Until recently, cell sorting was a constant topic of conversation in Stacy Blain’s lab and not in a good way. Blain, an assistant professor of cell biology and pediatrics at SUNY Downstate Medical Center in Brooklyn, New York, recalls long strategy sessions with her senior graduate student on coaxing their ancient, huge cell sorter to perform. But since purchasing a compact, highly automated Bio-Rad S3 cell sorter in January 2014, her team zips through its sorts and can move on to thinking about their research questions.
“It is really a piece of equipment for small labs who want to ask questions, and don’t want the sorting to take on a life of its own,” she says. “The sorting is just a means to get you a tool to do the experiment.”
The S3 also makes it easier for Blain, who codirects a small core facility for her department, to train users and leave them to work unsupervised while she teaches classes or does her own research.
Instruments for fluorescence-activated cell sorting were once uniformly bulky and required experts at core facilities to operate. But a new generation of smaller, cheaper sorters that have emerged in the past few years allows researchers to perform simple sorts on their own, often with only brief training.
The larger sorters are faster and can handle more colors, “but we didn’t need to sort with 10 colors,” says Blain. “We could get what we wanted with four colors,” and the smaller machines are still relatively fast, she said.
Managers of large core facilities are also feeling the draw. Smaller, less complex sorters “take a lot of pressure off our heavily used sorters,” says Aaron Rae, technical director of the pediatric flow-cytometry core at Emory University in Atlanta, Georgia. This has become useful as increasingly long, complex sorts of rare immune cell subsets have become possible. These compete for sorting time with popular simple sorts, such as ones using just green fluorescent protein (GFP).
Researchers increasingly are taking advantage of GFP-based cell sorting to isolate particular cell populations for sequencing or other further tests. Most recently, scientists making knockout cell lines using gene-editing CRISPR systems have started tagging their nucleases with GFP so they can sort out cells that are likely to have been successfully genetically engineered.
Small cell sorters are also attractive from a safety perspective: In recent years, cytometrists have become more aware of the danger of inhaling aerosolized droplets containing cells. Smaller sorters fit into standard biosafety cabinets or can be purchased with their own specially designed containment devices. Larger sorters can also be purchased with containment devices, but these are more expensive and can be “the size of a room,” said Rae.