New Method of Isothermal, Hairpin Assisted, Primer Independent Amplification of DNA

The isothermal amplification of nucleic acids refers to processes that quickly increase the amount of DNA at a constant temperature. These methods are mainly developed as alternatives to PCR for cases in which the application of a thermal cycler is not possible or the assay method must be as rapid as possible. We have developed a new method of isothermal amplification based on the formation of hairpins at the ends of DNA fragments containing palindromic sequences and increased by the hydrolysis of one or both DNA strands by restriction endonuclease, known as hairpin-assisted isothermal reaction (HAIR). The key steps in HAIR are the formation of a self-complementary hairpin and the DNA breakage introduced by nickase. The end hairpins facilitate primer-free amplification, the amplicon strand cleavage by nickase produces additional 3′ ends that serve as new amplification points, and the amount of DNA can increase exponentially. The rate of amplification in HAIR is more than five times the rate of loop-mediated isothermal amplification (LAMP), and the total amount of DNA product of HAIR is more than double the amount of the LAMP product.