Dopamine (DA), one of the most prominent catecholamine neurotransmitter existing human’s circulation system and cerebrospinal fluid, plays a crucial role in several neurological disorders. According to research, the normal content of DA in healthy people was in the range of 1.3 - 2.6 μM (i.e. 0.26 μg/mL - 0.54 μg/mL), which indicated that when the DA concentration was abnormal in human plasma, it could lead to certain neurological disease such as schizophrenia, or Parkinson’s disease (PD).
In clinical diagnosis, positron emission tomography (PET) or single-photon emission computed tomography (SPECT) are harnessed to detect changes in striatal DA level. On the other hand, ELISA Kit and electrochemical detection (ECD) for HPLC are extremely selective and sensitive detection techniques, however, they are actually time-consuming, costly and complicated in clinical detection. Thus, we aimed to design a fabrication for a biochip detecting for DA would be so facile and cheap that have an inclination to be employed for the clinical detection in the near future.
We immobilized the DBA onto amine groups-modified chips by covalent binding with GA linker. The amine groups modified chips were fabricated with branched polyethylenimine (bPEI). After that, we employed two sensing system for detection as soon as DA was captured by DBA. In the first system, was adopted based on the oxidation reaction of DA induced by sodium hydroxide (NaOH), causing the color of supernatant altering from transparent to brownish accompanied by a specific absorbance spectrum.
The second system the BSA-Au nanoclusters (BSA-Au NCs) can be quenched with the increasing concentration of DA based on PET mechanism.
In this study, the biochip prepared was able to detect DA with linear range from 1 ng/mL, to 10 mg/mL and a limit of detection (LOD) as low as 0.1 ng/mL based on fluorescence quenching system, which was in the detecting range of DA in human serum concentration. Also the results of interference test (e.g. ascorbic acid, glucose, alanine, uric acid, etc.) showed that our designed system was selective and specific. With those advantages, the biochip for DA detection certainly has potentiality to be applied in the clinical detection in the near future.