A sensitive impedimetric DNA biosensor for the determination of the HIV gene based on electrochemically reduced graphene oxide

Abstract

A sensitive impedimetric DNA biosensor for the determination of the HIV-1 gene was developed by employing electrochemically reduced graphene oxide (ERGO) as a sensing platform. The DNA biosensor was fabricated by drop-coating graphene oxide (GO) on a glassy carbon (GC) electrode and covalently immobilizing the designed single-stranded DNA (ssDNA) probe onto the GO using carbodiimide chemistry. The GO was later electrochemically reduced to obtain ERGO and applied to genosensing. Upon the occurrence of hybridisation events between the surface-confined ssDNA probe with the target DNA in solution to form double-stranded DNA (dsDNA) at the electrode surface, the negative charge in the electrode/electrolyte interface, and as such, the electron transfer resistance of the electrodes toward the [Fe(CN)₆]^3−/4− redox couple were changed. This change was used for impedimetric DNA biosensing. It was found that the employment of ERGO as an immobilization platform efficiently accelerated the electron transfer and enhanced the EIS response of the DNA biosensor. Under the conditions employed in this study, the change in the electron transfer resistance was linear with the logarithm of the concentration of target DNA within a concentration range of 1.0 × 10⁻¹² to 1.0 × 10⁻⁹ M, with a detection limit of 3.0 × 10⁻¹³ M (S/N = 3). This strategy eliminated the requirement for DNA labelling, greatly simplifying the procedure. This work demonstrates that the employment of GO as an immobilization platform and ERGO as a biosensing platform is a promising approach to designing impedimetric aptasensors with high sensitivity and selectivity.