High Tech Meets Low Tech

An inexpensive diagnostic test made from paper has been developed that can assess liver health in 15 minutes and for only pennies a test. The test uses a single drop of blood from a finger prick to measure the presence of liver enzymes, and doesn't require the presence of a laboratory, instruments, or syringes. If liver enzymes are present in the blood, wells within the paper will show a color change, which are be color matched to a scale to determine approximate degree of concentration. A color change indicates the concentration range of enzymes present. Though this can be checked by eye, greater accuracy could be achieved by scanning the paper with a smartphone, which are incredibly prevalent throughout regions in which the kit would be used.

Liver damage can be a consequence of taking antiretroviral drugs, which are prescribed to HIV patients. Because of the high HIV infection rates in poor countries, liver problems are on the rise, so the ability to cheaply monitor blood is important to prevent potentially fatal side effects of the drugs meant to save people’s lives.

The paper uses patterns, channels, and assay zones (or wells) of water-repellent materials on a piece of paper about the size of a postage stamp. Biological and chemical assay reagents are then deposited in the wells. When blood, urine, saliva, sweat or other biological samples are applied to it, the paper wicks the sample through the channels to the assay zones, without external pumps or power. Upon contact, the assay zone quickly changes color and results are then easily read by comparing the color change with a printed reference scale. After use, it can be easily disposed of by burning.

These patterned paper-based devices can be embedded with electrical circuitry to enable resistive heating, electrochemical assays, or initial processing of assay results. Multiple sheets of patterned paper can be stacked to generate three-dimensional devices capable of automatically performing a variety of complex fluid operations such as splitting, filtration, mixing, and separations.

The postage stamp-sized paper diagnostics system was developed in the laboratory of Harvard Professor George Whitesides seven years ago. With funding from the Bill and Melinda Gates Foundation, Professor Whitesides started the non-profit organization, Diagnostics For All., and looked to improve the health of the poorest areas of the world. The team is also working on malaria and dengue fever tests.

An ink jet printer using wax ink prints a pattern on two sheets of paper. One sheet contains reagents that react with liver enzymes, the other dyes that change color if a reaction occurs. The two sheets are fused together by heating, so that channels or wells that can be used as miniaturized test tubes for reactions are produced. A plasma filter is added and the three are laminated together, and cut into postage stamp size squares. The rest of the world could also benefit from this low cost efficient healthcare.