Tian-Cai Liu

The Fluorescence Bioassay Platforms on Quantum Dots Nanoparticles

In this paper, we present the optical properties and the platforms on fluorescent quantum dots for biological labeling, biomedical engineering and biosensor in molecular imaging. Quantum dots possess several properties that make them very attractive for fluorescent tagging: broad excitation spectrum, narrow emission spectrum, precise tunability of their emission peak, longer fluorescence lifetime than organic fluorophores and negligible photobleaching. We describe how to take such advantages of quantum dots to develop the technology and employ it to build assay platforms. Finally, ultrasensitivity, multicolor, and multiplexing of the technology of semiconductor quantum dots open up promising and interesting possibilities for bioassay platform.

Quantum dot optical encoded polystyrene beads for DNA detection

A novel multiplex analysis technology based on quantum dot (QD) optical encoded beads was studied. Carboxyl functionalized polystyrene beads, about 100 microm in size, were precisely encoded by the various ratios of two types of QDs whose emission wavelengths are 576 and 628 nm, respectively. Then the different encoded beads were covalently immobilized with different probes in the existing of sulfo-NHS and 1-[3-(Dimethylamino) propyl]-3-ethylcarbodiimide methiodide, and the probe density could reach to 3.1 mmol/g. These probe-linked encoded beads were used to detect the target DNA sequences in complex DNA solution by hybridization. Hybridization was visualized using fluorescein isothiocynate-labeled DNA sequences. The results show that the QDs and target signals can be obviously identified from a single-bead-level spectrum. This technology can detect DNA targets effectively with a detection limit of 0.2 microg/mL in complex solution.

A feasible and quantitative encoding method for microbeads with multicolor quantum dots.

Multicolor encoded beads were achieved by incorporating two color core-shell quantum dots (QDs) (CdSe/ZnS) to commercial polystyrene (PS) beads. By controlling the concentration ratios of the two quantum dots (QDs) in doping solutions, a series of codes with different intensity ratios were obtained. Based on the multiple encoded carboxylic modified polystyrene beads, fluorescent dyes labeled antibodies were distinguished successfully on the beads’ surface. It suggests that the encoded beads from this method have the practicability in biological applications and chemical analysis.

Quantitative doping of commercial polystyrene microbeads with quantum dots

Microbeads with embedded encode characteristics are of considerable interest due to their potential use in multiplexed bioassays, high-throughput screening and combinatorial chemistry. Lots of encoding strategies for tagging or labeling microbeads have arisen in the past couple of years. Compared with the organic dye counterparts, the ideal optical properties of quantum dots (QDs) (e.g. characteristic narrow and symmetric spectra, size-tunable emission and simultaneous excitation) make it possible to tag microbeads in a quantitative way. In this paper, quantitative doping of commercial polystyrene microbeads with single color quantum dots was reported. A detailed analysis of the optical characteristics of the QD-tagged microbeads was presented based on the combination of fluorescent spectroscopy and microscope imaging.

Synthesis and properties of quantum dots optical probes for bio-imaging

A novel green synthesis of semiconductor nanoparticles was introduced and it was used as optical probes for bio-imaging. Quantum dots are known as <10nm scaled semiconductor nanoparticles, which could dramatically improve fluorescent imaging. Since these nanocrystals act as robust broadly tunable nano-emitters that can be excited by a single light source, they could pride significant advantages over current labels (e.g. traditional organic dyes, isotope and fluorescent proteins) in vitro and in vivo. As for a novel green synthesis, the usage of dangerous organic composites under rigorously air-free conditions was avoided, and ZnS-capped CdSe semiconductor nanoparticles was prepared economically. And the surface of as- synthesized nanoparticle would be modified by hydrophilic molecules for optical bio-probes. Moreover, such optical probes under aqueous biological conditions could maintain many characters: economy, photostability, colloidal stability, efficient fluorescence, low non-specific adsorption, biological compatibility and validity for multiplex assays.