Development of graphene-based electrochemical sensors for agrochemical and biomedical monitoring

Abstract

Agrochemicals are overwhelmingly utilized to sustain food for the population, yet are often found in non-target mediums, which affect non-target organisms. Various herbicides, insecticides, fungicides, and fertilizers are commonly used commercially and residentially. Neonicotinoids are a rapidly growing class of agrochemicals that account for the largest share of insecticides globally, which mitigate a range of pests that can harm global food production. Though necessary for proper food safety and security, the vast usage of neonicotinoids has generated criticism for its non-target migration and effects on aquatic invertebrates, honeybees, and even within dairy products. To ensure proper agricultural stewardship, there is a need to understand how prevalent neonicotinoids are in the environment as there are currently no commercially available field deployable sensors. Just as alarming, glyphosate, a globally applied herbicide, has been relatively undetectable in field samples outside of gold-standard techniques. Its presumed nontoxicity towards humans has been contested by the International Agency for Research on Cancer (IARC), while it has been detected in farmers’ urine, surface waters, and crop residues. As researchers explore the potential genotoxicity and oxidative stress associated with glyphosate, a growing awareness of the importance of responsible herbicide stewardship has highlighted the need for monitoring in agricultural fields, surface water, and food products. Detection of glyphosate is hindered by the lack of field-deployable and easy-to-use sensors that circumvent sample transportation to limited laboratories that possess the equipment needed for detection. In addition to the agricultural sector, biomedical domains often require real-time analysis of various biomarkers. For instance, the detection of uric acid, calcium, cysteine, and glucose concentrations in bodily fluids could indicate or diagnose oral cancers, diabetes, and other diseases. Herein, agrochemical and biomedical sensors fabricated using laser-induced graphene (LIG), a scalable and direct-write approach to sensor fabrication, have been developed to detect major neonicotinoids, glyphosate, uric acid, and calcium in the presence of common interferent species. The developed sensors were further validated in complex fluids including spiked river water and food slurries, which demonstrate the utility of these devices as cost-effective and point-of-care tools.