O. Adegoke, N.N. Daeid
University of Dundee,
United Kingdom
Keywords: nanozyme, colorimetric, hybrid, nanoparticle, graphene, aptamer
Summary:
The outcome of investigative cases relating to the illegal possession of illicit drugs is heavily dependent on test results which shows if the suspected person is in possession of the drug in question. Colour spot tests, popularly known as presumptive tests are useful in providing rapid qualitative identification of a controlled drug, enabling prompt action to be implemented at the scene of investigation. The production, consumption and commercialization of illicit substances remain a serious concern in many countries. Within the context of production and exploitation, amphetamine-type stimulants (ATS) such as methamphetamine (MAMP) and amphetamine (AMP) dominate the illicit drug market [1]. Colorimetric spot test such as Marquis, Simon’s and Mandelin are the gold standard test used in ATS presumptive analysis. Despite their wide 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. The limitation of colour spot test was highlighted recently in a case where unknown heart-shaped drugs were seized in Italy and presumptively identified as ATS using the Marquis test. However, further confirmatory test unraveled the drugs as containing methyltestosterone, methanedone and androgen steroids with no trace of ATS being present [2]. Poor sensitivity of the colorimetric test due to the small amount of sample being tested also contributes to false negative results. In addition, the handling of colour spot reagents also poses increased health risk as many of the chemicals being used are highly corrosive and toxic. There is therefore an increased interest in the development of highly selective, ultrasensitive, rapid and safe-to-use colour spot test for accurate on-site ATS detection and the potential way forward lies in the use of nanotechnology-based biosensor technology. 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 enhancer. GO was first bound to CTAB-AuNPs via electrostatic interaction to form a GO-CTAB-AuNP hybrid nanozyme complex. A DNA aptamer, specific to the ATS was thereafter bound to the GO-CTAB-AuNP hybrid nanozyme 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 strong blue colour selective to the target ATS. To the best of our knowledge, the aptamer-GO-AuNP-hemin peroxidase mimic biosensor for ATS is the first of its kind and can colorimetrically detect both AMP and MAMP in ~1 minute (min) with high sensitivity and selectivity. Reference [1]. A. Argente-García, N. Jornet-Martínez, R. Herráez-Hernández*, P. Campíns-Falcó, Anal. Chim. Acta 943 (2016) 123-130. [2]. D. Favretto, F. Castagna, S. Maietti, R. Boscolo‐Berto, D.S. Ferrara. J Pharm Biomed Anal. 83 (2013) 260‐264.