Electrochemical Detection of Cortisol by Silver Nanoparticle-Modified Molecularly Imprinted Polymer-Coated Pencil Graphite Electrodes

The sensitive cortisoldetection by an electrochemicalsensor basedon silver nanoparticle-doped molecularly imprinted polymer was successfullyimproved. This study describes the method development for cortisoldetection in both aqueous solution and biological samples using molecularlyimprinted poly(hydroxyethyl methacrylate-N-methacryloyl-(l)-histidine methyl ester)-coated pencil graphite electrodesmodified with silver nanoparticles (AgNPs) by differential pulse voltammetry(DPV). The cortisol-imprinted pencil graphite electrode (PGE) hasa large surface area because of doped AgNPs with enhanced electroactivity.The prepared molecularly imprinted polymer was characterized by scanningelectron microscopy. The DPV response of the synthesized electrodewith outstanding electrical conductivity was clarified. Cortisol-imprintedpolymer-coated PGEs (MIP), cortisol-imprinted polymer-coated PGEswith AgNPs (MIP@AgNPs), and nonimprinted polymer-coated PGEs withAgNPs (NIP@AgNPs) were evaluated for sensitive and selective detectionof cortisol in aqueous solution. Five different cortisol concentrations(0.395, 0.791, 1.32, 2.64, and 3.96 nM) were applied to the MIP@AgNPs,and signal responses were detected by the DPV with a regression coefficient(R (2)) value of 0.9951. The modified electrodeshowed good electrocatalytic activity toward cortisol for the linearconcentration range from 0.395 to 3.96 nM, and a low limit of detectionwas recorded as 0.214 nM. The results indicate that the MIP@AgNPssensor has great potential for sensitive and selective cortisol determinationin biological samples.