PCR (Polymerase Chain Reaction) is one of the most commonly used techniques in molecular biology and diagnostic experiments. Its accuracy depends on multiple factors, including the reaction system, instrument setup, and the quality of consumables. PCR consumables are not only reaction containers but also directly affect temperature conduction, evaporation loss, reaction uniformity, and result reproducibility. Choosing the right consumables can significantly improve experimental success rates and reduce errors and costs.

1. What are PCR consumables?

PCR consumables refer to disposable laboratory items specifically designed for PCR workflows. These items are typically made from high-purity polypropylene (PP) and are manufactured to withstand repeated thermal cycling while maintaining chemical stability and sample integrity. They are essential components in molecular biology, clinical diagnostics, genetic testing, and life science research.

Why are PCR consumables generally made of polypropylene (PP)?

PCR consumables are generally made of polypropylene (PP) because it is a biologically inert material, its surface does not easily adhere to biomolecules, and it has good chemical resistance and temperature tolerance (it can be autoclaved at 121 degrees Celsius and can withstand temperature changes during thermal cycling). These materials usually come into direct contact with reagents or samples, therefore, high-quality materials and good processing techniques are required during production.

2. Common types of PCR consumables

• Individual PCR Tube

Main specifications: 0.2 ml pcr tubes(flat cap/domed cap); 0.5 ml pcr tubes(flat cap).

Flat cap provides precise fluorescence signal transmission for qPCR; facilitates labeling. Domed cap contacts the PCR instrument’s heated cap, reducing pressure-induced deformation of the reaction tube; however, it affects fluorescence signal transmission and cannot be used in qPCR experiments.

• PCR Strip Tubes

Main specifications:

4-strip PCR tubes(trasparent). 0.1mL PCR 4-tube strips with individual caps are specially designed for QIAGEN®/Corbett Rotor-Gene® instruments. 

8 strip pcr tubes(pcr strip tubes with attached caps/8 strip pcr tubes individually attached caps; white/transparent). 

12 strip PCR tubes. 

PCR tubes are mainly available in three colors: transparent, frosted, and white. The color of the tube body does not affect DNA amplification. However, in quantitative fluorescence PCR experiments, compared to transparent tubes, frosted and white tubes reduce fluorescence loss due to lower light transmittance, allowing more signals to be reflected back to the fluorescence detection module, thus increasing the signal-to-noise ratio. Furthermore, white and frosted tube walls can better prevent signal interference between wells, minimizing variations in repeated experiments.

The fluorescence detection module is located above the heating module (top-reading signal): transparent, frosted, and white tubes can all be used, but frosted and white tubes are more recommended; signal-to-noise ratio: white > frosted > transparent; for example, with Bio-Rad CFX or Roche 480 real-time PCR instruments, white PCR tubes are recommended. The fluorescence detection module is located below the heating module (bottom-reading or side-reading signal): only transparent tubes can be used.

• PCR Plates

Non-skirt PCR plates: Lacking edge panels, compatible with most PCR and qPCR instruments, easy to cut, but offer poor pipetting stability and require a plate holder; not suitable for automated applications.

Semi-skirted PCR plates: Available in various colors, detachable, facilitates sample classification and management in high-throughput experiments, compatible with labels or barcodes and automated applications, and offers good pipetting stability.

Full-skirted PCR plates: Features edges with the full height of the plate, suitable for automated laboratory applications, compatible with labels and barcodes, offers good mechanical strength, can be used with PCR instruments with protruding modules, provides high pipetting stability, and facilitates handling and movement by robotic grippers.

3. How does the volume of the PCR tube affect the amplification results?

• Dead Volume

When the same volume of reaction solution is added, the space above the reaction solution (also known as dead volume) in a 0.1ml tube is significantly smaller compared to a 0.2ml tube, resulting in less wasted space. During the experiment, as the heating module of the PCR instrument gradually heats up, the water vapor generated inside the tube enters the space above the reaction solution. The 0.2ml tube accommodates more water vapor, leading to the concentration of the reaction solution. Changes in the reaction solution’s composition then affect thermal conductivity and liquid temperature, thus impacting the stability and accuracy of the experimental results. Conversely, for a 0.1ml tube, the dead volume is greatly reduced, resulting in a more stable reaction composition and better reproducibility.

• Condensation on the Tube Walls

Since the water vapor in the 0.2 ml tube has to travel a longer distance through the exposed portion before reaching the heated lid at the top, it inevitably leads to the formation of condensation on the tube walls. This is detrimental to quantitative fluorescence PCR experiments. The condensed water droplets act like tiny lenses, causing refraction and scattering of fluorescence, degrading and attenuating the consistency of the detector signal, and reducing sensitivity.

Because the 0.1ml tubes are fully enclosed by the heating module of the PCR instrument, only a very small portion is exposed outside the heating module, and the distance to the heated lid is also shorter. This greatly reduces the formation of condensation on the tube walls and the possibility of contamination from condensation, resulting in more accurate experimental data.

• Fluorescence Capture Rate

Due to increasingly high reagent costs, the reaction volume in experimental designs is becoming smaller and smaller, most commonly 20-25 µl. Even in quantitative PCR experiments, it’s not uncommon to see users working with 5-10 µl, which is more than sufficient for 0.1 ml tubes; even adding 50 µl is easily manageable.

For top-detection fluorescence quantitative PCR instruments, at the same volume, the lower the height of the PCR tube, the shorter the distance the light travels from the excitation light entering the reaction solution to the generated fluorescence being received by the detector (i.e., the shorter the optical path). This results in a higher fluorescence capture rate by the detector and better experimental results.

Summary

Choosing the right PCR consumables requires balancing experimental needs, instrument compatibility, thermal performance, optical properties, sealing integrity, contamination control, and workflow considerations. Informed decisions lead to more reliable assays, reduced failures, and efficient lab throughput.