A peroxidase-mimicking Bi₂S₃ nanozyme-based biosensor: colorimetric assay for dopamine detection with a smartphone...

Dopamine is a crucial neurotransmitter that performs a vital role in several biological systems in the body. Abnormal dopamine concentrations in the human body can cause serious diseases. Therefore, simple, sensitive and highly accurate determination of dopamine levels is vital. In this study, a nanozyme-based colorimetric biosensor for the determination of dopamine was developed. Bi₂S₃ nanoflowers were used as nanozymes. Bi₂S₃ nanoflowers were synthesized using the hydrothermal method, and their peroxidase-mimic activity was identified. Based on this property, dopamine detection was performed. All critical parameters, such as incubation temperature and duration affecting enzyme activity, Bi₂S₃ nanozyme stock solution volume, and mixing type, were optimized using a univariate optimization approach. In this developed method, measurements were performed using UV-VIS spectrophotometry and a smartphone-based colorimetric system. Determination of dopamine was performed based on the decrease in absorbance and color change caused by the inhibitory effect of dopamine on the oxidation of TMB. Radical scavenging experiments confirmed that hydroxyl radicals (˙OH) play an active role in the peroxidase-like catalytic mechanism of the Bi₂S₃ nanozyme. Recovery experiments were performed on two different drug samples to validate the developed method. The recovery results demonstrated the applicability of the developed method to real samples. To the best of our knowledge, Bi₂S₃ nanoflowers have not previously been reported as nanozymes for the determination of dopamine or similar organic analytes. In this study, the Bi₂S₃-TMB-H₂O₂ system was proposed as a novel nanozyme based method for the determination of dopamine.