Josh P. Roberts has an M.A. in the history and philosophy of science, and he also went through the Ph.D. program in molecular, cellular, developmental biology, and genetics at the University of Minnesota, with dissertation research in ocular immunology.
It’s hard to say what exactly defines a “personal” flow cytometer (or cell analyzer). Is it price? Footprint? Ease of maintenance? It’s certainly not functional capabilities, which in some cases rival just about anything found in a core lab.
No, what perhaps comes closest to defining a personal flow cytometer is ease-of-use. Personal cell analyzers are benchtop instruments that generally don't require a skilled dedicated operator to use.
Ease-of-use is in fact a major theme running through most vendors’ descriptions of their own cell analyzer instruments. That may mean anything from user installation, to push-button sample acquisition, to automated compensation to walk-away shutdown. All of which, to anyone familiar with the way flow cytometry was done even in the aughts, is huge.
Of course, a graphite pencil is easy to use too, but Van Gogh couldn’t have created The Starry Night with one. Here we survey the field and give you tips for what to consider the next time you want to add a little color to your own workflow.
Open or closed?
Personal instruments may be ideal for pre-set routines. EMD Millipore’s Muse® Cell Analyzer, for example—a sub-$15,000, toaster-sized single-laser flow cytometer—has about 25 pre-designed assay kits and optimized software programs that were developed for the system, with applications for cell health, cell signaling and immunology, explains product manager Louise Rollins.
"Muse is the perfect option for simple, convenient, flow based analysis for routine applications, where researchers don't have the budget or complex software expertise necessary to operate the more sophisticated, versatile flow systems," Rollins says.
But Muse is a closed system.
Most research cytometers, in contrast, are open, offering users control over the instrument’s parameters and allowing them to design their own experiments.
Many systems are open in another sense as well. A given product line can often be configured with custom numbers and types of lasers, detection channels and other features as well. Thermo Fishers’ new Attune® NxT Acoustic Focusing Cytometer, for example, is “designed to meet all the lab needs,” says senior marketing development manager Shane Oram.
For basic green fluorescent protein (GFP) or bacterial work a one-laser, four-color instrument would likely suffice. Yet the field-upgradable modular instrument can grow with the lab’s research, Oram says. “The one-laser version is actually the exact same as the four-laser version, just missing the additional lasers, PMTs [photomultiplier tubes] and filters. But the fluidics, electronics and everything else are exactly the same.”
But not every component on every system is field-upgradable, so if there’s a feature you anticipate needing in the future, make sure your purchase will be accommodate it when the time comes. Customers opting for EMD Millipore’s guava easyCyte™ line, for example, need to decide at the time of purchase both how many lasers and colors they want, and whether they are interested in the HT version (equipped with an automated liquid handler to handle up to 10 tubes or a 96-well plate) or the less expensive single-tube option.
The optics
The complexity of a flow cytometry experiment that an instrument can run is largely a function of its optical configuration.
In a typical flow cytometry experiment, researchers label cells with one or more fluorescent probes, one for each parameter of interest. For example, they may use propidium iodide to stain the DNA of all cells and an antibody against a cell-surface marker to flag, say, CD4+ T cells. As cells travel single-file at high speed past one or more light sources and detectors, their fluorescent characteristics—color and intensity—are recorded. So, too, are the cells’ light-scattering properties: Forward scatter (FSC), which is a rough indicator of particle size, and side scatter (SSC), a measure of granularity. (“Number of colors,” “detection channels,” and “parameters” are often used interchangeably, although the latter two will technically be a larger number in that it includes FSC and SSC. If in doubt, ask.)
Thus even in the simplest experiments at least three parameters are typically recorded for each and every cell—generally many tens to hundreds of thousands of them—allowing researchers to quickly generate powerful statistics.
Obviously, the more lasers and detectors your instrument has, the more you can do with it. But, as the number of lasers and colors increase, so does the price. For example, the one laser, three color ACEA NovoCyte™ costs under $40,000, while the same system with three lasers, 13 colors and the NovoSampler autosampler will set a lab back just under $100,000, says Rene Nunez, senior product marketing manager.
Thus, as you consider your options ask yourself what you realistically need your instrument to be able to do. You may be able to save some money if you opt for a cheaper instrument that can handle most of your lab’s day-to-day needs, especially if you have a core facility available to take up the slack on more complicated experiments.
The specs
When comparing instruments, it’s easy to get lost amid the noise of competing feature sets. Most personal cell analyzers yield absolute cell count without the use of counting beads. Some may be able to query up to 35,000 events per second or process 1 ml fluid/minute, while another boasts seven decades of dynamic range. For the vast majority of researchers, any of these instruments (properly configured) will allow them to do the vast majority of their research. That being said, there are some features and specifications that may matter to your research.
The Attune NxT uses acoustic waves to focus the cells (rather than traditional hydrodynamic focusing, which sends the cells through a rapid stream of sheath fluid). As such, the instrument can “vary the sample input rate without affecting sensitivity and precision,” says Oram, allowing both very dilute and very concentrated samples to be queried.
The easyCyte instruments, on the other hand, based on a microfluidic platform, can handle as few as 1,000 precious cells in a sample and generate less than 50 ml of non-toxic waste in eight hours of continuous use.
Beckman Coulter Life Science’s new 50-pound CytoFLEX, scheduled to launch in October, is a fixed alignment system that will be shipped directly to customers, who can install it themselves. Users will be “able to take it out of the box and install it and run QC, and be able to start acquiring their samples in less than an hour,” says senior marketing manager Sharlene Wright. Yet, “it has a higher performance than any of our other analyzers.”
Miltenyi Biotec’s MACSQuant® line features a magnetic column capable of enriching samples before the readout, while Orflo’s handheld, microfluidic Moxi Flow™ combines an impedance-based cell counter with a single color flow cytometer.
There are even personal benchtop cell sorters that let researchers analyze their samples and then, by sorting on individual populations, do follow-up experiments with those cells of interest. “They can answer questions they may not have even thought of before,” says Melissa Ma, global product manager at Bio-Rad Laboratories, which is about to release an updated version of the S3™ cell sorter, called the S3e™.
Whatever your needs, personal cell analyzers make it easy to let your research go with the flow.
Image: The Attune NxT Acoustic Focusing Cytometer, from Thermo Fisher Scientific/Life Technologies