Essential Tools at Macro Scale; Automation Friendly for Miniaturized Assays
Biological shakers are instruments used to agitate a collection of biological samples simultaneously. Shakers consist of a motor attached to a flat surface, with fasteners for securing labware whose contents require mixing. All points on the surface move in the same fashion within the x-y plane, either back and forth (reciprocal shakers) or in a circular motion (orbital shakers).
The principal application of shakers is for growing yeast, bacteria, or mammalian cells in specialized containers known as shaker bottles. Shaking promotes the growth of cells and microorganisms by improving aeration and oxygen transfer and by promoting more efficient mixing of cells with food and nutrients. Biological shakers generally operate at temperatures between ambient and 37ºC, but some models offer refrigeration, and high-temperature instruments operate at up to100ºC.
For years, shakers were instrumental in drug development and manufacture. Some important products are still produced in shaker bottles/flasks, as are most small-scale experimental cell cultures and fermentations. Shaker flasks are similar in design to Erlenmeyer flasks but may have a baffled bottom to promote mixing.
Orbital shakers were employed in the development of the antibiotic streptomycin in the 1950s and interferon in the 1980s. Today all new production-scale bioprocesses use much larger bioreactors, but chances are at some point they were first conceived using a shaker.
“Orbital shakers can accept vessels of almost any size or shape, from Erlenmeyer flasks to test tubes and vials, as well as trays for staining and destaining electrophoresis gels,” notes Janet O’Bryan, product manager at Thermo Fisher Scientific (Vernon Hills, Ill.)
Biological shakers are distributed by dozens of vendors. Choosing a shaker comes down to such features as heating/ cooling capability, capacity, shaking speed, orbital vs. reciprocating motion, ease of use, programmability, heating capability, and footprint. With research budgets tight and lab space even tighter, groups or departments are increasingly sharing shakers. “Customers frequently choose models based on how much space they require. It’s highly desirable to be able to stack shakers, pizza oven style, and keep them in a shared equipment room,” O’Bryan told Lab Manager.
Customers also value ease of use—the ability to utilize shakers fully, out of the box, with labware of any shape and size. Labware flexibility is particularly critical for shared instruments.
A start/stop mechanism is a feature that anyone who uses cotton “stoppers” in Erlenmeyer flasks will appreciate. Shakers that start or stop abruptly will cause fluid to splash up into the cotton, creating opportunities for contamination and loss of material. The soft-start feature is typically found on shakers with digital controls. Users who can tolerate abrupt starts and wish to save money can settle on a less expensive analog shaker.
As biology experiments and assays become smaller, vendors must accommodate the need to provide simple manipulations on a micro- or nanoscale that lab workers take for granted in the macro world. One such operation is mixing through agitation. Not all microplate-based assays require shaking, but those that do can use dedicated plate shakers from Thermo Scientific, Orbis, Troemner Henry, ForteBio, VWR Scientific, and others.
In addition to performing simple fluid mixing, microplate shakers facilitate chemical and mechanical cell lysis and the homogenization of inert samples, cells, or cell components; they also help emulsify liquid-liquid and solid-liquid mixtures. An efficient shaker can also reduce the time by half for assays that depend on rapid agitation, for example, detection of biomolecules through the interactions of biotin-labeled proteins and microscale biosensors coated with streptavidin.
Like their large-scale counterparts, microplate shakers operate at variable, user-specified speeds and employ mechanical agitation—rocking or circular (orbital) movement—to mix components within microplate wells. A typical microplate shaker handles all common plate densities, rotates at up to 1,500 rpm, and accommodates sample volumes of up to 250 microliters.
Most units are small and robust enough to operate inside incubators and cold rooms for assays requiring temperature control.
For reasons of dimension, performance and reliability are somewhat more critical for microplate shakers than for full-scale shakers. Operators can easily determine if the mixing processes are proceeding normally in normal-sized labware. Visualizing on a microliter scale, particularly for high-throughput experiments on densely formatted microtiter plates, is impossible.
Engineering issues also come into play for mixing very small samples. As sample volume decreases, mixing efficiently becomes an engineering problem, as the fluid’s low mass causes it to adhere to surfaces, says Sriram Kumaraswamy, Ph.D., product manager at ForteBio (Menlo Park, Calif.).
Plate shakers become the “slow step” in high-throughput workflows unless they are interoperable within a larger microtiter plate-handling environment, which generally includes a microplate handler. Essential integration features include a spring lock to retain the plate against the shaking surface and a robot-friendly lock/unlock mechanism. “Plate shakers, like other components in a microplate-handling system, should be automation-friendly,” notes Dr. Kumaraswamy.
Biological Shakers: Are you using a biological shaker in your lab? Are you considering purchasing a biological shaker soon? Lab Manager Magazine’s online surveys help improve the purchasing process and provide you with greater confidence in your final purchasing decision. To take the survey, please visit www.labmanager.com/biological-shakers.