Less and More Make up Two Trends in Unifying Samples
To unify a heterogeneous mixture, a scientist reaches for a homogenizer. “In molecular biological applications, many researchers who work with easily homogenizable sample types—such as bacteria, plant, and soft tissue—have already adopted some type of instrumentation,” says Jeffrey D. Whyte, product manager, molecular biology and radiochemicals at MP Biomedicals in Santa Ana, California. “Newer applications are being developed for the high-speed, high-performance class of bead beaters that use beads to impact the sample, and these include things like mixing suspensions, lotions, pastes, and dry-grinding solid materials.” Those needs arise in various industries, including cosmetics, materials research, and pharmaceuticals.
For the mechanical approach, homogenization relies on a motor and a mixer called the generator probe. “The technology comes down to the generator probe that interacts with the sample,” says Holly Yacko Archibald, director of sales at PRO Scientific in Oxford, Connecticut. “A mortar and pestle is great for hand grinding, but if you want the device to provide consistency, to give you the same results every day, that takes a mechanical homogenizer with a good generator probe.”
Depending on how a homogenizer is being used, different issues arise. As an example, Archibald says, “One popular application is work on RNA or DNA, and cross-contamination is a concern there.”
The probe can be one source of potential trouble. “There were 316 stainless-steel probes that could be more easily cleaned or taken apart,” says Archibald. “After that came disposable plastic probes and then packs of reusable stainless-steel probes.”
For instance, Archibald mentions the Pro Scientific Multi-Gen 7XL probes that are made of 316 stainless steel and polytetrafluoroethylene (PTFE). These come in multipacks so that the probe can be switched between samples and cleaned later, while still being durable for tough samples.
Pushing cleaning to a later time helps researchers get more done in less time. As Archibald says, “Researchers need to move more sample through and be more efficient, and that requires automated technology or even a homogenizer that can process multiple samples at once, like our Multi-Prep Rapid Homogenizer System that can process six samples at one time.”
Whyte also sees higher throughput as a trend. As an example, he mentions the FastPrep-96, which is a high-speed homogenizer that can handle two 96-well plates and a range of other containers, including 96 x 2-milliliter tubes, 45 x 4.5-milliliter tubes, and up to 2 x 250-milliliter grinding jars.
On the other hand, Refika Bilgic, managing director at IKA Works in Wilmington, North Carolina, says, “An important trend is the usage of single-use systems as sample sizes are increasingly becoming smaller and volumes of sample processing increase. Single-use systems serve as an efficient solution for busy labs—reducing risks of cross-contamination and saving time by eliminating the need of sample storage transfers and cleaning.”
For any homogenizer, the length of its lifetime depends on how it gets used. In a probe-based homogenizer, for example, “It can’t be run dry,” says Archibald. In addition, a probe-based homogenizer lasts much longer with some simple care. For example, Archibald says that the upper and lower bearings need to be replaced on a semi-regular basis. The specific replacement time depends on use, but doing the maintenance makes all the difference in longevity. “If it’s regularly maintained,” says Archibald, “I can have a customer using the same generator probe for 10 to 15 years.” On the other hand, she says, the wrong use can “destroy the probe in a day.”
Making those little repairs provides lots of return on the investment. A new generator probe can cost more than $1,000, but a pack of bearings costs only $30-$40.
In addition, getting the longest life from a homogenizer depends on taking it apart for cleaning once in a while. “There are a lot of economical homogenizers that don’t have a generator that you can take apart and maintain in that way,” says Archibald. “At some point, you need to rebuy the whole setup in that case.” She adds, “So you might look at a system that can be maintained, because a homogenizer should be an investment.”
Creating a shopping list
As overall advice, Whyte says, “A homogenizer must be applicable to your specific application and in the volumes that you’re interested in.”
That’s a good start, but Whyte provides even more shopping tips. He says that you should be sure that a homogenizer handles the number of samples that exist in your workflow. Also, check to be sure that a homogenizer can accommodate the variety of sample formats that might be needed, such as particular tubes or plates.
The electronics also matter. “Can you have walk-away performance and schedule rests between runs, especially for temperature-sensitive samples like RNAs or proteins?” Whyte asks. “Software features such as touch-screen programming and preloaded, optimized protocols should also be considered, as they can save time when optimizing new experiments.”
Paul R. Johnson, analytic R&D lab manager at Campbell University in Buies Creek, North Carolina, uses homogenizers to “make suspensions of, usually, a nonsoluble drug in a suspending agent—usually water— with some sort of additive in the water that will help to maintain a homogenous suspension.” The features that he likes in a homogenizer include a speed dial so, as he says, “You can go up and down on speed,” and “various styles of probes for making something in a small vial to a bigger batch.”
Overall, says Bilgic, “The most important factor is the cost of one homogenized sample. This means factoring in operating personnel cost as well as acquisition and maintenance costs for equipment.”
In the end, the features that matter in any homogenizer depend on the user. Only then will the fit be the most effective.
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