Femtogram-level VEGF detection via PEG-directed gold nanostructured electrochemical immunosensor

This study presents a novel electrochemical immunosensor designed for the highly sensitive detection of vascular endothelial growth factor (VEGF). The sensor utilizes gold nanostructures grown on fluorine-doped tin oxide (FTO) electrodes through a polyethylene glycol (PEG)-mediated electrochemical process. Fabrication involves a two-step immobilization strategy, combining physical vapor deposition (PVD) of a gold thin film with thermal annealing. The nanostructured electrode is subsequently modified electrochemically via PEG mediation, followed by antibody functionalization to enhance binding specificity. PEG-mediated control over nanostructure growth yields irregular short nanorods and leaf-like dendrites, significantly enhancing sensor performance. Extensive electrochemical analyses, including cyclic voltammetry and impedance spectroscopy, confirm improved sensitivity and stability. The optimized immunosensor achieves an ultralow detection limit of 6 fg/mL (corresponding to ~ 9500 VEGF molecules in 60 µL, and a broad linear detection range of 10 fg/mL to 10⁵ fg/mL, with excellent reproducibility. Given VEGF's pivotal role in angiogenesis and tumor progression, this ultrasensitive platform offers a promising tool for early cancer diagnostics.