables, contain arsenic as a contaminant. According to a new study, a few scientists have estimated that rice containing inorganic arsenic can give rise to more than 50,000 avoidable premature deaths every year.

The team integrated their newly developed arsenic sensors into rice plants and successfully tracked the levels of arsenic inside the rice plant and also in the root environment each second.

“New sensor technologies for arsenic, especially those that measure uptake within the living plant directly, can help with this problem in many ways. As a laboratory tool, our sensor technology can help plant biologists to breed rice plants that can resist arsenic. As a technology for the field, the sensors can form the basis for monitoring water supplies to remediate or address the problem of contaminated water,” explained Strano.

Humans subjected to prolonged exposure to arsenic can experience many negative health effects, including cardiovascular diseases, like heart attack, birth defects, diabetes, severe skin lesions, and different types of cancers, such as the skin, lung and bladder cancers, reports the WHO.

“However, despite much investment in research, there has been limited progress towards real-time monitoring of arsenic in the field. The plant nano-bionic sensors seem to fill this gap by enabling detection of arsenic at ppb levels in soils and potentially in water as well,” stated Ravi Naidu, CEO and managing director of the Cooperative Research Centre for Contamination Assessment and Remediation of the Environment at the University of Newcastle in Australia.

“While it may take several days to quantify arsenic using such a sensor, it is nevertheless a massive step forward in field monitoring of this dangerous toxin,” stated Naidu.

The team has now collaborated with the Singapore government and other stakeholders to bring this novel technology to numerous users and, according to them, these sensors will be economical for agricultural end-users and will help enhance the quality and yield of crops.