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. 2023 Jun 5;13(6):619.
doi: 10.3390/bios13060619.

A Label-Free Carbohydrate-Based Electrochemical Sensor to Detect Escherichia coli Pathogenic Bacteria Using D-mannose on a Glassy Carbon Electrode

Sakineh Hargol Zadeh  1 , Soheila Kashanian  1   2 , Maryam Nazari  1
Affiliations

A Label-Free Carbohydrate-Based Electrochemical Sensor to Detect Escherichia coli Pathogenic Bacteria Using D-mannose on a Glassy Carbon Electrode

Sakineh Hargol Zadeh et al. Biosensors (Basel). .

Abstract

Controlling water and food contamination by pathogenic organisms requires quick, simple, and low-cost methods. Using the affinity between mannose and type I fimbriae in the cell wall of Escherichia coli (E. coli) bacteria as evaluation elements compared to the conventional plate counting technique enables a reliable sensing platform for the detection of bacteria. In this study, a simple new sensor was developed based on electrochemical impedance spectroscopy (EIS) for rapid and sensitive detection of E. coli. The biorecogniton layer of the sensor was formed by covalent attachment of p-carboxyphenylamino mannose (PCAM) to gold nanoparticles (AuNPs) electrodeposited on the surface of a glassy carbon electrode (GCE). The resultant structure of PCAM was characterized and confirmed using a Fourier Transform Infrared Spectrometer (FTIR). The developed biosensor demonstrated a linear response with a logarithm of bacterial concentration (R2 = 0.998) in the range of 1.3 × 10 1~1.3 × 106 CFU·mL-1 with the limit of detection of 2 CFU·mL-1 within 60 min. The sensor did not generate any significant signals with two non-target strains, demonstrating the high selectivity of the developed biorecognition chemistry. The selectivity of the sensor and its applicability to analysis of the real samples were investigated in tap water and low-fat milk samples. Overall, the developed sensor showed to be promising for the detection of E. coli pathogens in water and low-fat milk due to its high sensitivity, short detection time, low cost, high specificity, and user-friendliness.

Keywords: adhesion FimH; electrochemical impedance spectroscopy; electrochemical sensing; electrodeposited; gold nanoparticles.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Scheme 1
Scheme 1
Schematic diagram of label-free carbohydrate-based electrochemical sensor for the detection of E.coli cells. (a) GCE bare, (b) electrodeposition AuNPs and formation GCE /AuNPs, (c) electrode incubation with Cyst and formation of GCE /AuNPs/Cyst, (d) stabilization of PCAM on the surface of the electrode and formation of GCE /AuNPs/Cyst/PCAM, (e) detection of E. coli bacteria by modified electrode (GCE /AuNPs/Cyst/PCAM).
Scheme 2
Scheme 2
The steps of para carboxyphenylamino mannose synthesis.
Figure 1
Figure 1
FESEM images of the electrodeposited gold nanoparticles and E. coli captured by PCAM on the modified GCE surface, (A) 10 μm scale and (B) 2 μm scale; the red arrow points to E. coli. (C) EDS of the modified surface of GCE.
Figure 2
Figure 2
FTIR mannose analysis and mannose derivation (PCAM).
Figure 3
Figure 3
(A) EIS Nyquist diagrams (−Z″ vs. Z′) of modified electrodes: (a) bare GCE, (b) AuNPs/GCE, (c) PCAM/Cyst/AuNPs/GCE, (d) E. coli/PCAM/Cyst/AuNPs/GCE. (B) CV and (C) DPV curves of the proposed nano-electrochemical biosensor after incubating with different concentrations of E. coli 1.3 × 101–1.3 × 106 CFU·mL−1 (from top to bottom; e to g) in [Fe(CN)6]3−/4− as electrolyte solution.
Figure 4
Figure 4
(A) Responses of electrochemical biosensor E. Coli (1.3 ×105 CFU·mL−1) in [Fe(CN)6]3−/4− as an electrolyte solution as a function of incubation time (from top to bottom 0–60 min); (A) the plot of peak current versus incubation time, (B) DPV responses in different incubation times.
Figure 5
Figure 5
(A) EIS was performed in a frequency range of 0.1 Hz to 100 kHz, at a potential of 0.24 V, and amplitude of 0.01 V at different concentration of E. coli, including (a): PCAM, (b): 1.3 × 101, (c): 1.3 × 102, (d): 1.3 × 103, (e): 1.3 × 104, (f): 1.3 × 105, (g): 1.3 × 106 CFU·mL−1. (B) Calibration curve obtained for ΔR versus Log of E. coli concentration in [Fe(CN)6]−3/−4.
Figure 6
Figure 6
Selectivity experiments using 106 CFU·mL−1 solutions of E. coli, Staphylococcus epidermidis (PTCC 1856), and Citrobacterfreundii (PTCC 1600).
Figure 7
Figure 7
EIS curves for the proposed biosensor in a solution containing [Fe(CN)6]−3/−4 after incubation with milk sample in a frequency range of 0.1 Hz to 100 kHz, at a potential of 0.24 V, and an amplitude of 0.01 V at different concentrations of E. coli, including (a): 1.3 × 101, (b): 1.3 × 102, (c): 1.3 × 103, and (d): 1.3 × 105 CFU·mL−1.
Figure 8
Figure 8
The plot ΔR versus Log of E. coli concentration.
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