| Functional nucleic acid is a nucleic acid molecule that specifically binds its target,or serves as a coenzyme to form a specific structure These have been used as key compositions in biological analysis,food testing,environmental analysis,pharmaceutical testing.The hybridization chain reaction(HCR)is a novel method in vitro nucleic acid constant temperature amplification technology.The experimental principle is based on two self-stable nucleic acid hairpin probe only in the presence of primer DNA to start hybridization to form long double-stranded,because this triggered chain produced by the reaction,can effectively reduce the false sun signal and the background signal.However,greater biosensing techniques are required with the development of scientific research.Therefore,accuracy strategies with high sensitivity and selectivity are attracte more concerns in chemistry analytical field.The hybridization chain reaction and DNA-scaffold technique were proposed to detect L-histidine and mental ions.The details are mainly performed as following:The hybridization chain reaction(HCR)based DNAzyme sensor was proposed involving G-quadruplexes as reporters.In the absence of L-histidine,the DNAzyme structure was so stable that primers of the HCR reaction were blocked in DNAzyme.The HCR reaction was suspended leading fluorescence negative.In the presence of L-histidine,DNAzymes cleave the substrates specifically,and release the split substrates worked as HCR primers.The primers hybridized with hairpin probes which trigger HCR to produce long double strand DNAs.A series of G-quadruplex formed in HCR products bind the zinc porphyrin that result the fluorescence enhancement.A good linear correlation was obtained between fluorescence change and the logarithm of the L-histidine concentration over the range from 1.500×10-9 to 5.00×1O-6mol L-1.The detection limit was estimated as 2.326×10-9 mol L-1.And the recoveries were 96.98%-103.3%for the actual samples.Compared with the traditional method,this method allowed to specifically determine L-histidine without enzyme or labeling,which shows a good potential in clinical analysis.A DNA probe with poly-thymine sequences was used to fabricate a label free fluorescent sensor for mercumy detection.Hg2+ ions specifically interact with thymine bases to form strong and stable thymine-Hg2+-thymine complexes(T-Hg2+-T)in DNA helex.SYBR Green I(SG)insert in the DNA dulex resulting high fluorescence.A good linear correlation was obtained between fluorescence change and the Hg2+concentration over the range from 4.000×10-8-1.0×10-5 mol·L-1.The detection limit was estimated as 3.924×10-8 mol·L-1.And the recoveries were 98.72%to 102.8%for the actual samples,indicating that the sensing system can be utilized for the determination of Hg2+ ions in the practical samples.A Double stranded DNA probe was used to fabricate a label free fluorescent sensor for copper ions detection.The Double-stranded DNA as recognition molecule,SYBR Green I(SG)fluorescent dye as a reporter group.SG is embedded in double-stranded DNA to enhance fluorescence.Due to the presence of fluorescence quenching in heavy metal ions,Cu2+ quenches the fluorescence of SG in embedded double-stranded DNA after addition of Cu2+.A good linear correlation was obtained between fluorescence change and the Cu2+ concentration over the range from 4.000x1 0-8-4.0×10-5 mot L-1.The detection limit was estimated as 1.235×10-9 mol·L-1.And the recoveries were 98.83%-103.8%for the actual samples.,so the sensor can be used for the measurement of Cu2+ in xiangjiang water samples. |
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