Direct detection of microRNA-126 at a femtomolar level using a glassy carbon electrode modified with chitosan, graphene sheets, and a poly(amidoamine) dendrimer composite with gold and silver nanoclusters.

We describe a strategy for the determination of microRNA-126 (miRNA-126) that is based on the use of a glassy carbon electrode modified with (a) carboxy-terminated generation 3.5 poly(amidoamine) (PAMAM) dendrimer; (b) gold and silver nanoclusters, and (c) a chitosan-graphen composite. A peptide nucleic acid (PNA) was immobilized on the surface and serves as a receptor to hybridize miRNA-126. Subsequently, a digoxin labeled signal DNA is specifically recognized by the PNA. The analytical signal was finally generated by adding anti-digoxin antibody labeled with horse radish peroxidase. The biosensor was characterized by differential pulse voltammetry. A linear current-concentration relationship is found for miRNA-126 at a working voltage of 208 mV in the 1.0 fM to 10 nM concentration range. The limit of detection is 0.79 fM (at an S/N of 3). This biosensor displays good reproducibility, stability and selectivity. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]