Thermal cyclers are essential tools in molecular biology, driving rapid and precise temperature changes crucial for PCR and other DNA amplification techniques. At the core of most plate- and platform-based cyclers are Peltier elements, which enable these temperature shifts through the Peltier effect—where heat is absorbed or released at the junction of two dissimilar materials when an electrical current is applied. However, as high-throughput demands grow and workflows evolve, innovations like water bath cyclers and advanced plate formats are emerging to enhance efficiency, increase throughput, and offer new solutions for large-scale genetic analyses.
Recent developments in thermal cyclers
Roche has updated the LightCycler with an increased capacity from a maximum of 384-well to 1,536-well plates, a per-assay throughput improvement of four-fold. Commensurate with this increase, per-reaction volumes have decreased substantially, with a maximum of two microliters, versus 10 microliters for the 384-well format.
There is throughput, and then there is throughput. Although Peltier elements can deliver predictable and rapid temperature ramps, the constant strain inherent in activating and reversing their potential can cause them to break down over time, and the emitted heat that must be vented can expand the functional footprint of qPCR cyclers well beyond their measured cubic allotment. Alternately, plates can be moved through multi-chambered, water-based thermal cyclers that maintain stable temperatures in discrete baths and thus eliminate by up to 40 percent the time associated with Peltier element temperature ramps.
Several high-throughput water bath cyclers are available, and can deploy 96-well, 384-well, or 1,536-well plates in rapid succession. Additionally, they can accommodate the ultimate solution for automated PCR, Array Tape, which obviates the need for plates and can be run almost continuously like newssheet under a printing press because of its low volume and thermal mass. These are endpoint machines optimized for standard PCR. As such, they are primed to take on workflows for large-scale analyses such as mapping genetic interactions, or KASP assays to identify rare single nucleotide polymorphisms in novel biomarkers.
The Hydrocycler2 from Biosearch Technologies/LGC uses a circulation jet to maintain homogeneous water temperatures and eliminate the radiative edge effect that can often impact the consistency of high-throughput PCR assays. It can process 145,000 samples per workday, and can be incorporated into automated workflows using liquid handlers and robotic arms to transit plates or Array Tape from bath to bath. The Soellex unit improves upon this number with a 230,400-sample capacity, via iteration of three Array Tape spools containing 200 x 384-well arrays per spool. For laboratories looking to automate their genetic analyses, there are attractive options for both real-time and endpoint assays, in configurations suitable for the benchtop.
