Studies On The Preparation Of Magnetic Nanomaterials And Their Applications For Detection Of Phenolic Compounds And Adenosine Triphosphate

Magnetic nanomaterials are gradually produced and developed new nanomaterials after the1970s, which are widely used in biomedicine, magnetic resonance imaging, catalysis, environmental remediation, bio-separation and biological sensing and so on. Magnetic nanomaterials have small particle size, large surface area and excellent magnetic property different from conventional magnetic materials, so it is favored by many researchers. Chemical and physical properties of Fe3O4(NPs) are extremely stable, and it is now in widespread use. However, compared to other nanomaterials, magnetic nonmaterials have their own weaknesses. Usually, magnetic particles were modified by physical and chemical methods, mainly in order to compensate for the defects of its antioxidant capacity, to embrace the biocompatibility and to enhance the dispersion stability. Furthermore, in order to make the magnetic nanoparticles have specific functions, different reactive functional groups (-NH2,-COOH) were conjugated onto surface of magnetic nanoparticles by surface modification. The main content of this paper is listed below:Firstly, Fe3O4NPs with good dispersion were synthesized via chemical precipitation. Vibrating sample magnetometer (VSM) was used to measure magnetization of Fe3O4NPs, and the large saturation magnetization of76.64emu g-1makes them very rapid separation to magnetic fields. Transmission electron microscopy (TEM) results show that the size distribution and is even with average size of particle9.1nm. The isoelectric point (IEP) of Fe3O4NPs was measured in the experiments, and can help us to control the charge density of metal oxides by adjusting the pH value. The mixed hemimicelles are formed by adding an appropriate amount of oppositely charged ionic liquid. The concentration of chlorophenols (2,4-dichlorophenol,2,4,6-trichlorophenol) are driven by both hydrophobic interactions and electrostatic attraction, resulting in the formation of mixed hemimicelles on the surface of magnetic NPs. The amount of the magnetic nanoparticles and C16mimBr, adsorption standing time, maximum extraction volume, desorption conditions and other factors were investigated. The eluate was detected at285nm by high performance liquid chromatography (HPLC-UV), and the satisfactory extraction recoveries (74-90%) for the two CPs were obtained with only a small amount of Fe3O4NPs (40mg) and C16mimBr (24mg).Secondly, a molecularly imprinted polymer (MIP) was prepared by using SiO2-coated Fe3O4 nanoparticles as the core and4-nitrophenol (4-NP) as a template molecule, methacrylic acid (MAA) as a functional monomer, and divinylbenzene as a polymeric matrix component. The structure of MIP was as follows:Fe3O4@SiO2@MIP. The M-MIP was characterized by X-ray diffractometer (XRD), Fourier-transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), thermogravimetric analysis (TGA), vibrating sample magnetometer (VSM), and Brunauer Emmett Teller (BET). The adsorption standing time, maximum adsorption capacity, desorption conditions and other factors were investigated. The size of MIP was from90-110nm, their saturation magnetization was76.64emu g-1, and the maximum adsorption capacity was found to be263mg g-1.The M-MIP was used for the fast and selective extraction of phenolic compounds from the environmental water samples. The method was successfully applied to analysis of environmental water samples, and the good results were obtained.Thirdly, the complementary oligonucleotide of the adenosine triphosphate (ATP) aptamer was immobilized onto magnetic nanoparticles (MNP), the ATP aptamer was hybridized onto oligonucleotide functional magnetic nanoparticles, and duplex hybridization model was built. A fluorescent aptamer sensor based on magnetic separation for assay (ATP) is proposed. The amount of ethidium bromide (EB) required for maximum intercalation of duplex DNA was studied based on the EB fluorescence intensity change at607nm. Thus, in the absence of ATP, the fluorescence intensity kept invariable. However, when ATP is introduced, a competition for ATP aptamer between ATP and the complementary oligonucleotide occurs. As a result, duplex hybridization model was forced to dissociate from the MNP surface based on the conformational switching from the aptamer duplex to the aptamer/target complex upon target binding, which induces the fluorescence change of intercalated EB emission. The fluorescence intensities were proportional to the concentration of ATP. Good selectivity between ATP and CTP, GTP or UTP has been demonstrated, which is due to the specific recognition between the ATP and ATP aptamer. The fluorescence intensity was linear with the concentration of ATP in the range of5-50μM, and the detection limits was0.49μM. The preliminary study on detection of ATP in real urine samples was also performed and showed the good character for ATP detection.