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•Taq DNA polymerases are combined by BSA hydrogels through the noncovalent bonds.•The temperature cycling triggers Taq DNA polymerases release to synthesize DNA.•The amplification velocity of PCR is controlled by the density of BSA hydrogels.•VC-PCR provides a wider detection window to analyze the difference of initial DNA.•Ct values are calibrated to more accurate detection to the initial content of DNA.
Taq DNA polymerase is the most widely used enzyme for PCR amplification and it contains 832 amino acids but no cysteines. Bovine serum albumin (BSA) is an 832-amino acid protein containing 35 cysteines, and at high temperature BSA can produce protein hydrogels through recombined disulfides and noncovalent bonds. When hydrogels are prepared using a mixture of Taq DNA polymerase and BSA, no disulfide bonds occur between them, and noncovalent bonds are the main forces holding together the Taq DNA polymerase with the hydrogels. During PCR amplification, temperature cycling can destroy the noncovalent bonds, thereby releasing Taq DNA polymerase from the hydrogels to synthesize DNA. The release rate, regulated through the variation of BSA concentration, allows for velocity-controlled amplification of DNA. As the amount of DNA products exceeds that of the Taq DNA polymerase released from hydrogels, a linear amplification replaces the exponential PCR amplification. When the amplification velocity begins to decrease, the time needed for reaching a plateau increase. This provides a broader detection window for the analysis of the end products, which correspond to the difference compared with the initial DNA concentration. The number of primers is continuously reduced with increasing cycles, which further causes a decline in the DNA amplification efficiency. The difference in the initial DNA template may cause a different consumption of primers, which can cause errors in the Ct values in the case of qPCR. Based on the slopes of the linear amplification curve, the Ct values can be calibrated to reduce this error, and a more accurate detection of the initial content of the target DNA can be implemented.