Surface Modification Of Nanomaterials Through Mussel-inspired Chemistry And Their Utilization For Construction Of Fluorescent DNA Sensors

The construction of fluorescent DNA sensor with excellent sensitivity,selectivity and biocompatibility is great important for the development and progress of environmental detection,medical diagnosis,fermentation industry,food industry and other fields.A lot of fluorescent DNA sensors based on nanomaterials have been developed previously and explored for detection of various biomolecules and metal ions.At present,different nanomaterials such as carbon nanomaterials,some emerged two-dimensional nanomaterials have been examined as the fluorescence quenching agents to fabricate the fluorescent DNA sensor systems.Although these nanomaterials display excellent fluorescence quenching effect,they also have some disadvantages,including complexity for preparation,high cost and poor biocompatibility.Therefore,the development of simple,effective and universal methods for preparation of nanocomposites-based fluorescence quenching agents is importance for fabrication of fluorescence DNA sensor systems.In this thesis,we prepared several fluorescence quenching agents through the mussel-inspired chemistry,which relied on the self-polymerization of dopamine to form polydopamine(PDA)and subsequent coating on the surface of targeted nanomaterials.The resultant nanocomposites displayed excellent fluorescence quenching capability and can be used for fabrication of the fluorescence DNA sensor systems to detect the ssDNA with specific DNA sequence and some metal ions.The major contexts of this thesis could be divided into the following three parts.(1)In chapter two,we prepared the nanocomposite of PDA-co-LDH based on PDA coated layered double hydroxides through mussel-inspired chemistry.With the great fluorescence quenching capability of PDA-co-LDH,we designed a fluorescence DNA sensor to detect ssDNA with specific DNA sequence.The preparation method of PDA-co-LDH are very simple that just need mix dopamine and Mg/Al-LDH in alkaline aqueous solution at room temperature.We demonstrated that the FAM-labled ssNDA probe could be effectively absorb on the surface of PDA-co-LDH,and make the fluorescence quenching.While the fluorescence could be recovered after the target ssDNA was added to form dsDNA.Based on the fluorescence changes,the target ssDNA can be facilely and quantitatively determined with the detection limit is about 1.0 pM.Further,PDA-co-LDH have an excellent sensitivity and selectivity that can discriminate the complementary and mismatched target DNA sequences.Thus this DNA sensor system could be potentially used for detection of other molecules through suitably design the sequence of DNA.(2)In chapter three,we prepared the PDA-co-SiO2 nanoparticles(called PDA-co-SiO2 NPs)through mussel-inspired chemistry modification of SiO2 NPs.With the PDA-co-SiO2 NPs atc as an efficiently fluorescence quencher,we designed a novel fluorescent DNA sensor to detected target ssDNA and Ag+ions.The preparation of PDA-co-SiO2 NPs are so simple that just need mix the SiO2 NPs with dopamine in aqueous solution under rather mild experimental conditions.The PDA-co-SiO2 NPs-based sensor systems possess excellent sensitivity and selectivity,fast response for detection of target ssDNA and Ag+ions based on different fluorescence quenching effect of PDA-co-Si02 NPs towards ssDNA and dsDNA.Furthermore,the high fluorescence quenching ability of PDA-co-SiO2 NPs allow quantitative detection of target ssDNA with a low detection limit of 1 nM.More importantly,this method would also be easily extended for preparation of many other PDA-based namomaterials for fabrication of fluorescent DNA sensors owing to the universal attachment of PDA with various materials and surface.(3)In chapter four,on the basis of the mussel-inspired chemistry,we prepared nanocomposite of PDA-co-KNTs through PDA modified kaolinite nanotubes(KNTs).The preparation process and atmosphere of PD A-co-KNTs are so simple and mild that only necessary to mix and stir KNTs and dopamine monomer in an alkaline solution at room temperature.Importantly,the PDA-co-KNTs possess great fluorescence quenching ability and discrimination ability between ssDNA and dsDNA,which could establish a fluorescent DNA sensor to detecte target ssDNA.In target ssDNA quantitatively detection,this sensor system based on PDA-co-KNTs show excellent sensitivity and fast response with a low detection limit of 0.9 nM.Furthermore,this DNA sensor could accurately discriminate mismatched target ssDNA with great selectivity.More importantly,due to PDA possess universal adhesion with any materials,the modified method in our research would be a widespread method to establish a fluorescent DNA sensor for various analytes detection.