Fabrication of a Free‐Standing MWCNT Electrode by Electric Field Force for an Ultra‐Sensitive MicroRNA‐21 Nano‐Genosensor

Abstract

Abstract Abnormal expression of microRNA‐21 (miR‐21) is considered to be closely associated with the pathogenesis of colorectal cancer. However, great challenges do exist for the development of ultra‐sensitive biosensors to detect the abnormal expression of miR‐21 due to the low concentration in serum (f m level) at the early stage of colorectal cancer. Therefore, electric field force is used to rotate and rearrange random multi‐walled carbon nanotubes (MWCNTs) at the microscale to improve the active sites of the electrode in this study. The free‐standing MWCNTs are densely and high‐orderly embedded into the bare electrode along the direction of the electric field. Compared to the bare electrode, the peak‐current response of the free‐standing MWCNT electrode improves by 150 times in cyclic voltammetric measurement. A nano‐genosensor based on the free‐standing MWCNT electrode is developed for measuring miR‐21. The nano‐genosensor for miR‐21 shows an ultra‐high sensitivity of 48.24 µA µ m −1 , a wide linear range from 0.01 × 10 −15 to 100 × 10 −12 m , and a low detection limit of 1.2 × 10 −18 m . The present nano‐genosensor shows superior performance for miR‐21 in human serum samples and demonstrates a potential application for the diagnosis of early stage colorectal cancer.