An electrochemical tyrosinamide aptasensor using a glassy carbon electrode modified by N-acetyl-L-cysteine-capped Ag-In-S QDs

This paper reports an aptamer-based green approach for the electrochemical evaluation of tyrosinamide (Tyr-NH2). In this regard, at the first step, an aqueous synthetic strategy for preparing N-acetyl-L-cysteine (NAC)-capped Ag-In-S (AIS) quantum dots (QDs) with bright yellow/orange emission was developed. The conjugation of AIS QDs to NAC-biomolecules provides opportunities for using them as luminescent contrast agents for living cell tracking and labeling or sensing studies. In the next step, the design stage of the aptasensor, the glassy carbon electrode (GCE) was modified with the MS QDs and then the Tyr-NH2 special aptamer, which has an amine group at its end, interacts with silver and indium ions at the surface of the AIS QDs and through the formation of covalent bonding of Ag-N and In-N, attaches to the GCE surface modified with the MS QDs. In this approach, for the first time, NAC-capped AIS QDs have been used to modify the electrode surface in the aptamer-based electrochemical sensor. The response changes of the [Fe(CN)(6)](4-/3-) as redox probe, during the modification of GCE surface, the fabrication and assessment of proposed aptasensing, using the cyclic voltammetry, differential pulse voltammetry and electrochemical impedance spectroscopy were recorded. The designed aptasensor for the Tyr-NH2 evaluation showed good linearity from 0.01 to 2.81 nM and 2.81-10.81 nM, and low detection limit of 3.34 pM. The obtained results of the stability, reproducibility and selectivity investigations implying that the reported aptasensor as the first aptamer-based electrochemical assay for Tyr-NH2, can be reliable for the determination of Tyr-NH2 in serum samples.