Zonghai Sheng

Quantum-dots-based fluoroimmunoassay for the rapid and sensitive detection of avian influenza virus subtype H5N1

The continuous spread of highly pathogenic avian influenza virus (AIV) subtype H5N1 is threatening the poultry industry and human health worldwide. Rapid and sensitive diagnostic methods are required for the H5N1 surveillance. In this study, the fluorescent (FL) probe of CdTe quantum dots (QDs) was designed using covalently linked rabbit anti-AIV H5N1 antibody. Based on these QD-antibody conjugates, a novel sandwich FL-linked immunosorbent assay (sFLISA) was developed for H5N1 viral antigen detection. The sFLISA allowed for H5N1 viral antigen determination in a linear range of 8.0 × 10(-3) to 5.1 × 10(-1) u2009μgu2009mL(-1) with the limit of detection (LOD) of 1.5 × 10(-4) u2009μgu2009mL(-1) . In comparison with virus isolation for 103 clinic samples, the sensitivity and specificity of sFLISA were found to be 93.6 and 91.1% respectively. The sFLISA supplied a novel approach to rapid and sensitive detection of AIV subtype H5N1 and showed great potential for biological applications in immunoassays.

A fast and sensitive immunoassay of avian influenza virus based on label-free quantum dot probe and lateral flow test strip

A novel fluorescence immunoassay method for fast and ultrasensitive detection of avian influenza virus (AIV) was developed. The immunoassay method which integrated lateral flow test strip technique with fluorescence immunoassay used the label-free and high luminescent quantum dots (QDs) as signal output. By the sandwich immunoreaction performed on lateral flow test strip, the gold nanoparticle (NP) labels were captured in the test zone and further dissolved to release a large number of gold ions as a signal transduction bridge that was detected by the QDs-based fluorescence quenching method. Under the optimal conditions, the relative fluorescence intensity of QDs was linear over the range of 0.27-12 ng mL(-1) AIV, and the limit of detection was estimated to be 0.09 ng mL(-1) which was 100-fold greater than enzyme-linked immunosorbent assay (ELISA). The sensitive and specific response was also coupled with high reproducibility in the proposed method. A series of six parallel measurements produced reproducible fluorescent signals with a relative standard deviation of 4.7%. The proposed method can be used to directly detect clinical sample without any pretreatment, and showed high efficiency (90.0%), sensitivity (100.0%) and specificity (88.2%) compared with virus isolation (gold method). The new method shows great promise for rapid, sensitive, and quantitative detection of AIV in-field or point-of-care diagnosis.

An ultrasensitive method for the detection of gene fragment from transgenics using label-free gold nanoparticle probe and dynamic light scattering

The detection of transgenic products is of great significance for the development of transgenic technique. In this paper, we developed a simple, rapid and ultrasensitive method for the detection of sequence-specific Nopaline synthase (NOS) gene from the transgenic plants using label-free gold nanoparticle (NP) probe and dynamic light scattering (DLS) technology. Gold NPs were stable in NaCl solution with the presence of NOS gene probe. On the contrary, they were aggregated in NaCl solution when the probe sequence was hybridized with target sequence. The change in the size of gold NPs can be detected by DLS technology with high sensitivity. Under the optimal conditions, the average hydrodynamic diameter of gold NPs was linear with the concentration of the target sequence ranging from 1.0×10(-13)mol L(-1) to 5.0×10(-9)mol L(-1), with a detection limit of 3.0×10(-14)mol L(-1) (S/N=3). The relative standard deviation (at 1.0×10(-9)mol L(-1) of target sequence) was 4.8% (n=11). The result shows that gold NPs-based DLS method has great potential in the analysis of transgenic products.

A novel method for sensing of methimazole using gold nanoparticle-catalyzed chemiluminescent reaction

Based on the inhibition effect of methimazole (MMI) on the reaction of luminol-H(2)O(2) catalyzed by gold nanoparticles, a novel chemiluminescence (CL) method was developed for the determination of MMI. Under the optimum conditions, the relative CL intensity was linearly related to MMI concentration in the range from 5.0 × 10(-8) to 5.0 × 10(-5) mol L(-1). The detection limit was 1.6 × 10(-8) mol L(-1) (S/N=3), and the RSD for 6.0 × 10(-6) mol L(-1) MMI was 4.83 (n=11). This method has high sensitivity, wide linear range, inexpensive instrumentation and has been applied to detect MMI in pharmaceutical tablets and pig serum samples. Furthermore, a possible reaction mechanism is discussed.

Quantum dots-gold(III)-based indirect fluorescence immunoassay for high-throughput screening of APP

Here we report a indirect fluorescence immunoassay for high-throughput screening of APP based on the fluorescence quenching of quantum dots by gold(III), which were dissolved from gold nanoparticles-Rabbit anti-Pig IgG conjugate, and further utilize this system to detect APP in pig serum with high sensitivity and specificity.

Ultrasensitive detection of porcine circovirus type 2 using gold(III) enhanced chemiluminescence immunoassay

Porcine circovirus type 2 (PCV2) is associated with many diseases especially postweaning multisystemic wasting syndrome (PMWS), which has brought huge economic loss to the swine industry worldwide. Viral detection will pave the way for this disease prevention. Herein, we developed a facile, rapid and ultrasensitive method for detection of PCV2 based on gold(III) enhanced chemiluminescence immunoassay (CLIA). The gold(III), dissolved from the gold nanoparticle-monoclonal antibody conjugate, served as an analyte for the indirect measurement of PCV2. Under the optimal conditions, the detection limit for the detection of PCV2 was 1.71 x 10(3) copies mL(-1). Moreover, the CLIA signal can be further enhanced by using hydroxylamine-amplified gold nanoparticles, and the limit of detection was as low as 2.67 x 10(2) copies mL(-1). Compared with conventional polymerase chain reaction (PCR), the proposed method has good sensitivity and reliability in analysis of 36 serum samples, and showed great potential in virus assays.