Fig 1.
Interdigitated electrode fabrication process.
Nine steps were followed to complete the fabrication of this device under room temperature.
Fig 2.
Preparation of sensing surface.
(a) Schematics of the DNA immobilization and hybridization process. This resistive DNA biosensor with titanium dioxide nanoparticles enhances the current signal that eliminates PCR. (b) SEM image of interdigitated electrodes. The average gap size between two aluminum finger-shaped electrodes is 16 μm.
Fig 3.
Measurements on sensing surface.
(a) XRD spectra of TiO2 thin film. Annealed TiO2 thin film was characterized to get highsurface crystallinity. (b) FESEM image of TiO2 nanoparticles. 100 k magnification was used to scan the TiO2 structure under ambient temperature.
Fig 4.
Experimental set-up of picoammeter for the TiO2 nanoparticle-based DNA biosensor.
Current responses show ability of the device to retain the same output current after hybridization and dehybridization of 1 μM targeted DNA.
Fig 5.
Steps were used for picoammeter-TiO2 nanoparticle DNA biosensor.
(a) Sensing surface. The device has sensing zone that uniformly covered with TiO2 nanoparticles on top of the fabricated aluminum electrodes. (b) Three steps involved in the measurements. It includes dropping of sample, drying the droplet and measuring the current response.
Fig 6.
Responses on the sensing surface.
(a) Current response of the 10 μM probe of E. coli O157:H7 ssDNA concentration measured over 8 months. Inset shows the corresponding histogram of the peak current values on a sensor for 8 months.(b) Current responses of different target DNA hybridized on the 10 μM probe DNA. These results proved the ability of the fabricated device to differentiate the positive and negative controls. (c)Current to voltage curves of the complemented target DNA concentrations. Inset shows the current values of different target DNA concentrations over the range 1E-12, 10E-12, 1E-9, 10E-9, 1E-6 and 10E-6 M. (d) Average current measurements of three different targeted DNA concentrations, 1 pM, 1 nM and 1 μM. The corresponding histogram shows the current values after 5 hybridization cycles.
Fig 7.
Current responses of different target DNA hybridized on the 10 μM probe DNA.
The target DNA was from the lysed E. coli O157:H7. Different concentrations of target DNA were tested.