Development of a point-of-care test for the detection of MDMA in latent fingerprints using surface plasmon resonance and lateral flow technology

Abstract

To date, a specific point-of-care test (POCT) for 3,4-methylenedioxymethamphetamine (MDMA, ecstasy, ‘E’) in latent fingerprints (LFPs) has not been explored. Other POCTs identify MDMA in sweat by detecting the drug as a cross-reactant rather than target analyte, thus decreasing the test's sensitivity. The study's aim was to design a sensitive POCT for the detection of MDMA in LFPs using surface plasmon resonance (SPR) and lateral flow immunoassay (LFA) technology. A high-affinity antibody binding pair was identified using the former technique, deeming the pair suitable for a LFA. Titrations of fluorescently labelled antibody and antigen concentrations were tested to identify a sharp drop-in signal upon the addition of MDMA to allow a clear distinction between negative and positive outcomes. We trialled the LFA by producing dose response curves with MDMA and a group of drugs that share a similar chemical structure to MDMA. These were generated through spiking the LFA with increasing levels of drug (0–400 pg/10 μl of MDMA; 0–10,000 pg/10 μl of cross-reactant). Fluorescent test signals were measured using a cartridge reader. The cut-off (threshold) 60 pg/10 μl calculated better cartridge performance (1.00 sensitivity, 0.95 specificity and 0.98 accuracy), when compared with 40 pg/10 μl. The biggest cross-reactant was PMMA (250%), followed by MDEA (183%), MBDB (167%), MDA (16%) and methamphetamine (16%). A sensitive LFP screening tool requiring no sample preparation was successfully designed.