Novel Chem/biosensing Methods Based On Poly(A) DNA-templated Gold Nanoclusters

Deoxyribonucleic acid?DNA?is an ideal building block for the synthesis of metal nanoclusters,which has many advantages,such as sequence programmability,specific molecular recognition,the ability of enzymatic scission and the rigidity of the double helix,etc.As a new type of fluorescent nanomaterials,gold nanoclusters have some advantages,such as simple synthesis,stable optical performance,diverse templates and light bleaching.etc.In recent years,gold nanoclusters have attracted the attention of researchers in the fields of electroanalytical chemistry,biological imaging,biosensing,medical detection and so on.In this paper,poly?A?DNA were used as synthesis templates to synthesis of gold nanoclusters?AuNCs?because of the excellent performance of DNA,AuNCs as the fluorescent probe,a series of new biosensing methods with high sensitivity and simple operation were developed for the detection of chem/biomolecules?such as tetracycline,melamine?.In addition,a new fluorescent biosensor platform has been developed for the general detection of DNA based on DNA-templated Au nanoclusters and guanine-rich?G-rich?DNA proximity-induced quenching.A universal and label free fluorescent biosensor platform was established for DNA and protein detection based on the interaction between DNA-AuNCs and MnO₂nanosheets.The main contents are as follows:1.A rapid and label-free fluorescence sensing strategy for tetracycline?TC?detection by using poly?A?DNA-templated AuNCs as fluorescent indicator.The method is based on poly?A?DNA as template and sodium citrate as reducing agent,and AuNCs is synthesized at 90 degree water bath.The AuNCs has the advantages of high fluorescence intensity and good stability.In the presence of TC,the fluorescence intensity of AuNCs was obviously reduced due to the interactions between the TC and the poly?A?DNA-templated AuNCs,Under the optimum conditions,the strategy permitted sensitive detection of TC within 10 minutes at room temperature in a linear range from 0.1 to 60?mol/L and with a limit of detection of 20 nmol/L.In addition,the sensor has been applied for the determination of TC in milk samples,with the recoveries ranging from 98.8%to 103.2%.2.A novel label-free and highly sensitive chemsensing platform for melamine?MA?detection based on poly?A?DNA-templated AuNCs.This strategy relied on the difference of combining ability between Hg²⁺-MA and Hg²⁺-AuNCs.In the presence of Hg²⁺,the fluorescence intensity of poly?A?DNA-templated AuNCs was quenched rapidly through the d¹⁰-d¹⁰metal interaction between Hg²⁺and Au⁺(5d¹⁰(Hg²⁺)-5d¹⁰?Au⁺?).When MA was introduced into the sensing system,the fluorescence recovery of the AuNCs was observed.It was mainly due to the formation of more stable complexes between Hg²⁺and MA.The complexation of Hg²⁺-MA was stronger than the interaction of Hg²⁺-Au⁺,which inhibited the quenching effect of Hg²⁺on the AuNCs and the the fluorescence signal of the system recovered.Under the optimum conditions,the strategy can realize the sensitive detection of MA in a linear range from 0.05?mol/L to 1?mol/L and with a limit of detection of 16.6 nmol/L.Additionally,the method had been used for the detection of MA content in milk samples.3.It was found that the fluorescence of DNA-AuNCs can be greatly quenched by photoinduced electron transfer?PET?when placed in proximity to guanine-rich DNA sequences.A universal fluorescent biosensing platform was developed for DNA detection based on the fluorescent quenching.In the absence of the target DNA?H1N1?,the guanine-rich DNA?6G probe 2?and AuNCs could not hybridize to form a stable double-stranded structure.And the fluorescence intensity could not be effectively quenched.In the presence of the target DNA H1N1,AuNCs and 6G probe 2 were hybridized with target H1N1 to form stable double-stranded structure.The fluorescence of DNA-AuNCs was quenched by proximity with a G-rich DNA through DNA hybridization.Under the optimum experimental conditions,the method exhibited sensitive detection of H1N1 in a linear range from 1 nmol/L to 100 nmol/L and with a limit of detection of 200 pmol/L.Meanwhile,the sensing strategy was universal and could be expanded to detect the other biomolecular through changing the sequences of the DNA probes.4.Based on the interaction between DNA-templated Au nanoclusters and MnO₂nanosheets,a label-free and universal fluorescence biosensing platform was consturcted for the recognizing of biomolecules by using the excellent fluorescent properties of poly?adenine??poly A?DNA templated-Au nanoclusters?DNA-AuNCs?and the good quenching ability of MnO₂ sheets.Due to the high quenching efficiency of MnO₂nanosheets,the luminescence of DNA-AuNCs was decreased.Because the single-stranded DNA-AuNCs was adsorbed onto the surface of MnO₂ nanosheets through the physical absorption behavior between nucleobases of ss-DNA and the basal plane of MnO₂ nanosheets.When the target was introduced into the system,the DNA-AuNCs can be hybridized with target DNA to form a stable double stranded structure,which resulting in desorption of DNA-AuNCs from the surface of MnO₂ sheets.Thus,the fluorescence signal of system was recovered.Similarly,in the presence of target thrombin,the DNA-AuNCs and thrombin can form complexes,and resulted in the luminescence of DNA-AuNCs.The strategy exhibited sensitive detection of thrombin in a linear range from 0.2 nmol/L to 20 nmol/L with a limit of detection of 100 pmol/L.Moreover,the method had the advantages of simple,low cost and high efficiency.