University of Maastricht spinout Sensip-dx has developed a sensor device that could significantly speed up microbiological testing, enabling food and beverage processors to detect the presence of pathogenic bacteria sooner.
According to Jaap Drenth, co-founder of Sensip-dx, his company’s rapid detection method could potentially prevent the occurrence of food safety incidents like the recent E.coli outbreak, in which dozens of people across multiple US states fell ill after eating contaminated carrots.
“A lot of the time, in vegetable processing, the issue has to do with rinse water. Carrots are washed to remove the soil, and this rinse water is being used over and over. So, if bacteria from the soil contaminates the water, it has plenty of opportunity to multiply,” Drenth explained.
“Our sensor technology offers a way of controlling rinse water for pathogenic bacteria. By giving fast results, it allows processors to identify the presence of bacteria and control it.”
The rapid detection technology in question uses sensors that consist of a tiny aluminium plate coated with a thin polymer layer. Action points or ‘receptors’ for a certain type of bacteria are imprinted within the polymer, and when a liquid containing bacteria flows over the sensor, only that type of bacteria binds itself to the receptor. The sensor detects the presence of the bacteria using thermal measurements – the higher the thermal resistance, the more bacteria are present.
Going into further detail about the design of the sensors, Drenth told Fi Global Insights: “We stop the polymerisation process partway through and physically press living bacteria into the half-cured polymer. This creates an imprint of the bacteria in the plastic, and it creates some chemical bonds between the surface and the bacteria.
“When we then put the polymer back in the oven, the polymerisation process continues but the bacteria die, so what remains is the imprint and the chemical bonds, which is what we refer to as the ‘action point’.”
The coated plate is then incorporated into a flow cell, which is initially filled with a neutral fluid, followed by the sample fluid, and finally the neutral fluid again.
“As the sample fluid enters the flow cell, bacteria will bind if they are present. The neutral fluid afterwards ensures that everything has gone except the bound bacteria when we take the thermal measurements,” said Drenth.
The receptor layer is subsequently heated via an attached copper plate, and thermal measurements determine the extent to which the heat is being transferred and how it is being transferred.
“If the thermal resistance has increased, this means that more bacteria are bound, indicating the presence of bacteria,” Drenth added.
The base technology itself is not new – molecularly imprinted polymers (MIPs) and surface imprinted polymers (SIPs) have been around for several decades and are used industrially for the purification of gases through solid phase extraction.
The University of Maastricht is behind much of the work that has advanced the technology for food applications. In 2016, for example, Dr Thomas Cleij and Dr Bart van Grinsven invented and patented the technique for using thermal resistance to detect the presence of bacteria. Sensip-dx was founded in 2020 to commercialise this technology, and, since then, the startup has conceived further ‘improvements’, such as incorporating the flow cell into a compact cartridge format, for which it is filing patents.
“We insert the sample fluid into the cartridge, put the cartridge in a machine, and wait for the results. That takes about 15 minutes,” Drenth explained.
This is considerably quicker than conventional methods for detecting foodborne bacterial pathogens, which are based on culturing the microorganisms on agar plates.
“The bacteria have to be incubated and, depending on the type of bacteria, this can take between one and three days,” Drenth noted.
As a result, these conventional methods are of fairly limited use for containing outbreaks, as by the time the results are available, the product is usually already on the shelf, which means a product recall is the only course of action.
In contrast, a rapid detection method such as Sensip-dx’s technology will allow manufacturers to test incoming ingredients or finished products before they are packed or leave the factory, so they can avoid costly recalls by controlling and eliminating the contamination.
The technology has been shown to be effective for all known foodborne bacterial pathogens and can be used to test a range of foods, including raw meat, nuts, grains, herbs, and vegetables, by creating a homogeneous sample.
However, the sensors are still some way off from being applied as an in-process detection method – Sensip-dx is currently working with some early business partners to develop tuned prototypes with a view to the first commercial products (for laboratory sampling) being ready by 2025.
“We have invested more than €2m in getting to where we are today, and we still have to invest more to get to market. We are selecting our early business partners carefully, as we want to be sure that we are targeting applications where they will gain a lot of value from using our technology,” said Drenth.
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