Researchers have developed a new tool for the rapid detection of a number of illicit drugs using only the sweat of an individual’s fingerprint.
Typically, the procedure to test for drugs in human beings necessitates the collection of blood or urine and laboratory-based analysis by gas or liquid chromatography with mass spectrometry. Unfortunately these standard methods are somewhat invasive, require potentially time-consuming laboratory-based analysis, and use complex pieces of analytical instrumentation requiring a trained operator to use. They are inevitably unsuitable for rapid, in-situ screening of potential drug users.
Researchers at the University of East Anglia and Intelligent Fingerprinting Ltd (a spin-out company from the university) have been working on a method of conducting simple, rapid drug analysis using sweat from a person’s finger. The technique has been developed to detect four classes of drugs – cannabis, cocaine, amphetamines and opiates, with cannabis being detected based on the presence of Δ9-tetrahydrocannabinol (THC), cocaine on the presence of benzoylecgonine, and opiates via the detection of morphine.
The finger of an individual is firmly pressed onto the Drug Screening Cartridge. This is then filled with a buffer solution before insertion into the reader for analysis. Capable of detecting drugs down to the picogram level, the system is a fluorescence-based lateral flow competition assay containing four drug-bovine serum albumin conjugate lines on a nitrocellulose test strip. In short, when a sample is introduced to the test strip, fluorescently-tagged antibodies pass over the conjugate lines. As these antibodies are specific to each drug class of interest, if that drug is present they will bind to the drug. At the end of the test, a fluorescence signal is measured. If none of the four drug classes were present, a maximum fluorescence signal will be obtained. However if any drugs were present to bind with the antibodies, there will be a decrease in the fluorescence signal proportional to the drug concentration. Within about 10 minutes, the device then gives a simple pass/fail response, requiring no specialist knowledge or excessive training to operate and interpret the results.
Furthermore, the technique has also been demonstrated to be effective when applied to the deceased. Researchers worked with a number of UK-based coroners to obtain fingerprint sweat samples from 75 deceased individuals. The most common drug detected was opiates, which is a logical finding considering the number of terminally ill patients who are prescribed morphine during palliative care.
In order to compare the new technique with those typically employed in the detection of drugs in human beings, analysis of blood samples was conducted by LC-MS-MS. The results between the two methods correlated well, with the accuracy between DSC of fingerprints and LC-MS-MS of blood being 88-97%, depending on the drug. This demonstrates the effectiveness of the method and its ability to stand up to existing techniques, though there are inevitably some shortcomings. Authors of the study have stated that there are known accuracy issues with lateral flow measurement devices, thus this new technology should be used as a presumptive screening method prior to confirmation by mass spectrometry. Furthermore, the range of target drugs is clearly currently limited, though future development could no doubt enable other classes of drug to be included.
Full details of the findings can be found in the Journal of Analytical Toxicology.
Hudson, T. Stuchinskaya, S. Ramma, J. Patel, C. Sievers, S. Goetz, S. Hines, E. Menzies and D. A. Russell, J. Anal. Toxicol., 2018, 6–10.
Forensic Magazine. Fingerprint Drug Screen Test Works on the Living and Deceased. [Available online] https://www.forensicmag.com/news/2018/10/fingerprint-drug-screen-test-works-living-and-deceased