Search

This work aims to develop cost-effective, simple and sensitive electrochemical biosensor for detection of microRNA-21. The combination of carbon black (CB) and gold nanoparticles (AuNPs) as nanohybrid was employed for the first time as a platform for microRNA-21 biosensor fabrication. The developed biosensor is based on the immobilization of thiolated capture probe (complementary sequence of microRNA-21) labeled with methylene blue on the surface of the pencil graphite electrode modified with CB/AuNPs nanohybrid. After hybridization with the target microRNA-21, the orientation of the labeled capture probe changed which causes a decrease of the response of methylene blue oxidation. Differential pulse voltammetry was used for monitoring the methylene blue response before and after hybridization. Under the optimal conditions, the developed biosensor was characterized using differential pulse voltammetry (DPV), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The detection of microRNA-21 was carried out using a DPV. A wide linear range was obtained between 2.9 fM and 0.7 µM of microRNA-21. The calculated limit of detection was 1 fM of microRNA-21. This approach shows a good reproducibility, stability and an excellent selectivity. The proposed biosensor was used for microRNA-21 analysis in serum and a satisfactory result was obtained.

Herein, a novel comparison study of microRNA-125a detection using electrochemical biosensors was investigated. Indeed, pencil graphite electrodes were modified with carbon black, multi-walled carbon nanotubes and graphene oxide nanomaterials and used as platform for microRNA-125a hybridization and analysis. Electrodes surface characterization was performed with cyclic voltammetry and electrochemical impedance spectroscopy. The detection of microRNA-125a was carried out using impedance spectroscopy. The lowest limit of microRNA-125a detection which equal to 10 pM (1 pg/mL) was obtained using pencil graphite electrode modified with carbon black. A linear response was obtained between 0.008 and 15 μg/mL, that corresponds to 1 nM and 2 μM. This simple and cheap developed biosensor presented good reproducibility and selectivity. The developed biosensor was employed for microRNA-125a detection in serum indicating that the proposed method could be used in clinical diagnostic assays.