Zhi-Quan Tian

Electrochemical tuning of luminescent carbon nanodots: from preparation to luminescence mechanism.

The size of C-nanodots can be electrochemically tuned by changing the applied potential during their preparation. The higher the applied potential, the smaller the resulting C-nanodots. Moreover, the surface oxidation degree of the C-nanodots can also be electrochemically tuned. The red-shift of emission independent of the size provides an insight into the luminescence mechanism of C-nanodots.

Fluorescent-magnetic-biotargeting multifunctional nanobioprobes for detecting and isolating multiple types of tumor cells.

Fluorescent-magnetic-biotargeting multifunctional nanobioprobes (FMBMNs) have attracted great attention in recent years due to their increasing, important applications in biomedical research, clinical diagnosis, and biomedicine. We have previously developed such nanobioprobes for the detection and isolation of a single kind of tumor cells. Detection and isolation of multiple tumor markers or tumor cells from complex samples sensitively and with high efficiency is critical for the early diagnosis of tumors, especially malignant tumors or cancers, which will improve clinical diagnosis outcomes and help to select effective treatment approaches. Here, we expanded the application of the monoclonal antibody (mAb)-coupled FMBMNs for multiplexed assays. Multiple types of cancer cells, such as leukemia cells and prostate cancer cells, were detected and collected from mixed samples within 25 min by using a magnet and an ordinary fluorescence microscope. The capture efficiencies of mAb-coupled FMBMNs for the above-mentioned two types of cells were 96% and 97%, respectively. Furthermore, by using the mAb-coupled FMBMNs, specific and sensitive detection and rapid separation of a small number of spiked leukemia cells and prostate cancer cells in a large population of cultured normal cells (about 0.01% were tumor cells) were achieved simply and inexpensively without any sample pretreatment before cell analysis. Therefore, mAb-coupled multicolor FMBMNs may be used for very sensitive detection and rapid isolation of multiple cancer cells in biomedical research and medical diagnostics.

Shifting and non-shifting fluorescence emitted by carbon nanodots

The shifting and non-shifting fluorescence at varied excitations are observed on carbon nanodots prepared by electro-oxidizing carbon paste electrodes with different compositions. The emissions are proposed to be mainly attributed to the surface states rising from surface oxidation of carbon nanodots.

Ag2Se Quantum Dots with Tunable Emission in the Second Near-Infrared Window

Quantum dots (QDs) with fluorescence in the second near-infrared window (NIR-II, 1000-1400 nm) are ideal fluorophores for in vivo imaging of deep tissue with high signal-to-noise ratios. Ag₂Se (bulk band gap 0.15 eV) is a promising candidate for preparing NIR-II QDs. By using 1-octanethiol as ligand to effectively balance the nucleation and growth, tuning the fluorescence of Ag₂Se QDs was successfully realized in the NIR-II window ranged from 1080 to 1330 nm. The prepared Ag₂Se QDs can be conveniently transferred to the aqueous phase by ligand exchange, showing great potential for multicolor NIR-II fluorescence imaging in vivo.

One-Step Sensitive Detection of Salmonella typhimurium by Coupling Magnetic Capture and Fluorescence Identification with Functional Nanospheres

Sensitive, rapid, and reliable detection of bacteria has always been pursued due to the great threat of the bacteria to human health. In this study, a convenient one-step strategy for detecting Salmonella typhimurium was developed. Immunomagnetic nanospheres (IMNS) and immunofluorescent nanospheres (IFNS) were used to specifically capture and recognize S. typhimurium simultaneously. After magnetic separation, the sandwich immune complexes (IMNS-bacteria-IFNS) were detected under a fluorescence microscope with a detection limit as low as ca. 10 CFU/mL. When they were detected by fluorescence spectrometer, a linear range was exhibited at the concentration from 10(5) to 10(7) CFU/mL with R(2) = 0.9994. Compared with the two-step detection strategy, in which the bacteria were first captured with the IMNS and subsequently identified with the IFNS, this one-step strategy simplified the detection process and improved the sensitivity. Escherichia coli and Shigella flexneri both showed negative results with this method, indicating that this method had excellent selectivity and specificity. Moreover, this method had strong anti-interference ability, and it had been successfully used to detect S. typhimurium in synthetic samples (milk, fetal bovine serum, and urine), showing the potential application in practice.

Biofunctionalization of fluorescent-magnetic-bifunctional nanospheres and their applications

Hydrazide-containing bifunctional nanospheres were covalently coupled on the surface with IgG, avidin, and biotin, to generate novel fluorescent-magnetic-biotargeting trifunctional nanospheres, which can be used in a number of biomedical applications, including visual sorting and manipulation of apoptotic cells as demonstrated here.

Visualizing the endocytic and exocytic processes of wheat germ agglutinin by quantum dot-based single-particle tracking

Wheat germ agglutinin (WGA) is a paradigm for understanding intracellular transport of lectins. As a protein exploiting the receptor-mediated endocytosis for internalization, WGA is also a valuable model system for exploring the endocytic and exocytic pathway. In this study, quantum dot-based single-particle tracking was performed to investigate the transport of WGA in live cells, revealing firstly that the endocytic and exocytic processes of WGA were both actin- and microtubule-dependent, each including five stages. The vesicle fusion event occurred near the cytomembrane, followed by two destinies with WGA: shedding to the extracellular or reversing to the cytoplasm. These findings suggest a distinct and dynamic scenario for the transport of lectins following a receptor-mediated endo/exocytic pathway in live cells. This is important for the application of lectins as drug carriers and antineoplastic drugs in medicine, and also offers insights into the pathway of endocytosis and exocytosis.

Mechanism-Oriented Controllability of Intracellular Quantum Dots Formation: The Role of Glutathione Metabolic Pathway

Microbial cells have shown a great potential to biosynthesize inorganic nanoparticles within their orderly regulated intracellular environment. However, very little is known about the mechanism of nanoparticle biosynthesis. Therefore, it is difficult to control intracellular synthesis through the manipulation of biological processes. Here, we present a mechanism-oriented strategy for controlling the biosynthesis of fluorescent CdSe quantum dots (QDs) by means of metabolic engineering in yeast cells. Using genetic techniques, we demonstrated that the glutathione metabolic pathway controls the intracellular CdSe QD formation. Inspired from this mechanism, the controllability of CdSe QD yield was realized through engineering the glutathione metabolism in genetically modified yeast cells. The yeast cells were homogeneously transformed into more efficient cell-factories at the single-cell level, providing a specific way to direct the cellular metabolism toward CdSe QD formation. This work could provide the foundation for the future development of nanomaterial biosynthesis.

High-efficiency dual labeling of influenza virus for single-virus imaging

Many viruses invade host cells by entering the cells and releasing their genome for replication, which are remarkable incidents for viral infection. Therefore, the viral internal and external components should be simultaneously labeled and dynamically tracked at single-virus level for further understanding viral infection mechanisms. However, most of the previously reported methods have very low labeling efficiency and require considerable time and effort, which is laborious and inconvenient for researchers. In this work, we report a general strategy to high-efficiently label viral envelope and genome for single-virus imaging with quantum dots (QDs) and Syto 82, respectively. It was found that nearly all viral envelopes could be labeled with QDs with superior stability, which makes it possible to realize global and long-term tracking of single virus in individual cells. Effectively labeling their genome with Syto 82, about 90% of QDs-labeled viruses could be used to monitor the viral genome signal, which may provide valuable information for deeply studying viral genome transport. This is very important and meaningful to investigate the viral infection mechanism. Our labeling strategy has advantage in commonality, convenience and efficiency, which is expected to be widely used in biological research.

Myosin-driven intercellular transportation of wheat germ agglutinin mediated by membrane nanotubes between human lung cancer cells.

Membrane nanotubes can facilitate direct intercellular communication between cells and provide a unique channel for intercellular transfer of cellular contents. However, the transport mechanisms of membrane nanotubes remain poorly understood between cancer cells. Also largely unknown is the transport pattern mediated by membrane nanotubes. In this work, wheat germ agglutinin (WGA), a widely used drug carrier and potential antineoplastic drug, was labeled with quantum dots (QDs-WGA) as a model for exploring the intercellular transportation via membrane nanotubes. We found that membrane nanotubes allowed effective transfer of QDs-WGA. Long-term single-particle tracking indicated that the movements of QDs-WGA exhibited a slow and directed motion pattern in nanotubes. Significantly, the transport of QDs-WGA was driven by myosin molecular motors in an active and unidirectional manner. These results contribute to a better understanding of cell-to-cell communication for cancer research.