Photochemical Preparation Of Gold-modified Magnetic Composites And Their Preliminary Application As Carrier For Bioseperation

Recently, gold-modified magnetic composites (GMCs) as a kind of carrier for bioseperation have been attracting many attentions, owing to their advantages of simplicity and high efficiency in magnetic seperation process, as well as the unique properties of gold nanoparticles in optics, electricity and surface chemistry. The concrete work of this paper involves:a) photochemical synthesis of GMCs based on two different magnetic polymer particles with amino groups obtained respectively from photopolymerization and in-situ precipitation, and b) a preliminary application of GMCs in bioseparation.1.Core-shell Fe3O4-poly(allylamine-co-poly(ethylene glycol) methyl ether methacrylate) nanoparticles (Fe3O4/p(AAM-co-mPEGMA)) were prepared by photochemical copolymerization of allylamine (AAM) and poly(ethylene glycol) methyl ether methacrylate (mPEGMA) in Fe3O4nanoparticles suspension, characteried by FTIR,TGA,TEM,PCSand VSM. The nanoparticles with an average size of70nm showed high saturation magnetization (30.2emu/g) and good dispersion stability. Besides, the density of amino groups on Fe3O4/p(AAM-co-mPEGMA) can be also changed by varing the amount of AAM and input time of the comonomer mPEGMA.2.GMCs with size ranging from200nm to300nm were prepared from HAuCl4solution in the presence of actone and isopropanol under UV irradiation, using Fe3O4/p(AAM-co-mPEGMA) as the magnetic core. The UV-vis absorption spectra indicated that the low concentration of actone and isopropanol resulted in a induction period for the formation of gold nanoclusters. Au nanoparticles with larger size and higher concentration were formed as the HAuCl4concentration was increased. Furthermore, the reaction rate was affected by light intensity. All of them result from the yield of acetone ketyl radicals and Au nanocluster nucleation-growth transition. TEM indicated that the synthesized Au nanoparticles immobilized on the magnetic polymer particles had an average size of20nm. The magnetic response time of GMCs, with a high saturation magnetization of28.8emu/g, was less than4minutes, which met requirements of bioseparation.3.Polyethylenimine(PEI)-coated magnetite (Fe3O4/PEI), a kind of amino-functionalized magnetic polymer nanoparticles, was synthesized by in-situ precipitation method in the presence of PEI, and used to fabricate GMCs (Fe3O4/PEI/Au) by the proposed photochemical technique. The results showed that the irregularly shaped and submicron GMCs contained Au nanoparticles with varous sizes from13nm to23nm and the magnetization was about36.9emu/g.4.A process of DNA seperation and detection based upon the hybridization of target DNA molecules to GMCs probes with surface immobilized thiol-derivatized single-stranded oligonucleotides was performed to assess the feasibility of bioseperation using GMCs as carriers. The amount of alkanethiol-oligonucleotides loaded on Fe3O4/p(AAM-co-mPEGMA)/Au was determined to be131pmol/mg GMCs, larger than that of Fe3O4/PEI/Au. Specific seperation and detection of the target with a concentration of50nM from aqueous solution consisting of proteins and nucleotides with radom consequence was conducted using Fe3O4/p(AAM-co-mPEGMA)/Au as magnetic carriers.