Electrochemical detection of DNA hybridization based on bismuth oxide nanoparticles/chitosan-modified electrodes with methylene blue as an electrochemical indicator

The detection of DNA hybridization is of central importance to the diagnostic and treatment of genetic diseases, for the detection of infectious agents, and for reliable forensic analysis. The technique for the detection of DNA hybridization has attracted many attentions. Many methods for detecting hybridization have been developed, including electrochemical, optical, microgravimetric methods and surface plasma resonance. As compared with other detection techniques, the main advantages of electrochemical techniques are their low cost, small size, and convenience for integration and microminaturization. Hence, DNA electrochemical biosensors have been rapidly developed recently. An electrochemical DNA biosensor based on nanoparticles bismuth oxide Bi₂O₃ for DNA immobilization and hybridization detection is presented in this paper. The nano Bi₂O₃/chitosanmodified gold electrode (AuE) was fabricated and oligonucleotides were immobilized onto the AuE surface with the use of activating reagents water soluble 1-ethyl-3(3´dimethylaminopropyl)-carbodiimide (EDC) and N-hydroxy sulfosuccinimide (NHS). Hybridization was induced by exposure of the ssDNA-containing AuE to complementary target DNA in solution. The electrochemical behavior of methylene blue (MB) on the ssDNA and dsDNA modified electrode were carefully monitored by cyclic voltammetry (CV) analysis. The increases in the anodic peak current of MB were observed upon hybridization of probe with the target complementary DNA. Selectivity and sensitivity of this assay were also investigated in order to determine the specificity of the hybridization detection (Fig. 2). This is the first application of chitosan combined with nano Bi₂O₃ for the fabrication of an electrochemical DNA biosensor with a favorable performance for the detection of specific hybridization.