Liquid-Handling Equipment Evolves To Suit Large-Scale Applications

Sidebar: Selected Suppliers of Liquid-Handling Equipment Liquid-handling equipment has always been central to biomedical research. Pipettes and pumps must be accurate and resist contamination, yet work quickly and comfortably in repetitive procedures. While pipettes and pumps will remain key components of experimental protocols, new types of large-scale research will require more automation and miniaturization in liquid-handling capabilities. Both the Human Genome Project and combinatorial chemistry experiments will be sending many new chemical compounds into the drug discovery and development pipeline. These compounds include genes, antisense oligonucleotides, and peptides. "The number of compounds that will be tested for potential activity in understanding a disease state or providing a diagnostic or therapeutic tool will continue to increase at a massive rate," predicts Charles Powell, group leader in robotics/DNA at Beckman Instruments Inc. in Fullerton, Calif. "There will be a great need to handle a larger number of compounds dissolved in liquids and a diversity of assays to adequately measure them." Pharmaceutical firms are gearing up to accelerate screening of chemical compounds for potential drug activity, such as enzyme inhibition or receptor binding. James Fergus, a senior associate scientist at Parke-Davis/Warner-Lambert Corp. in Ann Arbor, Mich., works in a high-throughput drug-screening laboratory. "Our liquid-handling needs include diluting and moving test samples from plate to plate. Our format is to transfer small amounts of samples to secondary plates that contain as little as 1 µl or less of liquid, and then conduct biochemical assays," he says. SIMULTANEOUS TRANSFER: Systems in Tomtec's Quadra 96 series offer 96 individual pistons for transfer of liquid into all wells of a microplate. Most drug-discovery research currently screens compounds using 96-well microtiter plates, but the trend is toward 384-well plates. Fergus's group uses the Quadra 96-well liquid handling system from Orange, Conn.-based Tomtec and the Biomek 2000 Laboratory Automation Workstation from Beckman Instruments, which can each be adapted for 384-well plates. But the volume of the group's work may soon exceed the capacities of available tools. "We will be increasing our library of test sample plates tenfold in the next year or so," Fergus forecasts. "So what used to be adequate to test 200 plates in three months will balloon to testing 2,000 plates" in that time. The pharmaceutical industry isn't the only one requiring liquid-handling expertise. At Embrex Inc. in Research Triangle Park, N.C., liquid-handling technology is speeding poultry vaccination. Embrex's Inovoject system immunizes chicks a few days before hatching by injecting vaccine into chicken eggs. Before Inovoject, one person could vaccinate 3,000 chicks per hour using a syringe pump. "The automated system vaccinates 30,000 to 80,000 eggs per hour, with two people working. And it's much nicer for the animal, which doesn't have to be stuck [by a needle]," maintains senior engineer Jack Hebrank. The Inovoject system uses pumps manufactured in-house at Embrex; from Cole-Parmer Instrument Co. of Vernon Hills, Ill.; and from Oyster Bay Pump Co. of Oyster Bay, N.Y. The pumps control the injections and cleanse the syringes twice daily. Pipettes and pumps are also a staple of teaching labs. "For students using stock solutions, we use a [Westbury, N.Y.-based] Brinkman Instruments Inc. pipette pump that attaches directly to the reagent bottle. The initial expense was great, but over the long run, the accuracy, lack of contamination of stock solutions, and safety have made them well worth the investment," claims Kirsten Mahovlich, a laboratory technologist in the department of biology at the University of Toledo. Robert Moss, an associate professor of biology at Wofford College in Spartanburg, S.C., tries to give his students an opportunity to handle real research tools. His department uses pipettes from Rainin Instrument Co. of Emeryville, Calif. "It takes students a while to learn how to use them properly, but since they are what are used in real research labs, we want them training on them," he comments. Pipettes have evolved from little more than glass versions of drinking straws to diverse devices that may be electronic, multichannel, automated, or even robotic. Many researchers, including Francis Barany, an associate professor of microbiology at Cornell University Medical College in New York, recall the days of mouth pipetting. He remembers his father, Michael Barany, now a professor of biochemistry at the University of Illinois at Chicago's School of Medicine, mouth pipetting at the Institute for Muscular Dystrophy in New York more than 20 years ago. "My dad was one of the all-time great pipettors," says the younger Barany. "He would pipette hundreds of times for an experiment, and he perfected a way of balancing the pipette in the test tube so it would stay at an angle while the reagent drained to the bottom of the tube, without the pipette getting contaminated. He could have three or four pipettes going at the same time." Mouth pipetting gave way to squeeze bulbs and then trigger-action delivery mechanisms in the 1970s, as research began demanding a greater range of liquid volumes. Notes Powell: "Mouth pipetting stopped with the advent of larger-volume pipettes from such companies as Rainin and [Reno. Nev.-based] Hamilton Co., as well as modified assays in which the volume went way down, to microtiter plates. Researchers had to do dilutions to get the right titer." Today's pipettes share features that make them easy to use and accurate. They are typically slender and light, with thermal insulation (to counter sweaty hands). Most have preset volumes, built-in tip ejectors, and ways to program the devices to repeatedly deliver the same volume. The general rule of pipette pricing seems to be that the less the researcher does, the higher the price. For example, Brinkman Instruments offers several lines of pipettes, each with different levels of automation. The Ultramicro Eppendorf Series 2100 pipettes deliver from 0.1 µl to 2.5 µl and cost $269. The motorized and microprocessor-controlled Electronic Pipette Model 4850 sells for $530 and has four programmable options: routine pipetting, repetitive pipetting, reverse pipetting, and filter-tip pipetting (which minimizes aerosol formation). For those with bigger budgets, the EDOS Electronic Dispensing System, at $2,970 to $3,325, stores up to 210 programs. EDOS can interface with a computer and fits a standard 96-well microtiter plate. SOLID CALIBRATION: Wheaton's Calibra digital micropipette offers a permanently calibrated series of fixed stops Vangard International Inc. of Neptune, N.J., also has different levels of automation. It distributes two types of Finnpipettes, a popular brand manufactured in Finland known for being adjustable and for their ability to be recalibrated. Single Finnpipettes sell for $179 to $199, and models that enable the user to choose the number and spacing of channels are $569. Labsystems Inc. of Needham Heights, Mass., markets a wider range of Finnpipettes. At the top of the line that Vangard distributes is the Biohit Proline Electronic Pipettor (not a Finnpipette), which is microprocessor-controlled and is priced at $825, $975, and $1,125, for four, eight, and 12 channels, respectively. Biohit pipettes offer four actions (pipetting, reverse pipetting, multiple dispensing, and dilution dispensing), come in six volumes, and can handle liquids of different viscosities. Calibra Digital Micropipettes from Wheaton Science Products in Millville, N.J., come in six preset volumes, each selling for $215 to $222, with capacities from 0.2 µl to 1,000 µl. The company also markets macropipettes for volumes of 0.2 ml to 10 ml. Rainin Instrument distributes Gilson pipettes, which are manufactured in France. Two models target different markets, and each sells for $225. The Classic Gilson Microman Pipette works by air displacement. An air space forms between the disposable pipette tip and the nondisposable piston that drives the liquid forward. The Classic model is recommended for volumes of 3 µl to 1,000 µl of blood products, gelatins, glue, oils, paints, and syrups. The Bio Gilson Microman works by positive displacement. The capillary tube and the piston are disposable, and an air space does not separate them. This prevents aerosol formation, minimizing contamination. The Bio version is recommended for polymerase chain reaction (PCR) work, in which contamination-free sampling is paramount and the viscous DNA is transferred in small volumes of 0.5 µl to 100 µl. Labsystems' Finnpipette P.C.R. also uses positive displacement and is available in two volume ranges, 0.5 µl to 25 µl and 20 µl to 200 µl. Robots can perform the highly repetitive tasks of liquid handling. The Biomek 2000 Laboratory Automation Workstation does practically everything but design experiments-it can be programmed to pipette, dilute, dispense, heat and cool, and wash plates, as well as transfer liquids. "A robotic system allows the researcher to load more samples, assay more plates, and walk away for a longer time," explains Powell. "The system also provides an audit, tracking and recording every step. In our view, one of the most significant benefits of automated liquid handling is not so much speed and throughput, but precision and reproducibility of assays." AUTOMATED: The MultiPROBE 104 liquid-handling system from Packard Instrument Co. Packard Instrument Co. of Meriden, Conn., offers the versatile MultiPROBE Robotic Liquid Handling System. It uses disposable and nondisposable pipette tips and can adapt tip spacing to particular container set-ups. MultiPROBE delivers volumes down to 1 µl, and reportedly can process 300 to 1,700 samples per hour. Positive liquid displacement drives the MultiPROBE system. It is an automated pipettor, operated via a syringe filled with a diluent. The syringe and pneumatics go to the sample, pick it up, and transfer it. The user programs the instrument to "learn" where the vessels are located, telling it the first and last position of plates, and to pick them up and transfer them to a certain place. MultiPROBE is used mostly in drug discovery and clinical diagnosis. The cost is $30,000 to $50,000. It also features bar-code reading, a growing necessity for high-throughput drug screening that enables researchers to track samples. The system can read 256 bar codes in less than 90 seconds, according to the company. Pumps propel liquids and come in different varieties, such as piston pumps and peristaltic pumps, suited for different applications. Many pumps are used in combination, and many are automated so that they function when the user programs them to. SMALRT PUMP: SciLog's UltraTec protein-purifaction system optimizes and documents ultrafiltration applications. "Piston pumps work well on clean, clear, liquids of low viscosity, such as organic solvents that would melt the [other] pump tubing," says Juliette Schick, president and founder of SciLog Inc., a pump manufacturer based in Madison, Wis. Peristaltic pumps are useful for biological processes in which purity is important. "A peristaltic pump is a tube associated with an inside pump that presses against a series of rollers. The pump pushes liquid through by squeezing the tube with the rollers, just like in the intestines," explains Lisa Spangler, senior technical specialist at Pharmacia Biotech Inc. in Piscataway, N.J. Peristaltic pumps avoid contamination because the liquid does not contact moving parts. Uses are diverse. Peristaltic pumps from Watson-Marlow Inc. of Wilmington, Mass., for example, are used to mix photographic chemicals, add liquid vitamins to dry cereals and pasteurized eggs to pasta, inject hormones and adhesives into estrogen transdermal patches, and fill containers with contrast agents for medical scanners. A peristaltic pump is at the heart of the Suprafusion 2500 Robotic Perfusion System, offered by Brandel Inc. of Gaithersburg, Md. The system can perfuse tissues with up to nine reagents and collect up to 20 effluents per sample. Co-owner Joseph Bertoncini describes how the system conducts receptor binding assays in neuroscience research: "The researcher labels tissue, then stimulates it to release neurotransmitters into solution. The neurotransmitters are washed into vials and placed on a scintillation counter, and the label coming off is counted." This assay screens compounds that bind to specific neurotransmitter receptors. The greater the binding, the more labeled neurotransmitter is displaced. The peristaltic pump controls the flow of buffers in the experiments. Beckman Instruments Inc. Brandel Inc. Brinkman Instrument Co. Hamilton Co. Harvard Apparatus Inc. Labsystems Inc. Oyster Bay Pump Co. Packard Instrument Co. Rainin Instrument Co. SciLog Inc. Tomtec Vangard International Inc. Watson-Marlow Inc. Wheaton Science Products A gentler and slower fluid flow is possible with a syringe pump, which does not pulse or cause contents to splash. Syringe pumps are used to infuse drugs, to add perfumes to cosmetics, and to spray smoky flavoring into synthetic bacon. Harvard Apparatus Inc. of South Natick, Mass. offers several syringe pumps. Another type of pump is what SciLog's Schick calls a "smart pump." SciLog's programmable pumps target specific applications, so researchers with similar needs "don't have to constantly try to reinvent the wheel," she says. "The programming is built into the pump. It is easy to implement-just plug it in and play. It saves the user trying to make several devices work together." An example of a smart pump, according to Schick, is one that "talks" with a toploading balance and dispenses liquid by weight rather than volume. "This is of interest to people who do synthesis, where it is very important to have high precision and reproducible results," she explains. "Instead of feeding liquid into a reactor at a rate of 5 ml per minute, you can do 5 grams per minute." SciLog's UltraTec pump has an electronic pressure sensor for filtration applications. "As a filter starts to accumulate debris, the pump automatically changes the rate of speed to maintain a constant pressure," says Schick. UltraTec includes six programmable alarms to alert users to elapsed time and variations in pressure, weight, and volume. The Oyster Bay Pump Co. customizes liquid handling, as the company's contribution to Embrex's Inovoject project demonstrates. Oyster Bay has also created the liquid-handling components of electrophoresis equipment aboard one of the space shuttles, a gel-cap-filling device for a pharmaceutical giant, and pumps for contact lens manufacturers. "We integrate systems to meet particular research needs," states Oyster Bay president Patrick Gaillard. "Very often, a researcher needs not just a syringe pump, but a decent volume delivered, or a device to move liquid or deliver it in the right doses. A researcher might need a continuous meter pump that keeps liquid moving and then dispenses it, or one that delivers a liquid from a syringe and goes back to the source, then dispenses it somewhere else." Gaillard and other innovators in liquid handling are looking forward to expanding markets as the results of genome projects and combinatorial chemistry experiments increasingly clog drug pipelines. Notes Gaillard: "We happened to have the right technology to handle microplates and liquids. Now the hot thing will be to see how the liquid-handling industry accommodates genome information." Ricki Lewis, a biology textbook author based in Scotia, N.Y., is online at 76715.3517@compuserve.com.

Liquid-Handling Equipment Evolves To Suit Large-Scale Applications

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