The development of conducting polymer incorporated with carbon materials-based electrochemical biosensors has been intensively studied due to their excellent electrical, optical, thermal, physical and chemical properties. In this work, a label-free electrochemical dopamine (DA) biosensor based on polyaniline (PANI) and its aminated derivative, i.e., poly(3-aminobenzylamine) (PABA), composited with functionalized multi-walled carbon nanotubes (f-CNTs), was developed to utilize a conducting polymer as a transducing material. The electrospun nanofibers of the composites were fabricated on the surface of fluorine-doped tin oxide (FTO)-coated glass substrate under the optimized condition. The PANI/f-CNTs and PABA/f-CNTs electrospun nanofibers were characterized by attenuated total reflectance–Fourier transform infrared (ATR-FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and transmission electron microscopy (TEM), which confirmed the existence of f-CNTs in the composites. The electroactivity of the electrospun nanofibers was investigated in phosphate buffer saline solution using cyclic voltammetry (CV) before being employed for label-free electrochemical detection of DA using differential pulse voltammetry (DPV). The sensing performances including sensitivity, selectivity, stability, repeatability and reproducibility of the fabricated electrospun nanofiber films were also electrochemically evaluated. The electrochemical DA biosensor based on PANI/f-CNTs and PABA/f-CNTs electrospun nanofibers exhibited a sensitivity of 6.88 µA·cm⁻²·µM⁻¹ and 7.27 µA·cm⁻²·µM⁻¹ in the linear range of 50–500 nM (R² = 0.98) with a limit of detection (LOD) of 0.0974 µM and 0.1554 µM, respectively. The obtained DA biosensor showed great stability, repeatability and reproducibility with precious selectivity under the common interferences, i.e., glucose, ascorbic acid and uric acid. Moreover, the developed electrochemical DA biosensor also showed the good reliability under detection of DA in artificial urine.

Dopamine (DA) is an important neurotransmitter which indicates the risk of several neurological diseases. The selective determination with low detection limit is necessary for early diagnosis and prevention of neurological diseases associated with abnormal concentration of DA. The purpose of this study is to fabricate a poly(3-aminobenzylamine)/poly(sodium 4-styrenesulfonate) (PABA/PSS) multilayer thin film for use as an electrochemical DA biosensor. The PABA was firstly synthesized using a chemical oxidation method of 3-aminobenzylamine (ABA) monomer with ammonium persulfate (APS) as an oxidant. For electrochemical biosensor, the PABA/PSS thin film was fabricated on fluorine doped tin oxide (FTO)-coated glass substrate using the layer-by-layer (LBL) self-assembly method. The optimized number of bilayers was achieved using SEM and cyclic voltammetry (CV) results. The electroactivity of the optimized LBL thin film toward detection of DA in neutral solution was studied by CV and amperometry. The PABA/PSS thin film showed good sensitivity for DA sensing with sensitivity of 6.922 nA·cm⁻²·µM⁻¹ and linear range of 0.1–1.0 µM (R² = 0.9934), with low detection limit of 0.0628 µM, long-term stability and good reproducibility. In addition, the selectivity of the PABA/PSS thin film for detection of DA under the common interferences (i.e., ascorbic acid, uric acid and glucose) was also presented. The prepared PABA/PSS thin film showed the powerful efficiency for future use as DA biosensor in real sample analysis.

Dopamine (DA) is a neurotransmitter that works in the brain. It plays several important roles in executive functions, including motor control, memory, mood, motivation, and reward. DA imbalances are associated with diseases in the nervous system such as Parkinson’s disease, schizophrenia, Alzheimer’s disease, and attention deficit hyperactivity disorder (ADHD). Therefore, the development of a biosensor for the detection of precise amounts of DA is of great interest. In this research, polypyrrole-3-carboxylic acid/polypyrrole/gold nanoparticle (PP3C/PPy/AuNPs) composites were developed for the electrochemical detection of DA. Firstly, a PP3C/PPy/AuNPs composite thin film was synthesized by electropolymerization on a fluorine-doped tin oxide (FTO)-coated glass substrate. Subsequently, cyclic voltammetry (CV), scanning electron microscopy (SEM), and differential pulse voltammetry (DPV) were used for the characterization and study of the efficiency of the obtained conducting polymer–gold nanoparticle composite thin film for the detection of DA. The proposed electrochemical sensor showed good sensitivity and selectivity for the detection of DA with a wide detection linear range from 5 to 180 μM (R² = 0.9913). The limit of detection (LOD) and limit of quantitation (LOQ) values were 9.72 nM and 0.032 μM, respectively. Therefore, it can be concluded that the electrochemically fabricated PP3C/PPy/AuNPs composite thin film can be applied as an electrochemical biosensor for the detection of dopamine for the early diagnosis of various neurological disorders in the future.