If you’ve ever sat opposite a doctor and wondered what she was scribbling on her notepad, the answer may soon not only be medical notes on your condition, but real-time chemical preparations for an instant diagnostic test.
Thanks to the work of a team of researchers from California Polytechnic State University, recently published in the journal Lab on a Chip, chemicals formed into pencils can be made to react with one another by simply drawing with them on paper. The team may have taken inspiration from colouring books for their take on a chemical toolkit, but their approach could make carrying out simple but common diagnostic tests based on chemical reactions – for example diabetes, HIV, or tests for environmental pollutants – much easier.
Here’s a picture of the pens,
Lorch provides a good description of the technology giving descriptions of reagents and paper-based microfluidics, as well as, describing how the researchers turned the concept of colouring pencils into a diagnostic tool.
Lorch also provides a description of a specific test (Note: Links have been removed),
The team demonstrated a potential use of the reagent pencil technique by using it in place of a common test used by diabetics to check their blood glucose levels, which involves reacting a pinprick blood sample with a chemical solution and examining the result.
One pencil was constructed with a mixture of enzymes, one called horseradish peroxidase (HRP) and the other glucose oxidase (GOx). A second pencil contained a reagent called ABTS. When combined in the presence of glucose these react together to give a blue-coloured product. Comparing the results from their pencils on the pad with the more traditional dropper method used by diabetics the team found the results were identical.
This new ‘pencil kit’ diagnostic technology is easy to use and features a big improvement over the current diagnostic tests,
This is of course extremely easy to set up. Traditional diagnostic tests require training, while this pad and pencil system requires no more than skill than required to colour within the lines. The reagents are extremely stable once made into pencils – usually they would degrade in a matter of days as liquids, limiting how and where the tests can be made. However the reagent pencils showed no sign of degrading after two months.
Being able to use the pencils for two months as opposed to liquids that remain viable for a few days? That’s a huge jump and it makes me wonder about using these kits in harsh conditions such as desert climates and/or emergency situations. Materials that don’t need to be refrigerated and could be used for up to two months and don’t require intensive training could be very helpful. Lorch suggests some other possibilities as well,
… There’s scope to monitor environmental pollutants, carry out diagnostic tests in remote locations – not to mention teach chemistry in primary schools.
Here’s a link to and a citation for the study on the ‘colouring pencil kit’,
Reagent pencils: a new technique for solvent-free deposition of reagents onto paper-based microfluidic devices by Haydn T. Mitchell, Isabelle C. Noxon, Cory A. Chaplan, Samantha J. Carlton, Cheyenne H. Liu, Kirsten A. Ganaja, Nathaniel W. Martinez, Chad E. Immoos, Philip J. Costanzo, and Andres W. Martinez. Lab Chip, 2015, Advance Article DOI: 10.1039/C5LC00297D First published online 08 Apr 2015
This paper is open access but you do have to register on the site unless you have another means of access.