When you think of DNA/RNA analysis in molecular biology, you think of thermal cyclers. Thermal cyclers (also known as PCR machines or thermocyclers) are laboratory equipment used to replicate, analyze, detect, and amplify segments of the DNA or RNA. They are also used for rapid diagnosis and to restrict enzyme digestion. Thermal cyclers are crucial to the smooth running of relevant laboratories; without them, work gets stalled. Thermal cyclers require careful consideration before purchase. There are features to look out for before buying a thermal cycler. This article is a guide to help you purchase a thermal cycler that suits your need.
Functioning of a Thermal cycle.
To understand which thermal cycler to choose, you must first understand the functions of a thermal cycle. A thermal cycler controls the temperature of the DNA/RNA mixture following programmed instructions. The thermal block that generates heat contains holes for tube placement. Samples to be analyzed are placed inside the tube, inserted into the hole, and temperature instruction set. The main attribute of a thermal cycler is its ability to maintain and change the temperature at a specific time following programmed instructions (instructions can be set through a computer, the machine itself, or using pre-programmed instruction).
Thermal cyclers are used in:
●Research laboratories for amplifying and replicating a particular DNA sequence,
●Forensic labs to detect a DNA sequence in fingerprint, body fluid, etc., and
●Diagnostic centers to detect genetic sequence and disease, pathogenic DNA/RNA in the body like Covid-19, HIV, Hepatitis, etc.
There are different types of thermal cyclers according to their sizes, models, and specifications. Here are things to consider when choosing a thermal cycler.
How fast the temperature change is.
A thermal cycler should change the temperature instantly, sustain the temperature for a particular time, and change it again. While this is ideal, not all thermal cyclers can change temperature instantaneously. Some thermal cyclers change the surrounding temperature of the tube before changing the temperature of the content. While most laboratory experiments require the fastest temperature change, some experiments can run with a not-so instant change. So, when buying a thermal cycler, ensure that the temperature change is as fast or as slow as you need it to be. For an instantaneous and uniform change, thermal cyclers with a silver heating block are preferable. Silver is a great conductor of heat; hence, it can initiate a temperature change as quickly as possible.
Sample capacity is also an important criterion to consider when choosing a thermal cycler. Sample capacity is the number of sample tubes the thermocycler machine can accommodate during one cycle of use. Sample capacity also includes the type and size of individual tubes the thermocyclers can accommodate. While thermal cyclers that use the 0.2ml PCR tubes are easy to find, you can also get other thermocyclers with different tube size capacities. Depending on how large the number of sample tubes you want to analyze per time, thermal cyclers with a single plate of holes, multiple plates with the same tube type, and multiple plates with different tube sizes. Consider the sample capacity you need, the size and type of sample bottles to be used, and buy a thermal cycler that fits your need. Also, consider future expansion of needed sample capacity and goals of use when purchasing a thermal cycler.
Closely related to the sample capacity of thermal cyclers is their size. Thermal cyclers come in different sizes and shapes. There are portable ones for personal use and small laboratories and industrial-sized ones for industrial laboratories. Consider the space in your laboratory for the thermal cycler. Buy one that fits the available space. Again, consider future use and the size of the thermal cycler you would need in the nearest future before settling for a particular size.
Mineral oil or heated lid?
The heating and cooling effect of thermal cyclers leads to evaporation and condensing of the sample fluid in the sample tubes. Evaporation and condensing change the concentration of reagents matter and alters the data and result of the PCR test. To prevent this from happening thermal cyclers come with either a mineral oil to top the reagents in the tube or a heated lid. While the mineral oil may be messy and difficult to deal with, especially when in haste, the heated lid is easier to use. There are also advances in the heated lid with newer models of thermal cyclers. Determine if you want a thermal cycler that uses mineral oil or a heated lid. Also, consider the type of heated lid that comes with each thermal cycler and how advanced they are.
Other advances in thermal cyclers
Newer models of thermal cyclers have advance specifications. These specifications include;
●Changeable heating blocks with different
sample tube capacities and sizes. Some heating blocks include capacity for plates instead of tubes.
●Multiple control for a single heating block. One heating block can have multiple control for various sections of the heating block.
●Independent control for multiple heating blocks. In older models, only one heat control is available per thermal cycler. However, newer models have the option of different heat control for multiple heating blocks. More than one experiment can be carried out in a thermal cycler at the same time. Thermal cyclers are also being created to reduce the time for common PCR experiments.
●Synchronization with smartphones and smartwatches. In recent models, thermal cyclers can be controlled without being in physical proximity to the machine. Smartphones and smartwatches can be used to control thermal cyclers from a distance using the internet. Results from the machine are sent directly to your smartphone or smartwatch.
These advanced specifications make the use of thermal cyclers easier. Consider how much advancement you want when buying a thermal cycler.