The cytometer chip is approximately 25 mm wide and 50 mm long (about 1 x 2 inches). The two bright blue spots are the points where the particles in the fluid are illuminated by laser light. Two fluorescence output signals from each point are carried off by fiber connections at right. There are five inputs at the top of the chip – one for the sample and four to create the fluid sheath.
Credit: G. Cooksey/NIST
Measuring the numbers and properties of cells moving in a stream — a process called flow cytometry — is critically important to diagnostic medicine, pharmaceutical research and biomedical science. Now researchers at the National Institute of Standards and Technology (NIST) have devised a way to make unprecedented improvements in the technique.
Flow cytometry typically entails marking cells with fluorescent material, shining laser light on them as they cross one particular point in a fluid channel about the size of a human hair — narrow enough that the cells generally move in single file — and recording the light emitted by the markers on the cell. Analyzing the emissions reveals various characteristics such as cell type, size, DNA content, and stage in the cell-division cycle.
But the conventional single-measurement method lacks a means to quantify the variations in its readings. For example, a cytometer that measures cancer biomarkers may use a specific measurement value to decide between healthy or diseased cells. One cell may return a slightly lower value, identifying it as healthy. But the range of values the instrument might return for repeated measurements of this cell is unknown.
That is problematic because it is not known how often the value might misrepresent the diagnosis. For example, high confidence is imperative when counting circulating tumor cells, which lead to cancer metastasis; there may ..
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