Have Easy-To-Use Cell Sorters Finally Arrived?

Patience may be a virtue. But in a lab that’s bustling with scientists conducting meaningful biological research, excessive waiting can be downright frustrating.

Such was the case leading up to 2012, when researchers at The University of Chicago Flow Cytometry Core Facility— known as UCFlow— would routinely wait as long as 16 days to be able to sort cells. Displeased with the resulting bottleneck, UCFlow’s Technical Director Ryan Duggan embarked on a search for a new cell sorter that would ease the lab’s workflow. His quest led him to the first benchtop cell sorter that actually lives up to its “easy-to-use” claim. This is his story.

Relief for an overburdened lab

UCFlow is one of 30 shared research facilities that serve faculty at University of Chicago. It sits in the basement of the beige-limestone Kovler Viral Oncology Laboratory, located on the campus’ west side. The facility houses flow cytometers, which analyze cells without sorting them, as well as cell sorters. Due to the complexity of the cell sorting hardware and software, only Duggan and his two technicians— along with a dozen trained users— can operate the equipment.

In addition to the intricacies of using the sorters, demand for the machines has been increasing. Among immunology researchers, there’s a growing need to isolate different classes and subclasses of cells. This need has led to the development of cell sorting devices equipped with more than eight different lasers and 15 to 20 detection channels for multicolor sorting. At the UCFlow, most of the sorting is completed using the facility’s two four-laser, 14-parameter BD FACSAria instruments. New users require eight to 10 hours of training, and operating the equipment requires constant attention. According to Duggan, users must “babysit” the cell sorters in case tubes fill up, samples run dry or the instrument gets clogged by bubbles.

And now a new wave of users is entering the cell-sorting scene, increasing demand even further— by up to one third— for the cell-sorting facilities at UCFlow. Spurred by the widespread use of green fluorescent and other fluorescently colored proteins, cell biologists are relying on cell sorters to purify cells with their proteins of interest. In contrast to the complex sorts required by immunologists, these kinds of sorts require at most four colors and one-to-two population sorting. But a technician still must monitor the instrument. The end result was wait-list times of four to 16 days for the facility’s services during daytime hours. UCFlow suffered from a constant state of oversubscription.

A new generation of compact cell sorters 

Duggan had been noticing a rush of individual labs buying their own instruments, usually one from a new generation of more compact, cost-effective and easier-to-use cell sorters. In these, he saw a possible means to address his burgeoning oversubscription problem. Buying a system that requires minimal instruction for users would free up the FACSArias for the more moderate (four to six colors, one to two populations) and more complex sorts (six-plus colors, four populations) they were designed to perform. But he was skeptical. He’d seen “user-friendly” machines before but they always failed to live up their claims, requiring far too much user intervention to manipulate the hardware.

Determined to find a solution, Duggan decided to test three personal cell sorters: the BD FACSJazz, Bio-Rad’s S3 cell sorter and the JSAN Jr. Swift. He found that the instruments were roughly comparable in terms of efficiency, purity and resolution (see table 1). But the S3 cell sorter outclassed the others in its ease of use.

The S3 and its highly automated software package were designed so even novice users can quickly set them up, Duggan says. And calibration, typically a real pain point for high-end instruments, requires no user involvement at all.

Instead of spending hours training each end user, Duggan found himself spending less than half an hour with each person, freeing up technician time and allowing operation of the instruments on an as-needed basis. Unlike other cell sorters with software that’s clearly “built by an engineer,” Duggan says the S3 takes all the stuff that normally clogs up the screen and puts it behind the scenes. That way, for instance, he doesn’t need to adjust his droplet frequency everyday. Just by clicking the power button— the only button on the whole instrument— the S3 performs a hands-off startup sequence that gives him the time to step away and make a cup of coffee while it automatically aligns the lasers, optimizes the droplet/side stream and turns the stream on. With one more click, the instrument completes a one-bead alignment QC and drop delay assessment. Then, a researcher can begin sorting.

Duggan says he was excited about the “neat little features” the S3 possesses, not found in other cell sorters—even the more sophisticated ones. Gone are the days of watching the collection tubes fill up, stopping the sort and inserting a new empty tube, he says. The S3 automatically knows when to move its arm, and will move to the next empty tube. It also can detect bubbles and clogs and stops the sorting process, thus preventing bad sorts. Duggan now has confidence that anything that can go wrong is accounted for– no more babysitting required. 

Even after three months of testing, the S3 cell sorter stood out as the optimal choice, Duggan says. The design’s simplicity and the minimal steps between “power-up” and “ready-to-sort” made it an attractive package. While it won’t replace all cell sorters, Duggan found that the instrument effectively supplemented his lab’s sorting needs by offloading simple two-four-color sorts that clogged up its schedule. Twenty percent of his monthly users (50 hours per month) now sort their cells on the S3. Wait times have now decreased to nine days.

The waiting is over

The size, price and simplicity of cell sorters such as the S3 will enable Duggan’s lab and other core flow facilities to increase their capacity and handle greater workloads. At the same time, they give individual labs an opportunity to take sorting into their own hands. Now that user-friendly cell sorters have finally arrived, waiting will be a thing of the past. 

For more information about how to start simplifying your cell sorts, check out the S3 Cell Sorter, or watch this video.