Differential photoelectrochemical DNA sensing by modulating the plasmonic properties of metal nanoparticles

Photoelectrochemical transduction methods are becoming a popular method to achieve the point-of-care device to detect various biomolecules. Herein, we present a differential assay to detect Au nanoparticle labeled-DNA strand with femtomolar sensitivity. To achieve the differential signaling, spatially separated multiplex electrodes were prepared by utilizing probe DNA as nano-spacers. The motional dynamics of the AuNP after hybridization determines the interaction between the TiO2 and Au NPs. The length of probe DNA determines whether Au NP will enhance or reduce the photocurrent via hot-electron transfer or steric hindrance, respectively. This differential assay demonstrated a limit-of-detection of 1fM and linear range of 10fM-10pM.