Researchers from KU Leuven (Belgium) have developed a 3D printing technique which extends the possibilities of lateral flow tests. These tests are widely used in the form of the classic pregnancy test and COVID-19 self-tests. With the new printing technique, advanced diagnostic tests can be produced, fast, inexpensive and easy to use.
The COVID-19 pandemic has made everyone aware of the importance of a rapid diagnosis. The sale of self-tests in pharmacies has been authorized in Belgium since the end of March. This self-test is a so-called lateral flow test. Using a wiper, a sample is taken through the nose. Then it is dissolved in a solvent and applied to the test kit. The absorbent material in the kit moves the sample downstream and contacts it with an antibody. If a virus is present, a colored line appears. The advantage of these tests is that they are inexpensive and do not require any specialized device.
Lateral flow tests are useful for simple tests that result in a yes-no answer, but not for tests that require a multi-step protocol. That is why the bioengineers at KU Leuven decided to develop a new type of lateral flow test with more capabilities.
Using a 3D printer, the researchers fabricated a 3D version of a lateral flow test. The base is a small block of porous polymer, in which “inks” with specific properties are printed in specific places. In this way, a network of channels and small “locks” is printed which allows flow to pass or blocks it where and when it is needed, without the need for moving parts. During the test, the sample is automatically guided through the different stages of the test. This way even complex protocols can be followed.
The researchers evaluated their technique replicating an ELISA (Enzyme-Linked Immunosorbent Assay), which is used to detect immunoglobulin E (IgE). Ig E is measured to diagnose allergies. In the laboratory, this test requires several steps, with different rinses and a change in acidity. The research team was able to perform all of this protocol using a printed test kit the size of a thick credit card.
Complexity is not a cost
“The advantage of 3D printing is that you can quickly adapt the design of one test to another protocol, for example, to detect a cancer biomarker. For the 3D printer, the complexity of the channel network does not matter ”, explains Dr. Cesar Parra. The 3D printing technique is also affordable and scalable. “In our lab, it costs around $ 1.50 to produce the prototype Ig E test, but if we can scale it up, it would be less than $ 1,” says Dr. Parra. This technique not only offers cheaper and faster diagnostic possibilities in developed countries, but also in countries where the medical infrastructure is less accessible and where there is a great need for affordable diagnostic tests.
The research group is currently designing their own 3D printer, which will be more flexible than the business model used in the current study. “An optimized printer is a bit like a mobile mini-factory that can quickly produce diagnostics. You can then create different types of tests just by uploading a different design file and ink. We want to continue our research into diagnostic challenges and applications with the help of partners, ”concludes Innovation Director Bart van Duffel.
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