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Electrochemically active nanostructured polypyrrole (PPy) coated with polyaniline (PANi) was deposited on the electrode followed by the gluteraldehyde (GA) attachment for grafting 5'-amine modified single strand DNA (ssDNA) to form the PPy-PANi-GA-ssDNA and DNA hybridization in phosphate buffer solution. Differential pulse voltammetry (DPV) was used to monitor the hybridization events with methylene blue as electrochemical indicator. The exhibited sensitivity and selectivity was attributed to 10 the nanotubical structure of PPy-PANi and 472 times greater conductivity than the conventional PPy-PANi composite. The biosensor has been characterized by Cyclic Voltammetry (CV), Electrochemical Impedance (EI), FT-IR, Differential Pulse Voltammetry (DPV) and Scanning Electron Microscope (SEM). This sensor showed good stability, selectivity and higher sensitivity than the MWCNT/AgNPs and PPy/MWCNT/AuNPs composites reported previously. The dynamic range observed was 1 ×10 -9 to 1 15 × 10 -13 M, with a lower detection limit 50 fM. 65 Furthermore, the preparation of nanostructure of conducting polymer is another issue currently limiting their application in biosensor. In general, hard-template and soft-template methods are widely employed in the synthesis of conducting polymer nanostrucutres. However, simple, efficient, controlled and large-70 scale synthesis method for preparation of conducting polymer nanostructure are still lacking.

The electrochemical behavior of riboflavin (RF) at a glassy carbon electrode modified with α-Fe2O3/MWCNT/AuNPs was investigated by cyclic voltammetry (CV) and square wave voltammetry (SWV).