Substrate displacement colorimetry for the detection of diarylethylamines

Abstract

In this work, a novel detection assay for the new psychoactive substance (NPS) 2-methoxiphenidine (2-MXP) and other diarylethylamines is introduced. The assay is based on the competitive displacement of dye molecules from molecularly imprinted polymers (MIPs) by the target molecule. The assay was fully characterized by studying the affinity of the MIP for six common dyes, expressed as the binding factor (BF). The results of this study indicate that the mathematical relationship between the BF of a dye and the imprinting factor (IF) for the target could be used for the prediction of the efficacy of the displacement assay. Dye-loaded MIP particles where incubated with the target, two adulterants and two legal pharmacological compounds. The target has a higher affinity for the MIP than the dye and displaces it out of the nanocavities of the receptor leading to a colour change in the filtrate that can be observed with the naked eye. Incubation of the MIP particles with the adulterants and legal medicines did not result in any observable change in absorbance. The robust, fast and low-cost nature of the assay, combined with its tailorable selectivity and generic nature, illustrate its potential as a pre-screening tool for the identification of narcotic substances in unidentified powders.

Point of Care Diagnostics in Resource-Limited Settings: A Review of the Present and Future of PoC in Its Most Needed Environment

“…The greater complexity of these devices is shown in their mechanisms of action, which are often optical, electro(chemical) or magnetic [ 8 ], but also include other mode of actions—e.g., thermal sensor systems [ 9 , 10 ]. Optical systems include more straightforward UV/Vis or fluorescence sensors, as well as more complex systems using quantum dot and surface-plasmon-resonance technology or even genetically encoded biosensors [ 11 , 12 , 13 , 14 ]. Examples of electro-(chemical) systems range from basic ampere or voltametric systems over graphene-based field-effect-transistors to DNA-annealing-based redox-reporter assays [ 15 , 16 , 17 , 18 ].…”

A Molecularly Imprinted Polymer-based Dye Displacement Assay for the Rapid Visual Detection of Amphetamine in Urine

“…The amount of the dye displaced by amphetamine was not seen to increase past the period of one minute, which could be due to the difference in the binding factor between the dye molecule and amphetamine. It was shown in a previous study (Lowdon et al [ 39 ]) that the difference in the binding affinities of the molecules was one of the driving forces behind the displacement reaction. It has previously been reported that the interaction was not as fast as it has been observed here; however, the difference in the binding factors in this scenario is much greater than previously reported.…”

“…The procedure for the synthesis of the optimized MIP followed the method previously reported [ 39 ]. In essence, a mixture of the functional monomer methacrylic acid (MAA, 0.27 mL, 3.1 mmol), functional crosslinker ethylene glycol dimethacrylate (EGDMA, 1.73 mL, 9.2 mmol) and thermal initiator azobisisobutyronitril (AIBN, 50 mg, 0.30 mmol) in 3 mL of dimethyl sulfoxide (DMSO), together with (±) amphetamine hydrochloride (50 mg, 0.29 mmol), was prepared in a 15 mL glass vial.…”

“…Benzofurazan dyes were used as examples, generating a competitive binding assay to detect the presence of six imprinted amine compounds. The authors of this paper extended the concept recently, presenting the use of commercially available dyes (malachite green) in a MIP-based dye displacement assay for the detection of diarylethylamines that was coined substrate displacement colorimetry (SDC) [ 39 ].…”

Studying the Effect of Adhesive Layer Composition on MIP‐Based Thermal Biosensing

“…MIP Synthesis : MIP and NIP particles were obtained using the same method described by Lowdon et al Briefly, MIPs were synthetized using methacrylic acid (MAA) as monomer and 2‐MXP as template. A mixture of 1.82 mmol MAA and 0.17 mmol 2‐MXP was dissolved in 3 mL of dimethylsulfoxide (DMSO).…”