With so many experiments performed in multiwell plates, keeping a lab’s workflow moving depends on a microplate reader. The best reader, though, depends on how it will be used and where.
According to Xavier Amouretti—manager, product management at BioTek Instruments—the two key drivers in selecting a microplate reader are: the type of assays and how many samples must be analyzed every day. In most cases, scientists run experiments in 96-well plates. “Going to 384- or 1536-well plates typically requires liquid-handling automation,” Amouretti says. “Otherwise, it’s painful to pipette your samples.”
In most academic labs, scientists stick with 96-well plates. “In pharma or biotech, where automation is more common, then it’s more beneficial to go to 384,” Amouretti explains. “That’s a very common plate format there for screening applications, because you can run more samples for less money per sample due to using less reagent, and when it comes to throughput, the main driver is typically cost per sample in a plate.”
The assay also impacts the options. “Some assays have limitations, like not being able to go to 1536, for example,” says Barbara Sonnenberg, product manager, multi-mode detection at Revvity.
In most cases, the measurement time per sample is about the same, regardless of the number of wells, but “with 1536, you don’t lose time swapping plates,” Amouretti adds.
How samples get analyzed also plays a part in the selection. “Running samples in duplicate, triplicate, etcetera, plays yet another role in format and throughput, which all helps dictate the correct approach for your assay,” says Rick Luedke, senior market manager at Tecan.
Sensitivity expectations
Some experts say that most any reader is sensitive enough, but a few disagree. For instance, Sonnenberg says, “There is still a big range of sensitivity.”
Sensitivity really matters with precious samples. “Then, scientists want to use a tiny amount of sample, and that requires high sensitivity,” Sonnenberg adds.
Throughput also interacts with sensitivity. “If you have a sample that is just bright enough to detect on a reader, then you need to sample longer,” Sonnenberg explains. “That can turn a one-minute detection into five minutes.” In a lab running five plates a day that won’t matter much, but running thousands of compounds or more makes the sensitivity a big part of reaching the necessary throughput, especially for targets that are more difficult to detect.
More than sensitivity, scientists should expect reliability. “When my machine gives me a number, is that a number I can trust?” Amouretti asks. “Does the vendor provide ways to check that my machine is performing optimally?” For example, a vendor should provide data that show a consistent temperature throughout a reader.
Other experts also mention the importance of accuracy. For example, Luedke says, “Besides sensitivity you should investigate areas like wavelength reproducibility and accuracy for monochromator-based systems to help give you a clearer picture of the data quality you can expect from the instrument.”
Finding flexibility
Most of today’s microplate readers provide three modes of detection: absorbance, fluorescence, and luminescence. From there, various options can be added. If scientists want to run cell-based assays, for example, environmental controls can be added.
The kind of lab can impact the required flexibility. “In academic labs, with many people using the instrument and maybe doing assay development, they need lots of flexibility, such as various detection technologies, and features, say in the software,” says Sonnenberg. “In a screening lab that runs the same assay every day and screens thousands of compounds, they need less flexibility, because they are probably only using one or two technologies.”
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Instruments that use filters require different ones for some applications, and that works best with more consistent applications. “With a monochromator,” Sonnenberg says, “you can put it on every wavelength, and this is good for assay development, because you don’t know what dye you’ll be using.”
Overall, the most basic plate readers are less likely to be upgradable than more expensive ones. “For a more expensive reader,” Sonnenberg says, “users should expect the ability to upgrade, such as adding accessories.”
The most desirable add-ons depend on the use. As an example, Luedke mentions “adding functions like Alphascreen or bottom reading, without forcing you to purchase an entirely new system.” He adds, “You need to feel comfortable that an instrument can grow with your needs, no matter how they may change in the future.”
For common upgrades, many users like adding injection systems or other forms of automation. “Some like to add an automated imaging system,” Amouretti says, “and we can do upgrades in the field for the most part.”
For flexibility, people tend to think about the hardware. “One piece, however, that often gets overlooked when discussing flexibility is software,” Luedke says. “Your system may have all the functionality in the world, but without easy-to-use software you can sometimes feel locked out of your own instrument.” He adds, “Approachable and intuitive software gives each user the freedom to use the instrument to suit their needs without requiring constant intervention and support, that is a huge component of flexibility.”
You need to be able to trust the data you get from a machine, because you will be making decisions downstream based on that data.
In the end, as Amouretti says, “you need to be able to trust the data you get from a machine, because you will be making decisions downstream based on that data.”
A reader in your pocket
At the University of California, Los Angeles (UCLA), a team of scientists—Aydogan Ozcan, Chancellor’s Professor, Dino Di Carlo, professor and vice chair in the department of bioengineering, and their colleagues—built a microplate reader from a cellphone. “We were motivated by the need to reduce costs of healthcare instrumentation in the U.S. in rural and underserved areas but also globally in order to expand access to diagnostic tests,” Di Carlo explains.
“Healthcare instruments have not benefited from mass production of electronic and optical components at the same order of magnitude that consumer electronic products—for example, cell phones—have, and so we chose to leverage those gains in consumer products and apply the same components to healthcare products.”
To make this work, the scientists developed a fiber array that carries light from a large area across a microplate to a smaller area that a cellphone camera can image. Di Carlo says the “design of the fiber array is one of the innovative aspects of this work.”
The UCLA team is already using this cellphone-based microplate reader in various projects, including nucleic acid–amplification tests, immunoassays, and antibiotic susceptibility tests. The system is also being used as part of a new NSF Engineering Research Center, called PATHS-UP, which stands for Precise Advanced Technologies and Health Systems for Underserved Populations.
As this work shows, one kind of technology can impact another—sometimes in ways that most people never expected. As the use of multiwall plates continues to expand, scientists will need all of the help that they can get reading the data as efficiently and affordably as possible. In more ways than one, getting the best platform can be just a phone call away.
Image: Some microplate readers include imaging. Image courtesy of BioTek Instruments.