Bromacil is a widely used herbicide that is known to contaminate environmental systems. Due to the hazards it presents and inefficient detection methods, it is necessary to create a rapid and efficient sensing device. Towards this end, we have utilized a stringent in vitro selection method to identify single-stranded DNA molecular recognition elements (MRE) specific for bromacil. We have identified one MRE with high affinity (？nM) and specificity for bromacil compared to negative targets of selection and other pesticides. The selected ssDNA MRE will be useful as the sensing element in a field-deployable bromacil detection device. 1. Introduction Bromacil is a widely used herbicide in the substituted uracil family that is commercially used in the United States for annual and perennial brush and weed control in citrus and pineapple crops as well as in nonagricultural settings [1]. It is available under trade names such as Hyvar and Krovar and is popular due to a long soil residence of more than a year [2]. Between 55,000 and 117,000 pounds of bromacil were used on California citrus crops from 1992 to 2001 [3]. The positive economic impacts of its widespread use have led to many years of continuous environmental exposure to bromacil. As a result of this widespread use, bromacil is a potentially hazardous environmental contaminant. It is known that bromacil is highly mobile in soils and can appear in ground waters following surface treatments, dependent upon soil composition and precipitation [4, 5]. This herbicide has been detected in groundwater wells and aquatic habitats at levels up to 5？μg/L [5–7]. With these high levels of environmental contamination, it is likely that both humans and other plants and animals will be exposed to bromacil. In fact, it has been shown that dairy milk from cows that consume bromacil-treated food has relatively high bromacil levels [8]. These levels of bromacil in natural systems have clear environmental and human health consequences. The growth inhibition EC50 of bromacil for various aquatic algae, plant, and invertebrate animal species ranges from 5 to 500？μg/L [7, 9]. Additionally, bromacil is a known toxin and developmental toxin to mice, rats, dogs, and sheep upon consumption and is a skin and mucosal irritant [10, 11]. Furthermore, bromacil is known to inhibit growth and nutrient uptake of human cell lines, be relatively genotoxic, and have carcinogenic potential [12–14]. Thus, bromacil is classified as a possible carcinogen by the US Environmental Protection Agency [9]. High levels of contamination and hazard risk
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