Plasma Functionalized Carbon Interfaces for Biosensor Application: Toward the Real-Time Detection of Escherichia coli O157: H7

Abstract

Nonthermal plasma, a nondestructive, fast, and highly reproducible surface functionalization technique, was used to introduce desired functional groups onto the surface of carbon powder. The primary benefit is that it is highly scalable, with a high throughput, making it easily adaptable to bulk production. The plasma functionalized carbon powder was later used to create highly specific and low-cost electrochemical biosensors. The functional groups on the carbon surface were confirmed using NH₃-temperature-programmed desorption (TPD) and X-ray photoelectron spectroscopy (XPS) analysis. In addition, for biosensing applications, a novel, cost-effective, robust, and scalable electrochemical sensor platform comprising in-house-fabricated carbon paste electrodes and a miniaturized E-cell was developed. Biotin-Streptavidin was chosen as a model ligand-analyte combination to demonstrate its applicability toward biosensor application, and then, the specific identification of the target Escherchia coli O157:H7 was accomplished using an anti-E. coli O157:H7 antibody-modified electrode. The proposed biosensing platform detected E. coli O157:H7 in a broad linear range of (1 × 10^-1-1 × 10⁶) CFU/mL, with a limit of detection (LOD) of 0.1 CFU/mL. In addition, the developed plasma functionalized carbon paste electrodes demonstrated high specificity for the target E. coli O157:H7 spiked in pond water, making them ideal for real-time bacterial detection.

Figure 1

Schematic diagram of the experimental setup for plasma carbon treatment.

Figure 2

(A) Schematic showing the steps required to form a bioelectrode to detect E. coli O157:H7. (B) Demonstration of bacterial detection in a miniaturized E-cell. (C) Experimental setup with the miniaturized E-Cell.

Figure 3

(A) Lissajous figure. (B) NH3-TPD for different functionalized carbons. (C) XPS analysis.

Figure 4

Biotin–Streptavidin detection. (A) Normalized current response obtained from DPV analysis for different concentrations of Streptavidin. (B) Normalized current response obtained from DPV analysis for different concentrations of PBS.

Figure 5

E. coli O157:H7 (EcO) detection, selectivity, and interference studies. (A) Normalized current response obtained from DPV analysis for various concentrations of E. coli O157:H7 at different incubation times (5 μg/mL anti-E. coli O157:H7 antibody concentration). (B) Normalized current response obtained from DPV analysis for various concentrations of E. coli O157:H7 at various concentrations of anti-E. coli O157:H7 antibody immobilized on a bioelectrode (incubation time of 30 min). (C) EIS analysis for various concentrations of E. coli O157:H7 detection (inset showing the modified Randle’s circuit). (D) Calibration graph showing the normalized charge transfer resistance obtained from EIS analysis for various concentrations of E. coli O157:H7 (5 μg/mL anti-E. coli O157:H7 antibody concentration with an incubation time of 30 min). (E) Selectivity and interference studies. (F) Bar graph showing the normalized charge transfer resistance obtained from EIS analysis for various concentrations of E. coli O157:H7 spiked in PBS and pond water.