A novel electrochemical biosensor for the detection of cancer biomarkers based on Au@nanoflower/metal oxide nanocomposites

Transition metal oxides as the next generation of 2-D materials have attracted widespread attention because of their unique electrochemical properties. In this study, the preparation of metal oxides (MO) involves a two-step process of a hydrothermal reaction with subsequent air annealing. First, the transition metal dichalcogenides (TMD) nanosheets were prepared by a hydrothermal method. Subsequently, the TMD nanosheets were converted to MO nanosheets via the thermal annealing method. In addition, Au@NFs nanocomposites were also prepared using an efficiently combined approach of hydrothermal process and in situ chemical synthesis method. Both XRD and TEM results illustrated that MO nanosheets and Au@NFs nanocomposites were successfully prepared. For the first time, a novel electrochemical immunosensor modified with Au@NFs/MO nanocomposites was fabricated by the solution-casting method for detecting the calreticulin (CRT) biomarkers. This construction step provides a suitable and simple method for the covalent attachment of modified SPCE and anti-CRT molecules. Bio-affinity interactions between CRT biomarkers and anti-CRT molecules were investigated by CV and EIS techniques. The CV and EIS results indicated that L-Cysteine and EDC/NHS modified-Au@NFs/MO/SPCE could increase the electron transfer ability. When EN-LC/Au@NFs/MO/SPCE was sequentially modified with anti-CRT, BSA, and CRT, the Rct value gradually increased to
$4433.71\ \varOmega$
, indicating that these non-conductive biomolecules were successfully immobilized. This result indicated that the CRT-immunosensors were successfully fabricated. In the future, the CRT-immunosensors are expected to detect real samples.