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By David Wold
The global COVID-19 pandemic is putting unprecedented pressure on laboratories to meet demand for accurate, large-scale, high-throughput testing. In such extreme circumstances, conserving samples and minimizing risk of contamination is vital, and it all boils down to having the right pump at the heart of your test instrument. For most molecular diagnostics instruments, an air displacement pipettor (ADP) with disposable tips is the preferred approach.
Automated air displacement pipetting offers greater precision and accuracy
ADPs have greatly evolved since the 1970s when they were first introduced as hand-held devices. Continuous improvement and adaptation of technologies for automated pipetting instruments has enabled higher quality and increased liquid-handling performance.
Like the name implies, air displacement pipettors use air rather than liquid displacement to aspirate and dispense fluids. As in widely used syringe pumps, the movement of a piston within a sealed chamber results in the positive and negative pressures needed to displace fluids. With an ADP, air remains above the liquid in a disposable tip, so there is never any contact between the drive mechanism and the liquid, minimizing the possibility of cross contamination. Air displacement is ideal for accurately and repeatedly dispensing volumes over a large volume range, from <1 to 1000 μL.
Depending on your application and workflow needs, air displacement pipetting may simplify instrument design by eliminating system liquids and associated components. It may also increase productivity by eliminating steps required to move liquids or flush the system. This makes it the perfect fit for testing with stringent hygiene requirements for large-scale COVID-19 genomics testing.
Choosing the right ADP for large-scale testing
Not all air displacement pipettors are created equal for COVID-19 testing and other applications that require a high degree of quality and process control. In addition to ensuring reliable, high-throughput, contamination-free pipetting, there are other equally important criteria, such as how easy the ADP is to set up and integrate into your robotic system.
Ideally, your ADP should be:
- Accurate and precise – with all pipetting parameters fully programmable, accuracy assured across your required pipetting range (e.g., from 1ul to 1000ul), and high pipetting resolution (e.g., 40,000 increments for 1000 ml).
- Flexible – offering you complete control over the pipetting parameters so that you can easily adapt to changing protocols. Also, to allow for maximum flexibility in your robotics design, look for an ADP that is as small and lightweight as possible, and has been designed specifically for (XYZ) robotic integration.
- Easy to integrate – with a compact modular design, standard communication protocols (e.g., RS-485 and CAN BUS) for easy programming, and an industry standard programming command set. You will be up and running sooner if your ADP provider also supplies all the right accessories and expert support to quickly integrate it with the controlling computer and your robotics. For example, the Cavro® ADP Starter Kit gives you everything you need in one convenient package to get started.
- Fully programmable – enabling you to write, test and run the scripts that control your ADP, with a full range of basic and advanced pipetting commands.
- Reliable - To ensure your ADP will be reliable even under the most demanding of circumstances, be sure to check the lifetime of the pump’s probe, plunger and seal assembly, whether the ADP will be maintenance-free, and the details of manufacturer’s warranty.
- Quality assured – designed and proven to satisfy rigorous quality standards including ISO13485 and ISO9001 requirements, and the US FDA's QS regulations.
Expertise is found in those with experience and knowledge
Finding an OEM partner with molecular diagnostics experience and a tested and proven pump for any COVID test instrument is essential. An experienced partner and market leader provides reassurance to any product manager, project leader, or engineer in need of a reliable pipetting solution.
Ensuring process security every step of the way
All Tecan Cavro brand components are designed and manufactured to our high standards, supported by more than 40 years of liquid-handling automation expertise.
The Cavro Air Displacement Pipettor ensures outstanding performance with on-board process security including error-handling, tip presence monitoring, an integrated pressure sensor, and plunger position monitoring.
Pressure-based liquid level detection (pLLD) operates by slow aspiration of air as the tip approaches the liquid surface. When the tip contacts the liquid surface, the pressure inside the tip decreases and onboard control electronics indicate the presence of the liquid. Effective liquid level sensing is vital for genomics testing and many other applications, helping to avoid erroneous results and reduce the risk of sample carry-over.
“The [Cavro] ADP’s pLLD capabilities have allowed us to develop an automated calibration algorithm to determine the correct Z-height for each pipetting step,” explains Dan Gibson, inventor of Gibson Assembly® molecular cloning methodology and Chief Technology Officer at Codex DNA. “This is something we simply wouldn’t have been able to replicate in-house in the 18 months it took from beginning the project to production of the first instrument.”
An Australian in vitro diagnostics (IVD) company, AusDiagnostics, had a similar experience. “We turned to Tecan because we were already using 10 Freedom EVO® 150 liquid handling workstations in the production of our kits, and so we trust their technology inherently,” says Professor Keith Stanley, Managing Director.
“Having already developed some of our own pipetting heads, we could admire the cleverness of Tecan’s technology, and see that the component met our precision and reproducibility needs. We were able to easily integrate the ADP into our own robotic platform, and it communicates seamlessly via a USB port.”
Crucially, disposable tips make the best choice to eliminate cross-contamination between biological samples during diagnostic testing. Tip quality can make or break system performance, and is a key contributor to reproducibility. Poor quality tips can leak, loosen, or even fall off— This is critical as the scientific, research and medical communities work together to keep up with the unprecedented testing required to contain and combat COVID-19.
The Cavro ADP’s precise and accurate dispensing as well as improved process security may just be the high-performance liquid handling you are seeking. Experience the ADP for yourself, try our Starter Kit. *
*Currently available only in the U.S.