Fig. 4.

(A): A schematic picture from the development of a voltammetric electrochemical HCV-RNA genosensor, first step: Fabrication of gold (Au) nanostructures modified indium tin oxide (ITO) substrate; Second step: immobilization of peptide nucleic acid (PNA-SH) onto Au nanodots modified ITO substrate; and Third step: probe binding with the complementary regions of HCV-RNA. (B): A schematic diagram of a label-free colorimetric SPR genosensor using gold nanoparticles for detection of unamplified 5′UTR of HCV RNA. In the presence of complementary target RNA and primer, the AuNPs were aggregated and the solution color changed from red to blue, while upon introduction of non-complementary target RNA, primers were adsorbed on AuNPs and the solution color remained red. (C): Schematic shows the structure of an impedimetric biosensor and detection of the target through the electrochemical impedance spectroscopy (EIS) strategy. The figures are obtained with permission from Refs. [140,152], and [176].