Improving and expanding the ways to prepare samples
Turning a sample into a suspension— the essence of homogenizing—occurs in a wide range of laboratory applications. In life science and clinical research, scientists often homogenize tissue samples for various analytical studies. One of the most common is the absorption, distribution, metabolism, and excretion process for testing new chemical entities. Homogenizers also assist scientists when formulating new food products or cosmetics. These devices even appear in a range of manufacturing processes, such as grinding silica and developing new resins with special additives to make computer components, says Stuart Gibb, director of lab and analytical sales at IKA Works (Wilmington, NC).
Homogenizers come in two main categories. Lab-size homogenizers handle small volumes, from the microliter scale to several liters. Process homogenizers—for large-scale manufacturing—handle volumes of 50 and more liters. Within those categories, the kinds of homogenizers seem nearly as broad as the range of manufacturers. For example, some homogenizers use sonication to break up tissue and others use mechanical mechanisms. Users can also equip the same homogenizer with a range of rotor-stator elements, including ones made specifically for the homogenization of soft or more fibrous tissue.
Kathrin Hielscher, marketing manager at Hielscher Ultrasonics (Teltow, Germany), says, “Ultrasonic homogenizing is very efficient for the creation of very small droplets, the disruption of cells, and the reduction of soft and hard particles.” With this technology, she says, “Homogenization is caused by ultrasonically generated cavitation. Ultrasonication allows for the variation of the specific parameters and thereby for the optimization of the whole homogenization process.”
Despite the variety of options that are currently available in tissue homogenization, researchers continue to want more features and capabilities out of their homogenizers. In addition, advances in other technologies— such as next-generation sequencing—can force advances in homogenizer technology.
At the Geisel School of Medicine at Dartmouth (Hanover, NH), Niles Donegan, Ph.D., a postdoctoral student in the department of microbiology & immunology, says, “Our lab uses two types of bead beaters to homogenize our bacteria, and one is definitely better than the other. One takes eight samples and the other takes 16, and the extra capacity is very much appreciated at times when I’m processing samples from a variety of time points.”
Speaking of time points, Donegan adds, “Having a timer is pretty useful on those machines, as it lets us do other things during the homogenization.” Still, Donegan would like more control. “What I would like to see is the ability to add a defined pause in a homogenization run. It may just be superstition, but our lab believes that homogenizing our cells for one minute, then [resting them] for [one] minute, then [doing] a second one-minute homogenization gives a good result,” he says. Nonetheless, “That means hanging around the homogenizer when I could be doing something else for those three minutes.”
Donegan also prefers reduced operating noise in the homogenizers he uses. “Noise production is probably the other major difference between our two machines, and while it’s usually tolerable to the person doing the procedure, it’s probably much less so to those in neighboring labs,” he says.
Most homogenizers can be used by hand, which is similar to using an immersion blender when cooking. In addition, such homogenizers can be placed in a stand to add a bit of automation to the process.
To give a user options, Hielscher says, “Our customers have the choice between analog and digital homogenizers. Further, we provide additional solutions such as indirect homogenization where the cavitational forces are transmitted via the test tube or vial into the liquid. The advantage is the avoidance of cross-contamination, as no tip/sonotrode has to be immersed into the liquid.”
“From a safety standpoint,” says Gibb, “you can also get a closed system.” In such devices, the material to be homogenized goes into a sealed tube with a self-contained, built-in rotor-stator. Moreover, these are disposable and can be used when handling contaminated samples. “This lets you homogenize safely and store the sample for later,” he says. This approach protects the user from the sample and the sample from potential contamination.
Gibb also points out ongoing trends in preparing samples for next-generation sequencing. “This uses very small volumes, and you need very reproducible results,” Gibb says. “We have many customers using our closed system to prepare their samples for their next-generation sequencers.” So specialized approaches to homogenization must be developed to handle specific tasks where ordinary homogenization does not provide the needed results. As Gibb says, “This is a core competency for IKA Works and we continue to push the technology to meet the customers’ needs.”
A homogenizer will spin faster in some applications and slower in others. “To meet the needed specifications for various applications,” says Gibb, “the device needs to be built from high-quality materials or the motor burns out easily.” IKA Works provides customers a three-year warranty, but Gibb says that a unit’s life expectancy sometimes depends on the abrasive nature of the samples being homogenized. So to meet that guarantee, IKA Works utilizes high-quality parts and strict quality control during manufacturing.
Given that so many research labs use homogenizers in so many different ways, scientists expect reliability—a long life—from these devices. Furthermore, researchers will continue to expect more features from this technology, and those features often revolve around increased user control and flexibility in how a homogenizer can be used. As the features in homogenizer technology expand, they will undoubtedly be integrated into other technologies that are concerned with mixing and stirring, be it for small- or large-scale applications.
For additional resources on homogenizers, including useful articles and a list of manufacturers, visit www.labmanager.com/Homogenizers
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