Emerging trends and future perspectives of thermal cyclers

Advancement in molecular biology, laboratory automation and microfluidic techniques continues to develop accessibility and applicability of these methods beyond the limits of conventional laboratory facilities and its role in clinical, forensic, and military applications. Because of which there is a growing demand to adapt molecular biology techniques like aliquoting, mixing, centrifuging and thermal cycling to compact automatic ready formats. The gold standard for molecular biology techniques for any disease identification, in high resource settings require nucleic acid identification tests (NAATs). The nucleic acid amplification procedure consisted of polymerase chain reaction (PCR) that requires thermal cyclers. Detection of amplified DNA is performed with specialized thermal cyclers which are capable of fluorescence detection.

Thermocyclers use different technologies to obtain temperature change. Peltier cooling, resistance heating, and passing air or water heating are the most common. Peltier effect is for cooling high-temperature components without needing refrigerants or compressors. These types of semiconductors apply low-power DC sources and move heat in the direction of the current. Heat moves from one direction of the module to another direction. So, one side will be cold, and the other be heated. The resistive heating element is a coiled wire, like the filament of a bulb, so it gets by applying electricity.

Thermal cyclists can also be heated by heating water or air outside and then passing through the samples. There are two main types of thermocyclers: standard PCR machines and real-time thermocyclers. Standard PCR machines have interchangeable blocks that accommodate tube strips or multi-well plates. It has multiple program options for different kinds of gene application requirements. It is robust and easy to use. Real-time thermocyclers have many applications in the quantitative determination of DNA or RNA in various assays, such as transgenic and pathogen detection, viral load detection, gene expression, and genotyping. The essential features of this technique are speed and high specificity.

Significant advancement has been made in several features of equipment for improving PCR experiments. Improved Peltier systems can heat and cool the block at a fast rate i.e., 60C per second enabling high-speed PCR to complete more PCR runs in a day. In the same way the heated lid is also a common feature of thermal cyclers that prevents condensation and evaporation of PCR samples during runs. Prior to the use of heated lid, samples were overlaid with mineral oil.

Benchtop thermal cyclers are also there with interchangeable blocks and are built with flexibility in sample throughput in mind. Benchtop thermal cyclers can accommodate up to 480,000 amplification reactions. High throughput automation in thermal cyclers is designed for hands-free operations and integration of robotic liquid handling platforms. Gradient thermal blocks were designed to achieve desired low and high temperatures around the theoretical annealing point in both the ends of a single metal block. Advanced gradient technology is also developed where insulated separate metal blocks replaces a single block that allows more precise temperature control for faster optimization. Innovations in PCR chemicals, reagents, and consumables like ultrathin-walled low profile PCR plastics, engineered DNA polymerases have highly enabled fastest PCR.

Nowadays the thermal cyclers are designed in such a way that easy programming of PCR protocols can be achieved. These protocols vary in DNA targets, DNA polymerases, primer sequences and experiment design. That’s why the thermal cyclers are equipped with intuitive user interfaces like easy programming and touch screens which enables them more efficient and faster PCR. Recent advancement also permits convenient access to thermal cyclers anytime, anywhere by connecting them with mobile device or desktop computer. Their connectivity with cloud offers enhanced accessibility at fingertips like creating and sharing protocols, monitoring PCR runs. Overall, continued innovations and advancement in thermal cyclers are beneficial in detecting DNA fragments of interest, in medicine to diagnose infectious or inherited diseases, and in forensic science and evolutionary studies.