They are identified through an iterative in vitro selection process, Systematic Evolution of Ligands by EXponential enrichment (SELEX), which can be tailored to produce molecules which are highly specific to one target analyte over potential interferents ( Ellington and Szostak, 1990 Tuerk and Gold, 1990 Kudłak and Wieczerzak, 2020). Aptamers are small, synthetically derived, single-stranded oligonucleotides which bind to their cognate target with high affinity and selectivity. In conjunction with these strategies, researchers are more commonly employing aptamers and nanomaterials as part of the solution to develop biosensors for environmental monitoring which move toward satisfying the ASSURED criteria. Other researchers have developed highly sensitive and specific assays which can be adapted for use with commercially available hand-held units, such as UV-Visible and fluorescence spectrometers, and lab-on-a-chip type designs which utilize miniaturized field-effect transistors and electrochemical analysis platforms, for example. In an effort to minimize these chain of analysis errors, many researchers have made efforts to develop inexpensive, portable platforms, including but not limited to paper-based sensors and smartphone-based analysis, which can be used for on-site detection. Many environmental contaminants of interest could be degraded during these steps, further compounding the challenges of detecting target analytes which may already be at low concentrations in complex matrices. The necessity of expensive equipment and highly trained personnel notwithstanding, to assess samples using gold standard methods like mass spectrometry or HPLC, it is often required that samples are collected, transferred, and pretreated before analysis ( Kudłak and Wieczerzak,2020). Though traditional methods boast high sensitivity and specificity, there are several challenges that remain in using these approaches for practical environmental monitoring. These criteria state that in order to be practical for use, a biosensor should be affordable, sensitive, specific, user-friendly, rapid and robust, equipment-free, and deliverable ( Weerathunge et al., 2019). Originally described by the World Health Organization as the ideal characteristics for point-of-care testing in low-resource settings, the ASSURED criteria stand as an excellent benchmark for the development of biosensors for environmental monitoring as well. ![]() Finally, a critical perspective on the field, and thoughts on future research directions will be offered.Īs the world population grows and the climate rapidly changes, the need for simple, cost-effective biosensors for environmental monitoring is becoming ever more apparent. Examples of these technologies will also be highlighted. Additionally, with innovative developments such as wearable devices, sentinel materials, and lab-on-a-chip designs, there exists significant potential for the development of multifunctional aptamer-based biosensors for environmental monitoring. This review will highlight recent examples in this area. The goal of much of this work is to develop cost-effective, user-friendly detection methods that can complement or replace traditional environmental monitoring strategies. ![]() Within this domain, aptamers have been combined with other technologies to develop biosensors with various signal outputs. This review will focus on recent aptamer-based developments for the detection of diverse environmental contaminants. Of particular relevance, aptamers have been selected and used to develop biosensors for environmental contaminants such as heavy metals, small-molecule agricultural toxins, and water-borne bacterial pathogens. Furthermore, nucleic acid aptamers can be selected for toxic targets which may prove difficult for antibody development. Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, ON, Canadaĭue to their relative synthetic and chemical simplicity compared to antibodies, aptamers afford enhanced stability and functionality for the detection of environmental contaminants and for use in environmental monitoring.
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