Electrochemical aptasensing of dopamine using a gold digital video disc platform modified with graphitic carbon nitride capped SiO2@Au core-shell nanoparticles

A novel disposable electrochemical aptasensor based on a bilayer nanocomposite consisting of graphitic carbon nitride (g-C₃N₄) nanosheets and silica@gold core-shell nanoparticles (SiO₂@AuNPs) at the surface of a gold electrode derived from gold digital video disc (GDVD) was introduced for dopamine (DA) determination. The g-C₃N₄ nanosheets were synthesized through pyrolysis of the melamine and urea precursors, and SiO₂@AuNPs were prepared through sol-gel process, and they were applied for the modification of the gold electrode with the aim of increasing the specific surface area and electrical conductivity. Moreover, AuNPs provided appropriate sites for the attachment of DA thiolated aptamer, as the recognition element, through formation of the thiol-gold chemical bonds. The prepared aptamer/SiO₂@AuNPs/g-C₃N₄/GDVD showed a high electrocatalytic activity for the quantitative determination of dopamine under the optimized experimental conditions with a wide linear range of 0.1 to 20 nM and a low detection limit of 0.05 nM. Also, the value of relative standard deviation for the sensor-to-sensor reproducibility was found to be 4.3%. In addition, the recovery study indicated the good accuracy of the proposed aptasensor in which the values of recoveries varied between 98 and 103% indicating that the proposed protocol is a promising tool for the sensitive and selective determination of dopamine in human plasma samples.