New Strategies Of Signal Amplification Based-on DNAzyme And HCR

Nucleic acid probes combined with the amplification technologies have beenincreasingly applied in sensitive detection of target, due to their simple design, flexiblesignal mechanism, good stability, and easy synthesis. Wherein, the catalytic ability ofDNAzyme/hemin complexes, which act as horseradish peroxidase (HRP), can beamplified250times than hemin. The long nicked duplex formed by hybridization chainreaction (HCR) can also be used as platform of signal amplification. Both of them areeasy to operate， and sensitive detection of target with signal amplification in aconstant temperature without enzyme-assisted. In this thesis, combining nucleic acidmolecular probes and amplification of DNAzyme and HCR，we achieve to detect targetwith colorimetric and SERS means. The contents of the thesis are as followed:(1) Combining the catalytic activity of DNAzyme and enhencement of ATP, anew catalytic sensing approach for ultrasensitive and selective detection of ATP basedon hemin/G-quadruplex-ATP DNAzyme (HGAD) is proposed.The simple hairpinstructure that included the HRP-mimicking DNAzyme in caged was designed.UponATP addition, it can trigger the hairpin conformation changes and form HGADcomplexes to catalyze the H2O2oxidation of ABTS2-to ABTS.-, which can beenhenced by ATP. The strategy has low background-signal and can achieve sensitiveand selective detection of small molecular with visible color changes.(2) A new approach for detection of DNA has been developed combining HCRand SERS enhancement. Upon the target DNA triggers HCR， a long nicked duplexwill be produecd，allowling the formation of HCR-Au through ligaton of biotin andavidin, which result in a significant Raman signal enhancement due to the closeproximity. This assay implemented highly sensitive and selective detection of DNAand the universality of the approach is achieved by virtue of altering the sequence ofH-Apt probe without change of H1, H2.(3)A approach for detection of cancer cells has been developed combining HCRand SERS enhancement on the bases of the last chapter. The initiator DNA triggersHCR and form HCR-Au through ligaton of biotin and avidin, which result in asignificant Raman signal enhancement due to the close proximity. When HCR-Auincubate with CEM cells, the detection of the single CEM cell level can be targeted to achieve with the advantage of high specificity, high sensitivity, high resolution andgood stability and so on.