The advent of microfluidics—using “chips” containing networks of tiny channels and chambers through which minute amounts of reagents move—in biological research has enabled scientists to examine rare or precious samples, which in the past could not be assayed because of their limited quantities or amounts. The miniaturizing technology boasts the advantages of less reagents used, assay automation, potential time and cost savings, reliability in moving tiny liquid samples, less contamination and often faster time to results.
A variety of fields—flow cytometry and cell sorting, DNA sequencing, gene expression, live-cell microscopy, point-of care diagnostics and drug discovery, to name but a few—are already incorporating microfluidics into their instrumentation, and the trend is likely to continue. Here are some examples of how microfluidic technology has recently been applied in different areas of bioresearch.
Live-cell microscopy
Microfluidics applied to cell-culture plates is the basis of EMD Millipore’s CellASIC® ONIX platform. This instrument and plates enable researchers to control the environment with precision during live-cell microscopy. Philip Lee, director of global marketing for cell-culture systems at EMD Millipore, sees a higher interest in microfluidics-based in vitro cell models. “This is particularly evident in cancer, toxicity and stem cell fields,” he says. “However, for cell-based applications, the commercial adoption of microfluidic products is still in the early phases.”
Separating and quantifying biomolecules
Microfluidic technology makes tiny separations of biomolecules possible—think of it as electrophoresis on a microchip. Revvity's LabChip® platform can quantify and measure sizes of biomolecules such as proteins, glycans, DNA and RNA. The LabChip®GX Touch™ instrument uses microfluidic chips that serially process from one to 384 samples. Low sample volumes (less than half a microliter) are “the key to accomplishing high-resolution separation in a short microfluidic channel with a fast separation time,” says Krystyna Hohenauer, Revvity’s portfolio director for automation and microfluidics.
The separation of each sample takes 30 to 80 seconds. First the channels are primed with separation matrix. Then samples are propelled through the matrix by a combination of pressure and electrokinetic flow. Depending on the type of assay, biomolecules are often fluorescently labeled inside the chip. Estimating the sizes and concentrations of fluorescent sample peaks is performed by comparing to known standards.
Microfluidics-based biomolecule separation enables greater throughput for researchers testing a vast number of experimental parameters—such as in quality-of-design approaches to biotherapeutics development. “Microfluidic analysis of protein integrity, purity and glycosylation is a key enabling technology for quality-by-design approaches,” says Hohenauer.
Gene expression and molecular biology
Microfluidic tools for molecular-biology and gene-expression assays are available from Thermo Fisher Scientific. The TaqMan Array Card, which contains 384 wells and microfluidic channels, also includes dried and pre-spotted assay reagents for gene expression, miRNA or genotyping studies. The card is unique in its design, says Poupak Farahani, Thermo Fisher Scientific’s product manager for TaqMan Arrays, incorporating eight loading ports to evenly distribute samples across the 1-microliter wells.
Although researchers in many fields benefit from time savings with microfluidics, Farahani says that setting up microfluidic experiments for molecular-biology and gene-expression assays can still be time consuming—or expensive, if you purchase sample-loading robotics. But “higher throughput should not mean higher complexity,” she says. “Setup with the TaqMan Array Card takes only 10 minutes without liquid-handling robotics.”
Additional advantages includes better assay reliability and validation, because each well is a completely inaccessible chamber within the microfluidic card. Thus samples are better protected from contamination than if they were in conventional 384-well plates. “Since the samples are evenly distributed throughout the card, results show tight reproducibility with a smaller chance of contamination,” Farahani says. Moreover, using the same thermocycling protocol per experimental setup helps standardize results, for more efficient data comparison. These features allow TaqMan Array Cards to provide standardization across a large number of samples, across multiple laboratories.
Flow cytometry and cell sorting
Microfluidics is also applying its advantages to flow cytometry and cell sorting. NanoCellect’s WOLF system sorts cells within a microfluidic cartridge. The closed cartridge makes it safer and easier for researchers compared with traditional flow cytometry, which can create aerosols during sorting. NanoCellect’s president and CEO, José Morachis, says the WOLF is gentler on cells than traditional flow cytometers, and the single-use, disposable cartridges prevent cross contamination. Because there are no aerosols and no danger of contaminating the cartridge interior, the WOLF can be used on the benchtop rather than in a safety hood.
Morachis believes microfluidics has particularly accelerated genomics and molecular-biology research. “Everything from sample prep to assay development has been improved with microfluidics in genomics,” he says. “NanoCellect sees the need to make sample prep much easier and less wasteful—get the right cells, don’t damage them and sequence them.” Overall, Morachis has seen microfluidics-based products become easier to use in the past couple of years. But there is still room for improvement.
With researchers from different scientific backgrounds and experience levels becoming more interested in microfluidics, many believe the technology needs to become more user-friendly. Lee agrees that making microfluidic technology accessible for all users remains a challenge. “Microfluidics products have historically focused on technology experts, who seek bleeding-edge capability and are more tolerant of design quirks,” he says. “As the user profile has shifted, the industry needs to emphasize product quality as well as ease of use in design.”
But the goal for any powerful scientific instrument is that a user-friendly interface on the outside intuitively and efficiently controls the staggeringly complex biological circuitry on the inside, with precision and reliability. “This will allow research scientists to stretch their imagination and answer even tougher questions without becoming a deep expert in cell sorting or library prep,” says Morachis. Incorporating the power of microfluidics into more instruments will almost surely offer researchers that luxury.