Six Degrees of Cytometry

Courtesy of Amnis High-throughput cell screening has been, and still is, a cornerstone of fast-paced drug-discovery labs, but nowadays speed is not always enough. Content is key, and a Seattle-based startup company has entered the high-throughput cell imaging market with a novel system that could dramatically increase the amount of information available in a given assay. Amnis' ImageStream™ system combines the throughput of flow cytometry with the imaging power of microscopy to offer fast multispectral imaging of moving cells. The system produces up to six separate images of each cell, including brightfield and darkfield images as well as four fluorescent channels. More than 25 parameters can be obtained for each image, and Amnis claims its system offers the highest amount of information per cell of any technology available. The theme of the technology, says chief technology officer David Basiji, is to "provide the high information content that you get with an image as you would in microscopy, but with six different images, and at the same time give you the statistical power of flow cytometry." By providing a mechanism to analyze large populations of cells, Basiji adds, the technology allows researchers to derive statistically significant conclusions from the imagery. The ImageStream system uses Time Delay Integration (TDI) CCD (charge-coupled device) detection to improve sensitivity and increase throughput. Unlike conventional CCD cameras, which read the entire array of pixel values on the CCD chip simultaneously, TDI detection reads the bottom row of pixels, shifts the data down by a row, and continues the process so that the data on the chip continuously moves along one axis, Basiji explains. "If you know how fast the cell is moving, you can synchronize the readout of the chip with the motion of the cell. In effect you're electronically panning the camera to track the motion of the cell," says Basiji. Thus, the system collects signals from the cell the entire time it is in front of the camera, "which can be 500-1,000 [times] longer than [with] ... a conventional imaging approach," Basiji adds. IN BETA TESTING The ImageStream 100 benchtop imaging cytometer can be used for any flow-cytometry assay. It is currently available for beta purchase and has already been tested by a number of academic and pharmaceutical laboratories. B. Robert Franza, research professor and director of the Cell Systems Initiative, University of Washington (UW/CSI), has been involved with Amnis from its inception and is currently helping to develop the next generation of the ImageStream system. The UW/CSI, he says, will have one of the first beta versions of the flow system and already has a backlog of "years worth of science enabled by the Amnis system." Franza says that the ImageStream will enable high-throughput in situ hybridization experiments with live cells once the chemistry is perfected; other potential applications include detection of rare cells and identification of subpopulations of cells. Users who have compared the system to traditional flow cytometry and confocal imaging systems found that Amnis' technology provides even more information than the two other systems combined and in some cases offers information unobtainable by other methods. In one example, presented at the International Society for Analytical Cytology XXI Congress in 2002, scientists at Amgen used the ImageStream system to identify not only specific cell lineages in murine bone marrow cells but also subpopulations of those cells according to physical characteristics. Such data, the study's authors say, would not have been obtainable with a standard flow cytometer. "If you're looking at different populations of cells ... you can find a really small population of cells that has very particular characteristics that you probably wouldn't have been able to see just by conventional flow cytometry or conventional confocal microscopy. You're able to look at the data in a number of different ways, to put it together and create different patterns out of it," says one beta-tester who requested anonymity. The user adds that the ImageStream system also can be used to study cell-cell interactions, as it can obtain brightfield images of individual cells as they pass through the laser for interrogation. In contrast, a flow cytometer provides signals that are relative to size and fluorescence but does not image each cell that is analyzed. Basiji says that the ImageStream system will ultimately replace flow cytometry, but that the first-generation instrument is not yet capable of cell sorting. "Other than that, I don't think there's really anything that a cytometer could do that we couldn't do as well or better, because we're essentially getting a few hundred times more information from a cell than a flow cytometer does," he says. --Aileen Constans function sendData() { document.frm.pathName.value = location.pathname; result = false if (document.frm.score[0].checked) result = true; if (document.frm.score[1].checked) result = true; if (document.frm.score[2].checked) result = true; if (document.frm.score[3].checked) result = true; if (document.frm.score[4].checked) result = true; if (!result) alert("Please select") return result; } .myradio{background-color : #94bee5} Please indicate on a 1 - 5 scale how strongly you would recommend this article to your colleagues? 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Six Degrees of Cytometry

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