Guangshun Yi

Synthesis and characterization of multi-functional nanoparticles possessing magnetic, up-conversion fluorescence and bio-affinity properties

Multi-functional nanoparticles possessing magnetic, up-conversion fluorescence and bio-affinity properties were synthesized and characterized. The particles have a core/shell structure. Iron oxide nanoparticles of 5–15 nm diameter were synthesized as the magnetic core. The core was covered with ytterbium and erbium co-doped sodium yttrium fluoride (NaYF4:Yb,Er), an efficient infrared-to-visible up-conversion phosphor. The phosphor shell was prepared by co-precipitation of the rare-earth metal salts with fluoride in the presence of EDTA and the magnetic nanoparticle. After the magnetic/fluorescent hybrid particle was coated with SiO2 and activated with glutaraldehyde, streptavidin was immobilized on the particle. The magnetic/fluorescent nanoparticles were found by transmission electron microscopy to be well-dispersed spherical particles with an average diameter of 68 nm. Both energy dispersive X-ray microanalysis and X-ray fluorescence spectra revealed the existence of iron in the particle. Measurements performed on a vibrating sample magnetometer obtained a strong magnetic response for the particle and fluorescence measurements demonstrated its up-conversion property. X-Ray diffraction analysis suggests the phosphor shell has the same structure as the pure NaYF4:Yb,Er nanoparticles we prepared in a previous study (G. S. Yi, H. C. Lu, S. Y. Zhao, Y. Ge, W. J. Yang, L. H. Guo, D. P. Chen and J. Cheng, submitted). Streptavidin-coated magnetic/fluorescent particles were found to bind specifically to a glass slide spotted with biotinylated IgG and emit up-conversion fluorescence, confirming the successful coating of the protein and retention of its optical activity and bio-affinity.

Microminiaturized immunoassays using quantum dots as fluorescent label by laser confocal scanning fluorescence detection.

An immunoassay readout method based on fluorescent imaging analysis with laser confocal scanning is described. The ZnS-coated CdSe quantum dots (ZnS/CdSe QDs) were linked to a detection antibody. Immunoassay was carried out on a glass chip using a sandwich assay approach, where antibody covalently bound to a glass chip was allowed to capture antigen specially. Afterwards, the detection antibody labeled with QD was allowed to bind selectively to the captured antigen. The fluorescent signals of the sandwich conjugate were detected by a laser confocal scanner. A diode laser was used to excite efficiently the fluorescent signals while bovine serum albumin was used to eliminate nonspecific binding sites. The detection limit of this approach was up to 10(-9) M under current experimental conditions. The specificity of the QDs-labeled immunoglobulin (IgG) was tested by an experiment using goat IgG and human IgG samples. The result was consistent with the binding specificity in a sandwich-type assay. The potential of this method to function as a simple and efficient readout strategy for immunoassay in biochip is discussed.

Synthesis and characterization of strongly fluorescent europium-doped calcium sulfide nanoparticles

Nanometer-sized europium-doped calcium sulfide (CaS–Eu) particles were synthesized for the first time for potential use in bioassays, in particular, in biochip-based analysis. The CaS–Eu nanoparticles were prepared through a wet chemical process in ethanol. The average diameter of the nanoparticles was about 15 nm. They were characterized by UV–Vis spectrometry, scanning electron microscopy, X-ray diffraction, fluorescence spectroscopy and X-ray sequential fluorescence spectroscopy. Both electron paramagnetic resonance measurement and an extensive washing experiment revealed that the dopant atoms were internal ions dispersed throughout the whole CaS–Eu nanoparticles. Factors affecting the fluorescent properties of the nanoparticles were examined. It was found that the emission wavelength of the CaS–Eu nanoparticles could be altered by partial replacement of calcium with other alkaline earth metals such as magnesium, strontium and barium, and this makes the nanoparticles ideal for use as biochips where a multicolor-based bioassay is common.

SOLID SUBSTRATE PHOSPHORESCENT IMMUNOASSAY BASED ON BIOCONJUGATED NANOPARTICLES

Room-temperature phosphorescent (RTP) immunoassay based on dye embedded polyglutaraldehyde nanoparticles was described. Phosphorescent nanoparticles had been covalently linked to antibody to probe specifically antigen. The immunoassay was conducted by the typical procedure of sandwich type assay with polyamide membrane (PAM) sheet as solid substrate. In comparison with single organic dye molecule, the nanoparticle probe was bright, and more stable against photobleaching. Moreover, the solid substrate at room temperature offered high signal and low background, which led to gain rather perfect sensitivity. The concentration of immunoglobulin (IgG) in reaction with nanoparticles was optimized and the dependence of the phosphorescence intensity on the concentration of antigen was studied.

AN IMPROVED METHOD FOR EFFICIENT AND CONVENIENT SYNTHESIS OF DIOCTANOYL PEROXIDE

ABSTRACT Octanoyl chloride in methylene dichloride was added to the hydrogen peroxide solution containing 5 mol.l−1 NaOH in water-cooled flask, the reaction was carried out with high yields in ten or more minutes under vigorous stirring. The product was characterized by elemental analysis, molecular weight and spectral (IR, 1H NMR) analysis. Furthermore, the method proposed has the advantages of operation at room temperature with safety, reliability and short time consuming.