Polymerization and isomerization cyclic amplification for nucleic acid detection with attomolar sensitivity

DNA amplification is one of the most valuable tools for the clinical diagnosis of nucleic acid-related diseases, but current techniques for DNA amplification are based on intermolecular polymerization reactions, resulting in the risk of errors in the intermolecular reaction pattern. In this article, we introduce the concept of intramolecular polymerization and isomerization cyclic amplification (PICA), which extends a short DNA strand to a long strand containing periodic repeats of a sequence through cyclic alternating polymerization and isomerization. To the best of our knowledge, this is the first time that a real ssDNA self-extension method without any additional auxiliary oligonucleotides has been reported. By interfacing PICA with external molecular elements, it can be programmed to respond to different targets. Herein, we designed two distinct types of amplified nucleic acid detection platforms that can be implemented with PICA, including cyclic reverse transcription (CRT) and cyclic replication (CR). We experimentally demonstrate the mechanisms of CRT-PICA and CR-PICA using mammalian miRNA and virus DNA. The results showed that this proposed detection platform has excellent sensitivity, selectivity, and reliability. The detection level could reach the aM level, that is, several copies of target molecules can be detected if a small volume is taken into account.