Electrochemical detection of cortisol using a structure-switching aptamer immobilized on gold nanoparticles-modified screen-printed electrodes

This paper demonstrated the fabrication of an electrochemical-based aptasensor for the specific detection of the stress hormone "Cortisol" in Saliva. Gold nanoparticles have been widely explored as an immobilization substrate for the aptamer due to the direct covalent attachment through thiol bonding. Here, cortisol-specific truncated 14-mer aptamer was immobilized onto the gold nanoparticles-decorated screen-printed electrodes. The aptasensor has a broad dynamic range of 0.1 pg/ ml-100 ng/ml with a detection limit of 0.25 pg/ml in buffer and 0.28 pg/ml in artificial saliva matrix. The sensitivity of the sensor was 1.53 mu A (pg/ml)(-1) in the buffer and 1.33 mu A (pg/ml)(-1) in the artificial saliva matrix. The proposed aptasensor has demonstrated high specificity towards cortisol and showed no change in the current signal towards the structural analogues of the cortisol. [GRAPHICS] .