The invention belongs to the technical field of
nucleic acid and particularly relates to a preparation method of high-concentration
circular DNA (deoxyribonucleic acid) or
RNA (ribonucleic acid). The method comprises the following steps of: mixing assistant template
DNA (hereinafter referred to as a splint), ligase and a
buffer solution of the ligase required by a cyclic reaction to prepare an initial
system, preparing an addition solution from single-stranded
DNA or
RNA (hereinafter referred to as a cyclic strand) and the
buffer solution of the ligase, adding a certain amount of the addition solution containing the cyclic strand into the initial
system every other certain time, allowing a concentration of the cyclic strand in the
system to increase 0.1-5 micrometers after adding the new cyclic strand each time, repeating the procedure for several times, after adding the addition solution containing the cyclic strand for the last time, allowing for reaction for 2-15h, and allowing a concentration
mole ratio of the splint to the cyclic strand in the system to be (1-10):1. The method is simple and easy to operate, does not require extreme conditions, and can achieve high yield preparation of
circular DNA or
RNA at the ultrahigh concentration of the cyclic strand (greater than or equal to 10 micrometers).