Electrochemical Aptamer-Based Sensor for Rapid Identification of Marijuana from Hemp

Marijuana is a plant from the Cannabis family and is the most widely abused illicit drug in the United States. Marijuana’s psychoactive effects originate from the compound Delta-9-tetrahydrocannabinol (THC). Since the 1970 Controlled Substances Act, all forms of marijuana have been illegal under federal law. However, with the recent passing of the Hemp Farming Act of 2018, Cannabis plants have been differentiated into two distinct species: hemp and marijuana. Hemp is a non-psychoactive species of Cannabis valued for its fibers and seeds which have been turned into a variety of commercial products. Per this recent legislation, hemp can now be cultivated in the United States and must possess no more than 0.3% THC by dry weight to remain legal for commercial use. In contrast, Cannabis possessing greater than 0.3% THC is characterized as marijuana and remains illegal under federal law. These two species of Cannabis are morphologically identical and cannot be visually differentiated, thus chemical analysis of THC content is required for identification. Current THC screening utilizes the Duquenois-Levine test which performs a chemical reaction with THC to produce a colored product. This color test is not specific, forming colored products with non-psychoactive cannabinoids commonly encountered in hemp, and is unable to give quantitative information on THC levels. Therefore, this color test is unsuitable for identification of marijuana from hemp. Hemp’s recent legalization will lead to an influx in suspected cannabis material. Without a reliable method for identifying marijuana from hemp, a large strain is placed on forensic labs as non-illicit hemp samples cannot be screened out. Aptamers, single-stranded RNA or DNA isolated in vitro via SELEX, specifically bind a desired target. Compared with chemical reagents employed in chemical spot tests, aptamers possess high target affinity and specificity. Moreover, they have superior chemical stability, and longer shelf life, making them ideal, low-cost reagents for a forensic laboratory setting. The researcher has previously isolated a high-affinity THC-binding DNA aptamer via SELEX. In this proposal, they will use an exonuclease-truncation strategy to engineer this aptamer with structure-switching functionality. They will then use this functionalized aptamer as recognition element to develop a rapid and interference-free electrochemical screening method for identification of marijuana from hemp. This sensor will allow forensic personnel to rapidly and accurately identify marijuana from hemp, to overcome recent challenges presented by the legalization of hemp.

Note: This project contains a research and/or development component, as defined in applicable law," and complies with Part 200 Uniform Requirements - 2 CFR 200.210(a)(14). ca/ncf