Your Useless Inkjet Printer Could Soon Be Used to Test for Disease

​Imagine being able to test your ground beef for E. coli or quickly determine if your kid has strep throat using tests printed at home using nothing but your humble inkjet. Researchers at McMaster University in Canada say they have discovered a way to do just that using specially-developed "bio ink" that works with any standard inkjet printer.

The "bio ink" is made using aptam​ers: synthetic pieces of DNA that bind to a specific, predetermined molecule. When aptamers bind to their complementary molecule, they emit a small signal which can be amplified through biosensors to produce a visual signal, such as light or color.

To create a test, paper is printed with a series of aptamers that are designed to detect different biomarkers—anything from C. difficile to E. coli. The printer applies the aptamers in a preset pattern (like 'e' for E. coli). Then you add the sample of your kid's spit or a swab from your hamburger and if the signal molecules are detected, the ink appears—sort of like a home pregnancy test.

Aptamers have been used in molecular diagnostics for years, but the process was more or less limited to test tubes, according to John Brennan, director of McMaster's Biointerfaces Institute and co-author of a study​ published in Chemistry on their new findings.

"What we wanted to do was figure out how to make this work effectively on a piece of paper," Brennan told me.

The biggest hurdle was that these tiny aptamers wouldn't "stick" to the paper when printed, until Brennan and his colleagues tried a method called "rolling circle amplification" to beef up the size of the aptamers.

"It takes a short piece of DNA and it turns it into a very long polymer of the DNA that's just repeating the small unit over and over and over again," Brennan said. "We go from something that's small and has a molecular weight of a few thousand atomic mass units to a few million. By doing this, we could stick it into a $30 inkjet printer and print it on paper and because it's so big, it can't move. It was sort of a little 'eureka' moment."

To translate this process into simple-to-use, print-at-home tests, Brennan says the aptamers could be pre-packaged like ink cartridges, with accompanying software to print off the corresponding tests.

This process could greatly simplify the diagnostic process, both in the doctor's office and out in the field, as well as in food processing and water management, Brennan said. Right now, when someone goes into a doctor's office coughing up phlegm, it can be difficult to diagnose. They may have asthma, a bacterial infection, or a viral infection, and the only way to know for sure is to send the patient to a lab for a blood test. This new technology would allow doctors to print off a piece of paper in their office, determine if an infection is bacterial or viral and go from there.

The tests could even be designed to detect early signs of cancer by measuring a protein called Platelet-derived growth factor, Brennan said, and would particularly useful for doctors doing fieldwork in remote locations. It's not the only technology capable of helping in this field—there are researchers developing all kinds of incredible, portable tech like a tiny mi​crochip that could run 100 tests on a single drop of blood—but it could be a useful contribution.

Brennan envisions that food processors could also use the technology to print labels that automatically detect common food-riding bugs such as E. coli and listeria. Though it would require clearing some regulatory hurdles, Brennan envisioned the technology being used at home, too.

"If you look in a standard university lab at what they would call a diagnostic system, it very often is this big, cumbersome box that has lots of expensive parts in it," Brennan said. "But this is as easy as using an office inkjet printer to produce literally tens of thousands of these tests per day."