Preparation And Electrochemical Characteristics Of Polyethyleneimine/silica/metal Ion Composite Nanoparticles

With rapid development of nanotechnology and emergence of novel materials,functional and cormposite nano materials have attracted much attention and have been widely used in chemical,electron,biological,medical diagnostics,environmental monitoring,materials,Nano-borne drug research and many other field.Among them,the silica nanocomposites receive more attention due to its unique propertie and had following advantages:(1)Silica Nanoparticles are often used as matrix materials due to it's chemical inert,low toxicity,good biological compatibility,Uniform and adjustable particle size.(2)Silica nanoparticles have active groups on their surfaces and easy to surface modification,so they show great promise in applications,in this thesis,we synthesized PEI/SiO2 NPs by using inverse microemulsion,based on the cordination effect between amino groups of PEI and Cu2+ or Ag+,the Cu2+/PEI/SiO2 NPs and Ag+/PEI/SiO2 NPs was prepared,mainly studied the electrochemical analysis characteristics of composite nanoparticles with ssDNA or dsDNA.and based on Ag+/PEI/SiO2 and Cu2+/PEI/SiO2 composite nanoparticles prepared two kinds of DNA nanoprobes,The electrochemical properties of Ag+ and Cu2+ in DNA nanoprobes were studied.The simultaneous detection of two-component MiRNA(miRNA)was realized.This thesis includes two parts,the first is review section and the other research section.Reviews brief introduced the synthesis methods of silica nanoparticles,Mainly intuoduced the recent development and applications of function silica nanoparticles in electroanalytical chemistry.Research report consists of the following two parts:1.The synthesis of Cu2+/PEI/Silica nanocomposites and investigate the Interaction between Cu2+/PEI/Silica nanoparticals and DNAReverse microemulsion method is adopted to synthesis PEI/Silica nanoparticals,Then Cu2+ was doped into the PEI/SiO2 nanoparticals based on the coordination chemical reaction between amino groiups on PEI and Cu2+ formed Cu2+/PEI/Silica composite nanoparticles,single and double stranded DNA in structure is quite different,which leads to great discriminating ability towards both ssDNA and ssDNA/miRNA,By self-assembling of the as-prepared composite nanoparticleson the Nafion/MWNTScomplex film coated grapite electrode,we could obtain an functional modified electrode and was detected by electrochemical method.the results show that The current of the Cu2+/PEI/SiO2/dsDNA mixture was obviously higher than that of Cu2+/PEI/SiO2/ssDNA mixture,which formed the base of DPV sensing the miRNA.we set up a simple and rapid,high sensitivity method to detect the microrRNA and apply this method to the detecte miRNA in human serum samples.2.Preparation of DNA nanoprobe based on Cu2+/PEI/Silica nanoparticals?Ag+/PEI/Silica nanoparticals and Bicomponent detection miRNAThe first work found that the Cu2+ on the surface of the Cu2+/PEI/SiO2 nanoparticles existed in the unsaturated state,and there is a coordination interaction between the exposed amino groups on the bases of ssDNA and Cu2+,and whereas the double-stranded DNA because of complementary base pairing formed a rigid double helix cannot interact with Cu2+/PEI/Silica nanoparticles,which resulted in the great discriminating ability towards both ssDNA and ssDNA,Based on these mentioned above,Ag+/PEI/Silica composite nanoparticles were prepared,which respectively interaction with ssDNA and dsDNA respectively,and the mixture of ssDNA/Ag+/PEI/Silica and dsDNA/Ag+/PEI/Silica was self-assembled on the Nafion/MWNTS film modified glassy carbon electrode surface and using HF in situ etching.Then detect the electrochemical singnal,Which shows great discriminating ability towards both ssDNA and ssDNA/MicroRNA and the response voltage is different from the mixture of DNA/Cu2+/PEI/Silica on the electrode surface.So we mixed the Cu2+/PEI/Silica and Ag+/PEI/Silica composite with two kinds of DNA Probes to form nanoprobes,DNA nanoprobes can stable adsorpted on the surface of nanoparticles,then add the complementary base pairing of DNA Target to the DNA probe solution to form rigid double-stranded DNA,Which lead the the DNA nanoprobes fell off from the surface of the nanoparticles,get a lot of naked,nanoparticles,these naked nanoparticles could assemble in the Nafion/MWNTS complex film modified electrodes surface,in situ etching with HF,and makes the metal ion Cu2+ and Ag+ release,and thus obtain high electrochemical signals at the same time,It is found that two sets of electrochemical signals can be found simultaneously.So the proposed idear may formed a basis for synthesize different M/PEI/Silica nanoparticles as the label tags for achieving the multi-targets detection.