UK/NETHERLANDS – Escherichia coli can now be detected in milk without sample preparation thanks to the development of a unique thermal biosensor for real-time detection.

The sensor has the potential to be a low-cost, quick instrument for onsite microbiological indication and would be simple to mass-produce.

The approach is based on screen-printed electrodes (SPEs), which are functionalized via a straightforward surface-imprinting method. This method is an easily scalable method for producing synthetic receptors.

The material proposed for imprinting is Polydimethylsiloxane (PDMS), a commercially available resin that is widely employed in soft lithographic applications. 

Its use reduces batch-to-batch variability in receptor preparation since no synthesis is required, and offers the ability to bind and sort bacteria when acting as a recognition element.

Due to their affordable and scalable production procedure, SPEs have recently grown in popularity for use in biosensor applications. The SPEs were used in combination with the heat transfer method to detect E. coli.

Escherichia coli, a key cause of foodborne diarrhea, is a widespread bacterium found in the human intestinal tract. The presence of this microorganism is employed as a hygiene environmental indicator.

Plate counting, which is still the gold standard detection methodology in most cases, requires long laboratory incubation times that can take several laboratory hours and transport to a lab facility, often external, which stretches the entire procedure over a few days, say the researchers. 

They add that polymerase-chain-reaction (PCR) is a promising alternative that is much faster and possesses sensitivity but also has some obstacles that impede its widespread implementation since it can be costly and requires specialized equipment and skilled operators.

Researchers used Cronobacter sakazakiiKlebsiella pneumonia, and Staphylococcus aureus to test the sensor’s selectivity.

The findings imply that the sensor can recognize food samples with a high bacterial load.

When compared to C. sakazakiiS. aureus, and K. pneumoniae, its reaction to E. coli was three times higher, and around two times higher, respectively.

It is suggested that the gadget be used as a quick pre-screening tool in conjunction with current best practices.

The sensor was tested in milk samples that had been inoculated with E. coli without the requirement for sample preparation in order to demonstrate the sensor’s usefulness. The outcomes matched those of a buffer experiment.

Overall, the sensor enables the label-free quantification of the pathogen using experimental protocols that call for little to no apparatus, as well as the real-time detection of E. coli.

The researchers urge more research to test the sensor in more complicated food products that could affect the sensor’s selectivity or sensitivity, such as increased fluid dairy products and extracted solid food products.

The study was a combined effort of researchers from the Sensor Engineering Department, Faculty of Science and Engineering, Maastricht University, and Faculty of Science and Engineering, Manchester Metropolitan University, United Kingdom.

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