Optimization of a gold electrodeposited platform for the development of electrochemical immunosensors: The case of study of acute kidney injury

In this work, we present a systematic approach for the optimization of a stable and reproducible platform for the development of unlabelled immunosensors based on electrodeposited (ED) gold nanoparticles (AuNPs) on screen-printed carbon electrodes (SPCEs). The modification was performed in a [AuCl₄]^- solution sweeping the potential between 1.1 V and - 0.1 V vs Ag/AgClsat. The influence of the gold concentration and number of ED scans on surface morphology was investigated through Scanning Electron Microscopy (SEM), Energy dispersive X-ray (EDX), and Cyclic Voltammetry (CV). The results were discussed by considering the average AuNPs diameter determined for each modification and by comparing the features of the realized platforms to those of commercial gold screen-printed electrodes (SPEs). The best performing platform in terms of electrochemical behaviour, stability, and reproducibility was selected for the development of a label-free immunosensor. The target analyte was neutrophil-associated lipocalin (NGAL), a 25 kDa protein that serves as a biomarker for Acute Kidney Injury (AKI), one of the primary causes of in-hospital mortality globally. In contrast to creatinine, NGAL allows for the early prediction of AKI-related clinical events, facilitating timely interventions, which could significantly enhance outcomes in high-risk patients. To this aim, the electrode surface was first modified with a self-assembled monolayer (SAM) of 3-mercaptopropionic acid (MPA) and then functionalized by immobilizing the NGAL antibody via EDC/NHS coupling. The LOD (0.56 μg/mL) and the high sensitivity obtained (21.8 μA mL/μg) were compatible with the diagnostic range required for AKI.