Low-Cost Diagnostics On A Piece Of Paper

Many clinical diagnostic methods are too complicated and too expensive to be used widely in developing countries. George M. Whitesides and his coworkers at Harvard University have thus come up with a practical method for making low-cost, portable, and simple multiplexed bioassays out of paper (Angew. Chem. Int. Ed., DOI: 10.1002/anie.200603817).

Their photolithography technique involves soaking chromatography paper in photoresist, using a mask and ultraviolet light to create a millimeter-sized channel and wells, and adding reagents for detecting multiple biological analytes.

The researchers made a glucose assay in one well based on the enzymatic oxidation of iodide to iodine with an accompanying color change from clear to brown. In a different well, they detect a protein on the basis of the color change of tetrabromophenol blue from yellow to blue when it binds the protein. The sample fluid fills the channel within a minute, and then more than 10 minutes are required for the colors to develop fully. The bioassay paper can detect clinically relevant concentrations of glucose and protein, the researchers report.