Biomimetic graphene oxide-cationic multi-shaped gold nanoparticle-hemin hybrid nanozyme: Tuning enhanced catalytic activity for the rapid colorimetric apta-biosensing of amphetamine-type stimulants.

Amphetamine-type stimulants are a class of illicit drug that constitutes a worldwide problem to which intelligence agencies, first responders and law enforcement are tasked with identifying them in unknown samples. We report on the development of a graphene oxide (GO)-cationic multi-shaped gold nanoparticle (AuNP)-hemin hybrid nanozyme as a new biomimetic catalytic-induced aptamer-based colorimetric biosensor platform for amphetamine (AMP) and methamphetamine (MAMP). GO was electrostatically bonded to cationic multi-shaped cetyltrimethylammonium bromide (CTAB)-AuNPs to form a GO-CTAB-AuNP hybrid nanozyme exhibiting enhanced catalytic activity in the presence of hemin. The binding of an MNS 4.1 anticocaine DNA aptamer on the GO-CTAB-AuNP-hemin nanozyme assembly and the subsequent catalytic oxidation by 3,3,5,5-tetramethylbenzidine in the presence of HO ensured that the colorimetric reaction was tuned to selectively detect AMP and MAMP with high sensitivity. Under optimum experimental conditions, AMP and MAMP were quantitatively detected within 1 min with a detection limit of 34.1 ng/mL and 28.6 ng/mL respectively. Selected substances and drugs, known to react positively to Marquis and Mandelin reagents (used in AMP and MAMP presumptive testing) and well-known adulterants, were tested for their affinity to react with the aptamer-based GO-CTAB-AuNP-hemin peroxidase mimic biosensor. The deep blue colorimetric reaction, specific to AMP and MAMP detection, was used as the basis to affirm the selectivity of the aptamer-based GO-CTAB-AuNP-hemin peroxidase mimic biosensor. We believe the colorimetric biosensor developed in this work demonstrates a promising new direction in presumptive testing for AMP and MAMP.