Substrate Displacement Colorimety for the Detection of Diarylethylamines

Abstract

Introduction: In this study a novel molecularly imprinted polymer (MIP) based dye displacement assay is introduced for the rapid detection of the new psychoactive substance (NPS) sub-class known as diarylethylamines. The competitive nature of the assay facilitates displacement of a pre-bound dye molecule by a selected target molecule in a process coined Substrate displacement colorimetry (SDC). Methods: The assay was fully characterized by conducting affinity studies on the synthesized MIP, evaluating multiple dyes and expressing these affinities as binding factors (BF). The result of this study indicates the mathematical relationship between the established BF and the imprinting factor (IF) of the MIP towards the target analyte (2-MXP), allowing a prediction of efficacy towards dye displacement. Off the back of this study, dye-loaded MIPs were incubated with two common adulterants, two legal pharmacological, and the target diarylethylamine assessing the selective nature of the assay. Results: Of the dye’s tested malachite green was found to displace most readily when incubated with the target analyte, demonstrating easily quantifiable concentrations even when exposed to lower concentration of analyte. When incubated with the fore mentioned adulterants and pharmacological molecules, no dye displacement was observed; yet the target analyte stimulated clear dye displacement coloring the filtrate from the assay. This dye displacement was shown to be quantifiable, with a dose response being generated and the linear range of the assay determined by means of UV-visible spectroscopy. Discussion: The low–cost, robust and rapid nature of the proposed assay, combined with its tailorable selectivity and generic nature makes this an ideal tool for the screening of unknown seized samples. Displaying high sensitivity towards the desired analyte without sacrificing selectivity to other molecules, generating a highly reliable analytical protocol that can be both qualitative and quantitative depending upon the environment it is employed (Figure 1). Figure 1. Dose response of the dye displacement assay when incubated with 2-MXP, and caffeineReference(s): Lowdon, J. W.; Eersels, K; Rogosic, R; Heidt, B; Diliën, H; Redeker, E. S; Peeters, M; Grinsven, B. v; Cleij, T. J. Substrate displacement colorimetry for the detection of diarylethylamine. Sensors & Actuators B: Chem. 2019, 282, p137-144 Figure 1