Research Development on Exosome Separation Technology.

Exosomes are special extracellular vesicles secreted by cells, which are of great significance in the basic research of life science and clinical application and has become a hot research field with rapid development in recent 10 years. Therefore, the isolation and separation of exosomes is particularly important for the research and application of exosomes. This paper aims to review the research progress of exosome isolation and separation methods in recent years, including ultracentrifugation, ultrafiltration, size­exclusion chromatography, precipitation, immunomagnetic bead capture method, aptamer-based isolation, and isolation methods based on microfluidic technology. It is generally accepted that most of the existing methods have limitations, for example, ultracentrifugation is time-consuming and laborious, and immunomagnetic bead capture method and aptamer-based separation method have small sample processing capacity and high cost. As a result, we also introduce some common situations in which two or more methods are combined for use. Finally, the separation and isolation methods including all those presented in this review were compared and summarized.

Synthesis of magnetic nanoparticles with an IDA or TED modified surface for purification and immobilization of poly-histidine tagged proteins.

Magnetic nanoparticles (MNPs) chelating with metal ions can specifically interact with poly-histidine peptides and facilitate immobilization and purification of proteins with poly-histidine tags. Fabrication of MNPs is generally complicated and time consuming. In this paper, we report the preparation of Ni(ii) ion chelated MNPs (Ni-MNPs) in two stages for protein immobilization and purification. In the first stage, organic ligands including pentadentate tris (carboxymethyl) ethylenediamine (TED) and tridentate iminodiacetic acid (IDA) and inorganic Fe3O4-SiO2 MNPs were synthesized separately. In the next stage, ligands were grafted to the surface of MNPs and MNPs with a TED or IDA modified surface were acquired, followed by chelating with Ni(ii) ions. The Ni(ii) ion chelated forms of MNPs (Ni-MNPs) were characterized including morphology, surface charge, structure, size distribution and magnetic response. Taking a his-tagged glycoside hydrolase DspB (Dispersin B) as the protein representative, specific interactions were confirmed between DspB and Ni-MNPs. Purification of his-tagged DspB was achieved with Ni-MNPs that exhibited better performance in terms of purity and activity of DspB than commercial Ni-NTA. Ni-MNPs as enzyme carriers for DspB also exhibited good compatibility and reasonable reusability as well as improved performance in various conditions.

Adherence and interaction of cationic quantum dots on bacterial surfaces.

Understanding molecular mechanisms of interactions between nanoparticles and bacteria is important and essential to develop nanotechnology for medical and environmental applications. Quantum dots (QDs) are specific nanoparticles with unique optical properties and high photochemical stability. In the present study, direct interactions were observed between cationic QDs and bacteria. Distinct fluorescence quenching patterns were developed when cationic QDs interacted with Gram negative and Gram positive bacteria. The aggregation of QDs on bacterial surface as well as fluorescence quenching depends upon the chemical composition and structure of the bacterial cell envelopes. The presence of lipopolysaccharide is unique to Gram-negative bacterial surface and provides negatively charge areas for absorbing cationic QDs. The effects of lipopolysaccharide were proved on fluorescence quenching of cationic QDs. In contrast to Gram-negative bacteria, the presence of teichoic acids is unique to Gram-positive bacterial cell wall and provides negatively charged sites for cationic QDs along the chain of teichoic-acid molecules, which may protect QDs from aggregation and fluorescence quenching. This study may not only provide insight into behaviors of QDs on bacterial cell surfaces but also open a new avenue for designing and applying QDs as biosensors in microbiology, medicine, and environmental science.

[Preparation of new lipid-hydroxyapatite-DNA complex and gene transfection reseach in eukaryotic cell].

This work was directed at obtaining a better gene carrier to improve the effects of gene delivery. Neutral liposomes made from cholesterol, lecithin and DOPE by reverse evaporation technique were used for encapsulating DNA-HAP complex which was made from DNA and optimized HAP. The sizes of complexes and the efficiency of encapsulation were detected. The efficiency of transfection into Hela cells was shown by observation of X-gal staining and measurement of transfection efficience. The average size of complexes was 643nm, the average encapsulating efficiency of DNA in microspheres reached 11.67%. These Lipid-Hydroxyapatite-DNA complex (LHD) could be transfected into mammalian cells. The Lipid-Hydroxyapatite-DNA complex prepared by reverse evaporation technique could be applied availably in DNA delivery system, and it gave another thinking to increase the gene transfection of non- viral genetic vector.