Abstract
The rapid sensing of drug compounds has traditionally relied on antibodies, enzymes and electrochemical reactions. These technologies can frequently produce false positives/negatives and require specific conditions to operate. Akin to antibodies, molecularly imprinted polymers (MIPs) are a more robust synthetic alternative with the ability to bind a target molecule with an affinity comparable to that of its natural counterparts. With this in mind, the research presented in this article introduces a facile MIP-based dye displacement assay for the detection of (±) amphetamine in urine. The selective nature of MIPs coupled with a displaceable dye enables the resulting low-cost assay to rapidly produce a clear visual confirmation of a target’s presence, offering huge commercial potential. The following manuscript characterizes the proposed assay, drawing attention to various facets of the sensor design and optimization. To this end, synthesis of a MIP tailored towards amphetamine is described, scrutinizing the composition and selectivity (ibuprofen, naproxen, 2-methoxphenidine, quetiapine) of the reported synthetic receptor. Dye selection for the development of the displacement assay follows, proceeded by optimization of the displacement process by investigating the time taken and the amount of MIP powder required for optimum displacement. An optimized dose–response curve is then presented, introducing (±) amphetamine hydrochloride (0.01–1 mg mL−1) to the engineered sensor and determining the limit of detection (LoD). The research culminates in the assay being used for the analysis of spiked urine samples (amphetamine, ibuprofen, naproxen, 2-methoxphenidine, quetiapine, bupropion, pheniramine, bromopheniramine) and evaluating its potential as a low-cost, rapid and selective method of analysis.
Highlights
Discovered in 1887, amphetamine has notoriously been a drug of abuse over the decades, with its uses varying as a cognitive enhancer, athletics enhancer, treatment for nasal congestion, an antidepressant, a euphoriant and even as an aphrodisiac [1,2,3,4]
The authors of this paper extended the concept recently, presenting the use of commercially available dyes in a molecularly imprinted polymers (MIPs)-based dye displacement assay for the detection of diarylethylamines that was coined substrate displacement colorimetry (SDC) [39]
Though the dyes tested primarily fell within a tricyclic structure, they all interacted differently towards the MIP (Supplementary Materials Figure S2)
Summary
Discovered in 1887, amphetamine has notoriously been a drug of abuse over the decades, with its uses varying as a cognitive enhancer, athletics enhancer, treatment for nasal congestion, an antidepressant, a euphoriant and even as an aphrodisiac [1,2,3,4]. This activity and the list of potential uses poses an issue from both a medical and analytical standpoint, giving rise to various challenges that must be overcome. Confirmation of the presence of amphetamine in a host’s urine is an analytical minefield, with current rapid screening methods failing (e.g., immunoassays, ELISA) to discriminate between amphetamine and related compounds such as tricyclic compounds, antidepressants (quetiapine, bupropion), anti-inflammatory drugs (ibuprofen, naproxen) certain antihistamines (pheniramine, bromopheniramine), nasal inhalers and even some cold/flu medications [6]. Urine analysis has the advantage of being noninvasive and posing no risk to the patient This removes the complexities and costs commonly associated with plasma analysis; the possibility of the detection of amphetamine in urine using molecularly imprinted polymers seems the most interesting route from a commercial point-of-view
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