Study On The New Colorimetric DNA Detection Assay Based On DNA Self-Assembly

DNA is an important genetic material of organisms, the early diagnosis and prevention of disease, identification of different species, monitor and protection of environment can realize by the detection of DNA, so the DNA detection is very important. This paper proposed a new type of enzyme-free exponential hairpin assembly reaction based on the enzyme-free signal amplification technology of DNA self-assembly, and study to apply the reaction to the DNA detection in a variety of ways.First, this paper put forward the exponential hairpin assembly on the basis of hybridization chain reaction, the reaction only required four hairpin DNAs, when the trigger was joined, it will spontaneously start under the drive of free energy and generate a large dendrimer architecture in a short time. the feasibility of the reaction was confirm by agarose gel electrophoresis, and the shape of the product was further characterize by atomic force microscopy. Adjusting the hairpin DNA concentration and reaction time can effectively influence the formation of the nanoporous mesh structure and the pore sizes range from 200 nm to 400 nm. The mesh structure can be used as a new type of DNA nanomaterial.Second, the nanomaterial can act as a carrier of signal amplification. Combined with the single-molecule fluorescence imaging detection technology and AuNPs colorimetric detection technology, the reaction was applied to the detection of DNA. The experimental results showed that the colorimetric detection technology can effectively eliminate the influence of the background signal and realize the sensitive detection of DNA. Under the optimum reaction condition, the detection result revealed a good linear relationship with the target concentration ranging from 25-10000 pM, the detection method can realize 25 pM of target DNA for the naked eye, which was about 400 times lower than that of conventional AuNP-based colorimetric biosensing, and achieved 11.2 pM of target DNA by UV-vis spectrophotometer. Moreover, this method showed good specificity to sing-base mutation.In this paper, a kind of DNA nanomaterial was built by DNA self-assembly and was used in colorimetric DNA detection. This method was rapid, short time-consuming and high detection sensitivity, and the result can be directly observed by the naked eye, so this method would hold great potential in point-of-care testing.