Biomedical subjects

Chun-Yang Zhang

Publications and source records attributed to Chun-Yang Zhang.

5 recordsLinked to original sources

PubMed2006

Quantum dot-based fluorescence resonance energy transfer with improved FRET efficiency in capillary flows.

Fluorescence resonance energy transfer (FRET)-based nanosensors with quantum dots (QDs) as donors and organic dyes as acceptors have long been of interest for the detection of biomolecules such as nucleic acids, but their low FRET efficiency in bulk solution has prevented the sensitive detection of nucleic acids due to the large size of the QDs and the long length of nucleic acids. Here we describe a novel approach to improve the detection sensitivity of QD-based nanosensors using single-molecule detection in a capillary flow. In comparison with bulk measurement, single-molecule detection in a capillary flow possesses the unique advantages of improved FRET efficiency, high sensitivity, prevention of photobleaching, and low sample consumption. Greater FRET efficiency was obtained due to the deformation of DNA in the capillary stream. This technique can be easily extended to sensitive bimolecular analysis in microfluidic chips, and it may also offer a promising approach to study the deformation of small nucleic acids in fluid flow.

DNA↗

PubMed2006

Homogenous rapid detection of nucleic acids using two-color quantum dots.

We report a homogenous method for rapid and sensitive detection of nucleic acids using two-color quantum dots (QDs) based on single-molecule coincidence detection. The streptavidin-coated quantum dots functioned as both a nano-scaffold and as a fluorescence pair for coincidence detection. Two biotinylated oligonucleotide probes were used to recognize and detect specific complementary target DNA through a sandwich hybridization reaction. The DNA hybrids were first caught and assembled on the surface of 605 nm-emitting QDs (605QDs) through specific streptavidin-biotin binding. The 525 nm-emitting QDs (525QDs) were then added to bind the other end of DNA hybrids. The coincidence signals were observed only when the presence of target DNA led to the formation of 605QD/DNA hybrid/525QD complexes. In comparison with a conventional QD-based assay, this assay provided high detection efficiency and short analysis time due to its high hybridization efficiency resulting from the high diffusion coefficient and no limitation of temperature treatment. This QD-based single-molecule coincidence detection offers a simple, rapid and ultra sensitive method for genomic DNA analysis in a homogenous format.

Animals↗

PubMed2005

Comparative quantification of nucleic acids using single-molecule detection and molecular beacons.

This paper reports a highly sensitive homogenous method for comparative quantification of nucleic acids based on single-molecule detection (SMD) and molecular beacons (MBs). Two different color MBs were used to perform a separation-free comparative hybridization assay for simultaneous quantification of both target and control strands. A fluorescent burst, emitted from a single hybrid when it passes through a minuscule laser-focused region, is detected with high signal-to-noise ratio (SNR) by using single-molecule fluorescence spectroscopy. Targets are quantified via counting of discrete fluorescent bursts. The high SNR achieved in both detection channels overcame the complications of fluorescent variability usually observed in dual-color ensemble measurements. In comparison with the conventional ensemble methods, this method improved the detection limit by 3 orders of magnitude and reduced the probe consumption by 6 orders of magnitude, facilitating a highly sensitive approach for comparative quantification of nucleic acids and offering great promise for genomic quantification without amplification.

Animals↗

PubMed2005

Single-quantum-dot-based DNA nanosensor.

Rapid and highly sensitive detection of DNA is critical in diagnosing genetic diseases. Conventional approaches often rely on cumbersome, semi-quantitative amplification of target DNA to improve detection sensitivity. In addition, most DNA detection systems (microarrays, for example), regardless of their need for target amplification, require separation of unhybridized DNA strands from hybridized stands immobilized on a solid substrate, and are thereby complicated by solution-surface binding kinetics. Here, we report an ultrasensitive nanosensor based on fluorescence resonance energy transfer (FRET) capable of detecting low concentrations of DNA in a separation-free format. This system uses quantum dots (QDs) linked to DNA probes to capture DNA targets. The target strand binds to a dye-labelled reporter strand thus forming a FRET donor-acceptor ensemble. The QD also functions as a concentrator that amplifies the target signal by confining several targets in a nanoscale domain. Unbound nanosensors produce near-zero background fluorescence, but on binding to even a small amount of target DNA (approximately 50 copies or less) they generate a very distinct FRET signal. A nanosensor-based oligonucleotide ligation assay has been demonstrated to successfully detect a point mutation typical of some ovarian tumours in clinical samples.

Animals↗

PubMed2002

[The role of human herpesvirus-8 infection in the pathogenesis of multiple myeloma].

Multiple myeloma is a B-cell neoplasm characterized by abnormal proliferation and accumulation of monoclonal plasma cells in the bone marrow. Recently some laboratories have detected human herpesvirus-8 (HHV-8) DNA sequences in bone marrow dendritic cells from myeloma patients. It has been suggested that the cytokines expressed by HHV-8 gene, such as vIRF, vIL-8R and vIL-6, may play a role in the pathogenesis of multiple myeloma. However, the majority of European investigators failed to find evidence to confirm this observation. It remains unclear whether HHV-8 is consequentially associated with myeloma or only a regional opportunistic infection. Controversy still focuses on the role of specific HHV-8 strains involved in pathogenesis of multiple myeloma and causality between the

Cytokines↗