The effect of gold nanostructure morphology on label-free electrochemical immunosensor design

In this research, various electrodeposition techniques were used to form gold nanostructures (AuNSs) on the surface of graphite rod electrode (GE). Three distinct AuNS morphologies on GE have been achieved based on the composition of electrodeposition solution. The use of H₂SO₄ as a supporting electrolyte resulted in the formation of smaller but more numerous AuNS_I with a modified electrode's electroactive surface area (EASA) of 0.213 cm². Exchanging the supporting electrolyte to KNO₃ and increasing HAuCl₄ concentration facilitated the formation of bigger AuNS_II particles with electrode EASA of 0.116 cm². Finally, a partial coverage of GE by branched gold nanostructures (AuNS_III) was achieved with an estimated EASA of 0.110 cm², when the HAuCl₄ and KNO₃ concentrations were increased further. Estimated values of heterogeneous electron transfer rate constant did not depend on AuNS morphology. Electrode modified with AuNS_I exhibited the highest bovine serum albumin (BSA) immobilization efficiency and the highest relative response for the detection of specific polyclonal antibodies against BSA (p-anti-BSA) compared to other modified electrodes. The limit of p-anti-BSA detection in PBS buffer was calculated as 0.63 nM, while in blood serum it was 0.71 nM. Linear ranges were from 1 to 7 nM and from 1 to 5 nM, respectively.