Step toward Roadside Sensing: Noninvasive Detection of a THC Metabolite from the Sweat Content of Fingerprints.

The sudden increase in states legalizing marijuana has forced law enforcement into a situation where the use and consumption are legal, but there are no limitations for what is acceptable for driving or operating machinery. Using ultraviolet-visible (UV-vis) spectroscopy, fingerprints from volunteers who had used marijuana were analyzed via a competitive immunoassay for the detection of Δ ⁹ -tetrahydrocannabinol (Δ ⁹ -THC), the main psychoactive component of marijuana, and 11-nor-9-carboxy-THC (THC-COOH), one of the main metabolites produced in the body following the use/consumption of THC-related products. In this research, the THC-COOH metabolite and the enzyme-labeled conjugate compete against each other as the antigens for the system. The antibody used in this assay has a greater affinity for the metabolite; so, as its concentration increases, the absorbance of the system decreases due to less binding of the enzyme-labeled conjugate.