Self-assembled gold nanoparticles for impedimetric and amperometric detection of a prostate cancer biomarker

A label-free dual-mode impedimetric and amperometric aptasensor platform was developed using a simple surface chemistry step to attach gold nanoparticles (AuNPs) to a gold planar surface. As a case study, the strategy was employed to detect prostate specific antigen (PSA), a biomarker for prostate cancer. An anti-PSA DNA aptamer was co-immobilised with either 6-mercapto-1-hexanol (MCH) or 6-(ferrocenyl)hexanethiol (FcSH) for both impedimetric or amperometric detection, respectively. We show that the use of AuNPs enables a significant improvement in the limit of impedimetric detection as compared to a standard binary self-assembled monolayer aptasensor. A PSA detection of as low as 10 pg/mL was achieved with a dynamic range from 10 pg/mL to 10 ng/mL, well within the clinically relevant values, whilst retaining high specificity of analysis. The reported approach can be easily generalised to various other bioreceptors and redox markers in order to perform multiplexing.