A sensitive and selective voltammetric biosensor composed of layer-by-layer (LbL) self-assembly of positively charged poly(diallyldimethylammonium)-wrapped oxidized single-walled carbon nanotubes (PDDA-oSWCNTs), negatively charged serotonin (5-hydroxytryptamine, 5-HT)-specific aptamer, and tyrosinase on Au nanoparticles deposited screen printed carbon electrode was developed for measurement of 5-HT. Surface characteristics of 5-HT biosensor were explored using scanning electron microscopy, X-ray photoelectron spectroscopy, and electrochemical impedance spectroscopy. The respective effects of 5-HT-specific aptamer and oSWCNTs on the detection of 5-HT were investigated by differential pulse voltammetry (DPV). The peak current at the potential of 0.29 V (vs. Ag/AgCl) increased with respect to 5-HT concentration resulting in two dynamic ranges from 0.05 to 0.5 and 1 to 20 μM with a limit of detection of 2 nM from the LbL biosensor in buffer solution, which were better than those without the LbL of aptamer and oSWCNTs. The developed biosensor was applied to the direct determination of 5-HT concentrations in undiluted healthy control and Internet gaming disorder serum samples. The results were verified by comparison with those from liquid chromatography-mass spectrometric analyses.
Keywords: Internet gaming disorder; Serotonin; Serotonin-specific aptamer; Single-walled carbon nanotubes; Tyrosinase; Voltammetric biosensor.