Issue Date: February 5, 2007
Low-Cost Paper Diagnostics
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 now 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 UV light to create a millimeter-sized channel and wells, and adding reagents for detecting multiple biological analytes from a single sample. In the example shown, one well contains a glucose assay based on the enzymatic oxidation of iodide to iodine with an accompanying color change from clear to brown. Another well detects 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, but more than 10 minutes is required for the colors to develop fully. The bioassay paper can detect clinically relevant concentrations of glucose and protein, the researchers report.
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