Brigham Young University researchers have developed a simple new way of detecting tiny concentrations (down to a nanogram – one billionth of a gram) of a given chemical without the use of any complicate and expensive equipment.
They created narrow channels within glass slides that are lined with receptors for the chemical to be quantified. When a sample drop is placed at one end of a channel, it is drawn in by capillary action. As the target molecules are captured by the receptors, the channel gradually becomes constricted. The distance that the liquid manages to travel is inversely proportional to the quantity of the target molecule in the sample.
From the study abstract:
We have tested these devices using the model system of biotin as a receptor and streptavidin as the target. We have also characterized three factors that influence flow distance: solution viscosity, device thickness, and channel height. We found that solution capillary flow distance scales with the negative logarithm of target concentration and have detected streptavidin concentrations as low as 1 ng/mL. Finally, we have identified and evaluated a plausible mechanism wherein time-dependent channel constriction in the first few millimeters leads to concentration-dependent flow distances.
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