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Environmental pollution has become a significant global concern for public health, the economy, and society. The presence of organic pollutants, heavy metals in the soil, ingestion of pesticides adhered to the fruits and vegetables, and the effect of pathogens and their toxins are considered seriously detrimental environmental issues. This article focuses on the recent advances of DNA-nanosensors for environmental monitoring that help keep track of contaminants more efficiently.
One of the major problems that require routine monitoring is water-borne pathogens, such as Cryptosporidium parvum. This pathogen contaminates drinking water and causes serious health complications even at a low concentration.
To avoid the occurrence of harmful environmental microorganisms, several healthcare agencies, regulatory agencies, and industrial sectors conduct routine monitoring to prevent harmful pathogen contaminations. However, these environmental sectors require more sophisticated diagnostic systems or test kits that are more sensitive, portable, and cost-effective.
Nanoscience researchers have successfully created highly sensitive pathogen diagnostics kits, nanobiosensors, and advanced imaging techniques with greater sensitivity and reliability. More recently, DNA-nanosensors are used to detect harmful microbial contaminants, toxins, and antibiotics. Some of the recent applications of DNA-nanosensors for environmental monitoring are discussed below.
Detection of Pathogens
Contamination of water and food products has become a global problem. Therefore, early detection of harmful microbial pathogens such as bacteria, fungi, and viruses at the lowest possible concentration is extremely essential to prevent contagious disease outbreaks, epidemics, or even pandemic-like situations.
DNA-nanosensors detect various pathogenic microorganisms such as Bacillus subtilis, Vibrio cholera, Aspergillus sp, Escherichia coli, methicillin-resistant Staphylococcus aureus (MRSA), and Candida sp. Researchers explained that in detecting water-borne microbe V. cholera, the DNA- nanosensor recognizes the O1 OmpW gene with two DNA probes. One of the most common DNA-nanosensors used for the detection of microorganisms is AuNP-based DNA nanosensors.
MRSA imparts antibiotic resistance due to the presence of a gene responsible for the production of penicillin-binding protein and mecA. The carboxyfluorescein DNA aptamer nanosensors detect these targeted sites to determine MRSA.
Detection of Antibiotics
The overuse of antibiotics in animal farms are extremely hazardous to humans and animals. The detection of contaminating antibiotics is essential for the animal farming industry and the industry that produces antibiotics. DNA-nanosensors are used for the identification of different antibiotics in complex biological medium and water. Detection of ofloxacin in water and synthetic urine samples is carried out using aptamer-AuNP nanosensors.
The detection of kanamycin present in pork meat and chicken liver is carried out using DNA aptamer-based nanosensors. Ampicillin in the human serum, milk samples, and river water is found by aptamer-nanosheet–gold electrode nanosensor.
This DNA based nanosensor is also used to detect carbendazim in commercially available orange juice and lettuce. The electrochemical DNA aptamer-based nanosensors are highly sensitive, rapid, specific, and cost-effective multiplexed analytical tools to detect various antibiotics.
Detection of Pesticides
As pesticide ingestion is extremely harmful to humans, food safety standards warrant sophisticated and sensitive means to detect pesticides. DNA-based nanosensors detect pesticides such as carbamates, triazines, organophosphorus, and neonicotinoids. The presence of acetamiprid in celery and green tea leaves is analyzed using a colorimetric DNA nanosensor. A single-stranded DNA aptamer-AgNPs nanosensors can sense organophosphate pesticides such as phorate.
Detection of Metals and Heavy Metals
The quality and quantity of agricultural produce are affected due to the presence of heavy metals such as chromium, lead, arsenic, cadmium, and mercury.
These metals disturb human metabolomics and cause considerable damage to organs. Exposure to a high concentration of heavy metals can even cause serious illness that can lead to death. Researchers have reported that heavy metal accumulation in a Chinese village was found in more than 250 vegetables, causing severe health issues. In humans, heavy metals such as chromium and lead cause non-cancerous health risks, while cadmium causes various cancer types. DNA aptamer-based nanosensors are used in the detection of arsenic (III).
Silver ions (Ag+) have a high affinity for cytosine-rich DNA, which is used to design DNA-nanosensors for visual detection of Ag+ in the river and tap water samples. Similarly, for the detection of Ag+ in the drinking water, a Kelvin Probe Force Microscopy-based DNA nanosensor is used. To detect mercury (Hg2+), the affinity of the thiamine-rich oligonucleotide for Hg2+ that ultimately prevents DNA elongation is used in the detection process. Lead and copper are toxic heavy metal pollutants that are commonly present in natural water. These heavy metals are often found using quantum dot-labeled DNAzymes nanosensors.
Detection of Other Toxic Pollutants
The presence of explosives, toxins, and contaminant dyes are found using DNA-nanosensors.
The detection of Fluorogenic Rhodamine B dye and Bisphenol A is conducted using DNA aptamer-based nanosensors.
Dopamine can be identified by DNA-CuNPs nanosensors. Chitosan carbon dot electrode immobilized with DNA detects the presence of mutagenic nitrosamines, namely, N-nitrosodimethylamine and N-nitrosodiethanolamine.
Cyanide can be detected by G-rich DNA-AgNCs nanosensors. Carbon nanotubes and graphene electrochemical sensors are used to identify mycotoxin. Additionally, a carbon dot-based DNA nanosensor has been used to detect mutagenic nitrosamines, namely N-nitrosodimethylamine and N-nitrosodiethanolamine.
This article shows how different DNA-nanosensors are used to identify various harmful pathogens, toxins, antibiotics, pesticides, and other environmental pollutants such as heavy metals.
Researchers have noted that DNA nanosensors are comparatively less explored for pathogenic virus and fungus detection.
DNA-based nanosensors' main advantages are their specificity and cost-effectiveness for the detection of diverse analytes amidst a complex medium.
References and Further Readings
Kumar, V., and Guleria, P. (2020) Application of DNA-Nanosensor for Environmental Monitoring: Recent Advances and Perspectives. Current Pollution Report. https://doi.org/10.1007/s40726-020-00165-1
Nikoleli, G.-P., et al. (2018) Lipid Membrane Nanosensors for Environmental Monitoring: The Art, the Opportunities, and the Challenges. Sensors, 18(1), 284. https://doi.org/10.3390/s18010284
Koedrith, P. et al. (2015) Recent Trends in Rapid Environmental Monitoring of Pathogens and Toxicants: Potential of Nanoparticle-Based Biosensor and Applications. The Scientific World Journal. Article ID 510982, https://doi.org/10.1155/2015/510982