Yuxiang Zhou

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, nand 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.

Automatic positioning and sensing microelectrode array (APSMEA) for multi-site electrophysiological recordings

Technological improvement of measurements for the electrical recordings from individual neurons within network is essential in neuroscience today. Here, we present a novel automatic positioning and sensing microelectrode array (APSMEA), which simultaneously positioned desired number of neurons onto 48 recording microelectrodes automatically and scathelessly by use of negative dielectrophoretic (DEP) forces, and facilitated the measurement of the electrophysiological activities of neuronal populations after functional synaptic connections formed between neurons. The results of multi-site electrophysiological recordings during drug administration also demonstrated the application of APSMEA in bioassay with cultured rat cortical neurons. Therefore, this device should benefit the investigation of neuronal networks in vitro with more comprehensive electrophysiological experiments, and also promise the possibility of a modular device for both cell manipulation and cell-based biosensor on microchip.

Structure and photoelectric properties of tetrakis(4-N-hexadecylpyridiniumyl)porphyrin/anthraquinone LB films

Using a 1∶1 tetrakis(4-N-hexadecylpyridiniumyl)porphyrin/anthraquinone (TC16PyP(4)/AnQ) mixture as film-forming material, the structure and properties of TC16PyP(4)/AnQ mixed monolayers or LB films were studied by π–A isotherms, UV–VIS absorption spectra, and low-angle X-ray diffraction (LAXD). The experimental results indicate that the TC16PyP(4)/AnQ mixture has good film-forming properties at the air/water interface. The TC16PyP(4)/AnQ mixed monolayer can be transferred to glass, quartz or SnO2 optically transparent electrode (OTE) substrates. Most AnQ molecules are incorporated into the cavities between the long alkyl chains of TC16PyP(4) molecules in the mixed monolayer or in LB films. The TC16PyP(4)/AnQ mixed LB films can be regarded as a two-dimensional host–guest system and show good stability and periodicity. The photovoltaic behaviour of an electrochemical cell containing a TC16PyP(4)/AnQ LB film, deposited on an SnO2 OTE, was also investigated. The photocurrent and photovoltage are apparently lower than those for the photocell of pure TC16PyP(4) LB films due to the incorporation of AnQ.

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.

Novel optical devices for gene disease diagnostics system

Binary optics has been interested widely in recent years, where the optical element can be fabricated on a thin glass plate with micro-ion-etching film layer. A novel optical scanning system for gene disease diagnostics is developed in this paper, where four kinds optical devices are used, such as beam arrays splitter, arrays lens, filter arrays element and detection arrays. A soft for binary device designing with iterative method is programmed. Two beam arrays splitters are designed and fabricated, where one devices can divide a beam into the 9x9 arrays , the other will divide a beam into the 13x13 arrays. The beam arrays splitter has a good diffraction efficiency >70%, and an even energy distribution. The gene disease diagnostics system is portable by biochip and binary optics technology.

Advanced optical design for biochip scanning system

Laboratory-on-a-chip has been interested widely in recent years, where the sample preparation, bio-chemical reaction, separation, detection and analysis, are performed in a small biochip which is only a fingernall dimension. In order to obtain a high detection sensitivity 1 fluors/micrometers 2 (one fluorescence molecular per square micrometer) in biochip scanning system, it is required that the scanning objective lens is a big numerical aperture (> 0.5), very small focal spot (< 5 micrometers ) and long back focal length (> 3 mm). In this paper, a combined lens is designed for the scanning objective lens, which is with big numerical aperture NA > 0.7, very small focal spot (< 2 micrometers ) and long back focal length (> 3 mm). The phase aberrations of combined lens, including the aspherical aberration and the chromatic aberration corresponding to wavelength 532 nm, 570 nm, 635 nm, 670 nm, are corrected very well. The encircled energy diagram of the lens is good to the diffraction limit. The focal spot diagram, the optical path difference diagram, the transverse ray fan plot and the modulation transfer function, are studied also. A novel confocal scanning system of biochip with the designed combined lens as the objective lens is developed, some experiment results in a multi-channel biochip are obtained.