Manufacturing of an electrochemical biosensing platform based on hybrid DNA hydrogel: Taking lung cancer-specific miR-21 as an example.

DNA hydrogel garnered increasing attention in the sensing and medical field owing to its native biocompatibility and mechanical stability. While electrochemistry serves as a quantitative and sensitive detection technique, electrochemical DNA hydrogel biosensor is rarely reported. Here, for the first time, we report an electrochemical biosensor based on hybrid DNA hydrogel immobilized on indium tin oxide/polyethylene terephthalate (ITO/PET) electrode for the detection of lung cancer-specific microRNA, miR-21. The biosensor is capable of detecting miR-21 at a concentration as low as 5nM (1 pmol) and linear read-out from 10nM to 50μM. Ferrocene-tagged recognition probes were cross-linked with DNAs grafted on the polyacrylamide backbones to form the hybrid DNA hydrogel, which was further immobilized on 3-(trimethoxysilyl)propyl methacrylate (KH 570) treated ITO electrode. When the recognition probe was hybridized with the target miR-21, the hydrogel dissolved, producing a loss of ferrocene tags and a reduction in current, detected by Cyclic Voltammetry (CV) and Differential Pulse Voltammetry (DPV). The material characteristics of the biosensor were verified using contact angle meter and Energy Dispersive Spectrometer (EDS). This novel biosensor holds great promise in early sensitive clinical diagnosis for a variety of cancer-specific biomarkers due to the flexible sequence design of the recognition probe.