Amplified electrochemical DNA-sensing of nanostructured metal oxide films deposited on disposable graphite electrodes functionalized by chemical vapor deposition

Metal oxide nanostructures offer interesting possibilities to design functional surfaces for bio-sensing applications, for instance, through higher surface area leading to enhanced immobilization of biomolecules, which increases the detection limit. Herein, an amplified electrochemical sensing method has been presented for the detection of DNA based on the readout resulting from chemical oxidation of guanine on nanoscaled metal oxides (TiO2, SnO2 and Fe3O4) obtained by chemical vapor deposition (CVD) onto pencil graphite electrode (PGE) as electrochemical transducer. The proposed strategy is suitable to produce cost-effective disposable sensor elements enabling quantitative detection of nanomolar concentrations of DNA. When preparing these metal oxide surfaces by CVD onto PGEs, the various experimental conditions; such as, the effect of different concentrations of 20 mer-bases DNA oligonucleotide (ODN20), and the surface pretreatment steps were studied to obtain better surface properties for DNA immobilization. The detection limit estimated for signal-to-noise ratios >3 corresponds to 21.3, 53.9 and 45.8 nmole/ml ODN20 concentrations for PGEs modified with TiO2, SnO2 and Fe3O4 films, respectively. The electrochemical detection of DNA onto metal oxide@PGEs is discussed together with the application potential.