Tryptophan is an essential amino acid that plays a crucial role in the human body, including normal growth and nerve transmission [1]. Since the human body is unable to produce tryptophan, it is essential to include it in the diet [2]. It is noteworthy that excessive amounts of tryptophan in the body can cause adverse effects such as nausea, drowsiness, dizziness and loss of appetite [3]. Therefore, developing an accurate, fast and low-cost approach to detect tryptophan levels in the diet is crucial. In this regard, the use of electrochemical aptasensors is a suitable method due to its advantages [4]. In this work, the hollow nanospheres of NiCo-MOF was synthesized via solvothermal method. Subsequently, Cu and Au were added to the MOF to enhance its conductivity and facilitate the connection between thiol groups of the aptamer and nanoparticles placed on the surface of the glassy carbon electrode. After characterizations the synthesized compound, each construction step of aptasensor was investigated through [Fe(CN)6] 3-/4-probe using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The EIS results for calibration showed that the designed aptasensor has the ability to measure tryptophan in a linear concentration range of 0.5 fM to 200 nM with a detection limit of 0.14 fM. According to the results, the prepared aptasensor exhibits a wide linear range, low detection limit, good repeatability with RSD = 1.37 % and stability. Finally, the ability of the proposed method was confirmed by measuring tryptophan in food samples such as wheat, chikpea and lentil.
