Image created by Dr. Michael J. Miller
In a recent article published in the journal LWT - Food Science and Technology, researchers presented a novel electrochemical sensor based on molecularly imprinted polymers (MIPs) integrated with screen-printed electrodes (SPE) that allows for rapid and specific detection of Salmonella typhimurium in food samples. The sensor aims to provide a more efficient alternative to conventional detection methods, thereby enhancing food safety protocols.
Background
Salmonella typhimurium is a foodborne pathogen responsible for numerous outbreaks of gastroenteritis worldwide. The ability to detect this bacterium quickly and accurately in food products is essential for preventing foodborne illnesses and ensuring food safety and public health.
Traditional methods for detecting these pathogens, such as polymerase chain reaction (PCR) and enzyme-linked immunosorbent assay (ELISA), often require extended periods for sample processing and analysis, which can delay timely interventions.
The introduction of molecularly imprinted polymers offers a promising solution, as these materials can be engineered to selectively bind specific target molecules, thereby improving the sensitivity and specificity of detection. The integration of these polymers with electrochemical sensors allows for real-time monitoring and rapid response to contamination, making it a valuable tool in food safety management.
The Current Study
In this study, the researchers constructed the sensor using screen-printed gold film electrodes, which were first cleaned with ethanol and deionized water, then dried under nitrogen. Electropolymerization of dopamine was performed in a Tris buffer (pH 8.5) containing 0.1 M dopamine using cyclic voltammetry (CV) at a scan rate of 50 mV/second for 10 cycles.
During this process, Salmonella typhimurium was introduced to create specific binding sites. After polymerization, the electrodes were rinsed, and bacteria were eluted using various agents, including sodium chloride and a mixture of 1 % Tween 80 and 10 % acetic acid, to optimize the removal of bacteria while preserving the imprinted sites.
To prepare the samples, 1 gram of minced pork or 1 milliliter of milk was combined with 1 milliliter of a Salmonella typhimurium suspension (104 CFU/ml) and then diluted 100 times with phosphate-buffered saline (PBS). A control group without bacteria was established. After mixing, 30 μl of each sample was incubated on the sensor for 4 minutes and rinsed with PBS. Electrochemical measurements were conducted using CV and differential pulse voltammetry (DPV) in a three-electrode system.
The CV was performed over a potential range of -0.2 to +0.8 V to assess redox behavior, while DPV enhanced sensitivity. Peak currents were analyzed to determine the presence of Salmonella typhimurium and calibration curves were constructed to evaluate sensitivity. Specificity tests were conducted with other pathogens. Statistical analysis, including t-tests, was performed to validate results, with a significance level of p < 0.05. This methodology highlights the innovative use of MIPs in enhancing food safety practices.
Results and Discussion
The results demonstrated that the electrochemical sensor effectively detected Salmonella typhimurium in both pork and milk samples. The sensor achieved a low detection limit of 101 CFU/ml, indicating its high sensitivity. The electrical signals generated from the contaminated samples were significantly higher than those from the blank control group, confirming the sensor's ability to identify the presence of the pathogen.
Notably, the signals from milk samples were slightly more pronounced than those from pork samples. This difference was attributed to the solid form of the pork, which might have obstructed the interaction between the bacteria and the sensor, possibly due to blockage by minced meat particles.
The study also explored the sensor's specificity by testing its response to other bacteria similar in size or shape to Salmonella typhimurium. The findings revealed that while some other bacterial species produced electrical signals, they were significantly lower than those generated by Salmonella typhimurium, underscoring the sensor's specificity. The optimal elution method was identified as a combination of 1 % Tween 80 and 10 % acetic acid, which effectively removed the bacteria from the polymer surface, enhancing the sensor's performance.
The rapid detection time of the sensor, which required only 4 minutes for incubation and less than 25 minutes for the entire process, represents a significant advancement over traditional methods. This efficiency is particularly beneficial in clinical and food safety applications, where timely results are crucial for preventing outbreaks.
Conclusion
In conclusion, the sensor demonstrated high sensitivity, specificity, and a significantly reduced detection time compared to conventional methods. The findings highlight the importance of innovative detection technologies in enhancing food safety and public health.
By providing a rapid and efficient means of identifying foodborne pathogens, this electrochemical sensor has the potential to transform food safety practices and contribute to the prevention of foodborne illnesses. Future research may focus on further optimizing the sensor's performance and expanding its applicability to a broader range of foodborne pathogens, ultimately leading to improved food safety outcomes.
Journal Reference
Wang Y., He X., et al. (2024). Rapid detection of Salmonella typhimurium in food samples using electrochemical sensor. LWT - Food Science and Technology 206, 116567. DOI: 10.1016/j.lwt.2024.116567