KU Leuven: 3D printing lays the foundation for a new arsenal of diagnostic tests

Researchers at KU Leuven have developed a 3D printing technique that extends the possibilities of lateral flow testing. Everyone is familiar with these tests in the form of the classic pregnancy test and the COVID-19 self-tests. With the new printing technique, advanced diagnostic tests can be produced that are quick, cheap and easy to use.

The COVID-19 pandemic has made everyone aware of the importance of prompt diagnosis and the complications that can accompany it. The sale of self-tests has been allowed in Belgium since the end of March.

This self-test is an example of a ‘lateral flow test’. With a wiper you take a sample through the nose. The sample is dissolved in a solvent and applied to the test kit. Absorbent material in the kit carries the sample and allows it to interact with an antibody. If virus is present, a colored dash will appear. The advantage of these tests is that they are cheap and do not require additional equipment.

This principle works well for simple tests that result in a yes-no answer, but not for tests that require multiple steps. That is why bio-engineers at KU Leuven went in search of a new type of lateral flow testing with more options.

Using a 3D printer, the researchers fabricated a 3D version of a lateral flow test. The basis for this is a block of porous polymer in which ‘inks’ with specific properties are printed at precise locations. In this way, a network of channels and small ‘locks’ is printed that block or let the flow through where and when it is needed, without the need for moving parts. During the test, the sample is automatically guided through the various test steps.

The researchers tested their technique using an ELISA test ( Enzyme-Linked Immunosorbent Assay ) to detect immunoglobulin E (IgE). Ig E is measured to diagnose allergies. In the lab, this test requires several steps, with different rinses and a change in acidity. The research team was able to perform the full analysis on a printed test kit the size of a thick bank card.

“The great thing about 3D printing is that you can quickly adapt the design in a digital way to another analysis, for example to detect a biomarker for cancer. For the 3D printer it does not matter how complex you make the network of channels ”, says Dr. Cesar Parra. The 3D printing technique is also affordable and scalable. “In our lab, the production cost of the IgE test prototype is around 1.50 euros, but if we can scale it up, it would be less than one euro,” says Dr. Parra. For example, the technique not only offers opportunities for cheaper and faster diagnosis in developed countries, but also in countries where the medical infrastructure is scarcer and where there is a need for affordable diagnostic tests.

The research group is currently designing its own 3D printer. It will be more flexible than the commercial model that was adapted for the current research. “You can see such an optimized printer as a mobile ‘mini factory’ with which you can quickly produce diagnostic tests. You simply adjust the design file and ink according to the type of test you want to print. We want to continue this research with the help of partners and work together on concrete diagnostic challenges and applications ”, innovation manager Bart van Duffel concludes.