Colour spot tests, more commonly referred to as presumptive tests are useful in providing rapid qualitative identification that a controlled drug may be present in a sample, enabling prompt action at the point of seizure. The production, consumption and commercialization of illicit substances remain a serious concern in most countries. Within the context of production and exploitation, amphetamine-type stimulants (ATS) such as methamphetamine (MAMP) and amphetamine (AMP) dominate the illicit drug market in many countries where the amount of confiscated ATS has drastically increased in recent years. Colorimetric spot test such as the Marquis, Simon’s and Mandelin tests are the ‘gold’ standard test used in ATS presumptive analysis. However, despite their wide-spread use in forensic analysis, there have been several reports of false positive results generated from chemical analysis of everyday items such as Epsom salts and Krispy Kreme crumbs. In this work, we report on a novel catalytic-enhanced peroxidase mimic biosensor for the colorimetric detection of AMP and MAMP using graphene oxide (GO)-multi-shaped cetyltrimethylammonium bromide (CTAB)-AuNPs hybrid nanozyme with DNA aptamer as a bioreceptor and hemin as a catalytic signal amplifier. GO was first bound to CTAB-AuNPs via electrostatic interaction to form a GO-CTAB-AuNP hybrid nanozyme complex. Then a DNA aptamer, specific to the target ATS was thereafter bound to the GO-CTAB-AuNP hybrid nanozyme surface to capture the target ATS. This was followed by the binding of hemin and the subsequent catalytic oxidation of 3,3,5,5-tetramethylbenzidine (TMB) by H2O2 to generate a deep blue colour specific to the target ATS. To the best of our knowledge, the aptamer-based peroxidase mimic biosensor for ATS is the first of its kind and can colorimetrically detect AMP and MAMP as individual compounds in ~1 minute (min) with high sensitivity and selectivity.

Enhanced peroxidase-like catalytic assay for the colorimetric aptamer-based biosensing of amphetamine-type stimulants using multi-shaped gold nanoparticle-graphene oxide-hemin hybrid nanozyme

2019 Fall National Meeting

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