Novel oxidoreductase-based sensor for optical neurotransmitter detection

In our previous work [1], we have reported the developed optical biosensor for detection of dopamine, where graphene quantum dots (GQDs) were used in the detection system. In such sensor dopamine molecules coated the GQD surface — as a result occurred quenching of fluorescence due to Resonance Energy Transfer (FRET). Changes in fluorescence corresponded to specific concentrations of the neurotransmitter in tested sample. Now we present constructed new optical biosensor for epinephrine detection, which proved a facile and convenient method for this neurotransmitter determination. Epinephrine does not possess any fluorescence properties in opposite to dopamine, so it was essential to prepare a new dye solution for detection system and carrier for epinephrine. The working Fe(II) solution was prepared freshly by mixing with the optimized alkaline buffer. To such prepared dye-solution epinephrine was added (different concentrations), and detected with LTCC (Low Temperature Co-fired Ceramics)-based sensor connected with immobilized biologically active material. An outer platinum electrode was modified with semi-conductive polymer layer based on 2-([2,2'-bithiophene]-5-yl)-6-([2,3'-bithiophene]-5'-yl)-4-(5-hexylthiophene-2-yl)pyridine and laccase, as a basis for determination system of epinephrine. In result, constructed biosensor exhibits good performance, strong affinity between enzyme and catecholamine, fast response and good linear range. Obtained results have shown that the developed system could be used in medical diagnostics for neurotransmitters convenient detection.