Poster V19 - A rapid electro analytical device platform for screening salmonella in water samples

Introduction: Salmonella contamination poses a significant global health threat, causing widespread foodborne illness. However, existing detection methods, primarily reliant on culture-based techniques, are limited in both sensitivity and speed. There is an urgent need to improve early detection to reduce the frequency and impact of Salmonella outbreaks. Our study introduces a portable electrochemical sensing platform capable of rapidly detecting Salmonella in potable water, with a turnaround time of approximately nine minutes. We assessed two sensor configurations: one utilizing pure gold (Au) and the other incorporating a zinc oxide thin film coated on the gold surface (Au/ZnO) to enhance sensing capabilities. Through comprehensive experimentation, we determined the Limit of Detection (LoD) values for the Au and Au/ZnO sensors to be 0.9 and 0.6 CFU/mL, respectively. Both sensors demonstrated consistent precision and reproducibility, with percentage coefficient of variation (%CV) consistently below 10%. Our findings highlight the platform's high sensitivity in detecting low Salmonella concentrations, offering potential as a rapid, on-site detection tool for water quality monitoring. This research paves the way for electrochemical-based sensors to play a vital role in food safety and public health, mitigating Salmonella outbreaks and improving water quality assessment.

Materials and

Methods: The study employed polyclonal Salmonella antibody (10 μg/mL) from Invitrogen and heat-killed Salmonella typhimurium cells at concentrations ranging from 10^1 to 10^6 CFU/mL. Dithiobis(sulfosuccinimidyl Propionate) (DTSSP) crosslinker (10 mM) and Phosphate Buffer Saline (PBS, pH 7.4) were sourced from Thermofisher Scientific Inc. Samples were stored at -20°C until use. Sensor fabrication utilized a portable printed circuit board (PCB) platform with gold (Au) surfaces and zinc oxide (ZnO) nanomaterial-coated electrodes. ATR-IR spectroscopy employed a Nicolet iS-50 FTIR instrument, while zeta potential measurements were conducted using a Malvern Zetasizer NanoZS.

In this study, both Au and Au/ZnO electrodes were used. They were modified with 10 mM DTSSP and Salmonella antibody (10 μg/mL in 250 μL PBS). After incubation at 4°C for 30 minutes, the electrodes were washed with PBS. Then, another DTSSP-antibody mixture was applied and incubated for 30 more minutes at room temperature. Real samples (5 μL) were applied and allowed to incubate for 9 minutes, followed by data recording using a reference potentiostat. Electrochemical impedance spectroscopy (EIS) with a minor 10 mV AC bias measured the electrochemical response, reflecting changes in the double layer charge due to Salmonella binding.

Results, Conclusions, and Discussions: The study utilized affinity-based functionalization for Salmonella detection, successfully modifying the electrode surface and confirming the antibody immobilization through FTIR analysis. Surface plasmon resonance studies elucidated antibody-antigen binding kinetics, validating the immunoassay stack's accuracy. Zeta potential measurements provided insights into Salmonella's surface charge and stability in potable water. Non-faradaic electrochemical impedance spectroscopy captured binding events at the electrode-electrolyte interface, highlighting the sensors' enhanced sensitivity in detecting Salmonella, particularly with Au/ZnO modification. Spike and recovery experiments demonstrated strong correlations between estimated and actual Salmonella concentrations, with both sensors exhibiting low limits of detection. Cross-reactivity studies confirmed the sensor platform's specificity, while correlation analysis between portable and benchtop devices validated field deployment feasibility. Reproducibility and repeatability tests showcased consistent sensor performance in detecting Salmonella in potable water matrices. Overall, the study's findings underscore the potential of electrochemical-based sensing platforms in mitigating bacterial outbreaks and ensuring the safety of potable water.

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