Sensitive electrochemical gold nanoparticle-based immunosensor for norovirus detection in food samples

Figures

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  Fig. 1. (A) Schematic preparation of the immunosensor for the NoV determination; (B) proposition of the chemical groups involved in the process of creating a stable matrix.

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  Fig. 2. SEM images of surface morphology of the electrode modified with: SAM (a), AuNPs (b), SAM/AuNPs (c), SAM/AuNPs/EDC/NHS (d), SAM/AuNPs/EDC/NHS/antibody (e).

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  Fig. 3. Nyquist (a) and Bode (b and c) representations of the impedance spectra recorded for unmodified and modified gold electrodes at EOC after 30 min of exposure in a solution of 0.1 M KNO3 with 5 mM [Fe(CN)6]3−/4−. Solid fitting lines refer to Model 2 from Fig. 4b.

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  Fig. 4. Electric equivalent circuits used for fitting the experimental impedance spectra recorded for both modified (a) and unmodified (b) gold electrodes.

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  Fig. 5. CV voltammogram presenting the preparation of the electrochemical immunosensor for the NoV detection to 5 mM ferri/ferrocyanide redox probe, KNO3 used as a supporting electrolyte; potential range: −0.4–0.6 V; scan rate: 50 mV s−1; vs. Ag|AgCl.

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  Fig. 6. (a) CV-voltammogram showing AuE/SAM/AuNPs/EDC/NHS/Ab/BSA in 5 mM ferri/ferrocyanide redox probe and 0.1 M KNO3 at different scanning rates (10–300 mV s−1); potential range: −0.4–0.6 V; vs. Ag|AgCl; (b) linear relationship between scan rate and current (Ipc – red line; Ipa – blue line).

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  Fig. 7. (a) Representative DPV-scans for different NoV dilutions in the potential range of 0–0.6 V vs. Ag/AgCl; (b) linear relationship between the current and NoV dilution.

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  Fig. 8. Recovery test of the immunosensor for NoV.

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  Fig. 9. Representative CV-scans of Au/SAM/AuNPs/EDC/NHS/Ab/BSA in the presence of 5 mM Fe(CN)63−/Fe(CN)64− in 0.1 M KNO3 after 2 weeks. Potential range: −0.4–0.6 V, scan rate 50 mV s−1, vs. Ag|AgCl electrode, 60 cycles.

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  Fig. 10. Reader tested samples submitted for RT-PCR analysis.

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  Fig. 11. Dilution series of norovirus detected by western blot technique (1st well contained molecular ladd 3-colour prestained protein marker (10–245 kDa) blirt, the rest of the wells contained mouse norovirus at a range of dilutions from 10−1 to 10−8).