A facile photoelectrochemical sensing platform for highly sensitive detection of dopamine secreted from nerve cells based on polydopamine sensitized TiO2 as photoelectric material

Dopamine (DA) is a catecholamine neurotransmitter in the brain, and changes in its concentration are closely related to neurological diseases. Thus, the development of a sensitive, cost-efficient and reliable method for DA monitoring has important application value. Herein, a photoelectrochemical (PEC) sensor based on TiO₂ and polydopamine-modified TiO₂ (PDA@TiO₂) was constructed to achieve highly sensitive detection of DA secreted from living nerve cells. Upon DA introduction, PDA@TiO₂ has a wide range of visible light absorption, promoting light absorption. The sensitization of PDA effectively improve the charge carrier transport efficiency, promote the photocatalytic activity of TiO₂. The coating of PDA promotes its hydrophilic properties, effectively excluded the biofouling macromolecules and interference signals, ensuring sensor reproducibility. The result reflected that the current reponse increase of PDA@TiO₂ is 3.5 times higher than the TiO₂ after DA reaction due to the PDA@TiO₂ can promote efficient carrier separation. The PDA@TiO₂ sensor has superior sensitivity, a wider detection linear range and long-term stability. Notably, this PEC sensor is characterized by its simplicity in fabrication, low production cost, and portability. Under optimized experimental conditions, the PDA@TiO₂ sensor showed a favorable linear response to DA using PBS incubated with pheochromocytoma (PC12) cells concentration ranging from 2 to 500 μM with a detection limit of 24.7 nM (S/N = 3). Meanwhile, the sensor was effectively applied to detect DA levels in PC12 cells. This work not only provides a new and efficient strategy for signal amplification, but also provides a promising candidate platform for sensitive detection of DA, offering a valuable tool for neuroscience and clinical diagnostics.