Will the Ct value be higher if domestic qPCR premix replaces imported ones?

In terms of procurement and pricing, domestic mixes are considerably cheaper than imported ones, but specifications, concentration, and whether ROX is pre-mixed all affect the unit price. It is recommended to first validate with a 1–2 mL trial size, then calculate usage based on your actual monthly sample volume, and order a 3–6 month supply at a time to avoid frequent switching between lots. Lead time is generally within one week, and local warehouses in Shanghai often have stock available. Ask clearly whether the product is light-protected, whether it is shipped with dry ice or ice packs, the shelf life, and the storage conditions after arrival. Aliquot and store at -20°C, avoid repeated freeze-thaw cycles, mix thoroughly before each use, and briefly centrifuge with a plate spinner.

Vazyme and TransGen can both substitute in routine quantitative cDNA expression analysis of mouse tissues. Vazyme's TB Green series has a large user base, while TransGen's TransStart Top Green performs comparably for certain low-copy targets. For selection, first confirm the instrument's fluorescence channels and ROX requirements: ABI 7500 and similar instruments require high ROX, while Bio-Rad CFX96 does not. Buy small packages and test each 1-2 times, using the same primers, cDNA, and program on the same plate to compare Ct values and melting curves. Do not focus only on absolute Ct values; examine standard curve efficiency and replicate well CV.

On the operational level, domestic mix may be more sensitive to primer dimers. It is recommended to reduce the final primer concentration from 250 nM to 200 nM, increase the annealing temperature by 1-2 ° C, and if necessary, use a two-step method to reduce non-specific amplification. After packaging 40-50 samples, centrifuge and check for air bubbles in the wells to avoid analyzing the edge wells without calibration. After different batches arrive, they are packaged and labeled separately. First, two high expression and two low expression templates are used for inter batch comparison to check for Ct range and melting temperature drift. This is more useful than simply comparing Ct values.

A high Ct value of 0.3-1 cycles is not uncommon when changing the mix, but the key is efficiency and specificity. It is recommended to dilute the same batch of cDNA by 5, 4, or 10 times, and run the standard curve on the same plate for both imported and domestic samples. Compare the slope, efficiency, R ², and melting curve. The focus of low copy genes is on the Ct difference of templates with less than 1000 copies. If the difference no longer widens, it is mainly due to differences in baseline algorithms or fluorescence intensity rather than sensitivity issues. A single peak melting curve and a shoulder peak of a primer free dimer are acceptable. Conduct preliminary experiments first and then replace in bulk.