Electrochemical Aptasensor for Sensitive Dopamine Detection Based on DNA Intercalation of Methylene Blue Using Highly Reliable Low Temperature Co-Fired Ceramic Chip

Dopamine (DA) is a neurotransmitter molecule with a variety of functions in the neuronal signal transduction and several critical illnesses. DA levels are related to the severity and progression of neurological disorders such as Parkinson's disease, attention deficit hyperactivity disorder, and Huntington's disease. Therefore, the selective and sensitive detection of dopamine is important for the early diagnosis of diseases related to pathological levels of dopamine. Enabling fast and real-time monitoring with low-cost and simple instrumentation, electrochemical biosensing shows great advantages for Point-of-Care-Testing (POCT). In this work, we have used DNA-aptamers conjugated with a methylene blue (MB) reporter molecule for electrochemical biosensing. Aptamer formed by oligonucleotide acids may lose its thermally stable functionality irreversibly under electrochemical reaction but are able to recover its function by self-refolding. Aptamers can form 3D complex structures and bind to their targets in a similar way as antibody-antigen interactions. However, the system can be regenerated thus rendering the biosensor available for further usage.<br/>We developed aptamer based electrochemical biosensing of dopamine molecule with enhanced detection signal using low-temperature co-fired ceramics (LTCC) chip and MB-conjugated aptamers. Aptamer probe with a sequence of 54 bases was synthesized with MB attached to the 3' end of the sequences and functionalized with thiol molecules at the 5' end. MB-anchored aptamer probe can be forced to associate from the interface after switching the structure of the aptamer by combining with DA. Aptamers have a smaller molecular size especially with relatively short sequences, therefore, the captured DA molecules are closer to the gold substrate of LTCC chips resulting in a stronger electrochemical signal from the MB molecules, thus providing better detection signals. The chips passivated with 6-MCH (6-mercapto-hexanol), can detect the dopamine with high sensitivity (&lt;10 nM). This label-free electrochemical aptasensor is simple, highly reliable and could have promising application in the analysis of dopamine in real clinical samples with recyclable properties.<br/>This research was financially supported by the Ministry of Trade, Industry and Energy (MOTIE) and Korea Institute for Advancement of Technology (KIAT) through the International Cooperative R&D program (Project No. P0019630) and National Research Foundation (NRF) of Korea under the “Korean-Swiss Science and Technology Program” (2019K1A3A1A1406720011).